Nature Unbound X – The next glaciation

by Javier

Summary: The IPCC expresses virtual certainty that a glaciation is not possible for the next 50 Kyr if CO2levels remain above 300 ppm. It is the long interglacial hypothesis. Analysis of interglacials of the past 800 Kyr shows they depend on obliquity-linked summer energy, ice-volume, and eccentricity, and they end at glacial inception after ~ 6000 years of Neoglaciation-type temperature decline. The lag between orbital forcing and ice volume change indicates the orbital threshold for glacial inception is crossed thousands of years before glacial inception, and the Holocene went through that threshold long ago. In the absence of sufficient anthropogenic forcing glacial inception should take place in 1500-2500 years. The long interglacial hypothesis rests on the wrong astronomical parameter, high-equilibrium climate sensitivity to CO2, and uncertain model predictions of very long-tailed CO2decay. It is not possible to determine at present if a glacial inception will take place over the next millennia. The precautionary principle indicates we should prepare for that eventuality as it would constitute the worst catastrophe humankind has ever faced.

Introduction

The expected timeframe for the next glaciation is so far in the future that traditionally it has only attracted academic interest. There was a small peak of popular interest in the early 1970’s at the end of the mid-20th century cooling period. In January 1972, geologists George Kukla and Robert Matthews organized a meeting on the end of the present interglacial, and afterwards they wrote president Richard Nixon calling for federal action on the observed climate deterioration that had the potential to lead to the next glaciation. Ironically, concerns over the end of the interglacial led to the creation of NOAA’s Climate Analysis Center in 1979 (Reeves & Gemmill, 2004), that would substantially contribute to global warming research. Some popular magazines reported about a coming ice age at times of harsh winter weather during the early 1970’s.

Current academic consensus is that a return to glacial conditions is not possible under any realistic condition for tens of thousands of years, and the IPCC expresses virtual certainty that a new glacial inception is not possible for the next 50 Kyr if CO2levels remain above 300 ppm (IPCC, AR5, 5.8.3, page 435, 2013). This claim expressed on so certain terms is in stark contrast with the lack of precedent for any interglacial spanning over two obliquity oscillations. In this final article, we are going to examine the soundness of these claims.

Interglacial evolution

Each interglacial is different. They all have different astronomical signatures, different initial conditions, different evolution, and are subjected to non-linear chaotic climate unpredictability. But they all take place during a single obliquity oscillation. Over the Pleistocene’s 2.6 million years 104 marine isotope stages (MIS) have been identified, half of them corresponding to warm periods. On average there is one every 50,000 years, almost corresponding to the obliquity frequency (41 Kyr). The match is not exact because some obliquity oscillations have failed to produce an interglacial.

For the last 800 Kyr, after the Mid-Pleistocene Transition (Figure 129), the planet has become so cold, and the ice-sheets grown so large, that to produce an interglacial outside the periods of high eccentricity requires the simultaneous concert of high obliquity, high northern summer insolation, and very large unstable ice sheets. This has had the effect of spacing interglacials from an obliquity-linked 41-Kyr cycle to its multiples 82 or 123 Kyr, whose average has been incorrectly termed the 100-Kyr cycle. A side effect is that after one or more obliquity oscillations without an interglacial the planet gets colder, and when an interglacial is finally produced, it reaches a warmer state. The climate of the planet has become more unstable in the Mid and Late Pleistocene, rapidly transitioning from more extreme cold to more extreme warm, and back, contributing to numerous species extinctions, and perhaps to the evolution of our species.

Figure 129. Geological subdivisions of the Middle and Late Pleistocene according to selected criteria. The past 800 Kyr correspond to the Middle and Late Pleistocene, when interglacials have become more spaced and climate oscillations larger. Source: International Commission on Stratigraphy.

The majority of interglacials of the past 800 Kyr are the product of very similar orbital and ice-volume conditions and present a common pattern (figure 130). The Holocene interglacial is the result of similar conditions, and belongs to this group. Nearly all exceptions can be explained in terms of particular orbital and ice volume conditions that do not apply to the Holocene (see The Glacial Cycle).

Figure 130. Average of six of the past ten interglacials. An average interglacial (black curve and 1σ grey bands) was constructed from EPICA Dome C deuterium data from interglacials MIS 5, 7c-a, 9e, 15a, 15c and 19c, after aligning them at the specified date. The obliquity for all of them (grey sinusoid continuous line) and the insolation curves at 65° N 21st June for all but MIS 7c (grey dotted line) were also averaged from the alignment. The thick line represents the different global substages of a typical interglacial. Sources: EPICA Dome C, Jouzel, et al. 2007. Astronomical data, Laskar, 2004.

Antarctica leads the deglaciation over the Northern Hemisphere and reaches its highest temperature at the obliquity peak when the Laurentide and Fennoscandian ice-sheets are not completely melted yet. The asynchrony between a Southern Hemisphere cooling from declining obliquity and low summer insolation, and a Northern Hemisphere warming from ice-sheets melting and high summer insolation results in a global optimum that has a different span depending on latitude. Interglacial temperature decline presents a delay with respect to obliquity decline of 5500-8000 years (figure 35), observed since the late Pliocene (Donders et al., 2018). This delay has been attributed to a lag in the ice volume change with respect to its rate of change (Huybers, 2009). Ocean thermal inertia could also contribute to the lag. When northern insolation is declining at its fastest rate, the interglacial enters a phase of slowly declining temperature (~ –0.2°C/millennium) that in the Holocene has been termed Neoglaciation. Despite temperature decline and modest glacier expansion, sea levels are quite stable over this period, as there is no significant ice-sheet build up. The Holocene has been clearly at this stage since ~ 5000 BP, until Modern Global Warming.

When northern summer insolation becomes low, and obliquity is at its fastest rate of decline, the interglacial reaches glacial inception. This tipping point appears to take place during a global LIA-type cold period when due to the start of ice-sheet build up, sea-level starts dropping. The intensification of ice-albedo and vegetation feedbacks result in a point of no return. Regardless of insolation changes, once glacial inception takes place, the glaciation will continue through advances and retreats in a relaxation-type dynamic until the conditions are met for a new interglacial. During the past 2.3 million years no interglacial has been able to continue from one obliquity oscillation to the next. Low obliquity conditions have always led to the end of the interglacial.

Despite their very different temporal scale, the similarities between Antarctic interglacial records and Greenland Dansgaard-Oeschger events (figure 131) suggest similar dynamics are at play. Both have been proposed to be astronomically paced (Milanković,1920; Rahmstorf, 2003). The warming phase is explosive, fed by a fast ice-melting feedback, producing an early peak. It appears to constitute an excitable system from a stable glacial state. A slow declining phase from the peak towards an inflection point (unstable point, figure 131) suggests a quasi-stable warm phase as the warming conditions wane. At the inflection point the intensification of the slow ice-accumulation feedback accelerates the cooling phase increasing the climatic instability and producing a faster relaxation towards the stable state. Fast-slow dynamics acting on excitation cycles have been discussed as an explanation for both Dansgaard-Oeschger events and interglacials (Crucifix, 2012), in which the cold stable and warm quasi-stable states constitute the different branches of a slow manifold in an excitable dynamic system.

Figure 131. Comparison of MIS 9e interglacial and Daansgard-Oechsger event 8. With a different time-scale, MIS 9e (continuous line, EPICA) and DO-8 (dashed line, GISP2) present a fast (excitation) transition from an excitable point, and a slow (relaxation) transition from an unstable point, between a stable cold state and a quasi-stable warm state. Sources: EPICA Dome C, Jouzel, J., et al. 2007. GISP2, Alley, R. 2000.

The last interglacial is usually referred as the Eemian, its stratigraphic name in Western Europe after the Dutch river Eem. The Eemian stratum is dated between 126-115 Kyr BP in Northern Europe and 126-110 Kyr BP in Southern Europe. MIS 5e is dated between 132-115 Kyr BP. Weichselian (also Wisconsinan or Würm) glacial inception takes place earlier, at 120 Kyr BP, when both Antarctica and Greenland initiate their cooling at a time when CO2shows a temporary decline, and methane and global sea level start declining (Spratt & Lisiecki, 2016; figure 132). At this time North Atlantic subpolar waters become colder and northern European boreal forests start retreating (Govin et al., 2015). Climate becomes more unstable and at 118.6 Kyr the Late Eemian Aridity Pulse (LEAP, Sirocko et al. 2005; figure 132), a 470-year cold and dry period, takes place in Central Europe. Only 1500 years later the C26 cold period is recognized in Greenland records (Govin et al., 2015). Finally, at 115 Kyr BP CO2levels start decreasing, with over 5,000 years delay to glacial inception. Temperate forest retreat reaches Southern Europe. Methane levels bottom at 113 Kyr BP, and CO2at 109 Kyr BP. Between 108 and 106 Kyr BP glacial conditions are established in most records (Govin et al., 2015). The first large iceberg discharge takes place at 107 Kyr BP, indicating well-developed ice sheets. While a deglaciation usually takes about 5,000 years, a glaciation requires almost 15,000 years.

Figure 132. The Eemian interglacial and its transition to the Weichselian glaciation. a)Obliquity configuration (continuous line; Laskar, 2004). b)Summer energy at 70°N (dashed line; Huybers, 2006). The dots indicate current values. c)Methane levels (continuous line; Loulergue et al., 2008). d)Carbon dioxide levels (dashed line; Bereiter et al., 2015). e)Interglacial profile (continuous line). f)Sea level (dashed line; Spratt & Lisiecki, 2016). g)Antarctic temperature anomaly (continuous line; Jouzel et al., 2007). h)Greenland temperature anomaly (dashed line; NEEM, 2013). H11: Heinrich event 11. LEAP: Late Eemian aridity pulse. C25 & C26: North Atlantic cold events 25 & 26.

Astronomical versus CO2forced interglacials

Louis Agassiz, building on Karl Schimper theory of past glaciations, presented in 1838 the evidence for ice ages. Their discovery fitted well with the still dominant geological catastrophism. The first astronomical theory of glacial ages was proposed by Joseph Adhémar in 1842, based on precession changes, and was followed by James Croll theory, based on eccentricity changes, in 1867. By then gradualist geologists strongly opposed astronomical theories as they rejected external influences on the evolution of the Earth. Croll’s theory, which focused on winter conditions at high eccentricity and low insolation from precession, did not match the evidence available at the time, and was rejected by most.

John Tyndall’s view in 1861 was more favorably received. After measuring CO2and water vapor heat absorbing properties, he proposed that changes in their atmospheric concentrations could explain all climate changes of the past. Thus, since the middle of the 19th century, astronomical and greenhouse gas theories of glacial ages have been put forward (Paillard, 2010). In 1896 Svante Arrhenius made the first calculations of the changes in CO2levels necessary to explain glaciations.

John Murphy in 1876 advanced the crucial hypothesis that long cool summers and short mild winters were the most favorable conditions for a glaciation. Milutin Milanković, adopting Murphy’s idea, published in 1920 the necessary calculations to explore the solar irradiance at different latitudes and seasons in great mathematical detail, and to relate these to the planetary energy balance (Berger, 2012). As a measure for the energy variation at high latitudes, he proposed the half-year caloric insolation, the summation of insolation from the 182 highest insolation days in a year. His theory of glaciations was not accepted until the 1970’s, when dating of marine cores revealed the predicted orbital frequencies in the ice proxies. When referring to the orbital changes and their effect, the phonetic term Milankovitch is generally used.

The evidence is so strong for the orbital-driven Pleistocene glacial oscillations, that it has become widely accepted as an exception to the CO2theory of climate. A common explanation is that very low CO2levels during the Pleistocene allowed glacial pacing by Milankovitch orbital changes. No alternative hypothesis has successfully explained why CO2levels would oscillate at Milankovitch frequencies. But since temperature and CO2levels follow Milankovitch oscillations, an unresolved question is how much of the temperature change is caused by the CO2change. Central to this question is the climate sensitivity to CO2at equilibrium (ECS). At one extreme, Carolyn Snyder (2016), attributes all temperature changes to CO2changes, estimating an Earth system sensitivity of 9°C warming per doubling of CO2over millennia (disputed for ignoring orbital forcing by Schmidt et al., 2017). At the other extreme, with an ECS of 1.5°C (Lewis & Curry, 2018), CO2contribution to the glacial-interglacial temperature change would be relatively minor (~ 15%).

21st June 65°N insolation versus summer energy

Milutin Milanković proposed that high-latitude caloric half-year summer insolation determined the amount of snow cover that can survive summer melt, causing ice-sheet growth or retreat. In Milanković’s caloric summer, despite not taking into account seasonal duration, precession is in control of the low latitudes while obliquity is in control of the high latitudes. However, Milanković’s concept of caloric summer was abandoned in favor of 21st June insolation after Berger (1978). 65°N summer insolation depends almost completely on precession, and was introduced into the first models (Kutzbach, 1981). It was quickly adopted as the Milankovitch parameter of choice despite not being Milanković’s proposal. This is an important mistake because precession as a glacial control has an Achille’s heel in Kepler’s second law. The closest the Earth is to the Sun during the Northern Hemisphere summer, the highest its velocity, and the shortest the summer. So, the number of days with enough insolation to melt the ice is lower, resulting in less melting. The SPECMAP project has literally carved in stone this mistake by tuning the oceanic isotopic records to precession, resulting in circular argumentation, as now precession affects climate as climate records are tuned to precession. But the imprinting of obliquity on climate is everywhere. Even in the tropics, where the effect of obliquity should be very low, there is a clear obliquity effect on climate proxies, like Mediterranean sapropel patterns resulting from the West African monsoon insolation-driven changes. An effect of the latitudinal insolation gradient, that depends mainly on obliquity, has been proposed as explanation (Bosmans et al., 2015).

The problems created using 65°N 21st June insolation as a Milankovitch parameter are numerous: the 100-Kyr problem, the causality problem (MIS 5e termination II), and the symmetry of glacial oscillations versus the hemispheric asymmetry of the insolation forcing. They were reviewed in The Glacial Cycle. It makes very difficult to explain why some insolation maxima produced interglacials and most didn’t. Additionally, it made it impossible to explain why in the Early Pleistocene the glacial cycle operated in the obliquity frequency.

Peter Huybers (2006) observed that the melting or growing of the ice-sheets must depend on the cumulative time spent at the ice-sheet border latitude above 0°C during a melting season. This observation led to the proposal of a Milankovitch parameter that is close to caloric summer but accounts better for the different duration of summers. He called it summer energy and is calculated by adding the day-time insolation energy (in GJ/m2) at 65°N for every day that was above a certain insolation threshold enough for ice-melting, that at 65°N was determined to be 275 W/m2(Huybers, 2006).

Didier Paillard (1998) added the last piece of the puzzle when he proposed a simple model that reproduced the glacial cycle by introducing an ice-volume factor that was needed to transition from interglacial to mild-glacial state, and from mild-glacial to full-glacial state. The model forbids the reverse transitions. In essence Paillard’s model introduced the brilliant concept that ice build-up made the transitions unidirectional towards full-glacial, and when ice-volume was very high, ice-sheet instability caused a glacial termination when enough summer energy was available.

Figure 133 explains how the glacial cycle depends on summer energy (mainly on obliquity), and on ice-volume, and how ice-volume responds to eccentricity. Figure 133a shows an ice-volume proxy (LR04 benthic δ18O) for the past 340 Kyr, overlain by the summer energy parameter that has been lagged by 6000 years, to account for the observed delay of the effect to the forcing (Huybers, 2009; Donders et al., 2018). By plotting ice-volume versus lagged summer energy (figure 133b), it is observed that during the 41-Kyr oscillations in summer energy, ice-volume starts and ends at repeatable states defined following Paillard (1998) as interglacial, mild-glacial, full-glacial, and deep-glacial.

Figure 133. The timing of Pleistocene glaciations as a function of summer energy, ice-volume and eccentricity. a)LR04 benthic stack as an ice proxy (multi-colored line; Lisiecki & Raymo, 2005) for the past 341 Kyr. The line was colored in 40-41 Kyr segments with orange-red tones for low ice segments, green tones for intermediate ice segments and blue tones for high ice segments, and dots of the same color at the start of each segment. Background color defines four different states, light orange for interglacial, light green for mild-glacial, light blue for full-glacial, and cyan for deep-glacial. Black curve is summer energy at 65°N with a 275 W/m2threshold (Huybers, 2006), lagged by 6000 years to compensate the delay between forcing and effect. Thick grey curve is eccentricity (without scale; Laskar, 2004). b)Plot of the multi-colored ice proxy curve versus summer energy. It is evident that the ice volume at the start of the orbital 41 Kyr oscillation in summer energy determines the subsequent ice volume evolution during the oscillation and the possibility of an interglacial taking place in that oscillation. c)Simple excitation/relaxation multi-state model explains the timing of Pleistocene glaciations. Under Early Pleistocene or high eccentricity conditions climate operates as a simple oscillatory system represented by dashed lines, reversibly transitioning at 41 Kyr frequency between mild-glacial (D) and cool interglacial (D’). Mid-Pleistocene transition when eccentricity is not high introduced an ice-volume requirement for excitation out of glacial conditions, represented by the downward arrow (A), and at the same time resulted in warmer interglacials (A’), as the upward arrow indicates. Depending on the speed of ice-volume accumulation, that is inversely correlated to eccentricity, the system must transition through one or two oscillations (two represented, B’ & C’) in the relaxation process to reach the excitable state (A). Low eccentricity favors high ice accumulation accelerating the relaxation (only one oscillation required). Medium eccentricity delays the relaxation as ice accumulates more slowly (two oscillations required). High eccentricity bypasses the ice requirement, returning the system to Early Pleistocene conditions as it happened in the C -> D transition 245 Kyr BP when due to high eccentricity MIS 7e was produced despite low ice-volume and being very late in the summer energy oscillation. The system transitioned back to Mid-Pleistocene conditions after MIS 7a-c (D -> C). The double dependency on ice-volume and eccentricity to produce interglacials results in the absence of a regular pattern. Interglacials are produced at 41, 82, or 123 Kyr intervals. However, the ice-volume dependency on eccentricity results in a 100-Kyr cycle on ice accumulation that is clearly appreciable in ice proxies.

A simple excitation/relaxation model (figure 133c) explains the timing of glaciations. During the Early Pleistocene the situation can be described by a reversible oscillation both in summer energy and ice-volume (dashed bi-directional orange arrow) between mild glacial (D) and cool interglacial (D’) at a 41-Kyr frequency. At the Mid-Pleistocene Transition the cooling of the world caused the beginning of the build-up of extensive continental ice-sheets outside the polar regions during glaciations. Now glacial periods would transition towards more extreme conditions until ice-volume would be so high as to cause high ice-sheet instability (A). This ice-sheet instability is reflected in massive iceberg discharge when perturbed, resulting in Heinrich events. Also, the rebound effect from ice-sheet instability causes warmer interglacials (A’). Mid and Late Pleistocene are characterized by bigger temperature swings between deep glacial and warm interglacial.

When the interglacial ends, the system must relax back to the initial (A) state, but the ice-volume required is so high that it must transition through one or two oscillations (two showed in figure 133c) during which little ice is melted during the summer energy increase (B -> B’, C -> C’), but considerable ice-sheet growth takes place during the summer energy decrease (B’ -> C, C’ -> A). This causes some glacial periods to last one or two complete obliquity oscillations.

Global ice-volume is under control of eccentricity, because high eccentricity enhances the effect of precession and low eccentricity damps it. When eccentricity is very high its effect is like returning to the Early Pleistocene, facilitating an interglacial at every summer energy oscillation. Under very high eccentricity intermediate ice-volume glacials (B, C) behave as Early Pleistocene glacials (D). This can be seen very clearly at the MIS 7e interglacial 245 Kyr ago (figure 133a). As the model indicates, the glacial state prior to MIS 7e was of full-glacial, with an ice-volume insufficient to produce an interglacial, thus little ice was melting despite high summer energy. However, when eccentricity became very high (figure 113a, grey curve), a late interglacial suddenly took place (C -> D transition) with very little time left before low obliquity put an end to it. Then, as eccentricity continued being very high, a new interglacial was produced (MIS 7c-a). Both MIS 7 interglacials happened due to high eccentricity, and they were cool interglacials of the Early Pleistocene type. The effect that high eccentricity has in promoting interglacials and low eccentricity in inhibiting them results in more ice-volume accumulating at times of lower eccentricity. The consequence is that although interglacials do not follow a 100-Kyr eccentricity cycle, ice-volume does present a 100-Kyr cycle (figure 133a).

To study the end of the present interglacial the relevant orbital parameters are summer energy (or obliquity) and eccentricity. By contrast, almost every study dealing with the issue has used the erroneous 65°N summer insolation parameter.

MIS 11c is a poor Holocene analog

Most authors use MIS 11c interglacial as analog to the Holocene, because of similarly low eccentricity. However, precession and obliquity do not align in the same way for MIS 11c as for the Holocene. MIS 11c is an anomalous interglacial in terms of duration, and clearly this is not due to low eccentricity as MIS 19c had similarly low eccentricity and a standard duration (figure 130).

During the Mid to Late Pleistocene only the combination of high obliquity and high 65°N summer insolation provides enough summer energy to terminate the glacial period. Afterwards (as in MIS 19c, figure 134), the fall in summer energy brings about glacial inception after a delay of several thousand years. In the case of MIS 11c, an unlikely coincidence of several factors working together resulted in the longest interglacial of the past million years. First, 65°N summer insolation was relatively high for many thousands of years before glacial termination, above 480 W/m2(today’s value). This, together with high ice-volume instability, could have “primed” the interglacial, that started unusually soon after summer energy began increasing, without the usual wait to obliquity increase. The obliquity peak took place right in the middle of two insolation peaks. It is extremely unusual that such combination would produce an interglacial in the Mid to Late Pleistocene, but in the case of MIS 11c the 65°N summer insolation at the minimum between the two insolation peaks never falls below 500 W/m2, a value higher than today’s. As a result, summer energy shows a very broad peak of 20,000 years, versus the usual 10-12,000 years. When summer energy was declining, came the second peak in 65°N summer insolation, increasing the temperature and producing a very warm interglacial, particularly so late. When finally, the orbital conditions were adequate for glacial inception the interglacial had lasted almost 25,000 years, almost double the usual duration. The high amount of heat gained during such a long interglacial caused the delay between falling summer energy and glacial inception to be of 10,000 years instead of the usual 6000. MIS 11c ended up lasting close to 35,000 years. However, despite such a long interglacial expanding two precession peaks, it could not extend from one obliquity oscillation to the next. Once glacial inception is reached there is no turning back even under rising obliquity and summer energy.

Figure 134. Low eccentricity interglacials of the past 800 Kyr. EPICA Dome C deuterium proxy expressed as temperature anomaly for MIS 1, MIS 11c, and MIS 19c, aligned at their interglacial start (vertical line). MIS 1 and MIS 19c have a similar orbital configuration with obliquity (continuous line) rising slightly ahead of northern summer insolation (dashed line) producing a peak in summer energy (dotted line) at the start of the interglacial. For MIS 11c northern summer insolation (dashed line), started increasing from a relatively high level several Kyr earlier than obliquity (continuous line), and continued being high for two oscillations resulting in a very wide summer energy peak (dotted line). When obliquity, northern summer insolation, and summer energy decreased for MIS 11c, there was a longer than usual delay until temperature fell. Despite its unusual length due to its unusual orbital configuration, MIS 11c could not continue through an obliquity minimum. The proximity of its obliquity minimum makes the Holocene orbital configuration unfavorable for a long interglacial. Sources: Jouzel et al., 2007; Laskar, 2004; Huybers, 2006.

MIS 19c is a better analog in terms of eccentricity, obliquity, and precession. The main difference is that low values in obliquity and insolation during MIS 19c, and relatively low ice-volume prior to it, resulted in a cool, short interglacial (figure 134). The values of obliquity, insolation, and summer energy were lower at MIS 19c glacial inception than they are currently.

The long interglacial hypothesis

Intermediate complexity (simplified) climate models have been used since the early 1990’s to explore glacial conditions under elevated CO2, and Loutre and Berger (2000) tried to specifically address the question of the end of the present interglacial. They found that at CO2concentrations of 210 ppm the ice-sheets would form at 15 Kyr AP (after present), while no ice-sheets form for 130 Kyr AP with CO2levels of 250 ppm. The 65°N summer insolation changes for the next 50 Kyr are so small that they find that with CO2levels reproducing Eemian Vostok records (a decrease from 296 to 184 ppm over the next 114 Kyr), the present interglacial should last ~ 50,000 years more. Since the only long interglacial of the Mid to Late Pleistocene is MIS 11c, it was confirmed as a suitable analog because it had similarly low 65°N summer insolation changes and relatively high CO2levels (as a warm interglacial).

The main conclusions from Loutre and Berger (2000), were that no insolation threshold will be crossed within the next 40 Kyr, and that a glacial inception within the next 50 Kyr would require unnaturally low CO2levels. This modeling result was confirmed multiple times (Cochelin et al., 2006; Mysak, 2008). Archer and Ganopolski (2005) painted a more drastic scenario, with the release of 5000 GtC (545 gigatonnes of carbon were released between 1870-2014) preventing glaciation for the next half million years. Ganopolski et al. (2016) determined a 65°N summer insolation/CO2threshold for glacial inception from model realizations (figure 135a). With such a threshold, not even the pre-industrial CO2level of 280 ppm could produce an interglacial at present (figure 135a), and present cumulative carbon emissions already preclude a glacial inception over the next 50 Kyr (figure 135b).

Figure 135. Model-derived critical insolation-CO2relation and the next glacial inception. a)Best-fit logarithmic relation (black line) between the maximum summer insolation at 65° N and the CO2threshold for glacial inception. The location of previous glacial inceptions in insolation-CO2phase space relative to the best-fit logarithmic curve (grey dots) shows a pre-industrial Holocene (green dot) that could not undergo glacial inception even in the absence of anthropogenic CO2. b)The top panel shows the temporal evolution of the maximum summer insolation at 65° N. The middle panel shows the simulated CO2concentration during the next 100,000 years for different cumulative CO2emission scenarios: 0 GtC anthropogenic emissions (blue), 500 GtC (orange), 1000 GtC (red) and 1500 GtC (dark red line). The bottom panel shows simulated ice volume corresponding to the different CO2emission scenarios. Individual simulations are shown for the 1500 GtC scenario; for the other scenarios, the range is given as shading. Source: Ganopolski et al., 2016.

The long Holocene interglacial hypothesis has become an axiom that is seldom questioned in the scientific literature and fully endorsed by the IPCC. However, this axiom is based exclusively on model studies that rest on three assumptions that have not been demonstrated:

1a. Glacial inception has depended in the past on 65°N summer insolation.

2a. Climate has a high sensitivity to CO2levels. Models produce an average of 3°C/doubling of CO2.

3a. CO2levels remain elevated for tens of thousands of years after a pulse (figure 135b).

If any or all the alternative possibilities were to be correct:

1b. Glacial inception depends on summer energy (obliquity).

2b. Climate has a low to medium sensitivity to CO2, ~ 1.5°C/doubling of CO2.

3b. CO2levels artificially elevated from a pulse can go back down close to baseline over a few centuries.

The prediction would be completely different.

We have already shown evidence that glacial inception is driven by the fall in obliquity, well reflected in summer energy, and not by 65°N summer insolation. Models don’t appear to be as sensitive to obliquity changes as climate. Another thing models ignore is that although low eccentricity promotes small changes in 65°N summer insolation due to a nearly circular orbit, it also clearly promotes ice-volume build up during low summer energy periods. The 100 and 400-Kyr eccentricity cycles are associated with high ice-volume at times of low eccentricity (figure 133a), and present eccentricity is very low and will decrease over the next 25 Kyr. MIS 11c, despite being a very long and very warm interglacial with high CO2levels, was followed by 60 Kyr of small 65°N summer insolation changes, analogous to what awaits in the future. During that period the planet managed to accumulate more ice than during the equivalent period after MIS 5e, when much higher insolation changes and higher eccentricity occurred. Models do not appropriately reflect the 100-Kyr ice cycle paleoclimatologists have recognized for the past five decades.

Not all authors have accepted the unproven model assumptions at face value. Tzedakis et al. (2012) circumvented the problem of CO2sensitivity by trying to determine the natural length of the Holocene under 245 ppm CO2using the MIS 19c analogy. If CO2sensitivity turns out to be low their scenario could be realistic. Their study concludes that with 245 ppm CO2the end of the current interglacial would occur within the next 1500 years.

Vettoretti and Peltier (2004, 2011) have questioned the soundness of the assumption that glacial inception depends on insolation and CO2. They studied separately the effect of the different components of orbital changes, finding that a low obliquity value is most important in determining the strength of the inception process, followed in order of importance by the magnitude of the eccentricity-precession forcing. They also find that areas of perennial snow cover are much more sensitive to the insolation regime than to GHG concentrations. They conclude with a glacial inception at the next obliquity minimum in 10 Kyr in the absence of modern anthropogenic forcing. These results contradict some of the assumptions of the long interglacial hypothesis.

The fat tail of anthropogenic CO2adjustment time

Despite intense research, knowledge of the carbon cycle is still very inadequate. Particularly net carbon fluxes between different reservoirs have a big uncertainty, due in great measure to large differences in regional measurements (Ballantyne et al., 2015; figure 136). Also sink behavior has been a source of significant surprises in the past (Schindler, 1999), due to the unexpected fast growth in net global carbon uptake by ocean and biosphere sinks (Ballantyne et al., 2015). Additionally, models indicate that the fraction of our emissions that remains in the atmosphere (airborne fraction) should increase over time, but we have evidence of the opposite (Keenan et al., 2016). Our imperfect knowledge of the carbon cycle is built into Earth Systems Models (ESM) that from different emissions scenarios produce the atmospheric CO2concentrations that General Circulation Models (GCM, or climate models) use as input. Millar et al. (2017) have shown that the ESMs are working incorrectly, and they contribute to current models running too hot.

Figure 136. Diagram of the global carbon budget. Major fluxes of C to the atmospheric reservoir of CO2 are from fossil fuel emissions (EF) and land use land conversion (EL) and are illustrated as red vectors. Net land (NL) uptake of C from the reservoir of atmospheric CO2is illustrated by green vectors and net ocean uptake (NO) is illustrated by blue vectors. The size of the vectors is proportional to the mass flux of C as indicated in petagrams of C per year. Error estimates for each flux in 2010 are expressed as ±2σ. Error estimates are of the same magnitude as the fluxes. Source: Ballantyne et al., 2015.

Given the problems delimitating and predicting the evolution of the carbon cycle over the past several decades it is surprising that the IPCC would write:

“The removal of all the human-emitted CO2from the atmosphere by natural processes will take a few hundred thousand years (high confidence) … we assessed that about 15 to 40% of CO2 emitted until 2100 will remain in the atmosphere longer than 1000 years” (IPCC AR5 WG1, 2013, page 472).

