Explaining(?) abrupt climate change

by Judith Curry

 . . . suggesting that Dansgaard-Oeschger events resulted from a combination of the effects of sea ice and ice shelves—structures that help define the margins of ice sheets—to account for both the rapid and the slower parts of the cycle.

I searched previous Climate Etc. posts, and it seems that I have not written previously on the topic of abrupt climate change. I guess I’m surprised, since I regard this as a very important topic.  Here I am referring to large changes, larger than the magnitude of say the 1976 climate shift which is sometimes referred to as an abrupt climate change.

For background information, I recommend the 2002 NRC report Abrupt Climate Change: Inevitable Surprises.  There is a more recent NRC report Abrupt Impacts of Climate Change: Anticipating Surprises.   Richard Harris has article on the recent NRC Report. For something that is quicker to read, see the Wikipedia. Jeff Masters has a pretty good overview article The Science of Abrupt Climate Change: Should We Be Worried?

The trigger for this particular post is this brief overview that appeared in Science:

H. Jesse Smith

Dansgaard-Oeschger (DO) cycles—rapid warming events with durations of approximately 1000 years, followed by a more gradual return to cold conditions—are some of the most dramatic examples of rapid climate change that occurred in the North Atlantic region over the last glacial period. Although there has been no lack of suggestions about their possible origins, all of the causal mechanisms proposed thus far have run into difficulty explaining one part of the cycle or another. Petersen et al. step into the fray, suggesting that DO events resulted from a combination of the effects of sea ice and ice shelves—structures that help define the margins of ice sheets—to account for both the rapid and the slower parts of the cycle. Their model relies on the ability of thin sea ice to respond quickly to changing environmental conditions and on the more gradual behavior of thick ice shelves to cause cooling. Although more work needs to be done to support this model, it is consistent with existing proxy records, model results, and modern observations.

The paper that is referred was published in Paleoceanography [link to abstract]:

A new mechanism for Dansgaard-Oeschger cycles

S. V. Petersen, D. P. Schrag, and P. U. Clark

Abstract. We present a new hypothesis to explain the millennial-scale temperature variability recorded in ice cores known as Dansgaard-Oeschger (DO) cycles. We propose that an ice shelf acted in concert with sea ice to set the slow and fast timescales of the DO cycle, respectively. The abrupt warming at the onset of a cycle is caused by the rapid retreat of sea ice after the collapse of an ice shelf. The gradual cooling during the subsequent interstadial phase is determined by the timescale of ice-shelf regrowth. Once the ice shelf reaches a critical size, sea ice expands, driving the climate rapidly back into stadial conditions. The stadial phase ends when warm subsurface waters penetrate beneath the ice shelf and cause it to collapse. This hypothesis explains the full shape of the DO cycle, the duration of the different phases, and the transitions between them and is supported by proxy records in the North Atlantic and Nordic Seas.

Some background  information from the Introduction:

During the last glacial period, the North Atlantic basin experienced a number of large and abrupt millennial-scale fluctuations in climate referred to as Dansgaard-Oeschger (DO) cycles. Ice cores from Greenland reveal that each cycle began with an abrupt warming from stadial to interstadial conditions. The effects of this warming extended across much of the Northern Hemisphere, while a near-simultaneous cooling occurred in Antarctica. Greenland ice core records then suggest gradual cooling during the initial stages of each interstadial phase, followed by abrupt cooling back to stadial conditions. 

A common explanation for these cycles involves changes in the Atlantic meridional overturning circulation (AMOC), perhaps triggered by freshwater forcing, but paleoceanographic evidence for these changes remains elusive. 

Description of the new hypothesis:

We propose a conceptual model for DO cycles that explains their characteristic temporal evolution and is supported by existing proxies of ice-sheet, climate, and AMOC variability. In particular, we adopt the sea-ice mechanism of Li et al. [2005, 2010] to explain the fast-changing intervals of the DO cycles. We then invoke an ice shelf to explain the slower-changing phases of the DO cycles. From the perspective of the atmosphere, an ice shelf looks the same as sea ice in terms of its albedo and its insulating effects, which reduce the release of heat from the ocean. However, because ice shelves are much thicker than sea ice (hundreds of meters versus <10 m), they are largely insensitive to small changes in heat transport or wind stress.

We first consider the influence of an ice shelf covering a large region of the ocean east of Greenland in the Nordic Seas. Given the sensitivity analysis by Li et al. [2010] and the number of proxies showing variability of the cryosphere on DO timescales in the Nordic Seas, we focus on an ice shelf along the eastern Greenland margin that could influence sea-ice cover in this region. We propose that the cooling effect of a large ice shelf combined with extensive sea-ice cover would result in regionally cold surface temperatures due to the insulating properties of the ice shelf and sea ice, as well as their effect on local albedo [Li et al., 2005, 2010]. This stadial climate would be maintained for as long as the ice shelf was present.

In the event of the ice shelf’s collapse, potentially caused by warming of subsurface waters, the only remaining ice cover would be sea ice and floating icebergs. A small change in wind stress or heat transport could quickly export or melt this ice, resulting in a large increase in open-ocean area and a corresponding large and abrupt warming over Greenland marking the start of a new DO cycle.

During the interstadial phase of a DO cycle, the near doubling of accumulation over the Greenland Ice Sheet that accompanies the warmer climate would induce a more positive mass balance, causing the ice shelf to begin reforming along the coast. Expansion of the ice shelf to cover increasingly more ocean surface area would cause air temperatures to gradually cool over Greenland. Once the shelf reached a critical size, it would cause sea ice to rapidly expand through the sea-ice-albedo feedback, driving climate back to stadial conditions and completing the DO cycle. The same cycle could not be achieved with multi-year sea ice because its regrowth timescale is inconsistent with the gradual decline of climate over the duration of the interstadial phase. In summary, our hypothesis combines the ability of sea ice in the Nordic Seas to explain the rapid transition into and out of the interstadial phase  with a gradually expanding ice shelf derived from eastern Greenland to  explain the progressive cooling during the interstadial, provide the mechanism to trigger sea-ice growth to cause the rapid cooling , and sustain the stadial climate once the ice shelf reaches steady state. The duration of the interstadial phase is determined by the time required to regrow the ice shelf to a threshold size, beyond which the local ice-albedo effect causes the rapid expansion of sea ice and the corresponding switch to a stadial climate. After a time, ice-shelf collapse, potentially due to subsurface warming, along with an associated rapid loss of sea ice causes the abrupt warming that starts a new DO cycle.

JC comments:  I find the ideas presented by Petersen et al. to be fascinating. I find the topic of abrupt climate change to be more more interesting scientifically than AGW, and potentially of greater societal significance (although one key question is the potential role of AGW in triggering an abrupt event).  IMO much more scientific effort should be focused on the topic of abrupt climate change.  The recent NRC Report targets some specific observing systems that would help understand and anticipate these changes.


152 responses to “Explaining(?) abrupt climate change

  1. Rob Starkey

    The question is whether the actual cause(s) of abrupt climate change are as important as the long term impacts of human relaesed CO2. It does not seem that scientific or economic truth appears to get in the way of many people’s beliefs and positions.

    • Ringo, where is the controlled experiment for your grand hypothesis? Might as well throw it back at you

      Where is it documented that a “Great Climate Shift of 1976” was anything more than the routine sloshing of the oceans?

      The inistence of ABCD perserveres and any kind of “just-so” story is worth a shot to lead on the gullible.

    • Rob Starkey

      You consistently seem to completely miss the overriding issues associated with climate change much as you did in your prior fascination with crude oil depletion. You laughably try to promote silly, simplistic trend analysis as some type of new grand theory as to what is or will happen to the climate.

      Do you deny abrupt climate changes have occurred in the past?

      Do you deny that abrupt climate change, regardless of the cause (and potentially at a regional level); is a threat to humans?

      Do you claim to know the root cause of those prior abrupt climate changes?
      Isn’t it reasonable to learn what the root cause(s) of prior abrupt climate change are so that humans will be better prepared to adapt if/when those conditions reoccur?

      Try learning more and making less stupid, prejudicial comments about Australians and others. All you are doing with your silly insults and superficial theories is repetitively showing yourself to be an idiot.

      • David Springer


        “i d i o t” is a blacklisted word which meant your comment went into moderation automatically and Curry had to approve it. She must agree that Webby is what you said he was. LOL

    • Robert I Ellison

      One might anticipate that an ENSO exspurt might understand this.