So, we were unable to predict a few decades ago that over 50% of our fast-growing emissions would disappear from the atmosphere without any time delay, or that the fraction removed could actually increase despite exponentially increasing emissions, yet we have high confidence that 15-40% will remain in the atmosphere 1000 years from now. Clearly, we hugely underestimated the carbon sinks capacity to deal with our emissions, so we cannot have high confidence in distant future predictions. The problem is that we are dealing with a situation without precedent and so the answers that we can obtain from science carry a huge uncertainty that cannot be properly constrained by evidence. The Paleocene-Eocene Thermal Maximum is usually cited as precedent; however, its isotopic carbon excursion took place so long ago that our poor knowledge of its source, amount, and release timescale precludes any meaningful estimation of its decay.

IPCC confidence comes essentially from David Archer’s studies, that since 1997 have become the authority of reference. It is clear that the unburial and release of huge carbon fossil stores constitutes a long-term perturbation of the carbon cycle. Since carbon only permanently exits the carbon cycle very slowly through calcium carbonate sea-bottom burial, and silicate rock weathering, the different compartments of the carbon cycle will have to deal with excess carbon for a very long time and this should necessarily lead to an equilibration between compartments at higher levels than prior to the perturbation. At present the complexity of the effects involved is being studied with box-modeling, but every step in the process requires taking assumptions. It is assumed that the land biosphere, that is currently a sink due to an increase in photosynthesis over respiration, should reach equilibrium within decades after the end of anthropogenic emissions and then become a net source as atmospheric levels decrease. The reduction in atmospheric CO2is then assumed to occur mainly through ocean uptake on a timescale of centuries, driven by changes in oceanic chemistry and ocean mixing. It is assumed that as more carbon dioxide dissolves in the ocean, it will compromise the ocean’s buffering capacity and that ocean acidification will increase the Revelle factor (dissolved CO2to dissolved inorganic carbon). This is then expected to reduce the efficiency of the ocean carbon sink until it stops taking CO2after ~ 1000 years when 14-30% of the maximum level reached remains in the atmosphere (Archer et al., 2005). Higher temperature is also expected to contribute to a decrease in the ocean carbon sink efficiency.

Archer’s (2005) worst case scenario involves anthropogenic emissions of 1600 GtC by 2100 (545 GtC emitted 1870-2014) and increasing afterwards. Up to 1000 GtC should be contributed by a reversal of the land biosphere and soils sinks, and the rest to 5000 GtC total contributed by permafrost and marine methane clathrate deposits. A more realistic scenario considering fossil fuel supply-side constrains and extrapolating observed warming leads to only 500-1000 GtC addition at most. But this amount disregards any effort to reduce emissions, while a higher certainty on CO2climatic effects should lead to more intense efforts to curtail emissions.

It is impossible to have a high confidence that 14-30% of the carbon emitted will remain in the atmosphere 1000 years from now. That number comes from a set of assumptions made using a poor understanding of the carbon cycle, and it could be much lower. Those models are unable to reproduce or explain the significant increase of 20 ppm in CO2that took place between 6000 and 600 BP. Initializing the models at 6000 BP doesn’t produce the pre-industrial CO2levels of 280 ppm, unless ad hocassumptions are introduced, indicating models cannot be trusted to project atmospheric CO2levels thousands of years into the future.

The National Research Council set in 2008 the “Committee on the Importance of Deep-Time Geologic Records for Understanding Climate Change.” This body produced in 2011 the report: “Understanding Earth’s Deep Past: Lessons for Our Climate Future.” This expert committee fully acknowledges the uncertainty present in CO2adjustment time estimates from box-models:

“Although box-model calculations should not be considered definitive, they do suggest that the fossil-fuel perturbation may interfere with the natural glacial-interglacial oscillation driven by predictable changes in Earth’s orbit, perhaps forestalling the onset of the next Northern Hemisphere ‘ice age’ by tens of thousands of years. A more convincing exposition of the central question of “how long” requires more comprehensive models. Scientific confidence in those models will only be high if they can be evaluated against observation. The historical record, and even the expanse of the Quaternary climate record, contains nothing comparable.”

The proposed fat-tail of anthropogenic CO2adjustment time should be taken as a possible scenario if certain assumptions are correct, and not what is expected to happen.

Glacial inception in the Holocene

Glacial inception is the transition from interglacial climate to glaciation, characterized by ice-sheet build up and falling sea-levels. However, there is no unambiguous definition of glacial inception that allows it to be placed at a specific point in time for each interglacial.

In the excitation/relaxation dynamic model of glaciations discussed above (figures 131 & 133), glacial inception can be understood as an irreversible commitment from a quasi-stable interglacial state into a relaxation process towards a stable glacial state, taking place once the conditions that made the interglacial possible have disappeared, and once the downward drift in temperature allows the boundary crossing at the commitment point (figure 131, unstable point).

A point of inflection can be observed in the Antarctic proxy temperature record of past interglacials. In each case the slowly declining temperature of the late interglacial suddenly accelerates into a terminal decline towards glacial conditions (figure 137). In the case of the Eemian interglacial, this inflection point takes place at 120 Kyr BP, when glacial inception has been defined by different criteria (figure 132). It can be shown that the inflection point in the cooling rate corresponds to glacial inception in all cases and can be explained as a point when the intensification of positive feedbacks (like ice-albedo, vegetation changes, or changes in oceanic currents), lead to a steepening of the equator-to-pole temperature gradient and the consequent accelerated cooling of the planet into glaciation.

Figure 137. Interglacial length normalization. The start of an interglacial is defined, as in the Holocene, by the time EPICA Dome C temperature anomaly reaches 0°C, or by extrapolating the rate of warming to the 0°C value. The end of an interglacial is defined at the inflection point where EPICA Dome C temperature anomaly increases its rate of cooling towards glacial values.

The start of an interglacial is also lacking a formal definition. In the case of the Holocene the start is formally placed ~ 11,700 years ago (Walker et al., 2009). At that time EPICA Dome C deuterium proxy temperature record shows no anomaly with respect to current value (0°C anomaly). For a consistent comparison we can define the start of every interglacial at the time they first reach 0°C anomaly in the EPICA Dome C record. For cooler interglacials that didn’t reach 0°C anomaly, picking a lower temperature would lead to overestimating their length, as a lower temperature is reached earlier. A more correct choice is to extrapolate the warming trend to the point where it would have reached 0°C anomaly, picking that time as the normalized start of the interglacial (figure 137; table 3). MIS 13a cannot be normalized and it is not analyzed under the criteria chosen here.

Table 3. Normalized interglacial length. Dates in years BP for the start, end, and length, of normalized interglacials. Dates between parenthesis are extrapolated from the rate of warming. These dates and lengths are used to compare interglacial orbital conditions in the rest of the article.

Normalized in this way interglacials are between 10 and 16 Kyr in length, with an average of 13 Kyr, with two exceptions: MIS 7e and MIS 11c. Orbital configuration explains MIS 7e and MIS 11c anomalous length (figure 138). A consistent rule is that all interglacials end when obliquity is low. No interglacial of the past 800 Kyr has gone beyond 15.5 Kyr from the obliquity maximum (figure 138a). Since MIS 7e had a late start with respect to the obliquity cycle it became a very short interglacial. Since MIS 11c started early in the obliquity cycle due to its unusual precessional insolation, it became a very long interglacial. Low eccentricity allows long interglacials when other conditions are present, but it does not cause them to be long.

Figure 138. Interglacial orbital configuration. a)Interglacial start and end dates (triangles) relative to the obliquity maximum. Light grey area indicates interglacial start for all interglacials except MIS 7e and MIS 11c that had an anomalous length due to starting too late and too early respectively in the obliquity cycle. Dark grey area indicates interglacial end for all interglacials. Circles indicate start and end of a typical interglacial with average 13 Kyr length. Interglacials start when obliquity is high and end when obliquity is low. b)Interglacial start and end dates (triangles) relative to the northern summer insolation maximum. Light grey area indicates interglacial start for all interglacials. Dark grey area indicates interglacial end for all interglacials. Circles indicate start and end of a typical interglacial with average 13 Kyr length. Interglacials start when insolation is high but can end at any time in the insolation cycle.

The other orbital rule is that interglacials of the past 800 Kyr start when the combination of obliquity and precessional insolation is high enough (high summer energy). Precessional insolation is irrelevant for glacial inception, as three interglacials were capable of surviving through an insolation minimum, yet they ended close to the next maximum, when obliquity dropped. A typical interglacial (figure 138, line between circles) starts 2000 years before obliquity maximum, and 1000 years before insolation maximum, and lasts 13,000 years. So far, the Holocene is extraordinarily close to a typical interglacial in astronomical terms and length.

Orbital configuration alone can explain when interglacials start and end, while changes in CO2levels cannot. Interglacial temperature is inversely correlated to ice volume (figure 133a; warmer interglacials correspond to previous higher ice-volume), and directly correlated to CO2(figure 110a). And ice-volume is inversely correlated to eccentricity (figure 133a). As it is difficult to explain why CO2levels would inversely correlate to prior ice-volume, the most likely explanation is that CO2levels are a consequence of temperature levels, not a cause (eccentricity -> ice-volume -> temperature -> CO2). Eemian glacial inception and the next 5000 years of cooling took place under stable 270 ppm CO2levels, indicating that glacial inception is responding to orbital changes, not CO2changes. Despite this evidence IPCC expresses virtual certainty that a new glacial inception is not possible for the next 50 Kyr if CO2levels remain above 300 ppm (IPCC, AR5, 5.8.3, 2013). Ice core measurements indicate CO2levels at past glacial inceptions have always been below 300 ppm, but there is simply no evidence indicating how high CO2levels must be to stop a glacial inception, if that is even possible.

It is widely known that there is a delay between the astronomical signal and the geological evidence of climate change, this delay, in the case of obliquity is ~ 6000 years (Huybers, 2009; Donders et al., 2018). The logical conclusion is that the astronomical threshold for glacial inception is crossed ~ 6000 years before it takes place. This inference is supported by the presence at the end of interglacials of a period of declining temperatures before the inflection point that indicates glacial inception has been reached (figure 137). In the Holocene that period is termed Neoglaciation, and it is also observed between 126-120 Kyr BP in the Eemian (figure 132).

Analysis of the orbital conditions that produce a glacial inception requires examining them 6000 years before the inflection point in the cooling rate at the end of the interglacial. Glacial inception does not take place at 65°N, but at 70°N, where ice sheets start to grow (Birch et al., 2017). Examination of 70°N summer energy (at 250 W/m2threshold) 6000 years before glacial inception (figure 139, diamonds) reveals a threshold at 4.96 GJ/m2when the glacial inception orbital “decision” has already been taken for all previous interglacials. Two interglacials, MIS 9e and MIS 5e, had a much higher summer energy at the orbital decision point. They have in common a well below average duration (10.7 and 11.4 Kyr), probably due to the early decision. They also have in common being warm interglacials at the beginning and suffering a very big drop in Antarctic temperature a few thousand years after starting. This appears to be a feature of short interglacials (figure 137). Whether this early cooling facilitated or caused an early decision to end the interglacial is unknown.

Figure 139. Orbital decision to end an interglacial. Summer energy at 70°N with a 250 W/m2threshold for the past 800 Kyr. Diamonds mark the position 6 Kyr before glacial inception as observed in the EPICA Dome C temperature proxy record for each interglacial except MIS 13. Dashed line marks the lowest value observed (4.96 GJ/m2). Six interglacials were very close to this value 6 Kyr prior to glacial inception. The Holocene (MIS 1) is already below that value.

The 4.96 GJ/m2limit was crossed by the Holocene 1500 years ago, so the orbital decision to end the Holocene has already been taken. By orbital considerations alone the Holocene doesn’t have more than 4500 years left before glacial inception, but it could have as little as 1000 years left if the start of the Neoglaciation 5000 years ago corresponds to the Holocene’s orbital decision. The average duration of Holocene-like interglacials is 13,800 years. That length would place the end of the Holocene, 2000 years from now, right at the center of the obliquity range for the end of every interglacial, 12 Kyr after the obliquity maximum (figure 138a, dark grey area). Between 1500-2500 years from now, there should be a period where two consecutive lows in the Eddy solar cycle separated by a low in the Bray solar cycle are expected, defining a period similar to 8.4-7.1 Kyr BP when eight solar grand minima took place in rapid succession (figure 122). 1500-2500 years from now looks like an excellent time for the next glacial inception.

The analysis of the leading orbital decision to the lagging glacial inception, 6 Kyr later, provides possible answers to some questions, like why the Holocene did not end at the LIA. Since the Neoglaciation started 5 Kyr BP, it is likely that the LIA took place too early, and the interglacial was too young then for glacial inception. The intense cooling accompanied by glacier extension, and a reduction from 280 to 270 ppm CO2(Eemian’s glacial inception level), indicates it was probably a close call, that resulted in a temperature rebound afterwards. Similarly, Ruddiman’s “Early anthropogenic hypothesis” (Ruddiman, 2007), that states that a glaciation was prevented by early agricultural release of greenhouse gases, is unnecessary. With or without human intervention the Holocene should not have ended yet. The question of the GHG increase during the Mid to Late Holocene remains controversial, but it is unrelated to the length of the present interglacial.

The next glaciation

Without human intervention the next glaciation should start in 1500-2500 years. The question that we cannot answer with any degree of certainty is how high CO2levels should have to be to prevent glacial inception. Summer energy is going to be very low for the next 20,000 years and that should require sufficiently elevated CO2levels for that long. Alternatively technology could develop to a point when it is possible for humankind to prevent the next glaciation. Those are questions that cannot be answered, but we can make reasonable inferences from what we do know.

Over the past 150 years it is calculated that we have produced 545 GtC leading to an increase in atmospheric CO2of 125 ppm. Estimates from reputable sources place fossil fuel peak production in a few decades (see 21st Century Climate Change). Even if fossil carbon is more abundant, we might already have extracted one-third to half of what we will extract over the next centuries. Supply constraints should limit our emissions even in the unlikely case that we don’t limit them ourselves as we are already doing. If these estimates are correct, peak atmospheric CO2levels should not go much above 550 ppm (figure 140, blue line). A rapid decline in CO2should follow as oceans and the biosphere absorb most of it, but according to current models about 320 ppm should remain for a very long time (figure 140, blue line; Archer, 2005). If this assumption is correct, the question is if 320 ppm of CO2could stop a glaciation, as the IPCC claims with virtual certainty. We know the Eemian entered glaciation with 270 ppm, 50 ppm below future estimated levels. An opposite result from just 50 ppm difference would require a very high climate sensitivity to CO2. The 93 ppm increase between 1959 and 2018 has been accompanied by climatic variability within interglacial range, as Holocene Climatic Optimum conditions have not been reproduced. Achieving changes of an interglacial-glacial scale might require a much larger amount of GHG than available.

Figure 140. Future climate forecasts for the next 80 Kyr. LR04 benthic stack global ice volume proxy for the past 30 Kyr (black curve; Lisiecki & Raymo, 2005). Orbital eccentricity for the past 30 Kyr and future 80 Kyr (dotted line; Laskar, 2004). Summer energy at 65°N with 275 W/m2threshold for the past 30 Kyr and the future 80 Kyr lagged by 6000 years (red curve; Huybers, 2006). Past CO2levels from ice cores and modeled long term CO2concentration evolution after a 1250 GtC pulse (cyan curve; Archer, 2005). Future global ice volume forecast considering only orbital conditions by reproducing ice volume change after MIS 11c, 402-322 Kyr BP, a period with similar orbital evolution (dark grey curve). Future global ice volume modeled after a 1000 GtC pulse, representing the long interglacial hypothesis (light grey curve; Ganopolski et al., 2016).

If humankind does not change it, glacial inception should take place in 1500-2500 years. Ice caps at Baffin Island (figure 141) and the Canadian Arctic Archipelago will start to grow, initiating the Laurentide ice sheet (Birch et al., 2017), while ice caps should also grow first over West Siberian islands. Glaciers in Norway should grow to the sea and start releasing icebergs due to increased winter precipitation. The Fennoscandian ice sheet growth, however, should be delayed by an intensification of AMOC, that is expected to bring more heat towards the Nordic seas (Born et al., 2010). In 10,000 years large ice sheets should have developed causing sea level to fall by 30-40 m. Current eccentricity is very low and is going to continue decreasing to almost zero over the next 25 Kyr (figure 140, dotted line). While low eccentricity prevents insolation from going too low, it also prevents it from going too high, so the ice accumulated over low summer energy periods doesn’t melt significantly during periods of higher summer energy. The result is that low eccentricity promotes a faster ice-sheet growth.

Figure 141. Baffin Island ice caps. The Barnes and Penny ice caps in Baffin Island (Canada) are the last remnants of the Laurentide ice sheet of the Wisconsinan glaciation. They are projected to disappear in 300 years if Modern Global Warming continues intensifying (Gilbert et al., 2017). Instead, together with the Canadian Arctic Archipelago and West Siberian islands, they might constitute the starting places for the next glaciation. Source: Public domain from NASA through Wikipedia.

The next high summer energy period in 35 Kyr cannot result in a new interglacial. Obliquity and insolation oscillations are misaligned during that period (not shown), and despite a rapid ice-sheet growth ice-volume should still be too low, so every necessary condition for a Late Pleistocene interglacial is missing in 35 Kyr. Quite the contrary, the low eccentricity should cause the ice-volume to grow through the summer energy peak as it happened during MIS 10 glacial period under similarly low eccentricity (figure 140, dark grey line). On the positive side, the rapid ice-volume accumulation over the next 60 Kyr should create the correct conditions for a new interglacial in 70 Kyr, when a correct orbital alignment and sufficient ice-volume should produce the next interglacial.

If Berger and Loutre (2002), Archer (2005), and Ganopolski et al. (2016) are correct, and the residual CO2in the atmosphere will allow, for the first time in two million years, the survival of an interglacial through an obliquity minimum, then the Holocene should last for at least 50 Kyr more (figure 140, light grey line).

Milankovitch forcing is a very powerful force when acting over millennia. With the help of the appropriate feedbacks it puts the planet into very cold glacial periods and then melts the ice sheets into warm interglacials. It is very difficult for scientists and people in general, living during a multi-centennial warming period characterized by a strong increase in GHG to imagine that on the long run Milankovitch forcing might win. The Romans that for many centuries lived in a warm world characterized by technical progress could not imagine that their mighty empire could fall amid a cooling and worsening climate and terrible plagues into a millennial dark age of lost knowledge and declining civilization. A new glacial period would constitute humankind’s biggest test and clearly has the potential to constitute its worst catastrophe. The precautionary principle requires that we start preparing for that possibility over the next decades and centuries while we are in a warm optimum, as cooling periods are rife with troubles.

For the past 2 million years, when obliquity declined enough a glacial period always followed. Obliquity is declining fast, and we should not have too much confidence on computer models that tell us this time will be different.

Conclusions

1) The glacial cycle fits a model of a stable glacial state that reaches an excitable point where fast excitation (rapid warming) takes it to a quasi-stable interglacial state that slowly degrades to an unstable point where a slow relaxation takes it back to the glacial state. This dynamic system is defined as a fast-slow excitable system around a two-branch slow manifold.

2) Interglacials of the Early Pleistocene, or later when eccentricity is very high, are determined exclusively by summer energy, the amount of energy above a melting threshold accumulated over the entire summer, a parameter that depends mainly on obliquity at high latitudes.

3) After the Mid-Pleistocene Transition when eccentricity is not very high, interglacials are determined by a combination of high summer energy and high ice-volume.

4) This dual interglacial determination that depends on summer energy, eccentricity, and ice-volume, results in an irregular pattern of interglacials after the Mid-Pleistocene Transition, but the negative correlation between eccentricity and ice volume results in a 100-Kyr cycle in ice-volume.

5) Due to the ~ 6000-yr lag between orbital forcing and ice-volume effect, the orbital threshold for glacial inception is crossed ~ 6000-yr before glacial inception. Analysis of the past 800 Kyr indicates the orbital threshold to terminate the Holocene was crossed long ago.

6) In the absence of sufficient anthropogenic forcing, glacial inception might take place in 1500-2500 years as determined by orbital parameters, average interglacial length, Neoglaciation length, and solar variability periodicities.

7) The long interglacial hypothesis rests on the wrong astronomical parameter, high equilibrium climate sensitivity to CO2, and uncertain model predictions of very long-term CO2decay rates. The virtual certainty by the IPCC that a glaciation is not possible for the next 50 Kyr if CO2levels remain above 300 ppm is unsupported by evidence.

Acknowledgements

I thank Andy May for reading the manuscript and improving its English, for his comments and continued support.

Bibliography

JC note:  This is the final installment in Javier’s series Nature Unbound.  This is a truly remarkable collection of essays, which has provided many insights.  A very special thank you to Javier for providing these articles.

521 responses to “Nature Unbound X – The next glaciation

  1. Thank you Dr. Judith Curry for the opportunity to publish them in your excellent blog. It is without doubt one of the best places for open climate discussion.

    • Javier, you mention that we might eventually have the technology to control glacial cycles. If Arctic Ocean circulation is a major part of the picture, we could mount a Herculean project to build a sub-sea dam across the deepest part of the channel between the Arctic Ocean and the North Atlantic Ocean. That should cause the Arctic Ocean to freeze over and reduce the available atmospheric moisture for precipitation of snow over the northern part of the surrounding continents. However, I would not recommend that. If that should result in warming of the North Atlantic and that be a major contributor to the precipitation, it would be a huge mistake and be hard to undo.

      Another possible but even larger project might be to create a deep channel across the Bering Sea to simulate pre-Pleistocene circulation. Again, I would not recommend that.

      So I favor your preference, which is to prepare for any eventuality, starting soon.

      • We could build a dam or dams and destroy the Arctic Circulation that has caused climate to be wonderful for ten thousand years, or we could study and learn more before we destroy what Mother Nature put here to make our lives wonderful.

    • Aaron Chmielewski

      It’s looking like there is a positive feedback in bio-uptake. As CO2 increases, plants provide more nutrients to symbiotic bacteria and fungi that make nitrogen and phosphorus biologically available.

    • Javier have you read about the 200 year Sunspot cycles on the effect on the Earth’s climate. A Russian scientist Dr. Habibullo Abdussamatov presented an article “The Sun defines the climate” what do you think of it?

  2. Thank you for this great article. I´ll study it again and more deep…

    Just one question: i think it is not possible to simulate the Eem interglacial with high sensitivity to CO2 changes, aka, high positive feedbacks during the early holocene and the following T decrease with relative low orbital eg. forcings….?

    • Botosenior, it is not possible to use complex GCM models to simulate hundreds or thousands of years of climate change, so climate modelers use intermediate complexity models that leave out many things, and usually incorporate specific modules to reproduce things that are not in GCM models, like vegetation changes feedbacks. So the result is even more uncertain than for the forecasting of the next decades. However it can be said that scientists “cheat” as they know the answer to the test beforehand, and they can play around with the models until they get a satisfactory answer. So they have been able to reproduce under very simplified conditions, playing with 65°N insolation and CO2 levels, the absence or presence of ice sheets at the Eemian deglaciation and posterior glaciation. However there are a lot of problems when the result is analyzed in detail. For example to get the glaciation started in their model analysis, Jochum et al., 2012 used an annual mean temperature 5°C lower than it should have been, raising doubts about what the models are really simulating.

      Jochum, M., A. Jahn, S. Peacock, D. A. Bailey, J. T. Fasullo, J. Kay, S. Levis, and B. Otto-Bliesner, 2012: True to Milankovitch: Glacial inception in the new Community Climate System Model. J. Climate, 25, 2226–2239
      https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-11-00044.1

      • OK, thanks. I was thinking more on starting at the early Eem with best parameter estimations and running a few millennia,…but in the end it does not make much sense i believe…
        I think you know the series at science of doom (ghosts of the past climate, termination of ice ages…). We really see a very interesting topic and as you show, mostly unknown, and / or unsolved questions.

        But, looking at the GCMs today, a brutal weakness is very massive. They can not even simulate natural, random climatic fluctuations on all timescales (over some years, at best). If one removes (IPCC graphics) all forcings, including volcano, sun, GHG, aerosols…we see a “cardiac arrest” for centuries. A T flat line climate without trends. No one in climatology would take such a nonsense seriously, but today’s mainstream climate policy prays these “curves” like the Bible. Even the minimal cooling between 1940 and 1970 could easily be a stochastic variation and many others. Climate needs no external forcing to change.
        But here in one very intelligent on the road, claiming to know, that climate needs only CO2, the Carbon JimD…:-) A copy paste ghostwriter of the “summaries for policy makers”

  3. Outstanding presentation again Javier. I hope the end of your series isn’t the last of your articles.

    “Milankovitch forcing is a very powerful force when acting over millennia. With the help of the appropriate feedbacks it puts the planet into very cold glacial periods and then melts the ice sheets into warm interglacials. It is very difficult for scientists and people in general, living during a multi-centennial warming period characterized by a strong increase in GHG to imagine that on the long run Milankovitch forcing might win. ”

    For short runs, substitute solar cycle forcing for Milankovitch forcing, which is another thing some scientists find difficult to imagine winning over GHGs, yet it does!

    People will adapt to the next glaciation, whether they like it or not.

    • “For short runs, substitute solar cycle forcing for Milankovitch forcing, which is another thing some scientists find difficult to imagine winning over GHGs, yet it does!”

      So why is the earth continuing to warm even though solar irradiation is low, and has been for some time? When will it “win out” over GHGs?

      • Scott,

        So why is the earth continuing to warm even though solar irradiation is low, and has been for some time?

        It is not. Solar activity has been below average since 2006, and the only significant warming since 2003 has been due to a very strong El Niño and is being erased as we speak. Since February 2006 the earth has been cooling significantly:

        So based on the evidence, since 2003 it is the CO2 hypothesis that is in trouble, not the solar hypothesis. The CO2 hypothesis is represented by the fine blue line indicated by CMIP5 models. Talk about failure.

      • Typo. Cooling since February 2016, not 2006.
        Two and a half years.

      • “When will it “win out” over GHGs?” – TSI/insolation is always winning.

        “why is the earth continuing to warm even though solar irradiation is low, and has been for some time?”

        Ocean heat content accumulation via high TSI/insolation from consecutive active-enough solar sunspot cycles. ‘Active enough’?

        Did you ever ask yourself how much solar energy over time is just enough to keep the ocean temperature constant? I did, the result is shown here:

        It means SC24 was active enough for net warming to date, unlike the Dalton minimum solar cycles 5 & 6, which were below the line.

      • Scott Koontz

        “Cooling since February 2016, not 2006.
        Two and a half years.”

        Short trends are overcome by longer trends. Earth still warming.

      • “Earth still warming.”

        Oh I agree that the planet is still warming. But this periods of cooling have the effect of reducing the long term warming rate which is not good for the dominant hypothesis that requires accelerating warming.

      • Scott Koontz

        “But this periods of cooling have the effect of reducing the long term warming rate which is not good for the dominant hypothesis that requires accelerating warming.”

        Um, no. Simply no. They do NOT reduce long-term warming, but are simply sine curves on an upward trend. Take all El Nino years, upward trend and increasing. Take all La Nina years, upward trend and increasing. Take all other years, upward trend and increasing.

        This is all far too simple: trend is up, trend is increasing. Movement of heat within the trend is duly noted, but not reducing long-term trends. The warming is primarily from changes to our atmosphere. You are talking about shifting heat that is already here, but aren’t answer how additional heat got here in the first place.

      • “Take all El Nino years, upward trend and increasing. Take all La Nina years, upward trend and increasing. Take all other years, upward trend and increasing.”

      • “They do NOT reduce long-term warming”

        Read again. I said warming RATE. The warming rate is the derivative of temperature increase over time. Any period of relative cooling goes to reduce this rate by decreasing the amount of warming and/or increasing the amount of time to warm.

        And this is the crucial part of the CO₂ hypothesis. Because if the warming rate does not accelerate proportionally to the addition of CO₂, then the warming cannot be caused by CO₂ exclusively.

        I already showed this figure:

        where it can be seen that the bulk of the increase in CO₂ forcing took place since 1950, while the warming appears to be oscillating over a long-term trend without clear acceleration.

        That graph questions that one of them is the main cause for the other.

        A multi-year cooling trend now is a serious problem for the hypothesis.

      • “Read again. I said warming RATE. The warming rate is the derivative of temperature increase over time. ”

        Read my post again. You seem to have alack of understanding of what an increasing trend is. OK, let’s have a look:

        “Take all El Nino years, upward trend and increasing. Take all La Nina years, upward trend and increasing. Take all other years, upward trend and increasing.”

        “And increasing.” What would that be? Ah yes, the second derivative. The rate. The rate is increasing. And your suggestion that the rate of increase is kept at bay because of shifting heat within oceans is absurd.

        Now, we both know that the earth is warming, that the heat is being trapped, and that the increasing trend or rate (see that word?) is noteworthy.

      • “You seem to have alack of understanding of what an increasing trend is. OK, let’s have a look:

        “Take all El Nino years, upward trend and increasing. Take all La Nina years, upward trend and increasing. Take all other years, upward trend and increasing.”

        “And increasing.” What would that be? Ah yes, the second derivative. The rate. The rate is increasing.”

        No. It is generally believed that Niño and Niña events compensate over time so they are climate neutral. Your example is just looking at the variability around the warming trend and detecting that there is a warming trend. That has nothing to do with the change in the rate of warming (acceleration of warming).

        Niño years have a linear trend (constant increase, no acceleration). Nina years have a linear trend (constant increase, no acceleration). Neutral years have a linear trend (constant increase, no acceleration).

        The rate of the warming trend is not changing.

        As the temperature is expected to be proportional to the logarithm of CO₂ concentration, and the logarithm of CO₂ concentration trend does have acceleration (its rate of increase is accelerating), the increase in temperature is lower than expected by the hypothesis.

        The temperature is not increasing as fast as required by the hypothesis, and any period of cooling will make that worse.

      • I’m not sure the ln(CO2) vs surface temperature argument is particularly compelling without some attempt to quantify and/or remove the effect of confounding natural factors ala Foster/Rahmstorf 2011.

        Per Pielke Sr, ocean heat content might be a better proxy as it represents the dominant sink for any radiative energy imbalance and is less sensitive to planetary internal heat redistribution phenomena.

  4. Question: how do these models handle the gradual rising of land previously covered by ice? The higher ground should help snow remain in summer time in northern facing slopes in the northern hemisphere.

    • Fernando, what I know about climate models is what is reported in the articles that I read. For the particular question that you ask me, it has been found that topography is a very important factor to get models to be able to reproduce glacial inception under realistic assumptions.

      One of the articles that deals with this issue in more detail is Birch et al., 2017: Glacial Inception on Baffin Island: The Role of Insolation, Meteorology, and Topography
      https://journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-16-0576.1

      “Geologic evidence suggests that the last glacial inception (115 kya) occurred within the mountains of Baffin Island. Global climate models (GCMs) have difficulty simulating this climate transition, likely because of their coarse horizontal resolution that smooths topography and necessitates the use of cumulus parameterizations. A regional configuration of the Weather Research and Forecasting (WRF) Model is used to simulate the small-scale topographic and cloud processes neglected by GCMs, and the sensitivity of the region to Milankovitch forcing, topography, and meteorology is tested. It is found that ice growth is possible with 115-kya insolation, realistic topography, and slightly colder-than-average meteorology, represented by specific years within the past three decades. The simulation with low GCM-like topography shows a negative surface mass balance, even with the relevant orbital parameter configuration, demonstrating the criticality of realistic topography.”