    • And RobbIE scores another “OWN GOAL!” with the link he provided

      The page concludes “By many measures this is a form of abrupt (albeit modest) climate change, and it has been shown by Lamont scientists to be marginally predictable a few years in advance.”

      So, who exactly was calling it a “Great” Climate Shift of 1976? It was the cadre of deniers, including McLean/Carter of Australia and Easterbrook amongst others.

    • Rob Starkey


      Thank you for that information. I noticed it went into moderation but didn’t understand why.

    • And of course the “great” climate shift of 1976 ended starting in 1989 when the SOI reverted back to its mean.

      For all the idjits out there, this is referred to as a multidecadal oscillation.

    • Robert I Ellison

      ‘On the interdecadal timescale, it was well known that the Pacific basin SST experienced a great climate regime shift (CRS) around 1976/1977 (Miller et al. 1994; Wang 1995), with a pronounced warming in the tropics and a cooling over the mid-latitudes. This CRS led to a significant circulation change over various regions of the globe, including East Asia (Chang et al. 2000a, b; Hung et al. 2004; Zhang et al. 2004; Kwon et al. 2005; Zhou et al. 2009; Li et al. 2010).’ http://download.springer.com/static/pdf/153/art%253A10.1007%252Fs00382-013-1867-9.pdf?auth66=1402168141_3708bb509382e688c1e72087fa7d711c&ext=.pdf

      ‘The use of a coupled ocean–atmosphere–sea ice model to hindcast (i.e., historical forecast) recent climate variability is described and illustrated for the cases of the 1976/77 and 1998/99 climate shift events in the Pacific. The initialization is achieved by running the coupled model in partially coupled mode whereby global observed wind stress anomalies are used to drive the ocean/sea ice component of the coupled model while maintaining the thermodynamic coupling between the ocean/sea ice and atmosphere components. Here it is shown that hindcast experiments can successfully capture many features associated with the 1976/77 and 1998/99 climate shifts. For instance, hindcast experiments started from the beginning of 1976 can capture sea surface temperature (SST) warming in the central-eastern equatorial Pacific and the positive phase of the Pacific decadal oscillation (PDO) throughout the 9 years following the 1976/77 climate shift, including the deepening of the Aleutian low pressure system. Hindcast experiments started from the beginning of 1998 can also capture part of the anomalous conditions during the 4 years after the 1998/99 climate. The authors argue that the dynamical adjustment of heat content anomalies that are present in the initial conditions in the tropics is important for the successful hindcast of the two climate shifts.’ http://journals.ametsoc.org/doi/abs/10.1175/JCLI-D-12-00626.1

      ‘The subject of decadal to inter-decadal climate variability is of intrinsic importance not only scientifically but also for society as a whole. Interpreting past such variability and making informed projections about potential future variability requires (i) identifying
      the dynamical processes internal to the climate system that underlie such variability (see e.g. Mantua et al. [1997]; Zhang et al. [1997]; Zhang et al. [2007]; Knight et al. [2005]; Dima and Lohmann [2007]), and (ii) recognizing the chain of events that mark the onset of large amplitude variability events, i.e., shifts in the climate state. Such shifts mark changes in the qualitative behavior of climate modes of variability, as well as breaks in trends of hemispheric and global mean temperature. The most celebrated of these shifts in the instrumental record occurred in 1976/77. That particular winter ushered in an extended period in which the tropical Pacific Ocean was warmer than normal, with strong El Nin˜o-Southern Oscillation (ENSO) events occurring after that time, contrasting with the weaker ENSO variability in the decades before (Hoerling et al. [2004]; Huang et al. [2005]). Global mean surface temperature also experienced a trend break, transitioning from cooling in the decades prior to 1976/77 to the strong warming that characterized the remainder of the century.’

      Modest? Predictable? Depends on how you define it.

      The change can be eyeballed in.


      Blue to 1976/77, red to 1998, blue again since – significant change to a globally significant system.

  2. potentially of greater societal significance

    I would say that is an understatement! It has all the ingredients as well. No control by Humans, and very low predictability. In other words, while we squabble about fractions of degrees, the planet throws multiple degrees at us in a relative heart beat!

    This is one area that really deserves more study.

    • ” In other words, while we squabble about fractions of degrees, the planet throws multiple degrees at us in a relative heart beat!”

      No such thing happened during any time in the last 5000 years.

      The only plausible cause of multiple degrees warming in the next 100 years is man. That’s why AGW is the concern.

  3. A fan of *MORE* discourse

    From Paleoclimate Implications for Human-Made Climate Change (Hansen and Sato, 2011)

    Section5.2. How slow are slow feedbacks?

    Observed time scales of GHG and surface albedo variability are the time scales of orbital variations, thus not necessarily an internal time scale of the feedback processes. Indeed, we do not expect slow feedbacks to be inherently that slow. We have argued [refs] that the ice sheet response to a strong rapid forcing is much faster than the time scale of orbital changes, with substantial response likely within a century.

    Debating what sea level will be on a specific date such as 2100, however, misses an important point concerning response times. The carbon cycle response time, i.e., the time required for CO2 from fossil fuel burning to be removed from the surface carbon reservoirs is many millennia [refs] . The ice sheet response time is clearly shorter than this carbon cycle response time, in view of the absence of a discernable lag between paleoclimate forcings and the maximum rate of ice sheet disintegration[refs] and in view of the fact that ice sheet disintegration proceeds at rates up to several meters of sea level rise per century [refs] even in response to weak paleoclimate forcings.

    Thus burning all or most fossil fuels guarantees tens of meters of sea level rise, as we have shown that the eventual sea level response is about 20 meters of sea level for each degree Celsius of global warming.

    We suggest that ice sheet disintegration will be a nonlinear process, spurred by an increasing forcing and by amplifying feedbacks, which is better characterized by a doubling time for the rate of mass disintegration, rather than a linear rate of mass change.

    If the doubling time is as short as a decade, multi-meter sea level rise could occur this century.

    Conclusion  It is interesting that you and James Hansen are evolving towards similar scientific conclusions, Judith Curry!

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    • Matthew R Marler

      A fan of *MORE* discourse: Quotes Hansen: If the doubling time is as short as a decade, multi-meter sea level rise could occur this century.

      Fan: Conclusion It is interesting that you and James Hansen are evolving towards similar scientific conclusions, Judith Curry!

      Professor Curry, quoting H. Jesse Smith: Dansgaard-Oeschger (DO) cycles—rapid warming events with durations of approximately 1000 years, followed by a more gradual return to cold conditions—are some of the most dramatic examples of rapid climate change that occurred in the North Atlantic region over the last glacial period.

      Where is the similarity, Fan? One writes of a possible (not yet observed) century long change within an interglacial period, and the other of a thousand-year change evident in ice core samples over a glacial period.

    • A fan of *MORE* discourse

      Curry/Dansgaard-Oeschger rapid warming drives Hansen/Sato rapid sea-level rise… and both are associated to nonlinear dynamics and amplifying feedbacks.

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    • Matthew R Marler

      a fan of *MORE* discourse: Curry/Dansgaard-Oeschger rapid warming drives Hansen/Sato rapid sea-level rise… and both are associated to nonlinear dynamics and amplifying feedbacks.

      Hansen/Sato rapid sea level rise is driven by a process that lasts 1,000 years? I would read a scientific report if you provided a link.

  4. The Very Reverend Jebediah Hypotenuse


    …one key question is the potential role of AGW in triggering an abrupt event…
    IMO much more scientific effort should be focused on the topic of abrupt climate change.

    Today’s rapid climate change will be tomorrow’s fond memory.

    Feedbacks. Methane from melting permafrost and clathrates is going to make CO2 forcing look tame and manageable by comparison.


    CCSP, 2008: Abrupt Climate Change. A report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research (Clark, P.U., A.J. Weaver (coordinating lead authors), E. Brook, E.R. Cook, T.L. Delworth, and K. Steffen (chapter lead authors)). U.S. Geological Survey

    • Jeb: That explains it,you are a methane clathrate – CO2 permafrost catastrophist nutter (not my words, Dr. Wm Connolley’s). You are aware that Greenland largely melted off during the last interglacial with no help from man and no boiling of the oceans. Those whom fail to map earth history are condemned to irrational panic and hyperbole.

    • The Very Reverend Jebediah Hypotenuse

      Explanations are noted, Howard.