      Many regions in Northern Canada and the mountains of Scandinavia (Scandes) display permanent small ice patches that developed around 5000 years ago when the Holocene Climatic Optimum ended, being further evidence that current global warming hasn’t reached the HCO conditions yet in those places. Most but not all of those ice patches are in North facing slopes, and they grew a lot during the LIA indicating they could act as topography-dependent nucleating sites for ice growth.

  5. Good review article, Javier.

  6. Most useful as to the Milankovitch cycle relationships. I think I may have your smoking gun, but have yet to publish, and it really demonstrates why CO2 is a complete red Herring when contrasted with the dominant control of the narrow range of variation between the very repeatable low and high temperatures limits of our strongly fed back ice age cycle. The limits and periodicity are so strongly nailed down, and perturbations so strongly restored to the main cycle when they happen, the theory that a puny few W/m^2 in the atmosphere where the much larger control of solar insolation, at both upper and lower limits, dominates can change this significantly is obviously delusional on the power physics.

  7. Climate Models that emphasize astronomical controls such as insolation and obliquity show glacial inception in the next 10 to 30 kyrs. These projections fit within the range of paleoclimate analogs and should be considered the base case. Models that project glacial inception in the next 50 to over 100 kyrs suggest that CO2 concentration affects climate more than astronomical variables. These projections are outside the range of past interglacial analogs and even exceed the duration of the entire interglacial-glacial cycle. They far exceed the analog datasets and should not yet be considered reliable as a base case scenario.
    https://wattsupwiththat.com/2017/09/21/climate-model-projections-significantly-diverge-from-paleoclimate-analogs/

  8. Working from your termination dates in figure 129:

    621 – 88 – 44
    533 – 109 – 36
    424 – 87 – 44
    337 – 94 – 47
    243 – 113 – 38
    130 – 116 – 39
    14

    I took the differences. Then divided them by 2 or 3 based on what looked right getting closer to 41k. So that averaged 41k +- 6.

    Then I looked at 101k, I just averaged the differences getting 101 +- 15.

    My notation above is only the maximum difference from the average.

    So our rules could be:
    101k +- 15k then warm.
    or
    Two roughly 41k cycles then warm. If not warming after 2 cycles, warm on the next cycle.

    What could explain the second rule is mass of ice. One cycle lacks sufficient mass. Two may have it, but if it doesn’t, the third cycle will.

    • Yes, exactly. And explaining the transition from the 41 Kyr to the “100 Kyr” periodicity becomes much easier.

  9. sheldonjwalker

    There are 2 updates to my website this week.

    1) Regional Warming.

    Each region (1/8 of the earth), now has a line graph, as well as a global warming contour map.

    The line graph also shows how variable the temperature anomaly is, over time. Compare the 2 most northern regions, and the most southern region, with the other regions.

    https://agree-to-disagree.com/new-regional-warming

    2) A new web page on Seasonal Warming.

    You may have read the lastest headlines, “Powerful evidence that climate change is altering seasonal temperatures”.

    They used satellite data. I have used weather balloon data to look at seaonal changes in the northern and southern hemispheres. You can compare contour maps, which are based on 3 month seasons (DJF, MAM, JJA, SON). Remember, when it is winter in the northern hemisphere, it is summer in the southern hemisphere.

    There are line graphs for every contour map. I may re-plot these. I adjusted each seasonal temperature series so that it started at zero. This was meant to make comparision easy. But looking at the line graphs, I think that I should have adjusted the LOESS smooth for each season, to start at zero. This would stop extreme values at the start of a seasonal temperature series, affecting the whole graph. See what you think.

    https://agree-to-disagree.com/seasonal-warming

    Here are 2 contour maps, showing warming rates in [Jun, Jul, Aug], for the northern and southern himispheres. Don’t tell warmists about the green pause from 1990 to 2005 in the southern hemisphere.

    I have spent a lot of time making my website look good on tablets, and mobiles, as well as desktops. Try it out, and let me know what you think.

  10. Javier, very interesting work and it seems very plausible to me. Perhaps our descendants will look back to your work as a ground-breaking early recognition of the major factors at play in leading to the next glacial period inception. Hopefully others will follow your lead and develop long range climate models that incorporate these factors.

    • Oz4caster. A thousand years is an awful lot of time. And even in science there is a lot of history rewriting going on. Climate scientists are saying now that they discovered the hiatus. Let’s say I’ll be happy if I contribute to a better knowledge by some of the people that read the blog.

  11. The Ice Ages didn’t start until after CO2 levels dropped from above 300 ppm to below 300 ppm which was 2.5 million years ago marking the start of the Pleistocene. If the Ice Ages could not exist the previous time with CO2 levels much higher than 300 ppm, why, and why not next time?

    • Correlation is not causation. You should read Jim Steele comment here:
      https://judithcurry.com/2018/08/08/hothouse-earth/#comment-877990
      He gives a most plausible physical explanation for the present ice age.

      • He doesn’t refute that reduced CO2 levels had a cooling effect. The previous discussion was about icehouses and hothouses and that was all about CO2, not ocean circulations. It is easy to explain from physics why past hothouses existed only in high CO2 conditions that themselves resulted from geological changes, and that just follows from the forcing because CO2 has a large enough effect by itself. The Ice Ages cannot exist at CO2 levels much above 300 ppm. If they could, why did they not?

      • The Late Ordovician Saharan Ice Age did take place at CO2 levels much above 300 ppm. Your argument is falsified.

        Also as CO2 levels are affected by temperature they tend to go down when there is cooling and up when there is warming.

      • Maybe you are unaware, even though I have pointed it out before, that the sun was weaker back then by several percent and each percent is worth a CO2 doubling. The sun, like all main sequence stars, is brightening at about 1% per 100 million years.

      • What going on with the SkS plots?

      • Ragnaar, read the left axis for the difference.

      • “the sun was weaker back then by several percent and each percent is worth a CO2 doubling.”

        The faint-Sun paradox is unsolved despite several hypotheses trying to explain it. Your presentation of everything as already solved, including the equivalence of Sun’s output changes in CO2 doublings is a manifestation of “the end of history” illusion applied to science.

        The end of history illusion.
        http://science.sciencemag.org/content/339/6115/96
        “We measured the personalities, values, and preferences of more than 19,000 people who ranged in age from 18 to 68 and asked them to report how much they had changed in the past decade and/or to predict how much they would change in the next decade. Young people, middle-aged people, and older people all believed they had changed a lot in the past but would change relatively little in the future.”

        You think science has learned a lot in the recent past but that its knowledge is near perfect and unlikely to change in the future. Your knowledge of the history of science is very incomplete. Our scientific knowledge is a mixture of things that are likely to be true, things that will turn out to be false, and holes that in some cases we are not even aware that they exist. Our knowledge of the distant past is particularly weak and likely to produce a stream of surprises as our knowledge advances. Many of the things you say with absolute certainty are probably wrong, but you are suffering so strongly from the end of science history illusion that you are completely unaware of it.

      • Javier,

        Is that how you address the faint sun paradox, with a non-sequitur?

        That the sun was weaker in the past is something you can bank on.
        That theory is supported by observations of thousands of stars.

      • No. The faint Sun paradox is not that the Sun was weaker in the distant past. The paradox is that the Earth does not appear to have been much colder. Perhaps you should read about the issue a little more. What Jim D exposed was the politically correct GHG hypothesis to solve the paradox. But there are several competing hypotheses to explain the paradox that you probably don’t know much about.

        Georg Feulner for example reviewed the question in 2012 and had this to say:

        “For more than four decades, scientists have been trying to find an answer to one of the most fundamental questions in paleoclimatology, the “faint young Sun problem.” For the early Earth, models of stellar evolution predict a solar energy input to the climate system that is about 25% lower than today. This would result in a completely frozen world over the first 2 billion years in the history of our planet if all other parameters controlling Earth’s climate had been the same. Yet there is ample evidence for the presence of liquid surface water and even life in the Archean (3.8 to 2.5 billion years before present), so some effect (or effects) must have been compensating for the faint young Sun. A wide range of possible solutions have been suggested and explored during the last four decades, with most studies focusing on higher concentrations of atmospheric greenhouse gases like carbon dioxide, methane, or ammonia. All of these solutions present considerable difficulties, however, so the faint young Sun problem cannot be regarded as solved.”

        Feulner, G. (2012). The faint young Sun problem. Reviews of Geophysics, 50(2).
        https://onlinelibrary.wiley.com/doi/pdf/10.1029/2011RG000375

        Rosing et al., in 2010 had this to say:

        “we hypothesize that a lower albedo on the Earth, owing to considerably less continental area and to the lack of biologically induced cloud condensation nuclei, made an important contribution to moderating surface temperature in the Archaean eon.”

        Rosing, M. T., Bird, D. K., Sleep, N. H., & Bjerrum, C. J. (2010). No climate paradox under the faint early Sun. Nature, 464(7289), 744.
        http://gondwanaresearch.com/hp/fys.pdf

        Only types like Jim D believe the paradox is solved by CO2. It might take decades to be solved or it might never be solved. We don’t know.

        So instead of expending your time critizacing me you could put it to better use researching the issue if it interests you.

      • Little touchy are we?

        So don’t answer arguments with a non-sequitur.

        I see you quickly found some cites that address the faint sun paradox.

        Part of the answer could lie in the presence of greenhouse gases, even those other than CO2.

        And the GHG is not an hypothesis, it is an observed fact, which the ABCD club wants to ignore.

        Put that in your essays and you might get some traction.

        And you can note that I didn’t describe or explain what the faint sun paradox was in my comment, only that the sun was indeed less energetic in the past.

        A couple other thing Fuelner has to say in the paper you cited.

        “The natural greenhouse effect is the cause for global
        average temperatures above the freezing point of water over
        much of the Earth’s history,”

        and

        “In summary, an enhanced greenhouse effect arguably
        still seems the most likely solution to the faint young
        Sun problem.”

        thanks

      • Bob,

        pretty much any time Javier makes a strong claim, it turns out either not to be supported by the cite, or a selective quotation at best.

        That Feulner one is typical, but Javier’s prodigious output makes it far too tedious to follow more than a small sample.

      • VTG, perhaps you or Bob could enlighten the rest of us with a post of your own or is that too tedious as well?

      • “And the GHG is not an hypothesis, it is an observed fact…”

        I’ll assume you meant GHE.

        “In science, a fact is a repeatable careful observation or measurement (by experimentation or other means), also called empirical evidence.”

        We can measure the temperature. We can measure the CO2 level. We have proxies for what those were in the past.

        The IPCC can help us with facts: For a doubling of CO2, we get from 1.5 to 4.5 C of GMST rise in the long run. With 66% confidence.

        So yes it is a fact, poorly constrained. Or maybe the relevant fact is carbon dioxide has an infrared emission spectra. That has been measured.

        Now when we take what the IPCC said above and carry it back 400 million years, that’s difficult.

        It is a fact that Acme Corporation has a profit margin from 15% to 45% with 66% confidence.

        It’s not anything but carbon. It’s understand what carbon does in the relevant areas, then move forward.

      • “I see you quickly found some cites that address the faint sun paradox.”

        Actually I have 5 articles about the Faint Sun Paradox in my hard drive. They are:

        Feulner2012
        Goldblatt2011
        Kasting2014
        Rosing2010
        Wolf2013

        They represent a diversity of points of view about the issue. I just chose two to answer you. It is not an issue that interests me particularly, that’s why I have so few articles about it. Nevertheless for most things related to climate science it is faster for me to look in my hard drive than run a search in the internet.

      • “That Feulner one is typical”

        Feulner is very clear that in his opinion the paradox cannot be regarded as solved. It is impossible to misquote that. It is in the abstract.

      • Javier, you shifted the argument to the Ordovician but conveniently omitted the fact that the sun was significantly weaker then which would have refuted your own argument. This was a red herring or just a poor rebuttal. You have to figure out why the earth did not stay frozen solid with 10-20 W/m2 less solar forcing than now. Higher GHG levels is one possible answer because they were known to exist in those eras.

      • It is widely recognized that a change in the solar constant of about 4.5% at the time of the late Ordovician glaciation is very insufficient to explain it. CO2 levels 440 Mya are estimated at 16 x PAL, so we are talking about 3-4 doublings of present levels.

        The problem is so tough that most hypothesis require a substantial drop in CO2 levels prior to the glaciation for which there is no evidence.

        How much CO2 levels would have had to go down to allow the glaciation depends crucially on the ECS, so we always go back to that. A question that nobody knows.

      • It is easy to account for ice in the Ordovician within the uncertainty to which CO2 is known. Anyway, it doesn’t depend on ECS, only forcing as long as solar variations have the same ECS to the same forcing. So we can make a direct comparison of a CO2 doubling to a 1% solar increase because these have the same forcing change. Similarly if albedo changes by 1% (from 30% to 29% for example). All of these have a forcing change near 4 W/m2.

      • Javier, were any of your references about the Ordovician because your quote from Feulner was clearly on a completely different era and maybe you didn’t notice you had shifted your argument to another era yet again. This is just a very slippery way of arguing.

      • Verytallguy,
        I find Javier’s posts to be long slogs, as we used to say in our more immature years, if you can’t dazzle them with brilliance, then baffle them with BS.

        Ragnaar, I am in the everything but cosmic rays camp. There is a long list on things that affect climate. If you declare that CO2 has no effect, which is the gist of what I understand Javier to be arguing, then you are not going to do a very good job explaining what is going on with the climate.

      • I find Javier’s posts to be long slogs

        Everybody is entitled to his opinion…

        If you declare that CO2 has no effect, which is the gist of what I understand Javier to be arguing

        …but not to his interpretation of what other people say. You must have not read my articles or understood them to sustain that opinion. I even discussed with our host my interpretation that the Cryosphere response is evidence that CO2 does have a significant climatic effect.

      • javier

        Feulner is very clear that in his opinion the paradox cannot be regarded as solved. It is impossible to misquote that. It is in the abstract.

        You’ll note that I did *not* say you misquoted your sources, but that you *selectively* quoted them.

        Feuler states both

        “the faint young Sun problem cannot be regarded as solved.”

        and

        “The natural greenhouse effect is the cause for global
        average temperatures above the freezing point of water over
        much of the Earth’s history”.

        Your citing the former but not the latter is the very epitome of selective quotation.

      • Quotes are always selective unless one copies the entire article. My quote of Feulner was extense (more than half of the abstract) and was not taken out of context.

        Your quibbling is noted.

      • Javier,

        Your attempted avoidance of Feulers emphasis on the importance of the greenhouse effect is amusing.

        “In summary, an enhanced greenhouse effect arguably
        still seems the most likely solution to the faint young
        Sun problem.”

      • Some people think they can know what other people have inside their heads. It is just a manifestation of hubris.

        Attributing specific intentions to other people’s actions is typical of political debates, but are completely out of place in scientific debates. My thoughts and intentions are not only unknown to you, but irrelevant in this context.

      • Javier,

        my post was purely based on your actions.

        Which were to quote the part of Feuler which supports your case whilst ignoring the part which directly contradicts it.

      • Except that no part of Feuler contradicts my case. The question, as always, is the value of ECS. The magnitude of the effect of non-condensing greenhouse gases is under discussion, not that they had an effect, which it is obvious.

        So you are starting on a false premise, which is usually the case when someone tries to get inside other people’s head.

      • VTG

        Your quoting the latter is of no significance. It should be obvious and Javier made clear his position on CO2. Stop being such a pain. You remind me of a guy who used to come into my office just to argue. He had no basis for an argument, he just enjoyed arguing. That was until my voice got a little loud and with tail between his legs he went back to his boss and tattled on me. What a little panzy he was.

      • “What a little panzy he was.”

        Keep it klassy, kid.

        Javier’s selective quotations and citations are what justify his conclusions. His reaction to Bob calling him out on it is instructive. Your reaction likewise.

      • No VTG, mi reaction was not to Bob calling me out but to his phrase:

        That the sun was weaker in the past is something you can bank on.

        To my knowledge nobody has questioned the sun was weaker in the past, not here, nor anywhere else. And that has nothing to do with the paradox. The paradox is that the Earth was not correspondingly cooler.

        With that phrase Bob shows that either he does not understand what the paradox is about or he does not understand my exchange about it with JimD, as clearly I did no in any time questioned that the sun was weaker when it was younger.

        So you are compounding on his mistake by adding yours, while at the same time questioning the motives of my quotations without any knowledge of them.

      • Of course, in my lexicon it refers to a lack of tough mindedness and a predilection to wilt when confronted with adversity. In current phraseology, known as a snowflake.

      • JimD, verypompousguy, Bob

        By what mechanism, do you propose, did atmospheric CO2 gradually fall in atmospheric concentration so as to EXACTLY counterbalance increasing solar radiation, giving the result of a stable life-supporting climate for 4 billion years. Is God involved?

      • As for a reason for a solar/CO2 balance, perhaps at the low end it will always be ended by volcanic periods that come inevitably from continental drift. At the high end, large amounts of CO2 lead to heat and vegetation in large quantities and that is self-limiting because of biological sequestration and geological/chemical processes that increase in rate with temperature.

      • @bobdroege
        > And the [GHE] is not an hypothesis, it is an observed fact, which the ABCD club wants to ignore

        Who is in this club ?

      • bobdroege:

        I was bringing up with the GHE being an observed fact. Last night I watched the Democratic candidate for governor in Minnesota use the word ‘Science’ like a cross warding off vampires.

        If it is a fact, it’s a poorly constrained one as I mentioned.

      • Thanks for the replies Javier, I know they are somewhat exasperating to write but I think many will find them educational.

        Thanks for the Feuler paper, I had not realized FYSP had quite so many potential explanations, or how closely linked some are to the very similar “water on early Mars” question. I especially like the Kasting 2010 reference: After four decades of research, the faint young Sun problem indeed “refuses to go away” [Kasting, 2010, p. 687].

    • Jim D:

      2.5 million years ago is nothing geologically speaking. Assume CO2 dropped below 300 ppm then. Why did it take so long for it to drop below 300 ppm?

      Above from: How the World Passed a Carbon Threshold and Why It Matters

      It was probably geological changes such as the Antarctic Circumpolar Current setting up as Steele wrote. The geological change lead the CO2. So the climate locked into making ice on Antarctica. I’ll say the best way to deplete CO2 from the system it to put it into the oceans.

      • The Antarctic circumpolar current had nothing to do with 2.5 million years ago when the Ice Ages began. Those are driven by the northern hemisphere insolation, but insolation alone is not enough without a sufficiently cold mean temperature that is provided by low CO2 levels. Also Greenland formed glaciers 15-20 million years ago as CO2 levels feill below 400 ppm. Ice formation had several tipping points, 450 ppm for Antarctica, 400 ppm for Greenland, 300 ppm for the other NH Ice Age glaciers. Sea levels have also changed accordingly.

      • I am going to report a e360.yale.edu Fail. I can’t locate the source of my above plot. I looked at the link I had above.

      • Well if not explaining the ice age start, why did it take so long for CO2 levels to fall below 300 ppm?

      • So long compared to what? This is geological time scales. We expect tens of millions of years for hundreds of ppm. The ocean and land can sequester carbon if left to themselves, but slowly.

      • I got it.
        “What is revealed is that despite a dramatic change in solar output, the combined climate forcing by CO2 and the Sun has remained relatively constant (Figure 2).” – Gavin Foster

        So with no forcing changes, what caused ice to stack on Antarctica?

      • There was quite a large drop in total forcing prior to 35 million years ago, so that hit a tipping point for Antarctica.

      • “There was quite a large drop in total forcing prior to 35 million years ago, so that hit a tipping point for Antarctica.”

        We don’t know of any such large drops in forcing and we don’t know of any tipping points in Antarctica.

        What we do know is that Antarctica moved very slowly towards the South Pole and got frozen very slowly, and altered the Southern Ocean currents very slowly. No tipping points are known. Perhaps the process accelerated once it got covered in ice even during summers, but we can only speculate on that.

      • Javier, it can be seen in Ragnaar’s plot, but this gives a better view of it. CO2 and temperature were dropping for millions of years prior to 35 million years ago when Antarctica first froze over, which marks the Eocene-Oligocene boundary.

      • JimD

        “CO2 and temperature were dropping for millions of years prior to 35 million years ago when Antarctica first froze over, which marks the Eocene-Oligocene boundary.”

        I did not discuss that. I discuss your statement that the process hit a tipping point. You have no evidence of the existence of a tipping point in that process. You are making that up. Perhaps when you put some food in the freezer you think it cools until it hits a tipping point. The truth is that it starts to freeze from the outside to the inside without any tipping points.

        To say there is a tipping point you need evidence supporting its existence.

      • When Antarctica froze 35 million years ago, the temperature dropped a lot faster, likely because of the albedo feedback a frozen Antarctica provides. That is a tipping point in the same sense as the Ice Age oscillations that are also largely amplified by the albedo changes of forming and melting ice sheets. There was also a large cooling 15 million years ago about when Greenland glaciated. Albedo feedback is a major player in these in coolings.

      • “When Antarctica froze 35 million years ago, the temperature dropped a lot faster, likely because of the albedo feedback a frozen Antarctica provides. That is a tipping point”

        I don’t know where you got your definition of a tipping point but a response that is proportional to the forcing + the feedbacks is not a tipping point.

        – I see tipping points.
        – How often do you see them?
        – All the time. They’re everywhere.

      • A tipping point is when a small change leads to a large response. The descent into an Ice Age is triggered by a small change with large feedbacks. That is a tipping point. Sea levels changed over 100 meters. If that is not a tipping point, what is? Antarctica would have done something similar to sea levels, and so would the melting of the glaciers be tipping points for sea levels. The gain or loss of these large continental glaciers would be the definition of a tipping point.

      • “A tipping point is when a small change leads to a large response. The descent into an Ice Age is triggered by a small change with large feedbacks. That is a tipping point. Sea levels changed over 100 meters. If that is not a tipping point, what is?”

        You are confusing or confused.

        Merriam Webster
        Definition of tipping point
        : the critical point in a situation, process, or system beyond which a significant and often unstoppable effect or change takes place

        Google dictionary
        tipping point
        noun
        the point at which a series of small changes or incidents becomes significant enough to cause a larger, more important change.

        So what was the small change that caused the large effect in the freezing of Antarctica?

        For what we know a small change in albedo caused a small freezing, and then another small change in albedo caused a little more freezing, and so on, until all of Antarctica was covered in ice. And it was a process that for all we know might have taken millions of years. The albedo changed gradually and the continent glaciated gradually.

        I fail to see any tipping point there. Any small change that precipitated a large abrupt effect and that was unstoppable or irreversible if the conditions had changed. Perhaps you can point that tipping point to me.

        I think a lot of people are inventing tipping points without any actual evidence that they do exist. If the conditions had reverted the process would have reverted. It just wasn’t so.

      • Javier, you would call the melting of Greenland a tipping point or that of the other ice age glaciers, probably. Or even if you don’t, I do. By that definition the reverse process is a tipping point for those glaciers. They can exist healthily under some conditions and not at all under marginally different conditions. In climate terms these are tipping points in both directions. There is no in-between for these glaciers and they have repercussions for the energy budget via their albedo. They also account for many meters of sea level. We’ve had a ten meters per millennium since the last Ice Age. That’s fast in climate terms – a tipping point, a vertical line on paleoclimate graphs that cover tens of millions of years.

      • “They can exist healthily under some conditions and not at all under marginally different conditions.”

        All that is bull$hit. Glaciers have been growing and waning repeatedly over the Holocene without ever hitting a tipping point. Your purposed Greenland tipping point is imaginary, as most of the things you talk about. Grow up and dig in the scientific literature for real evidence on the things you claim. Or otherwise don’t claim them.

        Most climate tipping points are theoretical. The best example we have of abrupt climate change are Dansgaard-Oeschger events, and they are reversible, because to the last of them they were all reverted. It is unclear if D-O events have a tipping point because we don’t know enough about how they are produced.

        So you are trying to scare people (or scare yourself) with a largely theoretical concept.

      • Javier, glaciers growing and waning, but not sea levels. We’re talking about continental glaciers, not small ones. These having tipping points. Sea-levels change by tens of feet when they melt. Look at the last 15000 years. Several large northern glaciers that existed at the beginning were completely gone 10000 years later (in a paleoclimate blink) due to small orbital changes compounded by major feedbacks in albedo and GHGs. Greenland is near them. Why would you not expect it to be next and with another small warming change triggering it? This should not be a complete surprise to you when you look at what glaciers have been doing in the last million years. It’s an on-off effect: glacials and interglacials. I call those tipping points because they have small triggers and large feedbacks with large consequences for sea level.

      • “These having tipping points.”

        Show me those tipping points. Remember I am a skeptic. Preferably with numbers that leave clear why they tip, or otherwise with scientific literature where the issue is defended.

        Those orbital changes that you call small are not small at all. The change in obliquity involves a huge change in the distribution of energy in the planet and directly affects the equator-to-pole temperature gradient. It is imprinted in the sapropels of the Mediterranean.

        And you know what? Those changes are going in the opposite direction to the one that worries you, as I have shown in the article. CO₂ hasn’t melted a single glacier on Earth, yet obliquity melted enough ice to raise sea level by 120 meters.

      • Javier, they observably tipped. They lost basically all their ice in 10k years. It was a runaway loss because of albedo and GHG feedbacks. You want to define a tipping point differently to a situation where Greenland could lose all its ice from these same reinforcing feedbacks? I am not sure what you are arguing about here.

      • “they observably tipped”

        Clearly you haven’t got any evidence, nor bibliography on those tipping points. More unsupported claims by you. Nothing new.

      • Jim D, after reading Javier’s comment “CO₂ hasn’t melted a single glacier on Earth, yet obliquity melted enough ice to raise sea level by 120 meters.” you should have known that you are off.

        Nobody is interested in further comments from your side. Please do like Javier did: first study, think about all pro’s and contra’s and after drawing your final conclusions: comment something you’ve checked over and over.

      • Javier, you have decided when a continental glacier disappears raising sea levels by tens of meters in a few thousand years, it is not a tipping point. This is not about references, but definitions. The loss of Greenland would not be a tipping point to you either. There are papers on climate tipping points, and the archetypal example is Greenland melting due to its self-reinforcing feedbacks.

      • Wim, low CO2 levels have permitted glaciers in the first place. The descent of CO2 levels from the Pliocene to the Pleistocene allowed Greenland to glaciate and the Ice Ages to start. There is work on this that you will also not be interested in.
        https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010PA002055
        This also works in reverse as CO2 levels return to those in the Pliocene. Take an interest in CO2 because it helps to explain a lot of paleoclimate transitions. The Eocene-Oligocene transition also occurred in a period of descending CO2 when Antarctica glaciated. There’s a pattern of glaciation during reducing CO2 levels and melting during rising CO2 levels. The reason is no mystery. It’s in geology textbooks.

      • “There are papers on climate tipping points, and the archetypal example is Greenland melting due to its self-reinforcing feedbacks.”

        Greenland is melting a tiny little bit now. If at some time the warming turns into a cooling, it will start gaining ice, and the self-reinforcing feedbacks will turn around and become self-reinforcing feedbacks towards ice growth. I fail to see a tipping point in that whole process that once reached will make Greenland melt much faster and irreversible or unstoppably. It is very easy: warming -> melt; cooling -> freeze. No tipping points.

      • Javier, so you would define the complete loss of the Greenland (or other major continental) glacier as a tipping point which is the context I use the term in. It is something that has verifiably happened to Greenland’s near neighbors 10k years ago.

      • “so you would define the complete loss of the Greenland (or other major continental) glacier as a tipping point”

        Obviously not. A tipping point must happen over a very short period of time (a point). If it takes a million years or 1,000 years it can’t be a tipping point. It is a process driven by forcings and feedbacks.

      • In climate, 1000 years is a very short period of time.

      • “In climate, 1000 years is a very short period of time.”

        Well, 600 years ago it was cooling considerably, and 150 years ago it was warming, so plenty of time for forcings and feedbacks to reverse. No tipping point there.

    • The Pleistocene ice age in the northern hemisphere began when the movement of continents sufficiently blocked the circulation in and out of the Arctic Ocean, and set the stage for the glacial cycles that are controlled by factors outside the earth (obliquity, precession and so forth as well described by Javier) and also by precipitation picked up from the Arctic and North Atlantic Oceans which falls as snow on the continents surrounding the Arctic Ocean. The lowering of sea level in glacial periods further blocks circulation and most likely contributes to a freezing over of the Arctic and reduction in the available precipitation for building and maintaining continental glaciers. After the breakup of thick and unstable continental glaciers, the rise in sea level contributes to the reduction in Arctic sea ice that we are seeing now.

      Many geologists consider the CO2 levels mainly a side-effect of ocean temperatures. I have yet to see the details of the early studies that determined the heat capturing properties of CO2, but as a geophysicist, I know that laboratory models are often a poor representation of the real earth. Likewise laboratory measurements using pure or high concentration CO2 may not well represent the Earth atmosphere where CO2 makes up about 4 parts in 10,000. Perhaps Judith can give us insight into those early studies and how they have been extrapolated into climate models.

      • Continental drift is about 20 km per million years. Your other part seems to be doubting science that goes back to Tyndall and Arrhenius, which is an interesting diversion from the reality of the greenhouse effect.

      • Tyndall and Arrhenius were already showed wrong in their hypothesis of GHG changes as an explanation for glacial periods, but it took almost 100 years to get good enough data for that. The problem is we can’t still demonstrate they are also wrong in their hypothesis for older climate changes because of lack of good information. I believe they will eventually be showed wrong and will joint Lamarck in the pantheon of interesting but wrong theories proposers.

      • Tyndall and Arrhenius did not know the CO2 levels in the Ice Ages so they could not be sure of the reason. It may have been a hypothesis by Arrhenius(?), but it never became a theory because there was no CO2 evidence at their time. However, now we have a lot of evidence of geological changes affecting CO2 levels, and high CO2 levels going with warmer periods. So now it is a theory because all the CO2 and temperature evidence supports it, and furthermore the Ice Ages did not start until CO2 levels were low enough, so in that sense Arrhenius would have been right when he said how much colder the world would be with half the CO2. That part is true. If we were to reduce CO2 to 140 ppm it would be very cold. I don’t think anyone disputes that.

      • If we were to reduce CO2 to 140 ppm it would be very cold. I don’t think anyone disputes that.

        If it got very cold the carbonated oceans would suck in the CO2, just like a carbonated drink. Not as a cause but as a result.

        We would die because we would not have anything to eat.

        At 140 ppm, few would be alive to dispute you, but you would not not likely be alive to dispute beck.

        What does this have to do with anything?

      • The problem is we can’t still demonstrate they are also wrong in their hypothesis for older climate changes because of lack of good information.

        Ice core data is good information, there is a lack of study of good information.

      • All you really need to know is that in warm times with thawed oceans, it snows more and it gets colder after. In cold times with frozen oceans, it snows less and it gets warmer after.

        This keeps temperature and sea level bounded.

      • Pope, through most of paleoclimate there was no ice, but the climate still changed a lot. Clearly snow had no effect. It was geology and GHGs on time scales of millions of years. Guess what? It’s GHGs again now.

      • “However, now we have a lot of evidence of geological changes affecting CO2 levels, and high CO2 levels going with warmer periods.”