      However, it seems to me that if one is fond of embracing scientific uncertainty, then to be consistent, one might allow for the possibility that atmospheric methane may have a significant role to play in the future of the human species.

      As for the last interglacial and mapping earth history – see “Milankovitch cycles”.

      And speaking of hyperbole: “boiling of the oceans”?

    • Why is it that The Great Pacific Climate Shift of 1976 is only really talked about on nutter sites?

      Did they start calling it Great to exaggerate its significance?

      Shouldn’t it really be called the 1976 inflection point in the PDO signal?

    • That explains it,you are a methane clathrate – CO2 permafrost catastrophist nutter (not my words, Dr. Wm Connolley’s).

      Here. And anybody that Mr. Wiki Nazi pans as being “these bozos” for being too alarmist must really be.

    • Steven Mosher

      “However, it seems to me that if one is fond of embracing scientific uncertainty, then to be consistent, one might allow for the possibility that atmospheric methane may have a significant role to play in the future of the human species.”

    • As Garth said “We fear change”

    • Guilty of Hyperbolic invective as charged!

      The embracement of uncertainty is not a contract to swallow the precautionary principle. Be that as it may, if the methane flatulance hypothesis comes true, we cannot stop it as we are committed to at least 800-ppmv CO2 at this point, so therefore, adaptation is the most worthy precaution, no?

    • The Very Reverend Jebediah Hypotenuse

      Oh dear:


      from which:

      In 2008 the United States Department of Energy National Laboratory system[28] and the United States Geological Survey’s Climate Change Science Program both identified potential clathrate destabilization in the Arctic as one of four most serious scenarios for abrupt climate change, which have been singled out for priority research. The USCCSP released a report in late December 2008 estimating the gravity of this risk. A 2012 assessment of the literature identifies methane hydrates on the Shelf of East Arctic Seas as a potential trigger.

    • Robert I Ellison

      ‘Catastrophic, widespread dissociation of methane gas hydrates will not be triggered by continued climate warming at contemporary rates (0.2ºC per decade; IPCC 2007) over timescales of a few hundred years. Most of Earth’s gas hydrates occur at low saturations and in sediments at such great depths below the seafloor or onshore permafrost that they will barely be affected by warming over even 103 yr. Even when CH4 is liberated from gas hydrates, oxidative and physical processes may greatly reduce the amount that reaches the atmosphere as CH4. The CO2 produced by oxidation of CH4 released from dissociating gas hydrates will likely have a greater impact on the Earth system (e.g., on ocean chemistry and atmospheric CO2 concentrations; Archer et al. 2009) than will the CH4 that remains after passing through various sinks.

      Contemporary and future gas hydrate degradation will occur primarily on the circum-Arctic Ocean continental shelves (Sector 2; Macdonald 1990, Lachenbruch et al. 1994, Maslin 2010), where subsea permafrost thawing and methane hydrate dissociation have been triggered by warming and inundation since Late Pleistocene time, and at the feather edge of the GHSZ on upper continental slopes (Sector 3), where the zone’s full thickness can dissociate rapidly due to modest warming of intermediate waters. More CH4 may be sequestered in upper continental slope gas hydrates than in those associated with subsea permafrost; however, CH4 that reaches the seafloor from dissociating Arctic Ocean shelf gas hydrates is much more likely to enter the atmosphere rapidly and as CH4, not CO2. Proof is still lacking that gas hydrate dissociation currently contributes to seepage from upper continental slopes or to elevated seawater CH4 concentrations on circum-Arctic Ocean shelves. An even greater challenge for the future is determining the contribution of global gas hydrate dissociation to contemporary and future atmospheric CH4 concentrations.’ http://www.nature.com/scitable/knowledge/library/methane-hydrates-and-contemporary-climate-change-24314790

    • Jeb: Do you have a reference for evidence of clathpharting occurring during the Pleistocene where the interglacial temperatures were significantly higher than now and Greenland was Ice-Free? I don’t recall seeing those sort of huge methane levels recorded in proxy records, but I may have missed it.

    • There is a non-zero chance that methane hydrate destabilization could result in a rapid acceleration in GH warming. CO2 as a trigger to something bigger. Of all the potential catastrophic consequences, this is probably the most troublesome, since it has happened before in Earth’s history from a lower carbon input to the atmosphere then we are seeing now.

      • David Springer

        There is a non-zero chance that God won’t let the climate destabilize because of the promise He made to Noah.

        You need to be a little more specific about those non-zero chances Gates.

    • R Gates, if a small temperature increase is enough to destabilise them then how come this doesn’t happen every summer?

    • There is evidence of methane hydrate destabilization at lower latitudes caused by recent increases in OHC. This is potentially significant for future warming potential, but also inconvenient for those who’d like to suggest the additional heat is harmlessly dispersed throughout the ocean depths: (not a hyperlink, need to copy and paste):

      As noted in this excellent research, there is some potential that this kind of methane release was triggered from natural volcanic CO2 release and initial warming during the PETM. The difference is this time it is the Human Carbon Volcano putting the CO2 in the atmosphere at a rate faster than natural volcanic activity did during the PETM.

      • @R Gates – Just a couple of suggestions.

        #1 – But a http:// in front of it. It makes it a link.
        #2 – never use IP addresses as they mask the domain and no one is going to follow them unless they want to trash their computer. Why did you not use the DNS name? reserve.cableplus.com.cn

    • Gates, it is interesting that life had no problem with the cold that would have been caused by all the aerosols released by the Siberean traps. So much for volcanic activity causing the LIA I suppose. It is interesting that all the sulfur released by these eruptions wouldn’t have caused acid rain to kill off plant life and allow nutrients to flow into the oceans causing anoxia like fertilizers do in the Gulf of Mexico. I guess that whole acid rain thing was just one big hoax. The entire idea that a little warming caused an extinction event but life had no problem at all with the other problems these eruptions would have caused seems ludicrous to me. The GHG effect has been known for some time. Can you show something written before 1975 that blames the extinction event on global wwarming or should I just mark this hypothesis down as faddish science?

    • Gates, same argument but disregard Siberean Flats. Wrong lets blame it on global warming extinction event.

    • Jeb Square
      The puzzle for everyone is that these methane deposits were formed from vegetable matter over millions of years and have been exposed and covered over time and again by the various hot and cold cycles over that time. There is no great bomb ready to go off. That would have already happened in the much hotter past and we are only seeing the remnants of all the methane formed and released in the past. It is natural, it has happened many times before and we are all still here. get over it.

    • R Gates, that paper is about the effects of changing ocean currents – a process which has been going on since the oceans first came into being.
      You’re always going on about the ocean heat not being spread evenly throughout the ocean – well that’s always been the case, except perhaps when it suits your cause to say otherwise.
      Ocean currents have always blown hot and cold – just like the winds, and just like the winds, they’ve changed direction, grown stronger and weaker, become more and less turbulent – in fact, the only constant is change.
      But, according to you, any change that occurs now simply must be down to mankind – particularly if the effects of such change could be adverse.

      Grow a pair of scepticles!

  5. I find the topic of abrupt climate change to be more more interesting scientifically than AGW, and potentially of greater societal significance (although one key question is the potential role of AGW in triggering an abrupt event).

    While I’ve read only the abstracts (so far), my immediate reaction is that we’re talking regional-scale phenomena here. Given that the effect of greater pCO2 (or other well-mixed non-condensing GHG’s) is greatest under cold, dry conditions, and that ice sheets of this sort would induce such conditions, both over themselves and with higher intensity over nearby, more permanent, ice cover, shouldn’t the possibility of more localized effects be added to the more “global” AGW?

    • michael hart

      That was my thought too. Did they decide to call it global cooling or regional cooling? (I can’t access the paywalled material).

    • Prof. Curry, I couldn’t find a way past the paywall for the article you mentioned, but while searching I did find Dansgaard-Oeschger cycles: Interactions between ocean and sea ice intrinsic to the Nordic seas by Trond M. Dokken, Kerim H. Nisancioglu, Camille Li David S. Battisti, and Catherine Kissel Paleoceanography, VOL. 28, 491–502, doi:10.1002/palo.20042, 2013, apparently not paywalled (at the link above).

      This article goes into interesting detail, especially WRT primary evidence. Note that the processes involved are regional, limited primarily to the Nordic Seas. So it makes sense that the direct effect of increased pCO2 at these local/regional levels may well have as much impact as “global warming”.

    • Welcome!

    • The Ice Ages also started out as regional phenomena governing the Arctic ice edge, not Antarctic, but the albedo change of spreading glaciers gave them global consequences. We should not underestimate the impact of ice area on the global temperature.

    • @Jim D…

      Total non sequitur. READ HARDER!

    • AK, so you think that the Ice Ages don’t start out as insolation minima at the Arctic ice edge. Thanks. I didn’t know where you stood on Milankovitch, but apparently it is just something else you don’t believe in.

      • David Springer

        Orbital eccentricities that make northern hemisphere summers cooler and winters simultaneously warmer are factors that favor NH glaciers. The favorable orbital configuration is not abrupt and lasts thousands of years near the peak. My presumption is that solar cycles and volcanoes come along during the favorable orbital configuration to form a rare perfect storm. Given thousands of years it’s inevitable that random volcanic eruptions will line up with peaks or troughs in centennial solar cycles.

    • @Jim D…

      I’m open-minded on the subject. But that’s not my point. I wasn’t talking about that, so it’s not relevant. A non sequitur.

      I’m talking about the local/regional effects of increased pCO2 (etc.) in some areas on the global climate, as perhaps being of the same order of magnitude as “global warming” produced by increased pCO2.

      In addition to the example above, the effect of increased Greenhouse “warming” in the TaklaMakan and/or Tibetan Plateau could have a pronounced effect on the evolution of Sudden Stratospheric Warming Events; these areas have been hypothesized to play a key role.

      Other examples are on my radar, but for the moment I have other things to do.

  6. pokerguy (aka al neipris)

    How foolish is a puny man like Obama, with his dreams of covering himself in glory by “waging war on climate change.” .

    “This was the moment when the rise of the oceans began to slow, and our planet began to heal” is a statement more suited to a lunatic, than the leader of the free world.

    I’ve never seen a more tone deaf bunch of people than global warming alarmists. History will not be kind.

    • pokerguy

      The BBC played the bit about the oceans slowing when showing a clip of Obama, in connection with the new American policy. To the British eye he is full of hubris. I must admit I laughed at his audacity. In his own way he comes over as just as idiotic and as full of his own importance as our Nick Clegg.

      Nick Clegg however isn’t the leader of the Free world. In fact he’s barely still the leader of the Lib Dem party


    • Yes pokerguy, hubris and hypocrisy too.

      The Obama administration, having failed to save the world
      from their own CO2 emissions has imposed a cap on emissions
      from energy funds provided by a US federal agency, the
      Overseas Private Investments Corps, an agency that finances
      international development.

      They’re restricting energy loans to poor countries that do not
      emit much carbon anyway and desperately need cheap energy
      to help them get out of poverty, bts


    • Rob Starkey


      Thanks for the link. Excellent summary of the some of the foolishness of current US policy.

  7. James the Elder

    Thus burning all or most fossil fuels guarantees tens of meters of sea level rise, as we have shown that the eventual sea level response is about 20 meters of sea level for each degree Celsius of global warming. ”

    So———–the Antarctic warms to -58C from -59C and we are supposed to run and hide?
    What if the abrupt climate change is toward COLD? Does Hansen dust off his global cooling screeds?

  8. ‘Abrupt’ Climate Change.

    Is that something that happens in a day? Week? Month? Year? Decade? Election Cycle?


  9. Was chloride measured in the ice cores? Wind would entrain sea water and deposit some on the ice. It might or might not be an indicator of ocean salinity as it would also depend on wind strength and direction.

  10. Because of the Clean Air Acts et al, hundreds of Megatons of aerosols have been removed from the atmosphere. This cleansing of the air is responsible for the abrupt warming that occurred 1970-2000, not CO2. Get real, folks, the science is NOT settled.

  11. Just yesterday I read an abstract that said continued abyssal warming will enhance ocean circulation, which would possibly make abrupt climate change 21st century even less likely than it already is.

  12. Walt Allensworth

    JC comments: … I find the topic of abrupt climate change to be more more interesting scientifically than AGW…


    The GISP-2 and Vostok ice core data shows dramatic temperature swings up (5C-10C) from the “base temperature” of about -55C during glacial periods, and these swings up (and then down) can occur in relatively short periods of time – decades to just a century or two.

    As in: http://clasfaculty.ucdenver.edu/callen/1202/Landscapes/Glac/GlacialClimSetting/GISP2_temperature_graph_sm.gif

    Drops out of the periodic interglacial periods appear the occur precipitously, but not as rapidly.

    It is very clear from the recent temperature records (last 500,000 years) that two basic set-points exist. In GISP-2 this is a temperature of about -30C (inter-glacials) and around -55C (glacial). Never do rapid swings exceed these bounds, but rapid swings occur from one bound to the other.

    There are so many questions raised by this behavior…

    Is GISP-2 and Vostok a good proxy for global temps and temp swings?

    What forces are at play that moderates temperatures to not go past these bounds of about -30C and -55C?

    Will these very same moderating forces provide negative feedback to Anthropogenic CO2 forcing? (i.e. reduce the TCR to ACO2).

    Since we are becoming overdue for another ice-age, would a successful attempt at reducing anthropogenic CO2 back to pre-industrial levels help initiate another ice-age?

  13. This post is clearly in the Climate Etc, Dumbest Topic Top 10.


  14. All weather is local. End of explanation.

  15. “Climate is nothing but,” says Lennart Bengtsson, “the sum of all weather events during some representative period of time. The length of this period cannot be strictly specified, but ought to encompass at least 100 years…”

  16. John Smith (it's my real name)

    I.m pretty sure the the weather in Europe went bad suddenly 1312-1314. Lots of records of failed harvest for decades. I don.t get it. Haven’t we seen many “abrupt” changes prior to the modern CO2 production era?

    • John Smith

      As someone who researches that era I can confirm that abrupt climate change is nothing out of the ordinary (unless you think history began in 1979 with satellites) .

      To know how common it is we need to define ‘abrupt.’ Is it a single year? 20 years? A century? And define ‘change’. A quarter, half or full degree? How long do the changes need to persist to be significant? A year, a decade or a century? Do the changes need to be regional or global?

      Judith has quoted some examples in the article but personally I would be more worried by those that occur within a human lifetime rather than millennia.

      I wrote about ‘noticeable climate change in this article carried here;

      As well as ‘noticeable’ some of them were also ‘abrupt’.


  17. Rud Istvan

    This post got me doing some quick background reading. Led to the Younger Dryas, more interesting than the DOs that occurred during the glacial rather than interglacial phase where we now are. Two competing hypotheses (cosmic, Lake Aggasiz) for apparent shutdown of North Atlantic overturning.
    Neither explains the sudden end of YD that may have been as abrupt as 3 decades. Sudden beginning, sure something big could have happened suddenly. But Sudden end?
    A puzzle worthy of much more research.

    • The cause for most of the many sudden climactic shifts through Earth’s history have been credited to volcanic eruptions and all of such shifts have been downward.

    • The Very Reverend Jebediah Hypotenuse

      Neither explains the sudden end of YD that may have been as abrupt as 3 decades. Sudden beginning, sure something big could have happened suddenly. But Sudden end?

      Your “quick background reading” has you convinced that scientists are on the wrong track…
      Stop the presses!

      A puzzle worthy of much more research.

      Start the presses!
      Rud Istvan supports much more research in climate science!

    • Speaking of the Younger Dryas, fresh melt water blanketing the North Atlantic during a period of rapid glacial melting would give rise to a anomalously low temperature reading in a period that may actually be experiencing rapid warming. This may explain the Younger Dryas. Glacial ice is already depleted in O18 because it is excluded from the solid phase during freezing. When melting begins the O18 depleted water blankets the surface of the North Atlantic. Now the melt water evaporates producing doubly depleted water vapor which then falls on Greenland as snow and is incorporated into the ice cores which now show a false low temperature reading as a result.

      This paper deals with the transition from stadial (cold) to interstadial (warm) conditions, so that the discharge of melt water into the North Atlantic would mask the actual warmup and the ice cores would show anomalously low temperatures. If I am correct, when the melt ceases and the melt water is dispersed (within 10 years) the ice cores show a rapid temperature change that had actually begun many years previously (as evidenced by the warm spike at the start of the Younger Dryas).

    • Robert I Ellison

      With abrupt change the driver is always feedbacks in ice sheet growth and decline.