        More importantly we are doing the ultimate experiment to find out. We are doubling the amount of CO₂ in the atmosphere.

        Regrettably (or luckily) it does not appear to be working.

        You can change CO₂ by changing temperature, but it appears it is much harder to change temperature by changing CO₂.

      • The results of that experiment look fairy conclusive.

      • “The results of that experiment look fairy conclusive.”

        Only if you tamper with the graphical representation

        It will be fun to add 2018.

      • Even with your tampering you get the same gradient as Lovejoy. It works out at 2.3 C per doubling. The line you label diagonal would be about 20% larger.

      • “Even with your tampering you get the same gradient as Lovejoy. It works out at 2.3 C per doubling.”

        What I get is evidence that the changing temperature is responding to other factors besides CO₂. There are 4 clear segments (dashed lines) with different slope. Clearly the slope (rate of change) does not depend solely on CO₂. Assuming that the slope is due only to CO₂ and calculating 2.3° C per doubling from there is a clear mistake.

      • Javier, no one said there are no other factors. 1910-1940 had a solar strengthening that shows up. It was below the fitted line in 1910 because the sun was weaker, and maybe it should be again now with the sun in a similar state. Aerosol increases show up in the 1960’s going with so-called global dimming. These factors account for deviations ~0.1 C from the mean warming due to CO2 alone plus you’ll see the effects of volcanoes and El Ninos. However, given these, a transient rate of 2.3 C per doubling fits even down to the fact of 75% of the forcing change and warming being since 1950. Both trends accelerated in proportion which kept the line straight.

      • “These factors account for deviations ~0.1 C from the mean warming due to CO2 alone”

        Jim D, if you could calculate the warming due to CO₂ alone you would be getting the Nobel prize. Scientists have been discussing the ECS for the past 35 years, so no. We don’t know how much warming is due to CO₂, and therefore you don’t have a certain explanation for that graph. That graph is evidence only that a warming has taken place as CO₂ was increasing. Period.

      • Javier, you started it when you said we are doing that experiment of adding a lot of CO2 and not detecting anything. I say yes we are and it is as much as would have been expected. The graph supports that. The experiment verifies the theory. If anyone gets a Nobel prize, it would have been Arrhenius because this was all known before, and no one is surprised.

      • “you started it when you said we are doing that experiment of adding a lot of CO2 and not detecting anything.”

        And it is true. There was warming before we added the CO₂, and there is warming afterwards, and the warming rate hasn’t increased much. Ideally we should have chosen a cooling period to see if we could stop the cooling. But if we wait long enough we will get to that cooling period and then nobody will have any doubt.

      • Javier, the data is what would have been predicted down to the line you yourself fitted to it. If you’re going to wait for a cooling period to prove it is not really CO2, you have a long wait coming. As long as it keeps warming, you won’t believe it and 250 years of fitting the theory is apparently not long enough. Maybe you need another century and a doubling to even start to get an inkling it could possibly be CO2.

      • Jim D,
        you seem like one who believes he knows everything, but has never been interested in climatology. It’s boring to keep reading your learned by hard and copy paste formulations out from IPCC summaries for policymakers. These over simplified phrases have nothing to do with the big questions in climatology. There are many good and interesting postings in this forum, but no single one from you. Is boring trolling your favorite hobby?

      • Thanks for your input.

      • “the data is what would have been predicted down to the line you yourself fitted to it.”

        You’ve got to be kidding. In 1990 “Under the IPCC Business as Usual emissions of greenhouse gases the average rate of increase of global mean temperature during the next century is estimated to be 0.3°C per decade (with an uncertainty range of 0.2°C – 0.5°C)”
        IPCC FAR. 1990

        “For the next two decades, a warming of about 0.2°C per decade is projected.” [IPCC AR4 WG1 SPM, p 12]

        Warming rate since 1990 has been 0.358°C that amounts to 0.128°C per decade, according to HadCRUT 4.

        So no, the warming was greatly overestimated in the predictions.

      • “I get 0.18 C per decade.”

        Different way of calculating the trend. I divided the (13-month smoothed) warming by the time. WFT uses a least-squares trend.

    • JimD
      The Ice Ages didn’t start until after CO2 levels dropped
      Absolutely false. CO2 continues to rise for a few centuries after every single glacial inception. Remember – CO2 lags temperature in the Quaternary glacial temperature record.

      • The levels have not returned (until now) to the levels they had just before the Pleistocene when the average value was well over 300 ppm. This is the point. This is why they say maintaining somewhere above 300 ppm is enough to stop the next Ice Age.

      • maintaining high CO2 is what we need for life on earth as we know it.

        As for temperature regulation, water in all of its states is abundant, water regulates temperature, CO2 is here just to grow green stuff green for us to eat.

  12. Javier
    Thanks so much.

    Great job.

    Scott

  13. Thank you for this excellent paper. I’ve been looking for something like this for almost 30 years, from the time I first reviewed the literature on the astronomical theory of climate.
    The revision to the insolation curve by using integrated summer heat, rather than June 21 peak, makes great sense, and solves the problem of the conflicting 40,000-year and 100,000 (average)-year durations. As I recall, Hays, Imbrie, and Shackleton (1976) noted the unexpected appearance of the ~100,000-year cycle, when it was the 40,000 year obliquity cycle that was expected. That and the 6,000-year lag of ice volume to high latitude insolation produce quite a new picture of things.

    • Yes, the Hays et al., 1976 article is one of those landmark articles in science, like the Watson & Crick article on the structure of DNA.

      Imbrie et al., 1993 did a follow up on the 100 Kyr cycle that is also worth mentioning.
      Imbrie, J., et al. “On the structure and origin of major glaciation cycles 2. The 100,000-year cycle. Paleoceanography 8, 699-735.” (1993).
      I used its figure 1 in my article about the glacial cycle, because it is the only one I found that plotted the disparity between the forcing and effect of eccentricity at the right scale.

      I think that the problem that got everybody confused was the adoption of 65°N 21st June insolation as the Milankovitch factor. Despite the efforts by Peter Huybers and Chronis Tzedakis nearly every author continues the old mistaken way. There is a lot of inertia to correct consensus mistakes in science. According to Max Planck science advances one funeral at a time. Mistakes are not corrected. Their holders have to die.

  14. Yes it most plausible Javier, but then he goes on to say ….

    “This paper suggesting the Anthropocene is on the verge of inciting another Hothouse is just more fear mongering speculation attempting to demonize CO2 while ignoring all the physics that controlled how the earth evolved from a Hothouse 60 million years ago into the current Ice House today.

    What caused a hothouse back 60m ya does not have to be the only way to do it.
    Quite clearly that paper argues that via anthro CO2 build-up is another.
    Just another version of ABCD naysaying, based on comparison with an Earth that no longer exists.

    • Tony,

      We have no idea why there appears to be a 150 million years periodicity on icehouse-hothouse planet. It certainly does not appear to be CO2.


      FIG. 2 Two extraterrestrial “signals” have the same periodicity and phase as two independent terrestrial records.

      There is no recent enough precedent for the anthropogenic release of carbon. So every hypothesis about what might happen is unsupported by evidence.

      • It is CO2 because it is geology. Volcanic releases of CO2 and mountain building which leads to weathering and depletion. Geologists understand past climates in these terms.

      • I am not sure about the 150 milion years, but I know that our sun takes approximately 75 million years to travel from galactic arm to galactic arm. That cycle may combine with another cycle.

    • As has been said for generations now — greenhouse gases may indeed trigger abrupt and sometimes extreme change in the internal dynamics of the planet – at scales of moments to ages (Koutsoyiannis 2013). But this low probability event is balanced against economic, biophysical and humanitarian priorities.

      All could be improved with restoration in soils, forests and prairies of some of the 500 Gt carbon lost from terrestrial systems since the advent of agriculture (Rattan Lal) – while technology evolved over as little as decades in multiple sectors. This is the real business as usual scenario –

  15. First, that was an excellent read!

    How soon before we see your entire series in book form?

    • If you know of an editor that could be interested, let me know ;-)

      Skepticism is like poison for science books editors.

      • John A. Miller

        Stacey International is one -they published ‘Climate: The Counter Consensus’ by Prof. Robert Carter, and ‘The Hockey Stick Illusion’ by A.W. Montford. Or Clairview, which published Peter Taylor’s ‘Chill: A Reassessment of Global Warming Theory’.

        Just ask around -I’m sure these authors (and others likeminded) would be more than happy to help you.

      • Thanks for the tips.

      • John A. Miller

        Also, may I suggest ‘Winter is Coming’ as a title to your upcoming book, if you decide to write it? A little Game of Thrones pop culture reference can’t hurt.

  16. stevefitzpatrick

    Jim D,
    Antarctica started cyclical glaciation about 34 million years ago when the Drake passage opened (and gradually widened), isolating Antarctica from low latitude warmth. A permanent (non-cyclical) ice sheet has covered Antarctica for about 14 million years, when atmospheric CO2 was almost certainly well over 300 PPM (500? 600?). So melting of the Antarctic ice sheet is extremely unlikely during the brief (hundreds of years) pulse of atmospheric CO2 from ossil fuels. Earth has been in a northern glacial cycle for about 2.5 million years, although initially the cycles were only ~40,000 years long. Some researchers have suggested the closure of the isthmus of Panama near 2.5 million years ago was at least in part the cause for the start of norther hemisphere glacial cycles. In any case, absent very clear data on atmospheric CO2 from ~2.5 million years ago, it is impossible to say what level of atmospheric CO2 would stop the next northern glaciation.

    • The hothouse article suggested 450 ppm was the critical value for Antarctica and Hansen estimated it first dropped below about 450 ppm 35 million years ago. I think this current article suggests 300 ppm for the Arctic which is more prone to warming being mostly a water surface that easily clears with a warmer climate. Between 35 million and 2.5 million years CO2 did decrease for geological reasons from 450 ppm to 300 ppm. This is enough for a couple of degrees cooling with some albedo feedbacks.

      • JimD
        Just to be clear – you and your mates are saying that CO2 only, alone and unaided, changes climate temperature and nothing else has any relevance?

        For instance, the continental configuration resulting from tectonic drift, as of itself has no effect on global climate, except insofar as it changes CO2 concentrations.

        And ocean circulation also has no effect on climate, except insofar as it affects CO2 levels in the atmosphere.

        Is this indeed your position (as it would appear from your numerous statements)?

      • The sun has a lot of relevance as do volcanoes and other geological events that modulate GHG levels. So yes, for long term climate it is about the sun and the GHG level. The ocean cannot heat itself as its temperature responds rather than drives. If you have a mechanism by which the global ocean can change its mean temperature by several degrees (typical of difference between geological periods), say what it is, but convention is that it is the atmosphere and geology’s effect on it that govern multi-degree changes.

      • The ocean cannot heat itself as its temperature responds rather than drives. If you have a mechanism by which the global ocean can change its mean temperature by several degrees (typical of difference between geological periods), say what it is, but convention is that it is the atmosphere and geology’s effect on it that govern multi-degree changes.

        Yep, that is easy, in cold times the oceans cover polar oceans with sea ice and do not lose heat to the atmosphere. That conserves energy that is stored in the oceans. In warm times the sea ice cover thaws and the energy that was stored in the oceans is used for evaporation that produces snowfall that sequesters ice for the next cold period.

        That was not a hard question.

      • When it’s cold it is actually warm, and when it is warm it is actually cold. Do you see a flaw in that argument?

      • The ocean cannot heat itself as its temperature responds rather than drives.

        The sun heats the oceans. The polar oceans produce more snowfall in warm times and less snowfall in cold times and that does limit temperature bounds.

      • Currently it is supposed to be cooling in the Arctic according to Milankovitch but everything is warming and melting instead.

      • Warming and cooling emerge as more or less planetary energy storage. The direct energy effect of high NH insolation changes are negligible. Indirect responses include in albedo and warmth dependent variability in carbon dioxide and methane respiration.

        The triggers for climate shifts – when the ducks are in a row – may be multi-factorial. What it is not supposed to be as deduced from simple statements of pure causation matters not a whit either.

      • JimD
        Obliquity peaks correlate exactly with interglacials (every 2 or 3 which line up with an eccentricity peak) with a 6500 year delay. This is the time it takes solar forcing to change ocean temperature enough to move climate. The deep ocean, not just the surface. How come CO2 gets to change climate – also via insolation of the oceans – in real time, with no delay?

      • In that case it is not the ocean but a more subtle and slow sea-ice albedo effect which is very local and has a small global effect. CO2 is already 2 W/m2 global which is easily sufficient for warming the global surface as much as it has already.

  17. The precautionary principle indicates we should prepare for that eventuality as it would constitute the worst catastrophe humankind has ever faced.

    How droll!

  18. It ought to be no surprise that James Hansen says he doesn’t think there will be another glaciation in his book, Storms of My Grandchildren. In it, he also claims a future ice age could be prevented with the output of a single chlorofluorocarbon plant.

  19. I think the concept of CO2 being the control knob that controls the climate, if not originated by, was certainly popularized by Richard Alley. And I think he makes a pretty good case over geologic time. The thing about the lag between temperature and CO2 in the ice cores that really gets me, is that it lags by 800 or so freak’n years! Did the Medieval Warm Period cause the current upward slope of the Keeling curve?

    I would like to suggest that CO2, instead of being the control knob, is more like the trim wheel on an airplane. With a little extra effort, humanity may still be in control of the stick.

    • Warmer water holds less CO2, so there is that effect and it amounts to ~10 ppm per degree C. This explains what was happening to CO2 levels during the Ice Ages when they varied with ocean temperature. Of the increase of 120 ppm in the last 200 years about 10 ppm would have been from this effect, and the rest is us.

      • JIMD

        If it was us, no doubt you are giving suitable thanks to man for drastically improving your health, wealth and prosperity with his inventions during that time, as the Industrial revolution kick started the innovations of the modern age and the temperatures relented enough to make life comfortable, instead of a constant struggle

        tonyb

      • Yes, we have realized that it is now past a point of diminishing returns, turning to actual damage, where future generations gain more by transitioning away from CO2 emissions than by increasing them continuously.

      • Warmer water holds less CO2, so there is that effect and it amounts to ~10 ppm per degree C. This explains what was happening to CO2 levels during the Ice Ages when they varied with ocean temperature.

        Exceptions and Occam’s Razor.

        Exception: there was a significantly large amount of warmer water during the last glacial maximum. Further, while colder waters can contain greater amounts of CO2, ice effectively stops CO2 uptake at zero, and there was a lot of sea ice during the LGM:

        Occam’s Razor:
        Dust deposition in the polar ice indicates the glacials were much windier.
        The coefficient of CO2 mixing into the oceans, k, is a function of wind speed:

        Glacial CO2 decreased, because windier conditions mixed more of the atmospheric CO2 into the oceans.

        This is why oceanic CO2 uptake is greatest at approximately the mean jet stream latitudes:

      • Occams’s Razor. This is probably why you can’t explain why CO2 accurately follows the global temperature in the Ice Ages while I can with a simple explanation that warmer oceans hold less CO2.

      • Occams’s Razor. This is probably why you can’t explain why CO2 accurately follows the global temperature in the Ice Ages while I can with a simple explanation that warmer oceans hold less CO2.

        Windiness increased, and increased windiness means increased oceanic uptake – even with constant temperatures.

      • That’s rather wheels within wheels as an explanation. Not the simplest at all. Temperature is all you need to know.

      • @Jim D
        > we have realized that it is now past a point of diminishing returns, turning to actual damage

        “Realized” understood as the way people “realize” god. Something one’s psychology and politics won’t allow one to question. Misrepresenting the unsettled as settled.

      • The debate should be about whether we want to add hundreds of ppm to change the climate or stick as close to the past climate as possible. The first is just BAU, the second requires some realization of the situation and some effort.

      • Heureca!
        and now you claim, about 1°C warming since about 1800 is natural!
        Maybe you are right, but all your other postings are totally zero consistent with that.

      • I guess it follows naturally from adding 120 ppm CO2 to the atmosphere. Is that what you meant?

      • “The debate should be about whether we want to add hundreds of ppm to change the climate or stick as close to the past climate as possible.”

        That’s an opinion. Right now the debate is how much the climate will change if we add hundreds of ppm, because that is an answer that has not been provided by science. If the answer is that very little, why should we care?

      • We have past analogs of those climates in addition to models. It is not completely unknown. Here is just one recent example that seems to refute the idea that the tropics won’t warm.
        http://www.nessc.nl/polar-amplification/

      • “Here is just one recent example that seems to refute the idea that the tropics won’t warm.”

        Except that I won’t believe it because deep convection starts at ~ 27°C and temperatures above 30°C are very hard to reach in open oceans. So the proposed 34°C tropical SST goes against known physics.
        Those models are unreliable. Data from Eocene sirenian tooth enamel indicates otherwise:
        Clementz, M. T., & Sewall, J. O. (2011). Latitudinal gradients in greenhouse seawater δ18O: evidence from Eocene sirenian tooth enamel. Science, 332(6028), 455-458.

        “Our results, thus, suggest that the Eocene tropics were not only wetter but may have been cooler than foraminiferal δ¹⁸O data have previously indicated.”

        “It is not completely unknown.”

        As you can see our knowledge might be wrong.

      • You may have to revise your view in the light of the actual data. Here is another one.
        https://websites.pmc.ucsc.edu/~jzachos/pubs/Tierney_etal_2017_NatGeosci.pdf

      • “You may have to revise your view in the light of the actual data. Here is another one.”

        You’ve got to be kidding or you didn’t read your own cite. The letter amounts to a discussion about the uncertainties with a paleotemperature proxy between two groups. And it says:

        “The equable climate problem – the lingering mismatch between proxy data and model simulations – cannot be put to rest”

        So you are pointing me towards a discussion on the reliability of a proxy on the background of model-data disagreement.

        I can tell you I am not revising my view based on that [lack of] evidence.

      • You can search for recent work on Eocene SSTs as well. Everything I can find has temperatures well in excess of 30 C in the tropics. This doesn’t seem to be contended.
        https://people.ucsc.edu/~jzachos/migrated/eart290t/Readings/Tindall_etal_2011_EPSL.pdf
        http://www.pnas.org/content/early/2018/01/12/1714744115
        https://www.nap.edu/read/13111/chapter/5#35

      • Well, that is because it is from Zachos as well. You are looking at the output from the same author.

        The reference I put indicated that paleotemperature proxies might be biased because the world was a lot wetter. If this is correct then it doesn’t matter how many articles say paleotemperature proxies indicate very warm tropics. They would all suffer the same bias.

        The physics of deep convection is quite well known. Some authors claim deep convection took place at higher temperatures in the distant past, but they have failed to show the evidence for such unphysical claim.

        Sud, Y. C., Walker, G. K., & Lau, K. M. (1999). Mechanisms regulating sea‐surface temperatures and deep convection in the tropics. Geophysical research letters, 26(8), 1019-1022.

        “Scientific basis for the emergence of deep convection in the tropics at or above 28°C sea‐surface temperature (SST), and its proximity to the highest observed SST of about 30°C, is explained from first principles of moist convection and TOGA‐COARE data. Our calculations show that SST of 28–29°C is needed for charging the cloud‐base airmass with the required moist static energy for clouds to reach the upper troposphere (i.e., 200 hPa). Besides reducing solar irradiation by cloud‐cover, moist convection also produces cool and dry downdrafts, which promote oceanic cooling by increased sensible and latent heat fluxes at the surface. Consequently, the tropical ocean seesaws between the states of net energy absorber before, and net energy supplier after, the deep moist convection, which causes the SST to vacillate between 28° and 30°C. While dynamics of the large‐scale circulation embodying the easterly waves and Madden‐Julian Oscillations (MJOs) modulate moist convection, we show that the quasi‐stationary vertical profile of moist static energy of the tropics is the ultimate cause of the upper limit on tropical SSTs.”
        https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999GL900197

        The planet has many ways to regulate temperature. Otherwise we would not be here discussing this.

      • I think you have imprinted on the Scotese schematic and no paleo evidence is going to change your mind. You should look at more recent work with an open mind.

      • You are entitled to your thoughts. But thinking on what other people might think is prone to error. I have no problem in changing my views when evidence demands it. I have done so many times before and will do many times in the future. A few years ago I was convinced anthropogenic warming was a very serious problem. I changed my mind when I researched the evidence. I would have no problem changing my mind on Eocene tropical temperatures if good evidence is produced that SST in the open ocean can go significantly above 30°C without triggering deep convection.

      • Jim D | August 18, 2018 at 11:54 am | “We have past analogs of those climates in addition to models. It is not completely unknown. Here is just one recent example that seems to refute the idea that the tropics won’t warm.
        http://www.nessc.nl/polar-amplification/

        WR: Jim D, we are often fooled by the interpretation (!) of proxies. You can give them any temperature. Absolute temperatures need to be coupled to for example plant leaves that give us a correct idea of past temperatures and other climatological circumstances. As mentioned in an earlier comment on this site (https://judithcurry.com/2018/08/08/hothouse-earth/#comment-878062):

        Fossilized plant leaves give evidence for temperatures during a Hot House State. For example during the Maastrichtian. See PDF here: https://www.researchgate.net/publication/249550697_The_Maastrichtian_Late_Cretaceous_climate_in_the_Northern_Hemisphere
        Figure 2 of the article shows the interesting graphic about temperatures in the Maastrichtian: dashed line.

        Remark that plant leaves tell that during the Maastrichtian Hothouse the tropical temperatures were lower (!) than present. Which is possible when you take a reversed oceanic circulation in consideration.

      • My link was about the Eocene ocean temperatures when the continents and oceans were a little more similar to now. This is a more useful analog.

      • The debate is : How Much Warming, How Soon ?

        Not an easy question since can we still cannot actually separately measure the various climate forces – one of which is AGW – and so are reduced to modelling speculation. Compounded by the trustworthiness of government climate science increasingly in question.

        If the main non-fossil energy sources were anywhere near viable, then switching to them wouldn’t matter too much, regardless of whether CAGW and/or a tipping point kicks in in decades, centuries or millennia. But with the main ones (wind and solar – with their unreliable supply needing expensive backup), still having a full cost 2-3 times that of fossil energy, it certainly does matter.

        So : Is the modelling reliable and certain enough to warrant the certainty of ruinous cuts in living standards for everyone on the planet ?

        Or would it be better to see if the engineers of future generations can develop viable large-scale alternative energy before>/b> the public starts using them ?

    • My understanding is that CO2 measurements come from bubbles whereas temperature proxies are from the ice itself. The age of the two is different as air can exchange into the firn long after the original snow precipitated.

      I believe the oft-quoted 800 year lag number comes from Monnin (2001):
      http://science.sciencemag.org/content/291/5501/112

      Note they actually conclude 800+/-600 years, so considerable uncertainty.

      More recent research, Parrenin (2013), has brought this into question, and concludes “Changes in aCO2 and AT were synchronous… …within uncertainties.”, those uncertainties being within a hundred years or so.

      http://science.sciencemag.org/content/339/6123/1060

      I don’t know what is currently regarded as state of the art in this respect.

    • A good case? At the highest CO2 levels warming stops and it changes to cooling. At the lowest levels the cooling stops and it changes to warming.

      • I don’t agree with Potholer on everthing, but in the first seven minutes of his latest climate video, he makes a very good case that the seemingly unrelated CO2 levels and temperatures over geologic time can be reconciled by factoring in the sun’s thought to be increasing brightness:

      • Canman, there are alternative hypotheses, like the effect of the biosphere in maintaining planetary habitability conditions.

        I have always thought that it would be a cosmic coincidence that the Sun brightness increased for billions of years at a rate that was carefully matched by the decrease in greenhouse gases, unless a connection can be established between both.

        Another alternative explanation is that the water molecule does the trick of matching the changes in solar output, while the GHGs go along for the changing temperature ride.

      • Javier, I’m sure there are other hypotheses, but are they as well argued? The increasing sun brightness along with the period of mountain weathering in that video are very convincing. I would have to wonder about a biological hypothesis that takes place over hundreds of millions of years. It seems like there would be a lot of contingencies. I would even go so far as to say that Monkton and Moore using that graph without mentioning increasing sun brightness is a bit disingenuous.

      • “I’m sure there are other hypotheses, but are they as well argued?”

        That is a subjective matter. They are discussed in scientific articles and they all have proponents and detractors. No hypothesis has strong evidence, but in the current times the GHG hypothesis is more popular.

        I’ll copy to you an illustrative part from an article written by Colin Goldblatt in 2017 and available in Arxiv.
        Atmospheric evolution
        https://arxiv.org/pdf/1710.10557

        “The most remarkable observation of Earth history is the continual lineage of a single genesis of life spanning four billion years. Indeed, deep in the Archean record, the evidence for life is in general commensurate with the maximum that could be expected, given the preservation of the sedimentary record [Nisbet and Sleep, 2001]. Life requires temperature to be in a somewhat limited range, by necessity maintained for the entire length of the record. Three alternate explanations for this long-term homeostasis may be offered: luck, abiological regulation, or an explanation based on the action of life itself.

        Luck is a somewhat irrefutable option. Further disentanglement becomes difficult due to observer bias: our position as observers of this history is contingent on history itself: conditions must have been such that the long evolution to organisms with the science of geology and printing presses to make encyclopaedia could occur. Our ability to pose the question requires continual habitability, so the observation itself is bias; such is the weak anthropic principle [Watson, 1999].

        Abiological regulation is supported by evidence of chemical feedback processes contributing to climate regulation, with the negative feedback on temperature in the silicate weathering and carbonate deposition cycle [Walker et al., 1981] the seminal contribution. A purely abiological model would have these geochemical mechanisms regulate temperature to a level at which life is plausible, allowing life to adapt to the environment. There is little doubt that this represents part of the explanation, but the entanglement of life in these geochemical mechanisms, enhancing both weathering and carbonate deposition, makes isolation to only abiological processes rather difficult. Life and non-life processes are deeply entwined on Earth.

        Biological control was a part of Vernadsky’s original enunciation of the biosphere. Vernadsky [1926] described the biosphere as composing both living and non-living parts, the atmosphere being the type example of the latter. He saw life as the dominant geological force, and that the planetary scale influence of life has increased with time—i.e. that the biota controlled the atmospheric composition, and that the control has become stronger has evolved to increasing complexity and dominance. Written in Russian and French, Vernadsky’s original and visionary work on the biosphere was largely lost to anglophone science until David Langmuir’s 1970’s translation circulated in the late twentieth century, and was eventually published in 1998 [but see also Vernadsky, 1945].

        In western science, biological regulation was proposed by Lovelock [1972] with the Gaia hypothesis: “homoeostasis by and for the biosphere”. A modern statement of this is “Organisms and their environment evolve as a single, self-regulating system” [Lovelock, 2003]. Thus, not only are organisms selected for their environmental fitness, but are selected for their ability to modify the environment in beneficial ways [Lenton, 1998].

        It is plain that biology is deeply and intimately involved in the control of Earth’s atmospheric composition. The question of whether this has directionality—whether the biota regulates—is probably the single most important open question in the study of atmospheric evolution of Earth.”

        As you see this is an open question, and it is unlikely that the pure CO2 control of Earth’s temperature could be the answer. Indeed an explanation that puts CO2 as a secondary important factor is perfectly viable.

      • Biology certainly has some effects. I take it the oxygen in the atmosphere came from photosynthesis. I once remember a commenter at WUWT saying that if a lot of CO2 hadn’t been sequestered in microscopic sea shells, the Earth might have had the same fate as Venus. Perhaps this is the answer to Fermi’s paradox.

      • Water and water as ice and water vapor regulates the climate and temperature of earth, it does not matter what else matters, the water and ice and water vapor cycles can deal with whatever is second and third and all of the other stuff together.

      • Canman
        “Potholer” is a good name for your colleague. Apologetics for warming alarmism is all about skilfully climbing out of holes. Palaeo data utterly refuting CO2 driving climate? What could be a more satisfying challenge?

      • The “dim sun” is the most laughable fig leaf in the whole litany of warmist palaeo-apologetics.

      • Say what you want about the dim sun theory, it’s a very coherent explanation. The dimming sun should be a feature of astrophysics.

  20. Earth’s orbital parameters would likely be in harmonic agreement with long term Jovian cycles, which would be ordering long term cycles of solar magnetic activity levels, and solar wind strength.

  21. Interglacial Length.
    A given order of Jovian syzygies will only be typically maintained for 2 to 4 grand synodic periods of 4627 years before breaking down and not returning for tens of thousands of years. Interglacial length could be related to multiples this period, and its half period, which can be at 2224 years or 2403 years. (e.g. from 1306, to 3530 or 3709 AD)
    https://www.fourmilab.ch/cgi-bin/Solar
    That yields figures such as 11,478 years, 13,881 years, 16,105 years, 23,135 years.

    • Since the inter-glacial period is suppose to last about 22 thousand years I would guess that 11,478 would be closest sine the Holocene is already ove 10,000 years?

  22. @Javier

    Very nice and interesting analysis, thanks!
    How about this one, though?… it gives ome credit to dust deposition on polar ice as a starter of deglaciations:

    “Without these dust effects, glacial temperature and atmospheric CO2 concentrations would have been much more stable at higher, intermediate glacial levels.”

    http://www.pnas.org/content/early/2018/02/06/1708174115

    “In and out of glacial extremes by way of dust−climate feedbacks”, PNAS 2018

    • Thank you Roberto. It is always complicated to distinguish between cause and effect, between driving force and recruited feedback.

      The astronomical forcing is the only one that is externally predetermined to occur at certain times and we find interglacials occurring at some of those times. Nothing else can explain that distribution.

      Dust levels are a consequence of the deep glacial state that is accompanied by a very cold very dry world, with very little CO2. Without doubt dust levels are a feedback that contributes to the instability of large ice sheets, but we can only guess how important is that contribution.

      But for the interglacials that start from mild or full glacial conditions, dust levels are a lot less important.

      Then the coincidence between dust levels and interglacials is not as good as proponents of the hypothesis indicate.

      There are periods when there was a lot of dust and no interglacial was produced and periods with a lot less dust that did produce an interglacial.

      The problems start to show when you look at the details:

      Quite often terminations do not coincide with the time of high dust, and the difference amounts to many thousands of years. That dust was buried deep and moved around in the ice.

      In any case this has been discussed several times in the blog. For example:

      https://judithcurry.com/2016/10/02/dust-deposition-on-ice-sheets-a-mechanism-for-termination-of-ice-ages/

      So to me dust is another one of the important feedbacks that contribute to ice sheet instability and fast glacial termination, together with albedo, and low sea levels.

  23. There is a seeming paradox at the core of the ~100ky glacial problem following on from the mid Pleistocene transition. Why are there cold transitions when CO2 and warmth are greatest and warm transitions when they are least?

    “Why do ice ages occur? Surprisingly, even after many decades of paleoclimatic research we simply do not know for sure. Most scientists will agree that ice age cycles have something to do with precession: the slow wobble of the axis of the Earth. The ancient Egyptians and Greeks knew of precession and called it the Great Year, because it gives warm and cool seasons over its approximate 23,000-year cycle. But there is a problem with invoking the Great Year as the regulator of ice ages, because we should really get an interglacial warming every 23,000 years or so. And we don’t – they only happen every fourth or fifth Great Year.