  18. > I searched previous Climate Etc. posts, and it seems that I have not written previously on the topic of abrupt climate change. I guess I’m surprised, since I regard this as a very important topic.


    • Mentioned yes, devoted an entire thread to it no.

    • Steven Mosher

      dont worry Judith.

      Willard will point out that you said ‘have not written” rather than “did not devote an entire thread ”
      Then Josh and Rev will claim victory.

      Willard is good at search. dont ask him to count, however. or to read charitably.

    • I’d settle for “I devoted a blog post to abrupt climate change in the AR5, but not to abrupt climate change in general” on the basis of this hit:

      Section 12.5.5 in the WG1 Report provides some important insights on what is most commonly regarded as the ‘dangerous’ aspects of AGW.

      For background on this topic, see this previous Climate Etc. post Redefining dangerous climate change.

      I was pointed to section 12.5.5 by a post at BishopHill. The relevant text is below:

      12.5.5 Potentially Abrupt or Irreversible Changes


      My emphasis. This is the second hit. The first one is this very thread.

      I have not paid due diligence to the other 337 hits.

    • I’d even settle with “I’ve written about abrupt climate change in the context of the sensitivity debate”:

      [I]t is misleading to think of sensitivity in terms of a pdf (see my previous post on this here). Talking about the probability of a climate sensitivity fat tail is meaningless in my opinion. What is meaningful is the possibility of a scenario of abrupt climate change. While abrupt climate change is regarded as a possibility based upon paleoclimatic evidence of previous events, climate models are incapable of producing such emergent phenomena. The concept of abrupt climate change does not figure into any estimate of equilibrium sensitivity that I am aware of.


    • There’s also “natural climate variability as opposed to AGW”:

      My biggest concern is that by unduly (and almost exclusively) focusing on AGW that we are making a type 1 error: a possibility that has not been articulated might come true. These possibilities (e.g. abrupt climate change) are associated with natural climate variability, and possibly its interaction with AGW.


      Compare and contrast with what contains our current editorial: “I find the topic of abrupt climate change to be more more interesting scientifically than AGW, and potentially of greater societal significance (although one key question is the potential role of AGW in triggering an abrupt event).”

      The epistemic content is similar, while the epideictic content differs.

    • geez Willard, wth! Talk about obsession with ephemera!

      What matters from Judith’s comment is,

      “I regard this as a very important topic”

      and the content of the current thread, not whether she has ever mentioned abrupt climate change before.

    • > What matters from Judith’s comment is, “I regard this as a very important topic”

      Not only do I agree with that, Skiphil, but I could substantiate that claim.

      In fact, I just did.


      In return, I do hope you’ll agree with me that since at least 2000, Judy timeshares on just about any topic related to natural variability, including abrupt climate change, at least when comes the time to feed the uncertainty monster. See for instance:

      Ontic uncertainty in climate science derives from the complexity of the climate system and indeterminacy of human systems. Natural internal variability of the nonlinear climate system contributes to ontic uncertainty in climate simulations. The climate system is stochastically uncertain because of its chaotic nature, i.e. small differences in the initial conditions of a global climate model can yield very different results. Scenarios of global greenhouse gas emissions are inherently uncertain because they depend on human behaviour, e.g. the uncertainty of the future fertility rate and future economic development. Initial condition uncertainty is partly epistemic (inadequate and incomplete observations) and partly ontic (chaos).


      Vintage 2010. Imagine that.

    • willard,

      you regressing in age? You and Jeb must be the newest members of Joshua’s 7th grade Boys Club, whose (un)stated goal is to see how many yanks on Judith’s pony tail it takes to get her to notice you.

    • What do you think is the topic of today’s editorial, timg?

      Here are answer choices:

      (a) abrupt climate change;
      (b) Judy’s coverage of abrupt climate change;
      (c) some pointers on abrupt climate change;
      (d) recent papers on abrupt climate change;
      (e) explaining abrupt climate change;
      (f) Petersen et al’s idea new hypothesis to explain abrupt climate change;
      (g) abrupt climate change versus AGW;
      (h) a bit of everything above.

      Don’t forget to justify your choice.

      Good luck!

    • Steven Mosher

      Willard proves she mentioned the term.
      Playing stupid

    • Another use of “global climate change”, this time with “GCMs” and “emergent phenomena”:

      GCMs are currently incapable of simulating:

      Regional climate variability and change
      Network of teleconnection climate regimes on DEC-CEN timescales
      Predictions of emergent phenomena, e.g. abrupt climate change

      It is unlikely that the current path of development will improve this


    • > “global climate change”

      Make that “abrupt climate change.”

      Another use of “abrupt climate change,” this time with “our current approaches,” which I think refers to climate models:

      This is important, it speaks to broadening the range of possible scenarios and a scenario falsification approach. I’ve made the point numerous times is that our current approaches are neglecting the possibility of abrupt climate change (whether caused naturally, anthropogenically, or as a combination. It further emphasizes the need to understand shorter time scales before having confidence in predictions on longer time scales.


      The term was used in an epilogue to an argument against the overconfidence of climate modellers and the IPCC, because they were overprecise.

    • David Springer

      Willard and Mosher are both pedants.

      Write that down.

  19. son of mulder

    If the climate stoped having abrupt climate changes would that be real climate change?

    • Mike Flynn

      son of mulder,

      More like climate change change. I was going to say things could get even sillier, but I realised how silly that would be. Silly me!

      Live well and prosper,

      Mike Flynn.

    • michael hart

      Some of them might claim that the stability was unprecedented; only five years to save the planet, drone drone drone.

  20. “From the perspective of the atmosphere, an ice shelf looks the same as sea ice in terms of its albedo and its insulating effects, which reduce the release of heat from the ocean”

    I think this a very important sentence. The paradox is that when there is more sea ice at the Arctic, there is less heat transferred from the oceans into space. As sea ice disappears then more heat is lost.
    More ice cover, less cold saline dropping to the abyss and less ice cover, more cold saline dropping to the bottom. The layer cake disposition of cold brines from the poles will gradually work its way to the surface, with a lag of a thousand years or more.

  21. Don Monfort

    Err…Judith: ======> whatever…

    You need to put on your big boy pants and stop the motivated reasoning tribalism and stuff.

    (Little joshie is sick today. He asked me to fill in for him.)

    • Steven Mosher

      the second team Rev and willard are ‘on call’ today.

    • Don Monfort

      Yeah, little joshie says they are inadequate and he begged me to help them out.

    • The Very Reverend Jebediah Hypotenuse

      I would sacrifice anything come what might
      For the sake of having you near
      In spite of the warning voice that comes in the night
      And repeats how it yells in my ear
      Don’t you know, little fool
      You never can win
      Why not use your mentality
      Step up, wake up to reality
      But each time I do just the thought of you
      Makes me stop just before I begin
      ‘Cause I’ve got you under my skin
      Yes, I’ve got you under my skin

    • It might have been better in Bart R’s times. By chance Judy’s mandarins remain on guard, although bender may have been more entertaining.

      Here’s another interesting post on internal variability:

      Juoakola spotted an interesting paper, that I missed when it was originally published:



      This is a really provocative paper, that deals with many topics that have been discussed on previous threads, including chaos and complexity, prediction of emergent behavior, feedbacks and thresholds, natural internal modes and multidecadal ocean oscillations. Numerous examples are given of past abrupt climate changes.


      Our emphasis.

    • Don Monfort

      Off key, pitchy and your tone sucks. Stick with your day job, which I hear involves impersonating a scientist.

    • Don Monfort

      Put on your big coyote pants and stop whining.

    • Here, Don Don, the uncertainty monster to non-linear stuff:


      Notice the date.



  22. I like the theory. Ice insulates and melts from the bottom. If the normal state of the ice shelves is expansion, the counter to that is they break when they’ve over-reached or grown too large. They grow towards instability. Since the ice shelves insulate that is consistent with a cooling system. The needed warmer water during a cooling that leads to a break up may actually be the insulation of the ice.

    The question might, which works better? More insulation or more fuel? Their theory is consistent with fast warming, slow cooling.

    They’ve indicated the sea ice amplifies things, quickly I think. Sort of the same effect as CO2.

    Ice sheets from Science of Doom:

    “At the bottom, when the ice sheet is very thin, heat can be conducted through from the atmosphere to the base and make it melt – if the atmosphere is warm enough. As the ice sheet gets thicker, very little heat is conducted through. However, there are two important sources of heat for surface heating which results in “basal sliding”.”