    But why should the global climate give a selective response to orbital warming and cooling? (Called ‘forcing’ in the climate trade.) This is one of the great unknowns of modern science. Many suggestions have been made, from interstellar dust blocking sunlight to the weight of the ice sheets depressing the lithosphere and warming the ice. And yet all of these theories share one thing in common – they stretch credulity. The only thing that is certain, is that the science is not settled in this area of climate research.” https://climatechangedispatch.com/new-study-co2-is-only-a-bit-player-in-the-drama-of-world-climate.

    That it happens seems indisputable.

    • Most scientists will agree that ice age cycles have something to do with precession

      And they would be wrong, as I have showed. Huybers, Tzedakis, Crucifix, and others are the ones that are correct. The cycle is a lot more dependent on obliquity than on precession.

      • Javier’s unerring command of truth in these things is risible. But the key point was the seeming paradox of cold states emerging from warm and vice versa.

      • No paradox. Natural oscillations arise in complex systems subject to periodic forcings and subjected to reversible feedbacks.

      • So when it is warm with high CO2 – from bioenergetics with a very minor ocean outgassing term – the planet is plunged into a cold state as a result of dynamic planetary responses. What are the geophysics? It appears something to do with high northern summer insolation and AMOC. The latter suggests involvement of the polar annular mode in modulating Atlantic flows.

        The idea of a trigger for runaway ice sheet feedbacks might include a number of factors and is incompatible with simple cause and effect. The system shifts when the ducks are in a row – and the change in climate state emerges almost entirely – up to the 20th century – from the planetary response.

        Simply because you have a meme – in a language that is not that of dynamically complex, deterministically chaotic systems – doesn’t mean that you understand the mechanisms and can hand wave away the seeming paradox of Pleistocene glacials and interglacials. .

      • “the planet is plunged into a cold state as a result of dynamic planetary responses.”

        That is not correct. The default state during the Mid to Late Pleistocene is glaciated and the planet slowly slides back to it as soon as the conditions that made the interglacial possible disappear. I see you didn’t read or understood the article. Nothing triggers or forces the glaciation.

        “doesn’t mean that you understand the mechanisms and can hand wave away the seeming paradox of Pleistocene glacials and interglacials.”

        It is a paradox to you. Not to others. Read Peter Huybers articles and you might learn something about the glacial cycle.

      • https://judithcurry.com/2018/08/14/nature-unbound-x-the-next-glaciation/#comment-878548

        The conditions that cause interglacials – btw – are ice sheet retreat and warm state CO2 biokinetics.

      • “The conditions that cause interglacials – btw – are ice sheet retreat and warm state CO2 biokinetics.”

        So you say.

      • Of course I meant low NH summer insolation.

      • The idea of a trigger for runaway ice sheet feedbacks might include a number of factors and is incompatible with simple cause and effect.

        Ice sheets are caused by ice, ice on land is caused by snowfall, it snows more when oceans are thawed, ice sheets deplete when it is not snowing, ice sheets retreat when ice is depleted. This is not a process or cycle that has no kind of runaway.

      • This I wrote does not say what I meant.
        This is not a process or cycle that has no kind of runaway.

        This process or cycle has no runaway.

      • Runaway planetary responses are at the core of climate dynamics. But they seem to have limit states and – I presume – ergodicity.

        “Technically, an abrupt climate change occurs when the climate system is forced to cross some threshold, triggering a transition to a new state at a rate determined by the climate system itself and faster than the cause. Chaotic processes in the climate system may allow the cause of such an abrupt climate change to be undetectably small.”
        https://www.nap.edu/read/10136/chapter/3#14

        The key is that it can be much quicker and far bigger than change in external control variables. And if you are not talking the language of dynamical complexity – you are not speaking the right language for Earth system analysis or discussion.

      • “an abrupt climate change occurs when the climate system is forced to cross some threshold”

        Glaciations aren’t abrupt. They take ~15,000 years after ~ 6000 years of cooling. It is a long progressive process.

        “you are not speaking the right language”

        The language is only helping you disguise your lack of understanding.

      • The system – involving albedo and CO2 biokinetics – evolves at it own pace through fluid dynamics. Fluid dynamics says how and why the system evolves as it does with regimes and shifts.

        ‘The climate system has jumped from one mode of operation to another in the past. We are trying to understand how the earth’s climate system is engineered, so we can understand what it takes to trigger mode switches. Until we do, we cannot make good predictions about future climate change… Over the last several hundred thousand years, climate change has come mainly in discrete jumps that appear to be related to changes in the mode of thermohaline circulation. We place strong emphasis on using isotopes as a means to understand physical mixing and chemical cycling in the ocean, and the climate history as recorded in marine sediments.” Wally Broecker

        The fundamental deterministically chaotic mode of operation of the Earth system is not open for argument.

      • Lots of words for not saying anything, and Wallace Broecker being wrong as usual. There is no solid evidence that changes in the thermohaline circulation have affected significantly the astronomically ruled glacial cycle over the last several hundred thousand years. That’s the problem with being an oceanographer. All the problems look like currents.

      • The problem with dogmatists like Javier is confirmation bias. He rejects far too much science far too easily because it doesn’t match a narrative. And then discussion is curmudgeonly truncated. It’s a problem with sophomoric undergraduates.

      • That’s particularly funny from somebody that says that the energy changes are Earth albedo and CO2 biokinetics. There’s no possible discussion with somebody like you that immediately turns contemptuous and insulting.

      • Every discussion turns to the ‘correct’ interpretation and what I don’t know.

      • The energy changes are Earth albedo and temperature related CO2 biokinetics. These dynamic internal responses are much larger and faster than the original NH summer insolation changes and are thus seen as internal dynamics.

        I hope you come back when you get both scientific humility and a clue.

      • “I hope you come back when you get both scientific humility and a clue.”

        Apply that to yourself.

      • The response to Javier makes more sense a little higher in the thread.

      • “Technically, an abrupt climate change occurs when the climate system is forced to cross some threshold, triggering a transition to a new state at a rate determined by the climate system itself and faster than the cause.

        The threshold is simple, when oceans are cold the surface in Polar Regions are covered with sea ice and evaporation and snowfall is suppressed. When oceans are warm the surface in Polar Regions are thawed and evaporation and snowfall is huge. This causes cycles that do bound the temperature and sea level.

        Thus, a threshold! Sea ice forms and thaws quickly, depending on ocean temperatures.

      • Continue to ignore this and you will never understand ice cycles.

        it snows more when oceans are warm and thawed and it gets cold after

        it snows less when oceans are cold and frozen and it gets warm after

        ice core data tells us this.

      • “it snows more when oceans are warm and thawed and it gets cold after”

        You repeat this thousands of times as if it explained anything.

        The humidity needs to be transported poleward and the main factor is equator-to-pole temperature gradient, that depends on the insolation gradient, that depends on obliquity. The surface temperature near the equator changes very little during the glacial cycle. The temperature changes increase with latitude. Check Scotese:

      • I repeat this thousands of times because it explains everything.

      • The humidity needs to be transported poleward

        Oceans are transported poleward, in warm times the sea ice thaws and evaporation and snowfall occurs there. In cold times sea ice forms and blocks evaporation and snowfall does not occur there.

      • Javier,
        What I understand Scotese’s chart (and the text, and other studies as well)) shows is that when the planet was warmer the gradient from equator to poles was very much flatter. The tropics were only slightly warmer than now, but high latitudes were much warmer. There are many reasons including: where the tectonics plates are located, ocean gateways, allowing more flow of heat from tropics to high latitudes, better insulation with more CO2 in the atmosphere, the three main circulatory systems in each hemisphere coalesce into two then one – these occur as abrupt climate changes leading to warmer (better) high latitudes.

        Eric Barron (UCAR) had an excellent web site with an interesting chart showing equator to poles temperature gradients during in the Cretaceous. it showed the gradients were much flatter than what the GCM are projecting . – it shows much the same for the Cretaceous as the Scotese chart you posted. It shows very little change in the tropics but very large change at high latitude – crocodiles and palm trees living happily at the poles.

        What’s to fear from global warming. It’s all upside and little downside.

      • Peter Lang | August 18, 2018 at 9:04 am

        Peter Lang, to understand the Scotese graphic it is important to understand that a reversed (!) circulation system must have played a main role. To understand the oceans it is important to understand which water is welling down and where this happens/happened. Further explained in this post: https://wattsupwiththat.com/2018/06/15/how-the-earth-became-a-hothouse-by-h2o/

        Who understands the Hothouse system will more easily understand our Ice House system, characterized by ice cold [deep] oceans. The surface layer of the Earth (mainly oceans) cooled that much, that even relatively slight changes in orbit are causing huge climatic effects. With those very cold oceans only the most favourable orbital circumstances are good enough to bring the Earth back (for a while) in the warmer pre-Pleistocene system, characterized by a much higher stability than the one we can expect as soon as real cooling (LIA or colder) will announce itself. Warm is stable, cold is unstable: https://wattsupwiththat.com/2017/08/01/warm-is-stable-cold-is-change/

        Javier and Renee Hannon have done a great job in analyzing the orbital consequences for our Ice House age. For Renee Hannon see: https://wattsupwiththat.com/2018/03/28/modern-warming-climate-variablity-or-climate-change/

      • Wim R,

        Thank you. Good comments. I agree with all of them.

    • Ice ages occur because it snows too much and too much ice causes ice ages.

      It snows too much in warmest times when oceans are deep and warm. Energy and Moisture from the Oceans is used to produce snowfall.

    • Consensus Climate Scientists, Lukewarm Climate Scientists, Most Skeptic Climate Scientists, make oceans cold and use moisture and energy from cold frozen oceans to produce snowfall and cause an ice age.

      Mother Nature, covers cold oceans with sea ice, warms the tropical oceans with sunshine, continues the warming until enough energy and water is in the oceans. Then Mother Nature thaws the sea ice and produces snowfall using the moisture and energy in the deep warm oceans to produce snowfall in cold places, the cold places expand and then snowfall can be produced and dumped on places that are now cold enough.

      This story is told by the ice core data.

      • Mother Nature uses simple basic science and easy to understand methods.

      • Ice sheet growth is the difference between glacials and interglacials – but why don’t we then get random glacials when it is hot enough? The not so secret is NH ice sheet survival involving both insolation changes – from multiple factors far beyond the range of Tim Palmer’s little magnetic oscillator – and oceanic heat transport. This changes as shifts between multiple states as seen in the ice core record. Then there are nonlinear spikes in dust at cold and low CO2 states that might trigger rapid deglaciation.

  24. If global warming gets too much for you – we could try dumping rock in the lower passes of the Greenland-Scotland ridge to freeze the Bering Sea. The modelling seems simple enough. Ocean dynamics forced by flows across the ridge – although nonlinear planetary dynamics might give pause. If only I were a young engineer again – but I do know a guy..

    https://www.marum.de/en/Research/RACE/WP-1.3-Overflow-variability-at-the-Greenland-Scotland-Ridge-and-along-the-spreading-pathways-in-t…html

    To the tune of Bob Dylan’s ‘Forever Young’.

  25. Javier, very interesting, thanks!

    For me, figure 132 has a very interesting line. It is the Greenland temperature Anomaly, shown by h). This line has a warm uptick of Greenland temperatures just before the glacial inception at around 120,000 years BP. It reminds me to our present warm period, possibly somewhere at the end of our Holocene. At the time shown in the graphic, 120,000 years BP, human beings did not play any role at all, so this serious uptick had a completely natural cause. A considerable warm uptick at the end of the previous Interglacial.

    The Antarctic Temperature Anomaly g) shows a rise in temperature before the Northern Hemisphere (here: Greenland) warmed and shows also that the Southern Hemisphere’s cooling started earlier. Our present warming is something of the higher latitudes on the Northern Hemisphere, while the Southern Hemisphere stays far behind.

    Present obliquity and present high insolation curves already show a down going trend since thousands of years. The oceans are already cooling since some thousands of years as shown by Rosenthal et al. http://notrickszone.com/2016/12/12/another-new-paper-reveals-no-discernible-human-or-co2-influence-on-global-ocean-temperatures-climate/

    I would not be surprised when the next glacial inception would be ‘close’, in the range of ‘between now and 2000-3000 years’. All we need is some more wind on the right/wrong places that will bring up more of the deep ice cold oceans waters to the surface. Down in the ocean there is enough cooling capacity to bring us ten times into a next glacial.

    • Yes, the the temperature curves of the Eemian are quite interesting, I agree. Other interglacials show enhanced climate instability towards glacial inception (GI) in Antarctic records. This means more profound cooling and more intense warming. What the Holocene has experienced in the LIA and post-LIA warming can be construed as pre-GI instability, even if our increase in GHG has enhanced the present warming.

      I fear that unless the consensus hypothesis is correct, we are among the lucky ones living the Indian Summer of the Holocene.

      • Yes Javier, I agree with you about LIA warming and present warming as possible pre-GI instability as well. We should indeed enjoy living in the Indian Summer of the Holocene and have an eye on / prepare on what to do in case of eventual cooling.

        I am not afraid of an eventual warming: no one showed a way to heat up the oceans, necessary to get higher temperatures over 71% of the Earth. But cooling the oceans is simple. Where I live (Holland) instability in weather most times is associated with a lot of wind. Some Arctic cooling could raise instability, at least in the northern oceans on the Northern Hemisphere.

        But personally I prefer the slight warming we experience now.

    • Indeed according to Weaver et al 2003 (see fig 5) inception of the Holocene began in Antarctica, as much as 20,000 years ago, while Greenland began warming only ~15,000 years ago. If Antarctica led glacial termination, it would not be surprising if it led (is leading) glacial inception. It’s odd that no-one ever talks about the huge more or less permanent cold anomaly of SSTs around Antarctica.

      http://home.sandiego.edu/~sgray/MARS350/deglaciation.pdf



  26. A 50,000 year climate forecast– sure, but… what’s the weather going to be?


  27. Cycle 24 featuring the sun as a big no-show is now ove– what humanity is in store is anyone’s guess but we could be staring down the solar barrel of a bitter, relentless and loathsome cold extending the duration of a human lifetime, or more… it’s happened before! What’s more interesting than what’ll be happening 100 years from now is what Cycle 25 will bring.

    The figures suggest that we could even be heading for a mini ice age to rival the 70-year temperature drop that saw frost fairs held on the Thames in the 17th Century. ~Daily Mail (2012)

  28. interzonkomizar

    Hi Javier. Excellent. The final piece of the puzzle fits. Thank you for proposing logical starting and ending criteria for interglacials.
    .
    .
    Sandy,
    Minister of Future

  29. Javier
    This has been an outstanding series of posts covering a vast area of historical climate drivers few would be prepared to tackle. Thank you, and Judy for hosting it. What’s next ?
    Regards

    • I’m glad you liked it ozonebust. I don’t have plans or projects for any continuation. But If I get ideas on alternative views to climate issues I might write things that if I think have sufficient quality I might submit to Judith for consideration. So I do not discard some future article, but occasionally, not on a regular basis.

  30. Geoff Sherrington

    Javier,
    Thank you for the depth of your scholarship and the highlighting of some potential errors of significance in past work.
    The Establishment thoughts on the severity of future golbal temperatures depends in a large part on estimates of the “residence time” (or words of similar meaning) of the airborne fraction of CO2. You write that “IPCC confidence comes essentially from David Archer’s studies, that since 1997 have become the authority of reference.” So, I revisited some of Archer’s work and note this video https://www.youtube.com/watch?v=sRDjsuA0oJc from which I snipped this graph http://www.geoffstuff.com/Archer_CO2.jpg
    Archer uses an analogy to explain that there are stages over time for the removal of CO2 from the air, with some slow stages taking many thousands of years. The analogy is to gross radioactive decay of a material having several isotopes of different half life.
    That analogy is false and by extension, so are estimates for very long removal of the airborne CO2 fraction of the globe. The long, slow tail over time shown in his cartoon graph does not exist, because the life of CO2 is governed by the fastest of the removal processes. Only if the fastest one becomes saturated does the next fastest process cut in and sequentially prevent the long tail. The radioactive material analogy fails because the different isotopes have separate, independent chemistry and physics, while airborne CO2 (apart from some non-relevant isotopic composition) is one material with one set of chemical and physical properties. Geoff.

  31. Javier wrote:
    glacial inception takes place earlier, at 120 Kyr BP, when both Antarctica and Greenland initiate their cooling

    Look at chart 13. The ice accumulation increases as temperature increases.
    https://www.dropbox.com/s/8sb2yq2sk3ih7t9/Alex%20Pope%20-%20Ice%20on%20Land%20-%202017.ppsx?dl=0#

    The glacial inception takes place earlier, at 140 Kyr BP, when snowfall increases enough to cause both Antarctica and Greenland to increase ice volume. Cooling starts later after ice volume is enough to halt any retreat and initiate an advance. When it starts getting colder, that is because the ice age is already started producing more ice with snowfall. Snowfall happens the most when oceans that circulate in Polar Regions are deep enough and warm enough to promote evaporation. Ice ages are started by warm times, when there can be enough snowfall. Study and understand ice core data.

    • The plots are of ice core data, temperature and ice accumulation.

    • Ice ages are caused by ice. Ice is placed on the ground by snowfall. Snowfall comes from moisture and energy from warm thawed oceans. Only deep warm thawed oceans can cause ice ages.

      This is simple, Occam Razor simple, facts of nature.

      We did not start the next major ice age because the oceans did not get deep enough and warm enough when we came out of the last major ice age.

      The Holocene is the new normal.

  32. One major problem:

    About 14700 B.P. there was a rapid warming that almost increased the world mean temperatures up to a level that matched the Holocene optimum. This sharp temperature increase took place over a period of about 200 years. Presumably, the CO2 levels would have gone up very sharply as well, in response to the rapid increase in ocean temperatures.

    The world mean temperatures dropped over the next 1600 years until there was a rapid drop at the start of the Younger Drayas. There were one or two rapid drops in temperature in this 1600 year period between 14,500 and 12,900 B.P. One was called the Older Drayas but for the most part the drop in temperature was gradual.

    If there were elevated levels of CO2 around 14,500 B.P. (or not long after) that approached the modern pre-industrial levels of ~ 280 ppm, how did the Earth cool gradually over a period of ~ 1600 years [Note that this cooling had little or nothing to do with the rapid cooling at the start of the Younge Drayas around 12900 B.P.]?

    Most of the post interglacial coolings take 10,000 to 15,000 years but this one only took 1600 years. Surely this is not possible if the normal slow cooling from the orbital forcing is in place.

    • “The world mean temperatures dropped over the next 1600 years until there was a rapid drop at the start of the Younger Drayas.”

      Ian, how do you get the world mean temperature 14,000 years ago? I am not aware of any reconstruction that goes that far back, except the Shakun et al., 2012 that has very low resolution and does not show those features.

      If you are talking about Central Greenland records you cannot assume that changes there represent global changes. Furthermore, the profile of the Greenland changes you mention is not different from the profile of other greenlandic abrupt changes known as Dansgaard-Oeschger events. Rapid warming followed by slow temperature decline and then rapid return to cold conditions, rinse and repeat. It appears to have been a phenomenon specific of the North Atlantic region that affected the rest of the planet through teleconnections and the bipolar see-saw.

      • If you are talking about Central Greenland records you cannot assume that changes there represent global changes

        We do not have a long term temperature record for Central Greenland. Ice Core Records are a record of Ocean temperatures where the water came from that produced the snowfall. Ocean temperatures do represent ocean changes which do represent global changes.

    • Meltwater from the ice sheets was trapped on land. Meltwater dumps into the ocean causes cold spikes and mixing with ocean water allowed rapid warming. No outside influence could have caused the temperature spikes, you don’t change the ocean temperature quickly unless you dump ice water into it. There are records of the meltwater dumps. People don’t try to correlate the temperature spikes with meltwater dumps. That is their own fault.

  33. Mother Nature has been taking care of climate stuff for billions of years.

    Try to understand how she worked the problem and understand it very well before you second guess her and start trying to take over by messing up her atmosphere or anything else.

    In the same paper, people write about what they don’t understand and then they write about what they want to do to do to fix the problems. They don’t even have a clue if there is a problem.

  34. Javier wrote:

    Each interglacial is different. They all have different astronomical signatures, different initial conditions, different evolution, and are subjected to non-linear chaotic climate unpredictability.

    Each interglacial is the same. They all have cold times when it does not snow enough and it gets warm after that. The initial conditions are the same, the evolution of the cycles are the same. It always warms after a cold period. Temperatures and timing are a little different, but the data plots of the different cycles are very similar.

  35. Barn E. Rubble

    RE: popesclimatetheory | August 16, 2018 at 6:01 pm |
    “The initial conditions are the same, the evolution of the cycles are the same.”

    It was my understanding that ice ages were the result of when the Earth’s orbit was furthest from the sun, coinciding with the furthest northern axis tilt. Perhaps there’s more to it . . .

    • Don’t let anyone snow you, ice ages are when there is too much ice.
      Snowfall happens the most when the oceans are the deepest and the warmest and the most thawed. Ice age periods always have followed those warmest periods.

      That tilt stuff does resonate with the internal ice cycles, but the biggest help is when the warm tilt cycle helps provide the energy to power the snowfall. Then when the tilt causes colder, the ice is already advancing and also causing colder. The tilt always got all the credit, but we really know an ice age is when there is more ice. That can only happen if it gets warm enough to produce enough snowfall.

  36. Javier,
    You are correct in saying the temperature changes that I described were not applicable to the whole globe. However, your own plot shows that they were applicable to the 1/4 of the surface area of the Earth that is north of 30 degrees N.

    Can you explain to me how he CO2/H20 greenhouse gas amplification feedback can continue to operate in the Southern Hemisphere between 14500 and 12900 B.P. but not have any effect in the northern quarter of the Earth’s surface? You would have to have massive cooling processes operating in the Northern hemisphere in order to overcome the strong warming effects of the elevated CO2.

    • Easy, CO2 does not matter to temperature.

    • Ian,

      The effect of GHGs on glacial termination is accepted to be a second order effect by nearly all scientists. It can be easily defended that only 1/3 of the warming can come from GHGs. In my opinion it is probably even less. It has been shown that about half of the CO₂ increase must come from enhanced volcanic activity due to the response of the crust to the “sudden” melting of the ice sheets, so that means it is produced after the melting, not before.

      I wrote about it here:
      https://wattsupwiththat.com/2018/05/10/the-effect-of-volcanoes-on-climate-and-climate-on-volcanoes/

      So in essence climate cannot be ruled by GHGs at glacial terminations. It has been shown since the early 1970’s that Milankovitch does that trick.

      • It has been shown since the early 1970’s that Milankovitch does that trick.

        Ice ages are caused by ice, ice ages end when the ice has thawed, Milankovitch does correlate sometimes.

        An ice chest stays cold while ice is thawing, it warms after ice is depleted.

        It works the same way on earth. Earth is colder when more ice is thawing and warmer when less ice is thawing. Ice is cause and not result. It snows more in warmest times, that is when the most ice can be produced. It snows less in coldest times, that is when the most ice is thawing and depleting.

  37. Here’s another question Javier,

    Why do the D-O events effectively get muted during the top of the interglacials? [Note: I am not saying that the D-O events completely dissappear] They only appear to be prominent in the depths of the ice-ages and at the ramping up stage to the start of interglacials.

    • They are caused by meltwater dumps of ice water into the oceans.
      They happen when they are possible, when meltwater is there to dump.

    • Ian,

      The best hypothesis for D-O events is that warm subsurface waters brought North by AMOC get layered in the Nordic Seas below sea-ice, below a layer of fresh cold water, and below the saltier halocline.

      This configuration is metastable and its instability increases with time as the buoyancy of more warm saltier water has to be kept in check by the halocline.

      At periodical intervals the vertical stratification is broken (in my opinion and yours through a lunisolar tidal cycle), and the warm water accumulated for hundreds of years ascends melting the ice and releasing a huge amount of heat to the atmosphere.

      The conditions required for D-O events include sea levels between 45-90 m below current, and are inhibited by high obliquity. The cause is unknown. In my opinion tides are much stronger when sea levels are low, but when they are too low the area is too cold and has too much ice for the phenomenon to take place. Once an interglacial arrives, the D-O cycle, due to its nature, changes from a warming to a cooling cycle, and in the process shifts its phase 180°.

      You can read more and see the evidence for all this in:
      https://judithcurry.com/2017/02/17/nature-unbound-ii-the-dansgaard-oeschger-cycle/
      https://judithcurry.com/2017/09/15/nature-unbound-v-the-elusive-1500-year-holocene-cycle/

      • Salinity is playing a big role in the processes described above. Salinity depends on weather and circulation systems. Both are changing as a result of orbital circumstances.

        What happens when obliquity changes in the way that more warming will enter the northern regions is easy to imagine when you take a look at (all) the animations in the following link: https://climatereanalyzer.org/clim/animations/

        In fact, our seasons are nothing else than the result of an enormous half-yearly reversal of obliquity over the hemispheres. Imagine that all the changes shown in the animations are directed more to the north, some 200 kilometer, and to the south.

        And for salinity: imagine that the North Atlantic Gyre (the source of the most salty ocean waters in the world and source of the water that is driving the THC in the North Atlantic) must have known changes during the LGM and during the different orbital changes.

        Looking at the animations it is easy to imagine what the effect of longer/shorter summer and autumn seasons might be: up to seven days difference in season length by orbital reasons. See the variations in the different graphics for different time scales under ‘Graphical Analyses of the Lengths of the Seasons’ here: http://individual.utoronto.ca/kalendis/seasons.htm#eccent

      • Yes, salinity is a big factor. When the passageway of Panama closed, the Caribbean became very saline, because water continued being exported to the Pacific, but salt was left behind. The end result may very well have been an increase in very cold deep water formation (NADW), and the initiation of the freezing of Greenland.

      • Javier | August 18, 2018 at 12:13 pm |
        ” When the passageway of Panama closed, the Caribbean became very saline, because water continued being exported to the Pacific, but salt was left behind. ”

        WR: Javier, I suppose you meant ‘because water stopped being exported to the Pacific’. Closing a gap is closing a gap. Because of the closing the saline Atlantic waters were not exported to the Pacific and stayed in the Caribbean (to continue by the Gulf Stream to the poles):

      • Water is exported through the atmosphere. It evaporates in the Caribbean leaving the salt behind and it rains in the Pacific. Previously there was a compensating fresher water current going from the Pacific to the Caribbean through the Panama opening.

      • OK, Javier, agree with the evaporative effect. But I think another factor played a role as well. I don’t think that before closing [much] fresh water entered the Atlantic from the Pacific. The reason are the trade winds that are piling up warm waters in the Caribbean. In case of wider openings saline Atlantic water could have entered the Pacific, even below an eventual fresher inflow on the surface from the Pacific to the Atlantic. The higher salinity waters entering the Pacific (heavy, dense) would lower the sea level in the Pacific, enhancing the inflow of very saline Atlantic waters. This could have been a very effective way for the Atlantic to lose its salinity to the Pacific.

  38. Great post, Javier. Precession and obliquity essentially act as localized amplifiers of eccentricity. The MPT occurred when eccentricity fell below a threshold. What still troubles me is the lack of a ~400kyr eccentricity signal. One sees million year series that show an early eccentricity peak, without any other comparable peak. A million years must include an entire ~400kyr cycle. I believe Berger actually found strong spectral power at 400 in the Pliocene, just not in the Pleistocene.

    • Gymnosperm, this figure from Imbrie et al., 1993 (full ref in a comment above) explains the issue.

      The top part (A) is the calculated response to orbital changes in terms of W/m² at a certain high northern latitude. It has a range of 106 W/m² between ~ 420-540 W/m². Most of this insolation variation corresponds to the changes in precession, an important part to obliquity changes, and a tiny part to eccentricity changes, as the second line of graphs show. Per se eccentricity has a very small forcing, because it causes too small changes in insolation. That is the reason eccentricity frequencies did not show up in Milanković original calculations.

      The surprise came when scientists got the data for the ice proxy reflected in the bottom half of the figure (B). It didn’t agree with the calculations. The ‰ change in δ¹⁸O showed a smaller change in the precession frequency, an intermediate change in the obliquity frequency, and a very large change in the eccentricity frequency.

      Attempts to explain this disparity are behind all the problems for the complete resolution of the Milankovitch riddle. It has been recently solved, but most people, like Robert Ellison here, are still unaware, and it doesn’t figure in textbooks yet, only on a few scientific articles.

      Everybody agrees that the effect of eccentricity is not direct, but through its effect on precession and to a lesser extent in obliquity. A circular orbit essentially reduces the effect of precession to near zero, and decreases also the effect of obliquity, while a very eccentric orbit does the opposite.

      As the 100 Kyr frequency in eccentricity (it is actually 95 and 105) is closer to the precession and obliquity frequencies, that is the reason it has a more notable effect, through wave interference mechanisms. The 400 Kyr frequency in eccentricity, although it has a bigger amplitude, produces a smaller effect. Nevertheless, the effect of the 400 Kyr frequency is still detectable in the LR04 benthic stack:

      This figure from Clive Best (inverted to temperature) has fitted the 400 Kyr frequency between 3 and 5.3 Myr showing a detectable effect. Afterwards the oscillations became to large, obscuring the effect.

    • Javier,
      Did you read “snowball earth, the story of the once and future ice ages.”?
      by Douglas MacDougal in 2010.

      I thought the discussion was interesting like yours but more deep history and astronomical impacts on 65* N..
      Thanks so much for the hard work on your Nature Unbound series.
      Scott

    • Sorry, Frozen Earth.”
      Scott

    • Alan McIntire

      Speaking of Clive Best,

      http://clivebest.com/blog/?p=8187

      “….So when would the next ice age naturally begin had humans not burned any fossil fuels ? The Anglian interglacial some 400,000 years had similar orbital eccentricity to that during the Holocene. The preceding glaciation was also very severe like the that preceeding the Holocene.

      The Anglian interglacial lasted about 25,000 years which is roughly twice as long as average. Cooling initiated on a reducing obliquity coinciding with a northern summer minimum. The Holocene interglacial has northern and summer hemispheres inverted but obliquity still follows almost the same pattern. The minimum to which Ganopolski refers to as a close call pre-industrial inception is really nothing of the sort, since obliquity was still too high. I believe cooling would naturally begin another glaciation before 10 thousand years from now as we approach minimum obliquity. At the latest it starts 15,000 years from now.”

      • Dunno.

        The next obliquity minima actually coincides with a small summer insolation maxima of about 490W/m^2 at 65°N.

        If you consider the previous glaciations, they began roughly around
        400, 330, 240, 180, and 120 thousand years ago:

        These commencements all correspond to summer insolation max of around 460W/m^2. Such a minima will not occur again for another 180,000 years.

        So I’ll take the under on the ice age bet before then.

        This has ramifications.

        Given that there will be numerous orbital maxima between then and now, those who believe they are preserving Greenland’s ice and stiffling sea level rise, if even so, would only be forestalling the inevitable. Orbits will strip Greenland of its ice and fill the oceans.

  39. Barn E. Rubble

    RE: “. . .ice ages are when there is too much ice.”

    Ummm . . . that was also my understanding.

  40. Analysis of interglacials of the past 800 Kyr shows

    When it is warm and oceans are deep and thawed, it snows more. The length of the interglacials depend on the length of time it takes to pile up enough ice to advance significantly.

    It gets colder during the long cold part of the ice age because the ice sheets are thinning and spreading and as ice extent increases, cooling by reflecting and cooling by thawing both increase. Ice volume decreases during the long cold, sea level rise does not start because meltwater is trapped behind ice dam. The spikes of temperature during the ten thousand year warming are caused by meltwater surges when ice and land dams break.

    Cold times do not produce more ice. It takes energy to evaporate oceans, that happens more in warmer times. That energy is used to produce snow and the IR out is used to remove the energy from earth atmosphere. To produce ice you need energy in and energy removal. Check out any large ice machine. The requirements for earth to produce ice is the same, energy and moisture and energy removal. That is not available in cold times.

  41. Salvatore del Prete

    test

  42. Salvatore del Prete

    This is all interesting but I am focused on now- next 30 years, now that the two solar conditions have been met which are 10+ years of sub solar activity in general(2005- present ) followed by a period of time of very low average value solar parameters (late 2017-present). This is the first time since the Dalton Solar Minimum ended that this is now taking place.
    In addition the earth’s geo magnetic field is weakening which will compound all the given solar effects because they are in sync with one another. They are both weakening.

    The upshot of this is going to be overall lower sea surface temperatures(which I forecasted more then a year ago) which is now present and a slight uptick in albedo due to increases in major geological activity and cloud/snow coverage.

    I suspect year 2018 is the transitional year .

    Thresholds are important in that you can have items which influence the climate change but if they do not change enough the results to the climate are minimal. As an example I believe galactic cosmic rays do effect the climate if thresholds are met. They result in changing the global electric circuit , as well as global cloud coverage and explosive volcanic activity.
    Forbush events led support to the cloud coverage tie in to galactic cosmic rays.

    So in practical terms what is important to ascertain is what is the climate going to due now – next few years and this is my focus.
    I say AGW is over and a cooling trend is now in place will at a minimum be equal to the 1977 climatic shift except to colder rather then warmer conditions which it was back then.

    • Short term stuff is weather, climate is long term stuff.
      AGW never really happened so it cannot be over.
      Short term cooling trends do not define long term climate.]
      We are in a warm period and warm periods currently (during the recent ten thousand years) last a few hundred years. This will continue.
      We will have cooling and warming inside this warm period, but it will stay a warm period.

      • Salvatore del Prete

        No it won’t it is going to shift to cooling.

      • Salvatore del Prete

        The reality is since the Holocene Optimum we have been in an overall cooling trend punctuated by warm periods with each succeeding warm period being less warm then the previous one. We will know soon and climate can change in less then a decade, and that is not weather. Ice core data shows this to have happened many times.

        The slow gradual change of the climate is old school thinking. Climate can change very abruptly. I say a climatic shift is coming at the very least similar to that of the late 1970’s.

        Overall oceanic temperatures now off over .2c since last summer.

      • I say a climatic shift is coming at the very least similar to that of the late 1970’s.

        Those little shifts don’t mean much to long term changes, You could easily be right.

        The tilt of the earth has removed energy into the NH and increased energy into the SH over the past ten thousand years, The cooler warm peaks were NH peaks, the SH did not do the same. Check ice core data for Greenland and Antarctica. What has happened for ten thousand years will keep cycling in similar cycles inside the bounds of what has happened or in cycles that my get a little out of those bounds, but not much.

  43. Javier, thank you for this essay and for your responses to comments.

  44. Background conditions are set by interacting control variables – solar and orbital. The Earth system then evolves according to it’s own dynamic – with shifting albedo and CO2 biokinetics – crossing thresholds to emergent states when background conditions change a little.

    That’s the deterministically chaotic paradigm – there is evidence everywhere in climate series and nothing to suggest otherwise. I hesitate to use the term ‘scientific consensus’ – but there it is.

  45. At last an analysis of the only seriously significant aspect of potential climatic change that really impacts human civilisation. The rest can probably be filed in trivia.

  46. Last post hothouse earth, next one glaciation – do we have a spontaneous oscillation? Is it internal – or externally forced?

    • It is spontaneous no doubt. But it is an interesting dichotomy.

      Proponents of the hothouse scenario have realized there is no enough CO₂ to reach a hothouse, so they now go around saying that there is likely a threshold that will make most of the way possible in the absence of additional CO₂. Of course they say so without a modicum of evidence, but they are taken seriously.

      Proponents of the icehouse scenario have a huge amount of evidence for the past 50+ glaciations in the last 2.6 million years. Apparently that evidence amounts to nothing since the planet is modestly warming at a time nearly coincident with a large increase in atmospheric CO₂.

  47. Salvatore del Prete

    Any cooling no matter how slight will put more nails in the coffin of AGW theory.

  48. Figure 133 shows a large difference in temperature between the 80,000 and 285,000 BP slightly warmer periods, and the low at 162,000 years ago, despite similar obliquity and eccentricity. What happened there?

    • It is explained by the colors and letters. According to the model, MIS 7a-c was a cool interglacial (D’ type in fig 133c) due to very high eccentricity, so it cooled to a lower point at the start of MIS 6 (D type). Then a transition to lower eccentricity made MIS 6 become colder and accumulate more ice than MIS 8 or MIS 5 a-c.

  49. “…Our simulations suggest that a substantial fraction (60% to 80%) of the ice sheet was frozen to the bed for the first 75 kyr of the glacial cycle, thus strongly limiting basal flow. Subsequent doubling of the area of warm-based ice in response to ice sheet thickening and expansion and to the reduction in downward advection of cold ice may have enabled broad increases in geologically- and hydrologically-mediated fast ice flow during the last deglaciation.
    Increased dynamical activity of the ice sheet would lead to net thinning of the ice sheet interior and the transport of large amounts of ice into regions of intense ablation both south of the ice sheet and at the marine margins (via calving). This has the potential to provide a strong positive feedback on deglaciation.”

    https://scienceofdoom.com/2014/04/14/ghosts-of-climates-past-nineteen-ice-sheet-models-i/

    It seems to be an ice mass thing. They did the NH. You may see a 41k cycle in their plots, but it’s subjective.

    The paper:
    http://www.geo.oregonstate.edu/files/geo/marshall-clark-2002-grl.pdf

    Let’s say it is a 100k cycle that can’t be missed. What would the reason it can’t be missed? Ice mass volume. Some may believe, ice mass at a certain volume is required for a glacial termination.

    • Yes. The final phrase of the study:

      “Our results thus reinforce the notion that at a mature point in their life cycle, 100-kyr ice sheets become independent of orbital forcing and affect their own demise through internal feedbacks.”

      is consistent with the decision being taken by orbital forcing, but the realization being dependent on ice sheets dynamics that require large unstable ice sheets in most cases.

      • A while back I came across his post. It’s always stuck with me. For such a big change, I like a collapse. It also shaped my thought that the polar regions are active and not just a place to put stuff like ice. I sketched this:

        Literal basins of attraction. We know how slow Greenland and Antarctica melt. And we can contrast that with how long they take to rebuild. Then there’s a whole story to tell of what happens after the collapse gets going.

      • And another thing, in my sketch above, the middle bump can relax to equal the level of the upper basin. That is, the basin shape evolves over time.

      • Clearly there is evolution in the climatic condition of the planet. Since the Mid-Pleistocene transition the glaciated state has become a more powerful attractor. A fact usually ignored by proponents of the new hothouse paradigm. The last glacial period was the first to last 110,000 years in the entire Quaternary Ice Age. That’s a serious record.

      • The ice drives the glacial/interglacial cycle. It’s not just leftovers put into long term storage until later. Figuring CO2 is easy. Figuring potential of ice and oceans to their full depth, not so easy. CO2 draws a line over the planet and says this happens. What’s happening under the line? CO2 is a highschool science project.

      • Without the periodical astronomical kick in the orbit, the planet would be in a permanent glaciated state until the continents moved out of their present position.

        Most people believe an interglacial is a stable climate state that in the absence of a change will remain indefinitely. The kick out of the glaciation is over. We are going back to a glacial state already. No warming period can change that. Only if CO₂ is as persistent and powerful as the most alarmists fear we could be saved. Alas I don’t believe in a CO₂ savior.

      • Javier: “Only if CO₂ is as persistent and powerful as the most alarmists fear we could be saved. Alas I don’t believe in a CO₂ savior.”

        I share your vision, Javier. But I would add that in case of prolonged cooling humanity could use some ‘tricks’ to compensate the already started cooling. Some geoengineering tricks to keep the temperatures of the [deep] oceans that high that (full) reglaciation would be prevented.

      • I think Greenland with its albedo acts as an anchor for the Ice Ages. Until it melts substantially, Ice Ages would be possible, but it is not stable at 400 ppm, and if that is sustained for a few centuries, Greenland’s glacier will melt out. This would end the possibility of Ice Ages in an analog to the Pliocene conditions 3 million years ago where CO2 levels exceeded 300 ppm and Greenland’s glacier may not have been so extensive.
        https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010PA002055

      • “I think Greenland with its albedo acts as an anchor for the Ice Ages.”

        The glaciation of Greenland cannot be detected in the benthic reconstruction that shows a quite continuous cooling. I guess the planet disagrees.

      • Yes, Greenland, Arctic sea ice, snow-cover and other northern hemisphere glaciers all would have increased leading up to the first Ice Age. This would appear to have been a large-scale and gradual process unlike what happened with Antarctica 35 million years ago. The drop in sea levels during the Pliocene would be a clue to how gradual it as.

      • Thank God the cooling appears to have stopped. Must be that blessed CO₂.

      • Yep, end of the Ice Ages. Pliocene, here we come. Next up, Miocene, Oligocene then Eocene, sea levels rising the whole time.

      • “Pliocene, here we come.”

        In your CO₂ dreams. It might take another 30 million years.

      • Greenland’s melt rate will likely impact this century’s sea levels a lot becoming the top contributor to sea-level rise within a few decades, Antarctica following close behind.

      • “Greenland’s melt rate will likely impact this century’s sea levels a lot”

        Or not. Alarmist promises have a really bad record.

        https://wattsupwiththat.com/2017/10/30/some-failed-climate-predictions/

      • Some of those have no concept of acceleration. 3 C in century does not mean each decade has to have 0.3 C, perhaps 0.2 C earlier, 0.4 C later. Similarly for sea level, a meter by 2100 does not mean 10 cm per decade starting now, but that is a conservative estimate taking into account that a Greenland tipping point has been passed and its melting rate may have a doubling time of 10-20 years.

      • You are inventing all that. There’s no evidence that a tipping point has been passed in Greenland, and future warming is imaginary. We don’t know what temperature there will be in the future as we didn’t know in the past what temperature we would have now.

        A meter of sea level by 2100 is equally imaginary. There is no significant acceleration in sea level. Since October 2015 it has been increasing at less than 1 mm/year.

        You are just making scary things up without any connection with real evidence.

      • Greenland had no glacier in the Pliocene when CO2 levels were last in the 400 ppm range. It is not a stretch to suggest this level is incompatible with its existence and makes it unstable. Greenland did not contribute much to sea-level rise at the beginning of the 2000’s, but now it contributes about 25% of it already. These are things you can look up.

      • That two things took place at the same time is no evidence that they were causally connected. Or that the causal connection, if existed, went the way you propose.

        Greenland melts a ridiculous part of its mass every year, and some years it has such a growth in surface mass that it is doubtful it melts at all. Its contribution to sea level rise is calculated, not measured, and therefore a different calculation would give a different contribution. The sea level budget is one of the things one can trust least in climate science, and the bibliography is full of articles with disparities and discussions about it.

        As usual you thing science is settled your way.

      • https://curryja.files.wordpress.com/2018/06/screen-shot-2018-06-23-at-12-25-40-pm.png?w=500&h=571
        Judith posted this one. You can try to dispute it. What is most noticeable is that the upper wedge representing Greenland is growing.

      • There is no need to dispute it, because it is a calculation based on numerous assumptions, not a measurement. It is clear that a similar figure in a few years could have a different budget closing without causing any problem.

        There are discussions about if Antarctica is adding to sea level or subtracting from it. That’s our level of certainty on that subject.

        So the contribution from Greenland in that figure is growing because the people that made the figure think it is growing. It is a reasonable assumption because the sea level is increasing, but how much of that is due to Greenland, and how much it is changing we don’t know with any degree of certainty.

        To extrapolate from that figure that Greenland is going to melt in the future is sheer madness.

      • What would be the problem for you if it was Greenland? Why not just admit it is more likely than not that sea-level rise rates have grown 1 mm/yr since 1990 largely due to Greenland, because that is what the data says? You seem to have some preconceptions that makes you just reject certain published data. CO2 is another one. Eocene tropical warmth. The list goes on.

      • It is not what the data says. It is not good evidence. The uncertainty is almost as large as the number. You are ignoring that. I distinguish between data and evidence that one can trust that will stand the test of time, and data produced on unproven assumptions and incomplete and perhaps wrong models that may well be significantly revised in the future.

        Saying based on that type of data that Greenland is going to melt and will pass a tipping point is sheer madness. You are the one with a problem for reaching conclusions without firm evidence.

      • You seem to have decided already that it can’t possibly be right even when the data supports it independently with satellite budgets of the Greenland mass balance and sea level rise is accelerating. Data does not sway your preconception at all.

      • Sea level rise is not accelerating.

        https://climate.nasa.gov/vital-signs/sea-level/

        Data does not support your tenets.

      • The 20th century average is 1.5 mm/yr. The average since 1990 is 3 mm/yr. I count that as a doubling.

      • Yes you do that, and it is a mistake because one is from a selection of tide gauges and the other one from satellites. They are not measuring the same thing and you know it.

        For the past 25 years satellites show 3.4 mm/year, no detectable acceleration. If it doesn’t increase in 25 years, we shouldn’t believe claims that it will increase a lot more the next 75.

      • You have to decide how confident you are in the 20th century average being 1.5 mm/yr, but whether with tide gauges or satellites it has been over 3 mm/yr since 1990.

      • “You have to decide how confident you are in the 20th century average being 1.5 mm/yr, but whether with tide gauges or satellites it has been over 3 mm/yr since 1990.”

        No, because tide gauges measure sea level rise respect local land at the sea shore, and satellites measure sea level rise respect Earth’s geometry at the middle of the oceans and require very heavy processing of the data including models of GIA adjustment. You can’t extract any conclusion from compering two sets of completely different nature. It is perfectly possible that sea level rises 1.6 mm as measured by gauges and 3.4 mm as measured by satellites simultaneously.

      • Recent tide gauges also have 3 mm/yr since 1990, some even say they give more than the satellites.

      • Choosing the correct set of tides you can get any answer.

        I’ll go with the satellites, thanks. At least they give global data that is treated homogeneously, no matter the significance of the final value.

      • At least with tide gauges you can use the same ones as were used for the 20th century average, but satellites now give you a way to correct tide gauge averages.

      • And if your acceleration is not obvious in 25 years of data then it is an acceleration that it is not worth worrying about.

      • So you throw out the 20th century and then complain you don’t have enough data. Good one.

      • I don’t discard any data, I just analyze them separately to see what evidence they provide, as should be done.

        Tide gauges:
        1.6 mm/yr over the 20th century
        Small acceleration of 0.1 mm/decade²
        ~65-year oscillation

        Satellites
        3.4 mm/yr
        Non detectable acceleration in 25 years.

        Acceleration should have increased sea level rise by 0.25 mm/yr but the oscillation might obscure it.

        In any case there is nothing to worry. The increase is small, and the acceleration, even if present, is so small that we can’t detect it in 25 years.

        If warming continues, we should get ~ 0.3 m rise from 2000 to 2100. Interesting but not concerning.

      • My statement was that since 1990 the sea-level rise rate has been double the 20th century average. I mention this because it is a large acceleration in a short period of time. Most suggest that the acceleration doesn’t stop here. Judith’s company had an estimate that averaged 5 mm/yr by 2050, for example, and they may be conservative.

      • I already put my estimate that coincides with the IPCC AR4.

        Due to the ~60 year oscillation, I have calculated that by 2050 we should have a similar sea level increase as today, ~3.5 mm/yr.

      • CFAN had 3-8 inches 2017-2050. The whole 20th century rise was 6 inches, and this period is only 33 years. The upper end would be a fourfold increase in rate.
        https://curryja.files.wordpress.com/2017/11/sea-level-ins.pdf

      • We have to contrast all those calculations with the reality that in Mar 2016 sea level was 84.7 mm above 2000, and in Apr 2018 (latest NASA data), it was still 84.7 mm above 2000.

        Two years of no growth has only happened twice since 1993, in 1997-2000 and in 2009-2011.

        It sure doesn’t look like it is accelerating, and it doesn’t look like those predictions are going to be correct.

      • This is like saying the temperature is colder now than in 2016 so global warming has stopped, and nobody does that. There is a lot of annual variability, and averages over less than a few decades are worthless.

      • “averages over less than a few decades are worthless.”

        That’s your opinion. I think recent data is very indicative of what is going on, and the hiatus was not discovered by scientists. It was discovered by an skeptic looking at recent data.

      • For climate I don’t look at anythong less than decadal averages, and preferably 20-30 year averages. You can easily fool yourself with solar variations when using shorter periods.

      • That’s your choice. I look at all type of data and get the significance by comparing with similar periods in the past.

        We now have minipauses in:
        – Arctic sea ice since Sep 2007
        – Sea level rise since Oct 2015
        – Temperature since Feb 2016

        As the planet is warming, sea level is rising, and Arctic ice is melting, the chance that we would get all three at the same time without any relation is quite small. Somehow they must be related, but consensus scientists prefer to deny that it is happening rather than having to look for an explanation.

      • Cold times end when the ice is thawed. The blessed CO2 increases as the carbonated oceans warm, just like your coke or 7up.

      • For God’s shake, Pope. I was being sarcastic!

        We all got the basis of your climate theory the first time around. It is quite simple to understand. And the thousands of repetitions aren’t adding anything.

      • Some geoengineering tricks

        Don’t try to fix something you really don’t understand.

      • Javier,

        We now have minipauses in:
        – Arctic sea ice since Sep 2007
        – Sea level rise since Oct 2015
        – Temperature since Feb 2016

        The lower two are related – it’s ENSO. Look again at your dates for “minipauses” in sea level rise. They all correspond to transitions from El Nino to La Nina.

        Arctic sea ice is different, but then the timescale you’re talking about is completely different anyway. The Arctic is also a small region of the planet. In terms of those two global indicators, the sea level trend since 2007 is the largest 11-year trend in the altimeter record. And in GMST the trend since 2007 is one of the, if not possibly the highest, in the instrumental period.

        Even still, you’re not really talking about Arctic sea ice as a whole, you’re talking about the extent trend for a single calendar month – September. The annual average extent continues to decline, with 2016 setting a record comfortably lower than 2007, plus 2017 and likely 2018 are set to finish below 2007.

        There has been a seasonality change in the Arctic, with Summer temperatures declining since 2012 alongside strong Winter warming. Presumably this is associated with the AMOC flip happening at the same time.

      • Paul, El Niño ended two and a half years ago, and unlike previous strong Niños of the past 70 years, it wasn’t followed by a strong La Niña.

        Since El Niño ended, the situation at ENSO can be best described as neutral, so ENSO does not satisfactorily explain what is going on with the multi-pauses. They should have been over about a year ago.

        Regarding the Arctic, the declined has always been described in terms of the month with minimum extent. It seems miraculous that the minimum extent has not declined after the very warm years of 2014, 2015, 2016, 2017, and 2018. One is tempted to think that GSAT does not affect Arctic sea ice melting, contrary to what we have been told.

      • Javier,

        El Niño ended two and a half years ago, and unlike previous strong Niños of the past 70 years, it wasn’t followed by a strong La Niña.

        Yes, it ended and transitioned to negative ENSO, hence the SLR variability. Given that your reference frame is not “normal” but rather the 2016 peak, it’s actually unimportant whether or not we label what followed to be a strong La Nina (since that’s defined by difference from “normal”) – it’s only the magnitude of the swing from high to low which matters, and that swing is one of the largest of the past 70 years.

        They should have been over about a year ago.

        No, there’s no reason to believe that. ENSO indicators are well below 2015/2016 levels and the long-term trend only adds about 0.04-0.05degC, so we expect global average temperatures to still be lower than that peak. According to the NASA sea level data, sea levels were still sometimes lower 3 years after the 1997/98 El Nino peak. It was two years after the smaller 2009/10 peak before sea levels reached the same level for the first time. So far it’s just over 2 years since the 2015/16 peak in that NASA data.

        It seems miraculous that the minimum extent has not declined after the very warm years of 2014, 2015, 2016, 2017, and 2018. One is tempted to think that GSAT does not affect Arctic sea ice melting, contrary to what we have been told.

        I’m not sure who the “we” is, or who did the telling? I’ve certainly never been told that by listening to climate scientists. Arctic sea ice obviously responds to local Arctic conditions, not the global average, and 2014-2018 have not been warm years for Summer Arctic temperatures (generally speaking. 2016 was warm and ties with 2007 for September minimum).

      • “it’s only the magnitude of the swing from high to low which matters, and that swing is one of the largest of the past 70 years.”

        No. What matters is the temperature of the ocean, the strength of the winds, and all the other factors that go into the multivariate ENSO index. And as you can see, it never went deep into negative deviation.

        You can see by yourself that in 1998 MEI went from +3 to -1, 4 standard deviations in just a few months.

        For the last 2 years Niño 3.4 temperature has been moving essentially in the ± 0.5 neutral zone. It is unclear why global temperature has continued decreasing. ENSO area hasn’t contributed much, and 2 years is a long time for El Niño heat to be retained in the atmosphere. The North Atlantic, however, is cooling, at that is not part of ENSO.

        “Arctic sea ice obviously responds to local Arctic conditions”

        Good to know. Then this article in Science must be wrong:
        Observed Arctic sea-ice loss directly follows anthropogenic CO2 emission
        Dirk Notz, Julienne Stroeve
        “Why we are losing sea ice
        Arctic sea ice is disappearing rapidly, leading to predictions of an ice-free summer in the near future. Simulations of the timing of summer sea-ice loss differ substantially, making it difficult to evaluate the pace of the loss. Notz and Stroeve observed a linear relationship between the monthly-mean September sea-ice area and cumulative CO2 emissions. This allowed them to predict Arctic summer sea ice directly from the observational record. Interestingly, most models underestimate this loss.”

        “2014-2018 have not been warm years for Summer Arctic temperatures”

        But boy have they been warm in the winter. According to Mark Serreze that means a seasonally ice-free Arctic Ocean.
        https://e360.yale.edu/features/what-extremely-warm-winters-mean-for-the-future-of-the-arctic-serreze
        “The four lowest winter ice extents at the seasonal maximum, which occurs sometime in March, have all occurred in the past four years. It’s hastening that glide towards a seasonally ice-free Arctic Ocean.”
        He doesn’t say anything about cooler Arctic summers.

    • Increased dynamical activity of the ice sheet would lead to net thinning of the ice sheet interior and the transport of large amounts of ice into regions of intense ablation both south of the ice sheet and at the marine margins (via calving). This has the potential to provide a strong positive feedback on deglaciation.”

      There is some common sense in this statement.

      • As I said – energy dynamics – and thus warming and cooling – follow albedo changes at the ~100ky scale and emerge from ice sheet dynamics – followed closely in importance by temperature driven CO2 biokinetics in a hyper complex Earth system.

        It’s all ducks in a row – and keeping them there is a bitch.

      • When you understand the basic science, the ducks line up just like they should. I will explain something simple and important soon.

      • Different things need to happen the initiate ice sheet growth and a self reinforcing dynamic. Those are my ducks.

  50. This article by Javier is packed full of incredibly important and interesting facts and observations about the glacial period in which we live. The fact that certain contributors confess to finding it “a slog” tells you all you need to know about that attitude to and appetite for scientific information about glaciation, the only real and important climate issue, in agenda-subscribed establishment “scientists”. Revealing and sad.

    • People like to read things that reinforce their beliefs and their tribal sense over issues they have already reached a decision. That’s only natural. Some probably come here because they feel they have a duty to defend their position. I personally like the confrontation of ideas, as I get bored easily if everybody agrees with me. It doesn’t bother me that there’s people that don’t like what I write, but I prefer the people that are genuinely interested in knowledge and I don’t expect them to agree with me. Science is a discovery process that breeds on discussion.

      • Javier, excellent!
        I do like for people to agree with me. I also do learn when I am discussing and debating with people who disagree.

        Sorry, I missed that you were being being sarcastic!

  51. A coulpa years ago I ran a radiative model on a set of atmospheric profiles ( 12 different months ) modified for LGM ice coverage, land surface, orbital characteristics, and GHG estimates.

    This ignores dynamics ( not a gcm ) and ignores the elevation of glacial ice, but still interesting.

    It places CO2 in context of other sources of forcing during the LGM.

    CO2 did, of course, further the global annual mean radiative deficit.
    But interestingly, this was less than the shortwave effect of increased land surface and of course the shortwace albedo from increased ice:

    But ice doesn’t melt in the global mean, it melts instantaneously during peak radiance. The peak summer radiance changes for the region of Northern ice accumulation looks like this:

    The overwhelming factor determining an ice age is the presence or absence of ice to begin with. This explains the imperfection match of glacials with orbital forcing and the ‘stochastic resonance’ of ice accumulation.

    • This looks interesting TE, but the glacial cycle is just an intensification of the obliquity cycle, that has always have an impact on climate as far as we can tell, even when there wasn’t any ice in Greenland and Antarctica. So there was a cycle before there was ice in it.

      • Javier: “the obliquity cycle, that has always have an impact on climate as far as we can tell”

        WR: Agree. But Snow and Ice enhance the orbital effects enormously, visible in the high temperature changes between glacials and interglacials and in between a glacial.

        An important factor is played by water vapor, H2O. Ice coverage and snowy and cold conditions in general exponentially diminish water vapor (our main absorbing gas) over large surfaces. After that, straight radiation to space is enhanced exponentially and the Earth as a whole cools down a lot: glacials.

      • I also agree that ice has become a huge factor, being the main reversible feedback responsible for the increase in amplitude for the cycle. Warmer interglacials and cooler glacials.

        Despite interglacials becoming warmer and with more CO₂ in the Mid to Late Pleistocene. There’s never been a runaway effect. The logical expectation is that a glacial inception awaits sooner rather than later.

      • There are huge stabilizing factors in climate. Preventing the Earth to become too warm and preventing the Earth to become too cold. The ‘median’ is ‘somewhere’ made by the temperature of the deep oceans (as I have stated elsewhere) and there is an upward and a downward range.

        If warming could cause a runaway effect (or if cooling could do), than every warming or cooling for whatever reason would have to result in a runaway warming / cooling. For example an El Nino warming. But the Earth has many ‘limiting factors’ for every climate state / basic average temperature / general background temperature to stay around a certain centre.

        I suppose water vapor together with ‘clouds’ play the main role in stabilizing. A freezing cold results in less water vapor and in less clouds, causing more sun energy to be absorbed by the oceans, lifting up again surface temperatures. Stabilizing. A lot of warming causes a lot of water vapor in the air and a lot of reflecting clouds / haze etc., that are diminishing the absorption of sun energy by the oceans. Causing some cooling. Stabilizing.

        The water vapor / cloud variable is the big unknown.

        Besides, water vapor itself is a big amplifier of temperature movements because of her radiation absorption effect. The content of water vapor is highly variable, much more than CO2. Cooling causes less water vapor over the poles, causing more cooling (by a lack of absorption of outward radiation), the cooling is causing less water vapor etc. But warming results in less ice, much more water vapor in the air, much more absorption of by the surface radiated energy. An enhanced warming for the poles and for the Earth as a whole is the result.

        Because the thin surface layer of the oceans is faster to warm than the deep oceans can cool, the upward curve (warming) is steeper than the downward curve (glaciation). Water vapor has a more direct upward temperature result for the surface in case of enduring warming. But cooling the thick water layer of the deep oceans takes more time as water vapor diminished over the poles (which are relatively small areas, compared to the big evaporating areas [tropics, subtropics, mid latitudes] in case of warming). All the surplus energy of the deep oceans has to be lost (bit by bit) by the smaller polar regions. Which takes time.

      • “There are huge stabilizing factors in climate. Preventing the Earth to become too warm and preventing the Earth to become too cold.”

        Depends on your definition of too cold. If we pick a halfway eccentricity and obliquity and fix the orbit of the Earth so it does not change, the planet would simply go into a glacial state and would not come out of it in millions of years. All the feedbacks would probably make it oscillate chaotically between different depths of glaciation, but they could not put the planet into an interglacial. We already know that because between 105 Kyr ago and 20 Kyr ago no feedback and no orbital oscillation was capable of getting the planet out of its glacial state. It required high obliquity, high NH summer insolation, and very large ice sheets. Without any of those factors you get a glacial world until the continents move.

      • Interesting. But what if we would have fixed the orbit of the Earth at a moment that continents and oceans where in a better configuration to ‘conserve energy’ in the deep ocean than the present system does? I suppose that starting with warm oceans and another circulation pattern plus another positioning of continents and oceans, the Earth could stay in that warm situation. It is clear that present (!) configuration is the configuration belonging to an Ice House State (and on average a purely glacial state). Through the present ‘open door’ at the poles (by the lack of radiation absorbing water vapor at our icy poles) the Earth needs more energy than the fixed situation would deliver.

      • We already know that because

        No, you don’t already know, you don’t really suspect.

        Ice causes cold and lack of ice causes warm.

      • “what if we would have fixed the orbit of the Earth at a moment that continents and oceans where in a better configuration to ‘conserve energy’ in the deep ocean than the present system does?”

        Perhaps you could stabilize the system in a permanent interglacial with sufficiently high obliquity, northern insolation, and eccentricity, but I seriously doubt you could get enough energy to melt the polar ice caps. We are in an Ice Age regardless of orbital conditions.

      • Javier | August 19, 2018 at 3:10 pm |
        “Perhaps you could stabilize the system in a permanent interglacial with sufficiently high obliquity, northern insolation, and eccentricity, but I seriously doubt you could get enough energy to melt the polar ice caps. We are in an Ice Age regardless of orbital conditions.”

        WR: in the nearby future we will have nearly endless possibilities to manipulate the Earth. I think we can influence natural processes on Earth to prevent a further cooling of the Earth once the next glacial arrives. One possibility is to stop the heat loss over the Arctic region by diminishing the quantity of sea ice and enhancing in this way the radiation absorbing water vapor. Influencing the salinity of the Arctic could do some good work: mixing of layers is what could be enough (in the beginning). And just another possibility is the restoring of the warm deep water production by ‘evaporation projects’ in the subtropics. Large scale.

        I know those projects cannot totally prevent changes in climate (changes will always occur because of continuing orbital and other changes) but I think humanity could avoid the big disaster we would get when we really would glide into a new glacial.

        But to know what to do ‘in case of the arrival of the new glacial’, we first need sound science by which completely unbiased the best and most complete data will be assembled about present and past climates. For example: we will have to know about every cubic kilometre of the oceans (1.3 billion cubic kilometres) how it moves. And which patterns in the moving of the oceans are changing. An expensive long term project, but absolutely necessary to understand ‘the mother of climate’ the oceans are. The same we need to do with ‘the oceans daughter’: water vapor. Those two dominate what is happening on the surface of the Earth (under changing orbital circumstances and [slow] changes by continents, changes in topography and other physical processes).