    Sufficient basal sliding is the on position of the switch.

    More abrupt behavior:

    “This basal thermal evolution, a function of both climatic and ice sheet history, could enable a dynamical switch to widespread basal flow through the deglacial period. Because basal flow has the capacity to evacuate large amounts of ice from the interior of continental ice sheets, creating thin and climatically-vulnerable ice masses, this switch in flow regime may have played a significant role in glacial terminations and the 100-kyr glacial cycle.”

    Fast warming, slow cooling.

  23. So I assume since this is a life or death issue, that we have a special monitoring system in place that constantly measures the salinity and temperature at critical areas in the MOC? Anyone?

  24. Two books may help in understanding the problem faced by those concerned by the power of “consensus science”.

    In “Closing of the American Mind” Alan Bloom, himself a liberal professor at some elite universities, shows how, at these universities, consensus science has replaced scientific inquiry.

    In “Coming Apart” Charles Murray describes that graduate of Harvard, Princeton, and Yale generally wind up living in elitist clusters in Boston, New York, Washington, and San Francisco – and are overwhelmingly Liberal. Murray also adds, from his experience, that these people can be rated as “influential”.

  25. “IMO much more scientific effort should be focused on the topic of abrupt climate change.”

    Translated: “IMO much much more scientific effort should be focused on the topic of squiggology.”


  26. Antonio (AKA "Un físico")

    The new hypothesis says: “During the last glacial period, the North Atlantic basin experienced a number of large and abrupt millennial-scale fluctuations in climate referred to as Dansgaard-Oeschger (DO) cycles”.
    JC says: “I find the topic of abrupt climate change to be more more interesting scientifically than AGW, and potentially of greater societal significance (although one key question is the potential role of AGW in triggering an abrupt event)”.
    Well, I do not understand JC. If AGW is an invented nonsense (as it is) then, “the potential role of AGW in triggering an abrupt event” is ZERO.
    So, Judith Curry, what type of corruption makes all climate scientists to be blind to the truth gained by “statistics+physics” as in my:
    https://docs.google.com/file/d/0B4r_7eooq1u2TWRnRVhwSnNLc0k/ ? I honestly do not understand this.
    Furthermore, please notice that the above hypothesis talks about an abrupt millennial-scale fluctuations in climate: so here “abrupt” means that nothing will change for the next 50 years if Greenland’s ice “sinks”.

  27. Where is the harm in melting some ice and raising sea levels? It’s not going to happen all of a sudden so it’s not like people are going to drown from some sudden tidal wave. You are all such pessimists. It will be a great opportunity to develop new and better cities farther inland. Make sure your grandchildren are civil or contruction engineers there will be a huge demand. Personally I’d love to see Washington DC covered by 100 feet of water, preferrably with all the politicians still in the capitol building.

    • Rud Istvan

      There is a simpler DC solution.
      Curtail the coal plants providing DC with electricity. Sort of a jump start on the newly proposed EPA ‘Obumer’ regs. Guarantee nobody will stay in hot, muggy, formerly swampy DC (that is why neither Maryland nor Virginia wanted it, so ‘gave it’ to the Feds) during the summer without AC. SCOTUS has honored this tradition from the beginning. It is the legislative and executive branches that we need to work on. This solves 1/4 of the problem. Plus a government shut for the summer is a government we don’t have to pay for during the summer. That cuts the annual deficit by a quarter….

      Somehow, I doubt all this will happen. But there is an election this November, and it can have consequences. Don’t be passive.

  28. Rud Istvan

    Have now read about 15 papers today on the end of the YD. It really was abrupt. Not just in Greenland ice cores, Swedish insect ensembles and UK bog deposits. Had large abrupt impacts other than in Greenland and Europe. The southern ITCZ suddenly shifted hundreds of km north towards the equator in Africa, changing ‘dry’ to suddenly wet and formerly wet to suddenly dry. Both seen in African lake varves. Pacific ocean pH ( inferred from boron isotopes in Porities coral remains) in the south pacific (Tahiti and such) lowered by about 0.2 from 8.2 to 8.0 in less than 50 years with data granularity to 1-2 years in coral growth rings and with lab confirmed sensitivity to 0.01pH. Only explainable by a massive sudden shift in ocean upwelling/currents in that part of the Pacific, very far from the AMOC.
    Abrupt end YD Not explainable by declining YD melt water which would have led to a much more gradual shift. There was significant Iceland vulcanism at this exact point in time (ash in European varves) but volcanic aerosols should cool, not warm.

    Judith’s right. Much more study needed. What a fascinating puzzle concerning the only verifiable sudden large warming ‘tipping point’. Eemian fluctuations this great were over a few thousand years each way based on SLR and NEEM. RWP and MWP fluctuations were not nearly this large, and maybe not as abrupt.
    There is even a rather poor quality paper that tried to find statistical ‘end of YD’ early warning signs to apply to CAGW. A valiant but failed attempt.

  29. We can’t explain abrupt climate change. It’s the other way around: the existence of life is explained by abrupt climate change.

    For the last 100,000 years Earth has mostly been locked in an ice age punctuated only briefly by periods of warming such as the interglacial that gave birth to our species. If not for the current global warming period we would not be here.

    Earth has been locked in ice age conditions for more than 80% of the time over the last one million years. Those are all of the facts. Is it ‘gonna stay warm?

    That the Sun might now fall asleep in a deep minimum was suggested by solar scientists at a meeting in Kiruna in Sweden two years ago. So when Nigel Calder and I updated our book The Chilling Stars, we wrote a little provocatively that, we are advising our friends to enjoy global warming while it lasts. ~While the sun sleeps, Translation approved by Henrik Svensmark

  30. Couldn’t have been all that abrupt, hardly any signal recorded in Antarctic ice cores..More of a Northern Hemisphere High Latitude Regional Effect, so therefore means relatively little in the overall state of the climate system, besides indicating that during glaciation… there are glaciers.

  31. ” I find the topic of abrupt climate change to be more more interesting scientifically than AGW, and potentially of greater societal significance (although one key question is the potential role of AGW in triggering an abrupt event).” – JC

    Surely the A in AGW makes the ‘societal significance’ of it far greater than that of a unpredictable natural event, one which Judith acknowledges could be triggered by the said AGW.

    A hands down win for AGW.

    • Excellent point, Michael. Lets just ignore the reality of how the world actually functions under stress and instead fight the demons that live inside our heads. Based on your astrological thought process, you will recommend bloodletting of societies “bad humors”.

    • ” Lets just ignore the reality of how the world actually functions under stress and instead fight the demons that live inside our heads”

      Fascinating Howard.

      Can you tell us more?

    • Now tell the good people of San Francisco that earthquakes are of no societal significance

    • You seem to have missed the point. AGW is a fairly straightforward proposition and scientifically pretty well spelled out. Where as climate change is far more complicated full of whole fields of endeavor. It would be much MORE INTERESTING to any curious person including scientific curiosity. It wasn’t a statement of us vs them.

  32. curryja wrote:

    “I find the topic of abrupt climate change to be more more interesting scientifically than AGW, and potentially of greater societal significance (although one key question is the potential role of AGW in triggering an abrupt event).

    Seems like a winner hands down over AGW which is so mired down. Better for the soul and the intellect. Besides it is a conceptual cradle for unraveling AGW.

  33. Robert I Ellison

    I have now read about a million articles on abrupt climate change – and see abrupt change everywhere.

    Literally in the evolution of eddies in coupled ocean/atmosphere dynamics – described in first principles by the Navier-Stokes equations – to form stochastically forced standing waves in the Earth system at all scales in time and space. Clouds, cyclones, storm fronts, hydrological regimes, glacials and interglacials.

    ‘The modes of vibration associated with resonance in extended objects like strings and air columns have characteristic patterns called standing waves. These standing wave modes arise from the combination of reflection and interference such that the reflected waves interfere constructively with the incident waves.’ http://hyperphysics.phy-astr.gsu.edu/hbase/waves/standw.html

    This idea extends the concept of standing waves to stochastically forced resonance in the Earth system. We might easily call it regimes on decadal to millennial scales – but this misses an essential idea of resonant responses in ice, wind, currents, cloud, dust and biology in the complex system.