        For now we can forget CO2 and enjoy the benefits of an enhanced CO2. A sound [climate] science: that is what we need.

  52. The business of arguing about a few W/m^2 either way at what is an interglacial top temperature and humidity stae with the ice age cycle is SO missing the point. The Sun gives us a variable but roughly 340W/m^2. This varies by +/- 15% during a Milankovitch cycle, and for other reasons, like Solar Zits. Because the planet is mainly covered by a lot of water that emits water vapour according to its temperature of the oceans, we have a range of dominant water vapour based feedbacks that keep us securely within the ice age range of a few degrees in 300k or so, from the effect of cloud formation and albedo to impose cooling when warming occurs, 90 and 50W/m^2 respectively, that very effectively squeiched interglacial events flat in no time ,1Ka. Not bothered. In control.

    And water vapour works the other way, as we approach ice age floor temperature water vapour DOES get useful as clouds disappear and water vapour GHE kicks in, far more powerful than CO2 could ossibly imagine, to deliver enough warming to stop the ocean surface freezing over, at which point it would be game over and ice ball time as albedo goes to 0.14 from 0.3. I don’t know what the corrective feedback forcing range for GHE is, BUT rest assured the total range of feedback keeping us with the narrow limits of the ice age cycle are controlled by water vapour in its various forms, which are easily capable of correcting for half the forcing of all incident solar energy. CO2 at 1 W/m^2 is simply irrelevant system noise, and an effect of a warming perturbation, not a cause.
    CO2 may have other effects than it’s small contribution to GHE, such as the almost 1:1 (75%) response by plant growth that lowers land albedo, providing more heating. But whatever, water vapour is THE dominant control that simply regulates solar insolation to negate the various shifts in other smaller effects and maintain our equilibrium. The other problem , that I have an answer to, is what causes the interglacial that the water vapour as clouds very effectively caps the effect of after 7Ka, with a lot of surface cooling by cloud formation and preciitation as well as albedo, probably as wet as it gets globally, and keeps a lid on the repeat 100Ka warming attempt until the interglacial heat surge dissipates and the planet returns slowly to its stable ice age state again. Ahhhhhh.
    CO2 is really noise in this. Forgetaboutit. NO justification for all the taxes on cars, generation, and subsidies for what can’t deliver any of their promises. A climate change protection racket peddling snake oil cures for a fast buck. Double deceit.

  53. Since dwelling on my last question and scrutinising the chart, it seems to me that MIS 7a-c is actually an analogue of the post interglacial warmer periods around 80,000 and 285,000 years ago, and that MIS 7e is the primary interglacial. Meaning that glacial cycle frequency has recently shifted to around 115K years. I do have an exploratory harmonic handle on that figure, involving the big Jovian cycle of 4627.33 years, and the half period of the long term cycle of centennial solar minima of 3453.11 years.

    • “MIS 7a-c is actually an analogue of the post interglacial warmer periods”

      I know you don’t care, but you disagree with the experts that analyzed the question in great depth:
      Past Interglacials Working Group of PAGES. (2016). Interglacials of the last 800,000 years. Reviews of Geophysics, 54(1), 162-219.
      https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015RG000482

      They declared MIS 7a-c an interglacial, but not MIS 8 or MIS 5a-c.

      “I do have an exploratory harmonic handle on that figure, involving the big Jovian cycle of 4627.33 years”

      You are off by an order of magnitude. It is 41,000 years, not 4,600.

      • “You are off by an order of magnitude. It is 41,000 years, not 4,600.”

        In fact I was referring to a 115 kyr period in relation to a harmony of 4627.33 and of 1726.555 year cycles.

      • Closest harmonies:
        (4627.33 / 1726.55) x 3 = 8.04028 = 13882 yrs.
        (4627.33 / 1726.55) x 22 = 58.962 = 101801.26 yrs
        (4627.33 / 1726.55) x 25 = 67.00235 = 115683.25 yrs (error of 4 yrs)
        (4627.33 / 1726.55) x 28 = 75.0426 = 129565.24 yrs.

      • Numerology.

      • “They declared MIS 7a-c an interglacial, but not MIS 8 or MIS 5a-c.”

        ‘Yin and Berger [2010, 2012] chose a similar set of interglacials to simulate, using the expectation of a 100 ka cycle to justify including MIS 7e but not 7a-7c, and including MIS 15a but not 15e. Using our sea level definition, MIS 7a-7c and 7e, and also MIS 15a and 15e are all equally prominent within their respective stages, and as we do not assume a particular periodicity’

      • Long period multi-body fine synodic harmonies are not numerology Javier. For a start they order centennial solar minima, and a long cyclic pattern of centennial minima.

  54. Figure 133 has the mother of all figure captions! Must be a record. One question – if 65N summer insolation (determined by obliquity plus modulation of precession / eccentricity) is lagged 6000 years for ocean thermal “inertia”. Why then is eccentricity not also lagged 6000 years?

    Connected to that, in figure 132 the delay between steepening descent of temperatures signifying glacial inception, and CO2’s inflection toward faster decreasing concentration, is also about 6000 years. Do these two 6000 year lags have the same cause – the time taken for a significant change in ocean temperatures all the way to the bottom?

    Finally, regarding precession is it not the modulation of precession (wave change from lower to higher amplitude) that is more important than precession per se? That this modulation of precession directly determines 65N summer insolation, and that both of these follow eccentricity? Orbital geometry make this correlation inevitable. In this case, I would suggest simplifying Milankovitch orbital forcing dynamics by considering all these three causally linked parameters, modulation of precession, 65N summer insolation and eccentricity, as one and the same process of orbital forcing? I guess you effectively do this in your black line in figure 133.

    Thanks for ending the current Nature Unbound series on a stunning high note!

    • “Why then is eccentricity not also lagged 6000 years?”

      It is. It just doesn’t make any difference in the graph because eccentricity changes very slowly. But eccentricity has a big effect on precession, and a significant effect on obliquity, and those effects are lagged when summer energy is lagged.

      The cause for the lag is unknown. Most paleoscientists just tune the proxy records to astronomical changes making it disappear. The oceans’ thermal inertia is my best guess. There are other hypotheses like the lag between maximum rate of change and maximum change. It needs more studying, but if scientists keep compensating for it in proxy records by tuning it out, there is no incentive to study it.

      I really don’t know if the change in insolation is more important than the actual amount of insolation. That’s something that perhaps models can answer, although they are skewed towards numerical solutions, and the change in insolation would be more like altering the balance or the gradients.

      You are welcomed.

      • The lag component in a lot of oscillations seems to be a very difficult element of determining correlation and causation. With the ocean cycles and abyssal water not interfacing with the atmosphere for hundreds of years, I can see how there can be challenges in developing any precise relationships.

        Great series, BTW.

  55. Javier:

    I am guilty of skimming your article. Perhaps my brain works better with pictures. I’ll sometimes sketch things out. So my comments might apply to a limited number of people. Here:

    https://curryja.files.wordpress.com/2018/08/figure-133.png?w=434&zoom=2

    I think is exactly the illustration for the 41k argument. Panel b is some kind of ratio that scientists do for paleo. Panel c agrees with what I came up with above about 2 or 3 cycles. I came up with 41k as a rough average taken from your terminations dates. Your picture adds to the written explanation of my potential rules.

  56. I must say that this is most well researched and written article that I have read on this blog. Credit to Javier for his hard and thorough efforts. But I don’t believe for a moment that low eccentricity leads to both higher ice build up and warmer interglacials.

    The saw-tooth nature of glacial cycles as well as the noise patterns, and also the extra events like 7 a-c and 15 a, are an ideal fractal analogue of centennial to millennial scale complex multi-body heliocentric synodic cycles which slowly slip out of phase and then fall sharply back into sync again.

    If we look at interglacial intervals with respect to the fourfold pattern of interglacial events, between:
    19c and 11c,
    17c and 9e,
    15e and 7e,
    15a and 7a-c,
    13a and 5e,
    The intervals are all very close to 370k years, and 7 a-c and 15 a, are an intrinsic element of the 370k year pattern. But 370k years after 11c suggests that the Holocene should have started 40k years ago. Oops.

    Fig 2, page 6 of 58:
    https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015RG000482

    • Here is an analogue at the Holocene scale with GISP2. The patterns of warm and cold events repeat over a cycle of 3453 years.

      • In fact the shorter period which looks to be around 285K yrs, also occurs between the mirrored pairs of 15e – 9e, and 7a-c – 13a.

    • Another thing that I would expect with such cycles is symmetrical mirroring within the event sequence. Such as the warmer anomalies just over 27750 yrs before 7e, and just over 27750 yrs after 15a. With 27750 years being 3/4 of 37000 yrs.

      • Sorry I have missed some zero’s there, correction: 277.5ka and 370ka, and the 4.41pm comment should have been after the above one.

    • © Ulric Alexander Lyons 2018

  57. Javier,

    During the past 2.3 million years no interglacial has been able to continue from one obliquity oscillation to the next. Low obliquity conditions have always led to the end of the interglacial.

    What conditions are required to escape from the Pleistocene ice Age?

    The Permian-Carboniferous Ice age had cycles of glacial and interglacial periods similar to those experienced during the Pleistocene so far. However, it eventually escaped and, over the next 40 Ma, the planet’s average temperature warmed to the Triassic maximum (about 13 C warmer than now). Can you speculate on what conditions existed to enable the planet to escape that ice age and warm to much higher temperatures?

    Was the locations of the tectonic plates and ocean gateways a significant factor?

    • Peter Lang, Christopher Scotese was so kind to send me a couple of links. The following link is one of them and is a great one: http://dinosaurpictures.org/ancient-earth/#50

      You can move the globe with the mouse. And you can use the arrow keys on your keyboard to switch through periods. When you switch from 50 million years to 35 million years you see a big difference. (Note: I think 33 or 34 million years ago is more correct for the showed situation but for now that is less important. I will have to check the exact date).

      The difference between the shown periods is in the shallow and enclosed oceans, especially in the subtropical region south of Eurasia. The situation of 50 million years ago enabled warm deep water production. The situation of 35 (I think 33 or 34) million years ago lacked this situation. Present situation is enabling cold deep water production, while warm deep water production nearly stopped (except for the Mediterranean, the Red Sea and the Persian/Arabian Gulf and some small dispersed spots)

      Very interesting is also what happened with the Atlantic /Arctic region during the last 100 million years. I should write a post about that. Remember that the most saline waters nowadays are in the Atlantic Ocean. Gyres and the high pressure areas above the gyres enable enduring evaporation in the subtropics and a high salinity of the gyres results. In the last 20 million years the Arctic Ocean became well connected with the Atlantic (you will see the opening up of the North Atlantic). This opening up was enabling very cold deep water to leave the Arctic and in turn very saline warm water at the surface could enter the region. The high salinity has put in motion the high North Atlantic production of cold deep water: after cooling a deep sink of the dense water resulted. And as oceans cooled more and more, we became heading more and more to the Pleistocene.

      You will enjoy the use of the link.

      • Wim R,

        Thank you for your comment. All very interesting. I delays replying because I waas intending to make a more substantive comment, but I don’t have time at the moment. My question to Javier, which he hasn’t answered, is what conditions prevailed that enable Earth to escape from the Permian ice age.

      • Peter Lang, the ‘General Background Temperature’ of the Earth’ is what results as conditions cause cooling respectively warming of the Earth as a whole. ‘Conservation of Energy’ plays the main role. That ‘Conservation of Energy” takes place in/by the oceans (by warm respectively cold deep water production) and in the atmosphere (by [lack of] absorbing gases, water vapor (!) being the most important). The positioning of continents and the resulting configuration of continents and oceans is causing continuous warming respectively cooling of the Earth’s system.

        Your question about the Permian situation is interesting. I am preparing one or two posts (that I am used to publish on Wattsupwiththat) about the role of water vapor. Perhaps I will come back on the Permian situation in one of them or publish a separate post. In short the answer on your question is: the spreading and equator ward movement of continents has been the instigator of ‘warming’ at the end of the cold era: a newly developing warm deep water production and the rise in water vapor content in the atmosphere were causing more ‘Conservation of Energy’ by oceans and by the atmosphere and that process resulted in a continuous warming of the Earth. Until a further repositioning of continents and oceans started to reverse the warming process in a cooling process.

        In our present situation the Earth cooled that far that the Earth became extremely susceptible for relatively slight changes in orbit and other influences. Well analyzed by Javier and Renee Hannon.

    • Peter
      The Permian-Carboniferous Ice age had cycles of glacial and interglacial periods similar to those experienced during the Pleistocene so far.

      This is most interesting, I have been looking for research showing similar glacial-interglacial cycling in previous ice epochs, with the limitation being time resolution many Mya. Can you give any references for this (I believe ya! Just would love to see original data.)

      • Philsalmon,

        The link to the source I was referring to is broken. Below are some excerpts from another source (not published but with links to published sources) https://www.geocraft.com/WVFossils/Carboniferous_climate.html :

        Interestingly, the last half of the Carboniferous Period witnessed periods of significant ice cap formation over polar landmasses– particularly in the southern hemisphere. Alternating cool and warm periods during the ensuing Carboniferous Ice Age coincided with cycles of glacier expansion and retreat. Coastlines fluctuated, caused by a combination of both local basin subsidence and worldwide sea level changes. In West Virginia a complex system of meandering river deltas supported vast coal swamps that left repeating stratigraphic levels of peat bogs that later became coal, separated by layers of fluvial rocks like sandstone and shale when the deltas were building, and marine rocks like black shales and limestones when rising seas drowned coastlands. Accumulations of several thousand feet of these sediments over millions of years caused heat and pressure which transformed the soft sediments into rock and the peat layers into the 100 or so coal seams which today comprise the Great Bituminous Coalfields of the Eastern U.S. and Western Europe.

        Earth’s climate and atmosphere have varied greatly over geologic time. Our planet has mostly been much hotter and more humid than we know it to be today, and with far more carbon dioxide (the greenhouse gas) in the atmosphere than exists today. The notable exception is 300,000,000 years ago during the late Carboniferous Period, which resembles our own climate and atmosphere like no other.

        Basically, Earth undergoes alternating periods of ice ages and warming whenever a continuous continental landmass extends from one polar region to the other while at the same time there exists a large polar continent capable of supporting thick ice accumulations. These conditions existed 300 million years ago during the Carboniferous Period as they do for the Earth today. However for most of geologic history the distribution of the continents across the globe did not satisfy this criteria. Continental drift continually rearranges the continents, moving at rates of only a few centimeters per year.

        https://www.geocraft.com/WVFossils/Carboniferous_climate.html

  58. sheldonjwalker

    A challenge to the websites “Open Mind” and “AndThenTheresPhysics”

    In my opinion, “Open Mind” and “AndThenTheresPhysics”, are both just Alarmist echo chambers.

    They are NOT interested in open debate about global warming.

    The people who run these websites, and their followers, sit around insulting people who they see as “the enemy”. But they won’t engage with “the enemy”, in honest debate.

    They have insulting names for “the enemy”. “Deniers” is the most common.

    It is ironic, that Alarmists are actually the biggest “Deniers”.

    I have posted comments on both of these websites, in the last week. Anybody who reads my posts, knows that they are polite, they do not attack people, they do not use foul language, and they provide evidence to back up my views.

    Tamino always deletes my comments immediately. He doesn’t want his followers exposed to global warming heresy.

    AndThenTheresPhysics initially posted my comment, because he has not had contact with me before. After he checked out my website, he deleted most of my comment. The ideas on my website must be very scary, and AndThenTheresPhysics didn’t want his followers exposed to them.

    In response to my initial comment, AndThenTheresPhysics said, “I tend to have a low tolerance for comments that promotes scientific views that are clearly wrong. If you want to call that an “alarmist echo chamber” go ahead.”

    When did AndThenTheresPhysics become the God of Science, deciding what is right, and what is wrong.

    I thought that Science was an open ongoing debate, and that ideas which didn’t get disproved, became accepted. If you stop ideas being expressed, because you think that they are wrong, then it is no longer Science, it is Religion.

    My challenge to “Open Mind” and “AndThenTheresPhysics” is, decide what you want to be. An open forum for discussing global warming, or a bunch of losers, who sit around bitching and moaning.

    It’s YOUR choice.

    Your friend,

    Sheldon Walker
    https://agree-to-disagree.com

    • By far the worst sites for discussion are the “skeptic” sites. Heller-Goddard is nothing but insulting to people who understand the science more than him (most people, apparently), and his insults are those of a child. Don’t believe me? Read the comments. He thinks taking simple averages of raw data is the way to go.

      Watts does the same to a lesser degree, and can’t stand having comments from people who have degrees in science. His insistence that he knows more than climate scientist makes him look small.

      Curry is one of the better “skeptics.” It’s really odd that she understands adjustments yet allows “skeptics” who call them “fudging” or “fake” to comment freely. It’s all “we’re warming, but how could we possibly know why” stuff.

      These people need to decide if going against 100 years of actual physics is a scientific way to go. And they are going against every world science organization that has weighed in on this topic.

      • Scott Koontz: Watts does the same to a lesser degree, and can’t stand having comments from people who have degrees in science.

        That last is false. But anybody who posts there can expect energetic disputation..

      • “That last is false. But anybody who posts there can expect energetic disputation.”
        LOL, that’s the politically correct way of putting it.
        Amusing to see Monckton and Eschenbach at daggers in the Good Lord’s latest call for validation through “peer-review” there as the real nes have rubbished ir.
        As to ATTP’s “…. become the God of Science, deciding what is right, and what is wrong.”
        It’s his website and he doesn’t have it for clicks unlike Watts.
        And quite right he dosn’t entertain people arguing against empirical science. Science has been “arguing” that since Tyndall and Arrhenius and not been found wrong (Co2 drives temps when coming first).
        Watts would love to ban Nick Stokes, but he’s not given him grounds to do so, he regularly says such as “you are not an honest reasearcher”.
        So it goes down the rabbit-hole.

      • Geoff Sherrington

        Scott K and Tony Banton,

        Your big impediment is your confusion of science with belief.
        Science has yet to find a definitive way to separate natural from anthropogenic climate effects.
        Science has been unable to put a sensitivity number on the overall effect of GHG on the temperature of the atmosphere.
        Science has shown sea levels to be changing at much the same rate before and after the global GHG increase.
        Science has shown the frequency of damaging events like droughts, floods, hurricanes, fires to be much the same before and after the GHG increase.
        Science has confirmed and replicated increased growth of many significant biota under higher GHG in the air.

        About the only significant alarmist correlation with increasing GHG is temperature in a small window of time. But then, nobody has proven this to be causation.
        A strong belief that things ought to have been different to the science is a nothingness. Taken too far, as it has been, over and over, the belief in anti-science findings become no more than propaganda.
        You will find a smoother road when you face the realism of hard science, axe your strange belief systems and quit spreading propaganda.
        No senior, experienced, hard scientist will be likely to listen to you, except with pity, until you realize this. Geoff.

      • Scott and Tony

        Don’t get carried away with your own sense of infallibility. There are huge gaps in knowledge about climate but true believers like you two have been so brainwashed you can no longer think straight. Good luck in convincing yourselves you can.

      • Scott Koontz

        ‘No senior, experienced, hard scientist will be likely to listen to you, except with pity, until you realize this.”

        Why would they listen to me, when I’m simply listening to the experts and not Watts or Heller types?

        You’re an insulting child stating that they would listen with pity. Odd, because it is apparent that I have more science background to understand AGW than you, but do go on pretending that you have this covered. You’re definitely Heller-Watts material, and they’d love you there.

        Read up on how Watts said he’s believe the results of BEST, then ran away screaming. Read about Heller’s raw temp averages, and how the daily high temps of June 22 for one small midwest town means the earth must be cooling. Come back when you’re educated about these people.

        Seems the real scientists have been right about the forcings for more than three decades, and the “skeptics” have been pretending that the primary forcing is something other than CO2.

        Would a teaching climate scientist take pity on a “skeptic” for going wrong answers on the first quiz?

      • Scott Koontz

        “but true believers like you two have been so brainwashed you can no longer think straight. Good luck in convincing yourselves you can.”

        More insults. This is a science discussion site, right? Aren’t most of you pretending that you discuss science and that the other side (the super majority of scientists) are the ones who can’t stick to the topic?

        What’s with the “true believers” BS? I truly believe that our atmosphere has something to do with the obvious warming, because science. I truly believe the experts over people like Watts, Harrison, Bastasch, Monckton, Heller-Goddard. Is there a problem with “believing” the experts today?

      • Scott
        You ol’ stirrer – just had to start a mini flame war!
        Watts does the same to a lesser degree, and can’t stand having comments from people who have degrees in science.

        Most contributors to WUWT have degrees (I have 4), many of these had them before you were born.

        It’s all “we’re warming, but how could we possibly know why” stuff.

        We’ve always been warming and cooling you creationist. What is the reason for the current warming? The same reason as all the other warmings. The ocean is not static. Don’t believe me? Get Mummy and Daddy to take you for a holiday by the seaside.

      • “many of these had them before you were born.”

        You write well for an 80-yr-old. The insults are childish. Did you really think you knew my age?

        “What is the reason for the current warming? The same reason as all the other warmings. The ocean is not static.”

        Again with the non-science. Does the ocean warm on its own? No, it moves the heat around. Of COURSE the ocean is not static. The topic is why the earth is warming, and we all know that the oceans move heat around.

        “Don’t believe me? Get Mummy and Daddy to take you for a holiday by the seaside.”

        This is what we expect from childish posters like you. This is why actual skeptics leave “skeptic” sites. Why do you call your parents “Mummy and Daddy?” And why tell us about your holidays by the seaside? We really don’t care about your childhood, especially now that we know you are older than 80.

        Nice job. You prove my point about the childishness of these sites.

      • Scott

        Are the basement walls starting to close in on ya?

      • Scott
        You side-stepped the question of why all the other warmings happened previous to the modern warming of the last century. There have been about 19 similar such warmings during the Holocene. What caused the other 18? Why is the current warming – completely average in magnitude – any different?

      • Let’s just clear this up…
        What I said was that empirical science wasn’t up for discussion at ATTP’s Blog.
        By that I mean that it is empirically proven that CO2 is a GHG and that as such it’s anthroprogenically caused increasing atmospheric concentration must drive global atmospheric and ocean temps.
        No more no less.
        That isn’t belief as “belief” requires no evidence.
        Are you saying empirical science is not evidence?
        If you are not then I do not have “belief” I have knowledge … not 100% certain to be correct but as near as damn it.

      • “It’s really odd that she understands adjustments yet allows “skeptics” who call them “fudging” or “fake” to comment freely.”

        I don’t see it. I don’t think it’s worthy of mentioning. Sure, once in awhile. But what I quoted is not accurate insofar as there are ten more weighty things you could say about Climate Etc., rather than bring up some minor occasional thing. Sure, recently someone said the GHE doesn’t exist or something along those lines. A few of us gave a little push back. It was actually boring. And I think interest was lost.

      • “These people need to decide if going against 100 years of actual physics is a scientific way to go. And they are going against every world science organization that has weighed in on this topic.”

        100 years of actual physics can only tell a broad story of things. CO2 warms. CMIP grid sizes are atrocious. Cloud knowledge is terrible. Ocean data is spotty and short (ARGO start date). The carbon cycle is poorly constrained. Ocean currents, up and down welling might as well be what I know about it.

        100 years of actual physics is pathetic. At this rate it will take another 200 years and trillions of dollars. Someone made a product and it sucks. It hardly does a thing.

        I don’t care what every (not 90% of them) say about climate change. That’s politics. That’s them selling out.

      • philsalmon, you need to document each of your 18 other warmings because for most people the Holocene looks like this.

      • “for most people the Holocene looks like this.”

        That figure is wrong. Even the authors acknowledged it wasn’t statistically solid. Translated to “we made it up.”

        The people that think the Holocene temperature looks like that don’t know much about the Holocene.

      • “By that I mean that it is empirically proven that CO2 is a GHG and that as such it’s anthroprogenically caused increasing atmospheric concentration must drive global atmospheric and ocean temps.”

        I’d say that’s very likely, but not inevitable.

        Longwave TOA radiance is largely a function of greenhouse gas constinuency.
        But longwave TOA radiance also depends upon temperature vertical profile, humidity vertical profile, and cloud vertical profile.

        It’s conceivable and, by radiative model, demonstrable that certain changes could negate radiative forcing from increased CO2.

        Now, if such changes were to occur, and I’m not sure they’re at all likely, then that would constitute “climate change”, so in a sense, the only way for temperatures to not rise would be climate change.

        But it is possible.

      • Regarding the HCO maximum temperature chart above, remember what the proxy is actually capturing: temperature on days when snow fell on the top of Greenland, not temperature when snow melted.

        The most significance to ending glacials are the clearest and hottest days of summer, not much else. Days when snow fell are probably not very clear and not above freezing.

      • Javier, if anyone has a picture of 18 other Holocene warmings like the one in the past century, I have not seen it yet. More likely they misunderstood something and generated a wrong meme out of it, or made it up to fool the less wary, one or the other.

      • “if anyone has a picture of 18 other Holocene warmings like the one in the past century, I have not seen it yet.”

        There’s no such a picture, but there is evidence of previous periods of warming as intense as the current one. The one that put an end to the 8.2 kyr event for example.

      • Are they making up those 18 other warmings then? I am asking because I want to get at where this stuff comes from.

      • “Are they making up those 18 other warmings then?”

        Probably they are using GISP2.

        I analyzed periods of significant global climate change in Marcott’s ensemble. They all belong to the 2500-yr cycle.

        The present one is slightly more intense, but it is to be expected. After all CO₂ must have some effect.

      • The problem with using one site is that you can find any number of warmings in it that are not global. When they use proxies, they aim for a distribution of sites for a reason.

      • JimD
        Here is the temperature reconstruction of the Holocene based on GISP2 (Alley 2000) isotope ratios. The one that escaped the Shakun and Marcott pollen and midge ironing board. In other words, the real one. Not hard to find your 19 OMG global warmings here:

      • CO2 Jimmy will never try to think it over, he is like a fanatic religious believer, and a totally layman in climatology. Do not take too much care about those Troll Robots.

      • philsalmon, maybe you can fool the other skeptics with that, but data from one highly variable site does not represent global temperatures.
        https://www.skepticalscience.com/print.php?r=337

      • JimD
        Ocean sediments generally agree with GISP but not with the crowd of highly questionable biological “proxies” that Shakun / Marcott used.

        8000 years ago Greenland temperature changes by 4 degrees while the Marcott ironing board shows stasis. They can’t both be right.

        Shakun, Marcott and Pages2k have all done the same thing. Bring in as many weak proxies as possible to smudge the Holocene temperatures flat, then MNT an instrumental spike at the end.

        Holocene paleo climate is in a poor state. I interpret the Greenland ice cores plus sediment isotopes as the most reliable reconstructions.

        Greenland fluctuations come from the instability of the AMOC. I doubt that it is only Greenland that feels the effect of this.

      • Javier writes:
        “I analyzed periods of significant global climate change in Marcott’s ensemble. They all belong to the 2500-yr cycle.”

        The 5.2kyr and 8.2kyr episodes were warm for the mid latitudes, and cold for Greenland.

      • “The 5.2kyr and 8.2kyr episodes were warm for the mid latitudes, and cold for Greenland.”

        Sure. That’s why Ötzi got frozen 5.2 kyr ago. It was during a really warm event.

      • Javier confidently mocking once more, but fails to think it through. Is this the sole case of finds that melting Alpine ice has revealed, that fell there during a colder period rather than during a warmer period? More like Oetzi was hiking across a melting Schnidejoch like the couple that found him in the hot summer of 2003, and then got frozen over.

    • Scott Koontz

      In my opinion, “Open Mind” and “AndThenTheresPhysics”, are both just Alarmist echo chambers.

      I have to admit, those are great sites for discussion. The articles on Heller-Goddard’s use of cherry-picked summer high temps is spot on. Amazing how he uses a specific location (the US48), a specific starting point (100 years ago makes the dust-bowl era the beginning), summer only, simple averages (UGH!) and absolutely no adjustments because they are the devil, doncha know.

    • Sheldon,

      It is a real problem to find places where people with opposite ideas about the climate can discuss in a civilized manner. Climate Etc. is an outstanding case. I have been banned and censored from several sites including Tamino’s “Closed” Mind. But as a lukewarmer I have had problems with commenters at WUWT. I can only praise Anthony Watts for his openness (with a couple of exceptions) and he has a lot of patience with my tremendous intellectual battles with his illustrious guest Leif Svalgaard. On the other side of the divide I have yet to find someone willing to engage skeptics or allow them to freely express their opinions without censorship.

      It is clear that there is an asymmetry. Consensus builders do not foster discussions with skeptics, as if their hypothesis wasn’t good enough to withstand open challenge. I guess consensus builders are on a mission to convince the world and have little tolerance for dissent. Not a good sign.

      • very right! Thanks for your work and patience

      • Lol. And bonkers to boot. There is no point in them wasting any time on Sheldon.

        OT:

        Last Month Australia’s BoM had a graph completely at odds with what they were saying and with other ENSO prediction sites. It is now corrected:

      • Waiting for El Ninot again ?….

  59. They have insulting names for “the enemy”. “Deniers” is the most common.

    It is ironic, that Alarmists are actually the biggest “Deniers”.

    Dead right on that the Alarmists are actually the biggest “deniers”. Rational discussion is impossible with such people.

    A flowchart to help you determine if you’re having a rational discussion
    http://twentytwowords.com/a-flowchart-to-help-you-determine-if-youre-having-a-rational-discussion/

    • Scott Koontz

      “Alarmists”

      Hypocrisy. So are all the super-majority of climate scientists “alarmists”? Seems strange that you perceive the most knowledgeable on this topic as “the enemy. The majority of climate scientists are the more educated group with the most peer reviewed science and the most years of fine-tuned results.

      Science progresses, corrects, fine tunes. It bothers many on this site that the basic physics is well known and each decade is warmer despite their continued predictions of warming. Remember the “pause” that excited so many skeptics? You were watching the dog, and took your eyes off the man walking the dog.

      • You see something very wrong. Of course there is almost nobody in climatology science who would claim, CO2 and other GHG have no climate effect. But there is no “consensus” about the amount of the human part since the end of the LIA or future warming. So called alarmists claim catastrophic and near 100% human influence, their idiotic climate thinking is poorly reduced to CO2. Think over the politics behind all that…

      • So are all the super-majority of climate scientists “alarmists”?

        What exactly is the super-majority opinion?

        It is that atmospheric gasses active in the infra-red region ( tri-atomic or higher order, such as CO2, H2O, CH4, et. al. ) tend to reduce atmospheric emissivity.

        There are even certain predicted outcomes that follow and have been observed:
        increased tropospheric temperatures, decreased stratospheric temperatures, much greater increase of winter time Arctic ( due to increased latent heat release ).

        There are predicted outcomes that are still not very well measurable:
        Increased evaporation.

        And there are other outcomes, predicted, but contradicted by observations:
        upper tropospheric hot spot.