    ‘Recent scientific evidence shows that major and widespread climate changes have occurred with startling speed. For example, roughly half the north Atlantic warming since the last ice age was achieved in only a decade, and it was accompanied by significant climatic changes across most of the globe. Similar events, including local warmings as large as 16°C, occurred repeatedly during the slide into and climb out of the last ice age. Human civilizations arose after those extreme, global ice-age climate jumps. Severe droughts and other regional climate events during the current warm period have shown similar tendencies of abrupt onset and great persistence, often with adverse effects on societies.’

    The major changes – both warming and cooling – are associated with changes in North Atlantic Deep Water formation. There are two complementary ideas. The salt oscillator and the wind oscillator hypotheses. – http://www.nature.com/scitable/knowledge/library/abrupt-climate-change-during-the-last-ice-24288097

    The salt oscillator is implicated in major climate shifts. A warm, open Arctic increases evaporation and precipitation. The added spring melt freshens the surface of the Greenland and Norwegian Seas inhibiting deep water formation and the transport of heat north. The cooler conditions – along with low summer insolation – encourage the survival of ice sheets in a feedback.

    The wind oscillator seems associated with Dansgaard-Oeschger events in glacials and similar duration Bond events in intergalacials. The stochastic forcing of resonant modes appears to be related to solar UV/ozone top down modulation of the polar annular modes. The resonant modes translate in well understood physical processes to lower latitude ocean and circulation – including the PDO and ENSO – driving other resonant feedbacks in the Earth system.

    Thus we have not just decadal shifts in ENSO – http://www.ldeo.columbia.edu/res/div/ocp/arch/climate_shift.shtml – but 1000 odd year quasi periods as well as an intriguing shift from La Nina to El Nino dominance some 5,000 years ago.

    e.g. http://s1114.photobucket.com/user/Chief_Hydrologist/media/ENSO11000.gif.html?sort=3&o=226

    How does carbon dioxide fit in? It appears that there is a warm limit beyond which the system shifts and moves abruptly towards the mean.

    ‘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.’ Wally Broecker

  34. one key question is the potential role of AGW in triggering an abrupt event

    Sea ice is frozen sea water but ice shelves originate on land. How many years does it take for a frozen chunk of fresh water — moving at the speed of a glacier or sheet of ice — to become an ice shelf? Surely we’re talking about far longer than the latter half of the 20th century?

  35. John Smith (it's my real name)

    climatereason – tonyb – thanks much

  36. stevefitzpatrick

    Sudden? I think the issue is the degree of suddenness compared to individual human existence/awareness. If a ‘sudden’ change takes place over a century, then that is comparable to a period over which capital investment is depreciated to almost no value. The point is that the ‘cost’ of adaption is very sensitive to the time needed to adapt.. and that depends on the rate of change. There are degrees of suddenness. It really matters how fast.

  37. While the above by Petersen et al provides a reasonable explanation of DO events, it does not explain the 1940 singularity. Although the IPCC does not go that far back in explaining AGW, it erred by so doing, because the 1940 singularity is essential to understanding AGW. When the industrial revolution was still young was the time to see most clearly its effect on global temperature. After three decades of warming global temperature suddenly collapsed in 1940. Why? We do know from Met. Bureau’s own records that the then heat absorption mode of CO2 was close to saturation, so once saturation was reached global temperature would fall rapidly for that particular level of CO2 concentration. Why? Because the oceans would take decades to warm and were still pre-industrial revolution cold in 1940. Hence the 1940 temperature singularity.

    This 1940 collapse of temperature is clearly shown in the observational records of the my theoretical mdel underlined above as figure 1, while figure 2 shows how close we were to heat saturation in 1940.

  38. Stanley Cavell notices a social position he calls the village explainer.

  39. John Smith (it's my real name)

    tonyb – just read your paper – as I am an ordinary bloke it’s gonna take me a couple more reads – forgive me if I’m telling you something you already know, but I believe 14th century tax records in UK show in astonishing detail agricultural output down to the bushel – as I recall the loses become dramatic right about 1314 and remain bad beyond the plague. Seems to me this is a “noticeable” impact way beyond anything in 20th century – I don’t know of any eruptions, coal fired plants or nuke meltdowns in early 1300s – Thanks, I’m new to this issue and find most “climate change” discussions to be incredibly dumb (except ClimateEtc,) – the term “climate change” is dumb – obvious agitprop

    • Hi John Smith

      Yes, those crop records (amongst other information) are some of the things I research. We have the detailed records from several estates and these are the ones from the bishopric of Winchester. One set of these records were translated for me from the original Latin and French by someone on this very site. First some general comments.

      ‘Outstandingly bad harvests at least 15% below average in 1224, 1226, 1283, 1290, 1310, 1315, 1316, 1339, 1343, 1349, 1350.

      Outstandingly good harvests seem to occur when previous summer/autumn very dry winter hard or no ref i.e. average summer in which crop is harvested is very dry. Outstandingly bad harvests follow 2 weather patterns previous autumn wet or very wet, winter wet or fields under water due to wet autumn, summer wet as in the years 1224 1315 1316 1349 1350

      Or previous autumn wet, winter no ref i.e. average summer dry, as in 1226, 1283, 1290, 1310, 1339, 1343 and 1346

      Here are the records for the years around those you mention. We have other corroborating evidence to back up the crop records. Of course these are routinely dismissed as ‘anecdotal.’ by people who don’t like what history tells us. (incidentally history tells us it turned VERY hot and dry again in the latter part of the 14th century.)

      1312 winter wet summer no ref autumn very wet and long

      1313 winter wet summer no ref autumn very wet and long

      1314 winter hard summer no ref autumn very wet and long

      1315 winter wet flooding summer very wet flooding autumn very wet and long flooding

      1316 winter flooding summer unstable flooding autumn wet flooding

      1317 no weather ref but flooding reported.

      —— —–
      Hope this is of interest to you


    • John Smith (it’s my real name) | June 4, 2014 said: ”tonyb – just read your paper..”

      John, Tony is persistently trying to con the ”permanents” here that: ”the globe is spinning around England; actually around small part, around few farms in England”…? here it is:
      ‘’Outstandingly bad harvests at least 15% below average in 1224, 1226, 1283, 1290, 1310, 1315, 1316, 1339, 1343, 1349, 1350”.

      John, that was long before paper was invented in ”England” they were writing on very EXPENSIVE treated leather ”ALL in details recorded- OR was it written on 20century crisp paper by Met office especially for Tony…? Was it written by Merlin – and the temp was EXACTLY THE SAME at that time in Russia,,, Canada… India,.. Mexico, China… north Africa…. north Pacific – all those places and more, are in the northern hemisphere! Dish it to the monks Tony, you tell them

      Few months ago, when the floods were in England – it was DROUGHT in US, record braking heat simultaneously in Australia; in that same week! But of course; in the past where Tony harvest his crap, that wasn’t happening – the WHOLE planet was wet, or dry exactly the same as that part of England.

      1] if one year was cheating on tax and didn’t declare all grain / next year didn’t – following year locust damaged his crop – year after didn’t: so, bucketful of locust increased the temp on the WHOLE planet or at least in the northern hemisphere- WOW!!! Next year the farmer got sick and didn’t harvest on time and grain was fallen on the ground, but he was healthy the previous year – or, 3y after the neighbor’s goats damaged his crop = not much to harvest – two years after, well he just got drunk in the tavern, and didn’t do his job = one bottle of vino decreased the GLOBAL temp, by how much? what Tony’s GLOBAL temperature chart says for that year? 0,026C warmer, or colder – with precision, it’s more convincing, for the permanent commentators here

      Was the bushel engraved in Centigrades, or Fahrenheit at that time? Thanks Tony, your ”research” is a proof of collateral damage the permanents / monks have became – from the misleading propaganda… tragic but funny…

  40. David L. Hagen

    Abrupt Change!
    Don Easterbrook describes what is really abrupt climate change:

    4. About 13,000 years ago, global temperatures plunged sharply (~12 deg C; ~ 21 deg F) and a 1,300-year cold period, the Younger Dryas, began.
    5. 11,500 years ago, global temperatures rose sharply (~12 deg C; ~ 21 deg F), marking the end of the Younger Dryas cold period and the end of the Pliestocene Ice Age. The end of the Younger Dryas cold period warmed by 5 deg C (9 deg F) over 30-40 years and as much as 8 deg C (14 deg F) over 40 years.