        There is not a super-majority, probably closer to 50-50 that much other climate change will occur and certainly no consensus at all that dangerous climate change, despite alarmist proclamations otherwise, is at hand.

      • TE, there’s also that forcing that has risen to 2 W/m2 over the last century easily accounts for all the ocean heat content increase seen. So where did all that energy go if not into the ocean heat content, and then why did the ocean heat content rise so much if not from the CO2 forcing?

    • Scott Koontz,

      The science is not what is relevant for justifying policies for, or not, GHG emissions reduction polices. It is the impacts that are relevant. That is not climate scientist’s field of expertise. Alarmist like yourself need to understand the impacts of global warming. They are beneficial. Warming is beneficial. So there is no valid justification for wasting $ trillions and slowing global development on the basis of the climate alarmists beliefs and their inferences of catastrophic outcomes..

  60. Pingback: Weekly Climate and Energy News Roundup |

  61. With an exacting harmonic analysis of the mirrored period between interglacials 7a-c and 15e, with reference to the exhibited 370 kyr cyclicity and associated sub-harmonics, I reckon it should be possible to model mathematically why the so called 100 kyr sequence began, and why it is now ending.

    • In fact the mirroring about the center at interglacial 11c, goes beyond 5e and 17c, but breaks down with 19c and the Holocene.

    • The nominal interglacial interval is 85,000 years. Playing that against the 370,000 year pattern gives a clue to how the recent 115,000 year period could have arisen.

    • The red lines indicate the 370,000 periodicity. Measure them for yourself on Fig 2 of the paper.

    • An important clue is that the precise periods of 85kyr, 115kyr, 285kyr, and 370kyr, occur between various interglacial peaks, and to different peaks of the three dominant peaks in 7a-c. The mirror image of 15e is the same pattern, albeit weaker on its younger peaks.

    • It is also well apparent that the remaining non-interglacial warm features and spikes also conform to these periods and multiples of.

    • ‘Nullius in verba’

  62. Javier, I have thoroughly enjoyed reading your series of articles. I especially like your explaination on the role of eccentricity on global ice volume.

  63. nickreality65

    For the Radiative Green House Effect to function as advertised, i.e. warming the surface of the earth by 33 C, that surface must radiate as an ideal black body.

    But non-radiative heat transfer processes, i.e. conduction, convection, advection, latent/evaporation/condensation, of the contiguous atmospheric molecules render such ideal BB emission impossible.

    Trenberth says the ocean’s emissivity is 0.97. The turbulent non-radiative heat transfer processes are responsible for most of the heat movement from ocean to air and LWIR emissivity is more like 0.16.

    Without the ideal 396 W/m^2 upwelling BB radiation the 333 W/m^2 up/down/”back” GHG LWIR energy loop does not exist (TFK_bams09)

    and carbon dioxide does no warming

    and mankind does no climate changing.

    Got science? Well, BRING IT!!

  64. It is not cooling that has made for glacial cycles longer than 41kyrs, it is the longer cycles that allow for greater cooling.

  65. With the actual figures for the timing of each inter-glacial, one can accurately calculate where they occur in relation to the peaks in obliquity.

  66. Javier, the bottom line is that you are looking in the face of solar variability, which will be tightly constrained by the said synodic ‘numerology’. So there are no legitimate grounds for proposing a 6000 year delay to obliquity, when the precise timing of each inter-glacial, and much of the noise, belongs to a completely different set of frequencies.

  67. I received the below in an email last night. It refers to o an article “The Watery Planet Effect” by Geraint Hughes https://principia-scientific.org/the-watery-planet-effect/?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+psintl+%28Principia+Scientific+Intl+-+Latest+News%29.

    “[…] has sent around an article trying to calculate warming in the upper ocean as one of the key effects in global warming. This article omits the key thermo-dynamics of Antarctic Bottom Water. It is hard to produce a full mathematical thermodynamic model for the oceans using extensive observations as the Argo Buoy system of a few thousand buoys is only giving us a profile of the upper 2 kms.

    South America fully broke away from the West Antarctic Peninsula forming the Drake Passage less than 20 m yrs ago. This event caused the circumpolar current to form; a current of around 100 million cubic metres of water moving per second and the largest ocean current on Earth. The boundary separating the Earth’s oceans to the north from the Southern Ocean is called the Antarctic Convergence. At this circular boundary around 45 degrees S to 50 degrees S the temperature drops from 5.6C to less than 2.0C within about 50 kms (quite a spectacular change forming one of the largest ecological barriers on Earth). Below this boundary any pack ice that forms is less salty than the ocean water it comes from so the resultant surface waters are then more salty and heavier and sink to form the largest single body of ocean water on Earth.This “bottom water” that sinks and creeps north is initially around minus 0.5C. Over millions of years it has continued to form the bottom 2kms of deep water in the Atlantic, Pacific and Indian Oceans as far north as 10 degrees N!!!

    Since the formation of the Antarctic Convergence the Antarctic Bottom Water has been not only cooling the ocean, but probably has been the main factor in cooling the Earth over the last 6 + million years and forming a cooling trend over-riding the shorter temperature changes caused by recent ice ages. As the Earth cooled it first reacted to slight extra cooling effects of the 41,000 yr changes in axial tilt and then, when even cooler, it was sensitive to extra cooling variations caused by the 100,000 odd yr Milankovich cycles due to variations in the shape of the elliptical orbit. Note from the figure below that in the paleo-ocean temperature graph (of O18/O16 isotope variations) the 41,000 tilt cycles appear nearly 2 million years before the 100,000 year cycles in the last 1 million years. (It is not as if these cycles have not been around for millions and millions of years, but rather the Earth has to get to certain lower temperatures before their cooling effects are noticeable in the paleo-temperature record).

    Finally, I see no evidence that the oceans have been a key leading driver in modern global warming but only that variations in upwelling and sinking of ocean water can cause short-term cyclical climatic changes due to interchanges of heat with the atmosphere. The clearest cycle being the Pacific Decadal Oscillation of roughly 60 years with half cycles around 30 years. In Australia we are very aware of the more unpredictable El Nino-La Nina variations. (And there are other similar cycles in the Atlantic and Indian Oceans).

  68. Peter Lang, from the email you received: “Finally, I see no evidence that the oceans have been a key leading driver in modern global warming but only that variations in upwelling and sinking of ocean water can cause short-term cyclical climatic changes due to interchanges of heat with the atmosphere.”

    WR: I wrote about the role of oceanic upwelling and downwelling and longer term temperature effects in the following posts:
    https://wattsupwiththat.com/2016/12/26/warming-by-less-upwelling-of-cold-ocean-water/
    https://wattsupwiththat.com/2017/01/26/warming-and-the-pause-explained-by-wind-upwelling-and-mixing/
    https://wattsupwiththat.com/2017/07/17/the-role-of-ocean-upwelling-and-the-deep-ocean-in-the-glacial-cycles/

    The first link gives some simple calculations that show that a small difference in upwelling can explain all last century warming.

    The maps in the second link above show that wind is the driver in upwelling and mixing in the oceans. By mixing, wind must have a role in the salinity of the surface as well and by this must be influencing downwelling.

    Wind is very variable and seems to have a long cycle of 120 years or more. Interesting graphics of COADS data you will find under ‘wind speed departures’ in the following document: http://www.seafriends.org.nz/issues/global/fletcher.htm

    P.S. Very interesting link to ‘The Watery Planet Effect’ you gave above. After a quick look at the article: by other reasoning I already came (more or less) to the same conclusion. I will read the article well.

  69. Ulrich Lyons
    In more than 25 of your posts here, not a single mention of obliquity, precession or eccentricity.

    (Except at the very end, a negative reference to obliquity, opposing its role.)

    Are you asserting that the Milankovitch cycles are irrelevant to glacial-interglacial timing?

    Is the coincidence of every single interglacial with an ocean-lagged obliquity peak – many dozens of them – pure coincidence by chance? In your own postings you give much more authority to such phenomenological alignments. This is a profound inconsistency in your arguments.

    Milankovitch – free glaciation timing: seriously?

    • I have correctly stated that interglacial peaks of the last 800kyrs years are finely timed by something other than Milankovitch cycles. And that one can accurately calculate the timing of these interglacial peaks in relation to the peaks in obliquity. I would look for direct effects of maximum obliquity in the fast warming at the onset of interglacials, rather than greatly lagged effects at their peaks. That could have impacted about half of the cases in the last 800kyrs, though it is not dictating the timing as that also follows my figures and not the obliquity. And please do not put an ‘h’ at the end of my name.

      • “I have correctly stated that interglacial peaks of the last 800kyrs years are finely timed by something other than Milankovitch cycles.”

        You are just one of dozens of people that have a pet explanation for climate change that it is totally outside of current scientific understanding, and have little following, like popesclimatetheory, and melitamegalithic. The common factor is that the supposed evidence is either non-existent or can be interpreted differently.

      • Javier, the periods that I have identified are certainly not a ‘pet explanation’, they are an astute and skillful observation.

      • Which doesn’t mean you are correct with your explanation. It is clear that you, Pope and Melita cannot be correct at the same time. This is why the great majority of hypotheses about anything are wrong. There are nearly infinite explanations and all but one are wrong. The chances are that your three hypotheses, and many more, are wrong. It doesn’t matter how astute or skillful they are.

      • I have not yet developed a hypothesis, but that the periods are in very fine agreement in multiple cases shows that it certainly has got zero to do with chance. They are also intrinsic to the symmetry, which no one else has seen before.

      • Javier, look on the bright side. If you had not presented this article and that AGU paper link, I may have never spotted it.

    • More importantly though, it is shame that you are failing to appreciate what I have found. Like the exacting symmetry centered at interglacial 11c that has escaped attention for so long. It is through 14 years of tuning my lens to the complex nature of synodic cycles rather than Milankovitch cycles that I have learned to look for such patterns in data series.

  70. Great piece Javier. Just wanted to add it wasn’t just Kukla (though his name comes up most often):

    Hubert Lamb, Director of CRU, Sep 8 1972: “We are past the best of the inter-glacial period which happened between 7,000 and 3,000 years ago… we are on a definite downhill course for the next 200 years….The last 20 years of this century will be progressively colder.” http://news.google.com/newspapers?nid=336&dat=19720908&id=AiwcAAAAIBAJ&sjid=0VsEAAAAIBAJ&pg=5244,2536610

    John Firor, Excecutive Director of NCAR, 1973: “Temperatures have been high and steady, and steady has been more than high. Now it appears we’re going into a period where temperature will be low and variable, and variable will be more important than low.”

    Also since the claim about 1970s media is often hotly (and somewhat bizarrely) disputed, this link may be helpful if you don’t have it.

    hundreds of articles quoting scientists on the danger of global cooling
    http://www.populartechnology.net/2013/02/the-1970s-global-cooling-alarmism.html

  71. Great piece Javier. Just wanted to add it wasn’t just Kukla (though his name comes up most often):

    Hubert Lamb, Director of CRU, Sep 8 1972: “We are past the best of the inter-glacial period which happened between 7,000 and 3,000 years ago… we are on a definite downhill course for the next 200 years….The last 20 years of this century will be progressively colder.”

    John Firor, Excecutive Director of NCAR, 1973: “Temperatures have been high and steady, and steady has been more than high. Now it appears we’re going into a period where temperature will be low and variable, and variable will be more important than low.”

    Also since the claim about 1970s media is often hotly (and somewhat bizarrely) disputed, this link may be helpful if you don’t have it.

    hundreds of articles quoting scientists on the danger of global cooling
    http://www.populartechnology.net/2013/02/the-1970s-global-cooling-alarmism.html

  72. Great piece Javier. Just wanted to add it wasn’t just Kukla (though his name comes up most often):

    Hubert Lamb, Director of CRU, Sep 8 1972: “We are past the best of the inter-glacial period which happened between 7,000 and 3,000 years ago… we are on a definite downhill course for the next 200 years….The last 20 years of this century will be progressively colder.”

    John Firor, Excecutive Director of NCAR, 1973: “Temperatures have been high and steady, and steady has been more than high. Now it appears we’re going into a period where temperature will be low and variable, and variable will be more important than low.”

    Also since the claim about 1970s media is often hotly (and somewhat bizarrely) disputed, this link may be helpful if you don’t have it.

    hundreds of articles quoting scientists on the danger of global cooling
    www populartechnology.net/2013/02/the-1970s-global-cooling-alarmism html

    • Nice comment Talldave. Only the link does not give the wanted result. This link gives a result and you can do any search as well:
      http://www.populartechnology.net/search?q=the+1970s+global+cooling

      • Thanks Wim R, I had to try a few times, for some reason comment filters did not like when I posted links. That one works great.

    • Thank you Talldave2. Kukla continued having a very distinguished career until close to the time of his passing, quite recently. He has very interesting works defending that some of the climate changes we are experiencing would be required for a new glaciation. I didn’t discuss them for lack of space, for not agreeing much with them, and for not being cited much, but they demonstrate that he was clearly an out-of-the-box thinker, and who knows, he may be right.

      As an example take a look at this article’s abstract:

      Kukla, G., & Gavin, J. (2004). Milankovitch climate reinforcements. Global and Planetary Change, 40 (1-2), 27-48.
      https://courses.eas.ualberta.ca/eas570/tropics_glaciation.pdf

      “More than a century ago, British scientist John Tyndall argued that increased heating of the oceans was needed to start a glaciation (Tyndall, J., 1872). We show that he was essentially right and that the principal cause of Quaternary glaciations was the intensification of the hydrologic cycle by the warming of tropical oceans and increase of equator-to-pole temperature gradient, which led to the growth of land-based ice in the high latitudes. The change was due to decreased obliquity and to the increased intensity of the solar beam in boreal winter and spring at the expense of summer and autumn. This resulted in higher frequency of El Niño compared to La Niña anomalies. Decreased water vapor greenhouse forcing and increased reflection from expanding snowfields were also instrumental in the transition from the last interglacial into the glacial. The current orbital changes, although less extreme, are qualitatively similar. Association of recent positive seasonal anomalies of global mean temperature with El Niño events suggests that the ongoing global warming may have a significant, orbitally influenced natural component. The warming could continue even without an increase of greenhouse gases.”

      Sounds familiar? Popesclimatetheory believes he is original. What a masterpiece. He cites Tyndall, a sacred cow to the alarmists, as originator of the idea, and then he goes to conclude that CO₂ isn’t required for the warming.

  73. MIS 7a-c is very interesting. Its first peak is 115kyr past the peak of 9e, and the last peak of 7a-c at 200kyr ago, is just over 370kys past the peak of 15a. So for the symmetry to hold true, the first peak of 15e, should be 370kys plus the same small amount before the peak of 7e. Which it is.

    And while I am on 7a-c, maybe Javier can explain why his lagged obliquity for 7a-c looks so at odds with figure 4 in this paper:
    https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015RG000482

    • “maybe Javier can explain why his lagged obliquity for 7a-c looks so at odds with figure 4 in this paper:
      https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015RG000482

      Very easy. The dating of marine cores is extremely complicated. Lisiecki and Raymo fine tuned the dating of LR04 to astronomical data, as you can see if you read their papers. The problem is that since nearly everybody believes that the relevant parameter is insolation, the tuning is done to insolation. Figure 4 from that paper uses LR04 to match orbital changes. At the very least it is circular reasoning, at worst completely wrong.

      I use Epica Dome C data for matching climate to orbital changes. Ice cores, and particularly Epica Dome C are about one order of magnitude more precise in their dating, and are not orbitally tuned. This guarantees the data is independent and there is no circular reasoning. My results can be trusted better.

      • Your obliquity related signal at 7a-c is hugely displaced from a 41kyr periodicity.

      • No, it is not. Compare with the black curve in figure 133 a. The black curve is very dependent on obliquity.

      • The black line is peaking at 7a-c about 5,500 to 6,000 years before the regular 41kyr intervals.

      • That’s because it is not obliquity, but summer energy at 65°N, as the figure indicates. That data is directly originating from Peter Huybers as supplementary information to his article and can be publicly downloaded. I haven’t changed it except for the 6 kyr lag.

        The coincidence between MIS 7a-c and summer energy at 65°N is a very nice confirmation that it is the correct parameter ruling interglacials, and not your numerological lucubration.

      • “and not your numerological lucubration”

        Why the gratuitous insulting language? How about offering a link for this supplementary information.

      • “Why the gratuitous insulting language?”

        Because you are bothering other people with this issue before asking me for the information.

        “How about offering a link for this supplementary information.”

        If you ask, I provide.
        https://gcmd.nasa.gov/KeywordSearch/Metadata.do?Portal=amd&OrigMetadataNode=GCMD&EntryId=NOAA_NCDC_PALEO_2006-079

      • I have not ‘bothered’ anyone else with this issue, and your insult is directed at my findings on the timing of interglacials, and not at this issue.

      • That is not the link to the supplementary information for Huybers, and the real problem here is that the obliquity peak is at least 4kyrs past the first peak of 7a-c, and with your 6kyr lag, that becomes 10kyrs. That’s leaves rather a large time for Summer energy to be out of phase with obliquity.
        With your massive figure 138 errors, I’d never trust your results. And it’s not exactly your first post where I have identified major issues with your graphs and charts and your computational skills. Like where you counted 28 points in an events series as 28 intervals rather than 27 intervals. And never once do you acknowledge your errors when exposed.

      • The real problem here is that even when given the name of the author and year of the data you are unable to find his data in the paleo database, something that for any normal human being is a 5 minute search.

        Here you have another link:
        https://www.ncdc.noaa.gov/paleo-search/study/5792

        And in case you get lost and can’t find the appropriate file, here it is:
        https://www1.ncdc.noaa.gov/pub/data/paleo/climate_forcing/orbital_variations/huybers2006insolation/j_65north.txt

        Make sure you use the 275 W/m² threshold so you don’t come back complaining again.

        I couldn’t care less for your lack of trust as it comes from your inability to reproduce even the simplest of the graphs. Everything I do can be easily reproduced and checked by anyone with an internet connection. Or almost anyone.

      • Javier, although I like the elegance of your theory, your proof is always in the form of wiggle graphs where one should see the correlation. Statistically however, it is not convincing.

      • Hans, it is not up to me to find proof about something that has been published in the scientific literature by eminent specialized researchers like Peter Huybers or Christos Tzedakis. My graphs might help people see what they are proposing, but the demonstration corresponds to them.

  74. Global cooling would starve the world. Global warming would feed the world.

    Global warming is beneficial in total for all the impact sectors.

    Fossil evidence suggests the optimum temperature for life on Earth is about 7 C warmer than present – so no reason to fear catastrophe.

    Consider the perspective of time. The last time the planet was in a deep ice age similar to the one we are in now, which began about 3 Ma ago, was 300 Ma ago. It lasted about 70 Ma. It took 20 Ma to warm to to the optimum temperature, and another 20 Ma to reach the Triassic maximum (which was about 13C warmer than now).

    Given it took 20 Ma to warm to optimum last time, how could it possibly warm to even half that (i.e. warm by 3.5C), in hundreds or even thousands of years? How could the cold water in the deep oceans be warmed in such a period, especially given the issue with the ocean current circulating Antarctica – see the comment here: https://judithcurry.com/2018/08/14/nature-unbound-x-the-next-glaciation/#comment-878947

  75. Most of the start dates on Figure 138 are garbage. I measure the time between obliquity peaks and interglacial peaks *without* the 6kyr lag as:
    19c, -7.5 kyr
    17c, -6 kyr
    15e, -11 kyr (incorrectly labelled 15c)
    15a, -4.5 kyr
    13a, -5.5 kyr (not even listed)
    11c, -11 kyr
    9e, -4.5 kyr
    7e, -12 kyr
    7a-c, +4.5 kyr
    5e, -7.5 kyr
    From figure 4 here:
    https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2015RG000482

    • I guess you are commenting on the figures without reading the article, because the way the dates were obtained through a normalization criterion is explained in the text and in figure 137, and the dates are listed in table 3.

      You might disagree with my choices or methods, but the only garbage here are your comments.

      • Returning my apt description of your figure 138 as a baseless insult about my comment is really pathetic and immature, and it’s thoroughly narcissistic. Your chart is a total fabrication, it’s junk. The start dates on the top half are are in error by many thousands of years. Look at 7e, you have it lagged starting at 8kyr past the peak of obliquity, while with no lag it actually started 12kyr before the peak of obliquity. But you are having a hard time admitting it, behaviour that is nothing new from you.

      • In fact I made an error there, and I loathe making errors so I will admit it. 7e with 6kyr lag should start 6kyr after the peak of obliquity. But 7a-c which started 4.5kyr past the obliquity peak, with a 6kyr lag would be starting 10.5kyr past the obliquity peak.

      • Yet another error due to agitation. 7a-c is actually one of the better ones. 17c is about 6kyr out, 15e must be about 9kyr out, 15a is about 3kyr out. 11c started 11kyr after the obliquity peak, while your lagged start for 11c is 8.5kyr before the obliquity peak.

      • What you fail to understand is that there is no agreed upon date for the start of any interglacial except the Holocene in the literature, and interglacials have different temperatures and different profiles, as figure 137 aptly shows, so in the scientific literature on this issue, that you clearly have not read, each author chooses where to place the start or the end of interglacials. Instead of picking dates or copying them from someone else that picked them, I decided on a unifying criterion that I explained. I didn’t pick the dates, they come from applying that criterion, that is consistent with the placement of the start of the Holocene.

        That you disagree with my criterion is fine with me. Apply your own or pick the dates that please you most. I couldn’t care less.

        And if this issue interests you so much, write your own article about it, with your own conclusions, and post it. Claiming that mine is wrong because you disagree with the dates chosen for the start of interglacials is silly.

      • Actually I just confused myself there for a moment, 7a-c is junk too. It started 4.5kyr before the obliquity peak so lagging the obliquity 6kyr would put it 10.5kyrs before the obliquity peak.

      • “Claiming that mine is wrong because you disagree with the dates chosen for the start of interglacials is silly.”

        It is silly to claim that I am quibbling about the interglacial start dates. I am identifying massive errors in your figure 138.

      • “I am identifying massive errors in your figure 138.”

        While you are at it, don’t forget to inform P. C. Tzedakis (p.c.tzedakis at ucl.ac.uk) that his dates are garbage too and he has massive errors in his figure 6 in his article:
        Tzedakis, P. C., et al. “Can we predict the duration of an interglacial?.” Climate of the Past 8.5 (2012): 1473-1485.

        Our criteria to choose the start and end of interglacials is different. Mine is based on temperature values, while he doesn’t explain his. For most interglacials the differences are small, for a few they are larger. His interglacials tend to be longer. Figure 137 explains what I have considered interglacial and why. Nevertheless the message from his figure and mine is the same. Interglacials do not span over obliquity minima.

      • MIS 17 is a clear example of the problem of cool interglacials. As they only reach much lower temperatures, they reach them earlier and lose them later, so by most criteria it can be said that the length of cool interglacials is overestimated.

        I know that my decision to extrapolate to when they should have reached a higher temperature by their rate of warming is controversial, but it tries to correct the obvious problem of overestimating the length of cool interglacials. Otherwise when getting the average duration the result is also overestimated giving the impression that warm interglacials can last more than they actually do. Not including cool interglacials in calculations is another solution, but it reduces the sample size that is already quite small.

      • The majority of those are in rough agreement with what I measured from Figure 4 on the AGU paper.

      • And I am not interested in being sidetracked by specious ‘well you’ll have to disagree with all of these too’ arguments are that are not even true. I have made a clear case for massive irregularities in figure 138, and I have nothing further to say on the matter, as I have better things to do on this very subject.

      • They are not errors, but a CHOICE of a criterion clearly explained in the text of the article, illustrated in figure 137 so anybody can understand it (except perhaps you), and indicated in table 3.

        Apparently you have problems with the most simple things. As it is my choice of criterion for defining the start and end of interglacials, something over which there is no agreement in the research community and that varies from article to article, I understand that some people will disagree with me, and I have no problem with that.

        As the numbers are so important to you I see why you have a problem with that. You need interglacials to occur at a certain number or your pet theory sinks.

        The hypothesis I support, proposed by Huybers and Tzedakis, doesn’t have such requirements and the exact start and end of interglacials is not a requirement to it, as Tzedakis figure in the comment above shows. The link between interglacials and obliquity does not depend on such minor issues. It is not an hypothesis based on numerology.

      • On the contrary, you are doing 41kyr numerology with your figure 138. I have made measurements of common periods across the data series.

      • So 7a-c started 4.5kyr before the obliquity peak, and lagging the obliquity 6kyr would put it 10.5kyrs before the obliquity peak. That is a very long way off what your figure 138 shows.

      • p.s.
        As you have been so rudely dismissive about my original and important finding, it’s only fair for me to point out the major failures in your work. And it appears that it’s you who needs interglacials to occur at a certain number or your pet theory sinks. I just measured their actual intervals, and they are certainly finely timed by frequencies other than 41kyr obliquity.

  76. Your position of 7a-c here is also bogus:

    • No it is not. According to the homogeneous criterion chosen and explained, glacial inception for MIS 7c-a took place at 198,200 BP when EDC shows a point of inflection in temperature (see figure 137). 6 kyr before then it was 204 kyr BP. According to Huybers 70°N summer energy at 250 W/m2 threshold at 204 kyr BP was 4.989 GJ/m2.

      The position of the MIS 7c-a in that figure is correct at 204 kyr BP and 4.989 GJ/m2.

      If you don’t understand what I did, just re-read it until you do. If you don’t agree with my choices that is fine. Everybody is entitled to his opinion. But do not say that it is wrong or bogus, because that shows you didn’t understand it.

      • True, my mistake. I misread it as interglacial inception for some reason, probably due your rudeness of calling my comments garbage.

      • The first use of the word garbage in this page was in one of your comments referring to part of my work. And then your comments are full of mistakes, pure opinion, and ignore the explanations given in the article. You fully deserve it. My opinion of you can’t go any lower. I’ll be happy to ignore you from now on.

      • I certainly would not call all your comments garbage, and if you can explain the problems in figure 138, particularly the 6kyr lagged position of the start of MIS 7a-c in relation to the obliquity peak, then I would retract the criticism.

      • Until now you didn’t ask me to explain it. I will answer just this time for the benefit of other people reading through this in the future.

        MIS 7c-a was a relatively cool interglacial that did not reach the 0°C anomaly in Epica Dome C data that marks the beginning of the Holocene 11,700 years ago. It stopped warming when it reached -1°C at 215,000 yrs BP (EDC date 215011.3).

        But as I said, warm interglacials that warm for longer reach their peak temperature later and appear shorter, while cool interglacials reach their peak temperature much earlier and appear longer. Some interglacials, like MIS 11c reach their peak temperature really late, so measuring the length of an interglacial based on the time of the peak temperature is really a bad choice.

        I decided to measure the length of interglacials placing their start at the time they reach 0°C threshold, which is definitely an interglacial temperature and has the distinct advantage that it gives the Holocene its correct start date in EDC.

        For interglacials that were cooler and did not reach 0°C I decided to extrapolate the warming rate to the point in time they would have reached 0°C if they had continued warming. The difference is very small except in the case of MIS17. This allows to have a uniform criterion. Interglacials start when they reach 0°C or when they would have reached that temperature if they had continued warming at the rate they were warming. In the paper you cited, “Interglacials of the last 800,000 years,” they use 12 different criteria to define the duration of interglacials (their figure 15), so this is a scientifically respectable choice among many.

        In the case of MIS 7c-a that date is 214,200 yrs BP. The difference is very small, 800 years, and insignificant in orbital terms.

        So if MIS 7c-a started in 214.2 kyr BP, and the nearest obliquity maximum took place at 212 kyr BP with a value of 24.4546° according to Laskar, then in figure 138 MIS 7c-a is correctly shown starting 2 kyr before the obliquity maximum (dates BP go from higher to zero in the present).

        To see the effect of choosing 215 kyr BP as the start date for MIS 7c-a, it would make it start 1 kyr earlier, and that difference would barely be appreciable in figure 138.

        Your behavior regarding this issue has been unacceptable and baseless. I don’t have anything more to say. What you do or say is irrelevant to me.

      • Or rather the 6kyr lagged date of the obliquity peak in relation to the start date of MIS 7a-c.

      • Well that must be lagged obliquity in figure 138 else the rest would be impossible as they started AFTER the peaks in obliquity. So patently 7a-c is way out, and going by the AGU paper the obliquity peak is at least 4kyrs after the start of 7a-c. Lubricated numerology.

        J:
        “But as I said, warm interglacials that warm for longer reach their peak temperature later and appear shorter, while cool interglacials reach their peak temperature much earlier and appear longer.”

        Spin, there are several to exceptions to that. Plus 7a-c warmed twice after the initial peak, that’s obviously why it has an ‘a’, a ‘b’, and a ‘c’. I guess you missed that bit.

      • But as I said, warm interglacials that warm for longer reach their peak temperature later and appear shorter, while cool interglacials reach their peak temperature much earlier and appear longer.

        Snowfall rates in warmer interglacials is more and enough ice for the advance into the next ice age accumulates faster.
        Snowfall rates in cooler interglacials is less and it takes longer to build enough ice to advance into the next ice age.
        Ice ages happen when there is enough ice.

  77. Javier writes:
    “I couldn’t care less for your lack of trust as it comes from your inability to reproduce even the simplest of the graphs.”

    And how many times has it been solely me who has found major errors in your graphs on your series of posts here? Like I have also in this post. Or the time you counted 28 points as 28 intervals instead of 27:
    https://judithcurry.com/2017/12/02/nature-unbound-vi-centennial-to-millennial-solar-cycles/#comment-862728

    “And then your comments are full of mistakes, pure opinion, and ignore the explanations given in the article.”

    Unlike you I have a habit of correcting my mistakes. That’s the difference between science, and spin. You never admit to your mistakes.

  78. Javier,

    There is a forgotten 2.8 million year “super-cycle” in eccentricity.

    If you look back in LR04 exactly 2.8 million years ago then you will see that the then weak glacial cycle missed a 41,000y obliquity beat!

    P.S. I only just discovered this great article. Brilliant job!

  79. The climate of the planet has become more unstable in the Mid and Late Pleistocene

    When you don’t understand natural cycles, you treat a larger cycle as unstable when it is really just a cycle that resonated with larger bounds, but came back the other way just like all stable cycles do. Lack of understanding does not make or prove that anything is unstable.

    Of course, most everyone admits they don’t really understand why some cycles are larger than others, so they say they are more unstable. If they were unstable, one of them would take off and not come back. Earth climate is self correcting, it has always come back.

  80. An ice age is an internal cycle that is all about the ice. An ice age is caused after it snows enough. An ice age ends after it does not snow enough. It snows when there is water and energy in the oceans that causes evaporation and snowfall in places it is cold enough. The cold places grow as the ice age progresses. The snowfall stops when the oceans run out of enough water and/or energy to produce the snowfall. Snowfall requires both water and energy. Both are abundant in warm deep oceans and Both are not abundant in low cold oceans.

    Ice ages play out when low cold oceans do not produce snowfall to maintain the ice volume.

    This is simple, easy to understand, stuff! Someday, some of you will/may understand.

    Warming oceans promotes more snowfall in cold regions because of thawed oceans. Cooling oceans promotes less snowfall in cold regions because of frozen oceans. This is why climate temperature and sea level are bounded and change in cycles.