    Ch 1 Geologic Evidence of Recurring Climate Cycles, 5.1 Magnitude and Rate of Abrupt Climate Changes, p 22 in Evidence Based Climate Science
    Fig. 22 p 23 shows five events with temperature change from 15 to 24 deg F in 100 years.

    Doubling CO2 is just returning Earth to productive agricultural conditions.

  41. ”larger than the magnitude of say the 1976 climate shift which is sometimes referred to as an abrupt climate change”

    WRONG… THE TRUTH: 1976 was the year they changed massaging the numbers for phony GLOBAL cooling by year 2000, because of CO2 ” DIMMING effect”, to GLOBAL warming by year 2060 (which after was switched to 2100…

    Global warming by year 2100 is same as global cooling by year 2000 – mother of all lies… .”before 76” was overall SAME temp on the planet as it is today only the ”MASSAGING the numbers” was 180 degree in opposite direction. THE TRUTH WILL WIN!!!

    • You mean the aeroslol cooling effect from fossil fuels I think.

    • no JamesG, you maybe are too young, or wasn’t involved; but in the 70’s they were lying that: CO2 f
      goes up in the atmosphere and blocks big part of the sunlight = less sunlight on the ground = global cooling – so, they were presenting that is getting colder; same as now they are lying that the planet is getting warmer

      They were correct then that: CO2 does intercept some of the sunlight high up, where cooling is much more efficient, but, only 50% correct – because at night there is no sunlight to intercept – and didn’t know that: CO2 at night ”slows down cooling” SO: then was half lie / now is the other half LIE – THE TRUTH: intercepting sunlight high up = makes days cooler but nights warmer = overall is same temp always. Taking only the hottest minute in 24h and ignoring the other 1439 minutes is the biggest con! aerosols have nothing to do with the global temp. the ”self adjusting mechanism” is done by the expansion / shrinking of oxygen &nitrogen in change of temp; they are 998.999ppm of the atmosphere, the truth will win on the end! ever:http://globalwarmingdenier.wordpress.com/climate/

  42. The beauties of social justice, Obama style. The new anti-carbon regs are actually anti-poor people. What a shock.

    “According to recently-released data from the Labor Department’s Consumer Expenditure Survey, those in the lowest fifth of income earners spend the greatest share of their incomes on energy (defined as natural gas, electricity, and gasoline and motor oil). Earners in the lowest income quintile spend 24 percent of their pre-tax income on energy, while those in the highest income quintile spend 4 percent—the same as in 2012. Even though high-earners spend more on net, it is the poor who will have their budgets squeezed as they struggle to pay for gas and electricity.

    As E21 director Diana Furchtgott-Roth stated last week, this increases income inequality.

    The pain inflicted on the poorest Americas will not reduce global emissions. According to Manhattan Institute senior fellow Robert Bryce, “the EPA’s new rules will have a negligible [effect] when it comes to soaring global carbon dioxide emissions and surging global demand for coal.” Global CO2 emissions rose by 723 million tons in 2011, the latest data available. The Obama Administration’s goal would cut U.S. emissions by approximately that much over the course of 16 years.”


    • Yep, never mind the carbon, feel the serfdom.

    • HI Gary

      Here in the UK our energy prices are much higher than yours. Around a quarter of households are in fuel poverty but rather more only just above it. The poorest get social help to some extent. However the net effect is that those just above the fuel poverty line and those IN fuel poverty will not be heating their homes to anything like the extent they would like to.

      Typically this very large group would severely curtain the number of heating hours per day and also reduce the temperature to perhaps a barely tolerable level.

      So the bald figures hide the reality on the ground that high energy costs can not really be mitigated satisfactorily. The answer? Don’t go down the European road and pray for warm winters


    • Geez, Gary–I’ll bet dollars to donuts (ask Joe Romm! He’ll owe me a grand in six years…) that the impacts of the EPA rules will be even more negligible on our economy and energy availability and prices than their effect on the climate.

      Calm down.

      This is a political signal, not (obviously) an all-out war on carbon emissions. It’s meant to show good faith to other countries concerned about the issue and keep the faithful semi-satisfied.

      I’m in favor of this move and I haven’t really seen any good arguments against it that don’t amount to ‘We’re afraid it will cost us money to quit polluting.’ Maybe it will. But not as much as they’re ballparking now.

      Maybe get a grip would be better advice.

    • Tom Fuller,
      I’m not so sure you will win that bet. On January 1 2015 Schwarzenegger’s AB 32 carbon tax will kick in. Evan Darrell Steinberg democratic president of the senate is worried. It involves that fuel suppliers buy allowances to offset carbon. It is estimated to cost the California economy 2 billion dollars costing consumers anywhere from 12 to 40 cents at the pump. It is so complicated that it will make it hard for business planners and may cost even more due to supply and demand driving costs up.

      Steinbergs proposal:


  43. Well the skeptics see it that if nature is capable of such massive changes all by itself then there is no need for CO2 to explain any other warming effects. Hence expecting that manmade CO2 might cause an abrupt climate shift is merely gross pessimism with zero foundation – except perhaps an irrational hatred for oil companies. CO2 cannot explain any cooling event anywhere so it cannot be implicated in the warming half of the cycles either.

    Schrag is of course someone who stormed out of a congressional hearing (or somesuch other hearing but not listening forum) complaining loudly about the Bush administration being influenced by automobile manufacturers who were dragging their feet on CO2 reduction policy. Little realising in his diatriabe that auto-makers had always given the public a choice about whether to buy an economical car or a gas-guzzler but the public (including most of the new faux-greens) had opted for gas guzzlers because it was fashionable. Now it’s fashionable to pretend to care about the planet. Life goes on but people are as fickle as ever…

    I’m raather fond of Ruddimans idea that man has affected climate ever since he began agriculture. This current warm period is unnaturally long – we are overdue an ice age. Perhaps humans are good for the planet after all…Herecy!

  44. There was an abrupt climate change in my region and through Eastern Australia after 2007. It had to do with wind direction, oceanic influences and winter storminess, as well as rain. I noticed because I was often standing outside in a bamboo grove or on foot through scrub. The change was profound, even persisting through the 2009 El Nino conditions.

    While many noticed the increased rainfall, few remarked on the pronounced climate change that came with it and could be seen as causing it. (It seemed that the words “climate change” had been reserved for something else.) In Rome in the winter of 2005 I was startled by winter thunderstorms, something I could just remember experiencing in the 1950s and maybe1970s in Sydney. After 2007, winter thunder became commonplace where I live.

    Climate experts will have to start poking their heads outside and contemplating their subject. And when tempted to publish…stick their heads out again and contemplate again till the urge passes.

  45. I don’t think abrupt climate change is a serious threat. To the warm side you can only decrease the poleward gradient by so much before increased transfer of energy poleward becomes impractical and would have decreasing effects as it happened. To the cold side you would have to have some sort of extreme event such as a large chunk of Greenland’s ice falling off almost at once or you would have time to react to the increasing ice sheets with strategically placed black carbon to prevent it spreading further. Abrupt climate change is far more common in a glacial period than an interglacial.

  46. John Smith (it's my real name)

    tonyb – big fun for me – science geeks sleep through history class – history geeks sleep through science class – sounds like you stayed awake all day

  47. It is interesting that no one here seems to be talking about the increase in ocean heat content related to increased ice extent near Antarctica. The potential for abrupt climate change related to this exists. It is a positive feedback to warming, though the increased sea ice and warming connection is counter-intuitive unless you are willing to gain a bit more knowledge beyond the fake-skeptic memes.

    • If all you have is a hammer, everything looks like a nail.

    • maksimovich

      the advection of heat away from Antarctica by polar currents is a mix of both bottom topology and land differences viz a viz antarctic vs arctic eg Marshall 2013.

      as the century proceeds GHG and ozone hole forcing are likely to both contribute to warming around Antarctica. However, as we have
      seen, such warming effects are mitigated by advection of heat by ocean circulation away from Antarctica. The opposite happens over the Arctic where warming is accelerated by ocean heat transport across the Arctic circle.

      The feedbacks for SIE are negative eg albedo and CO2 transport from the SO.

    • eDim,
      Yes, one aspect of the thermodynamics of climate change is very simple. That is, over 99% of the earth’s heat capacity is carried by the oceans.

      That is a big bag of nails.

      I hope this helps your addled brain cope with basic science. Lesson: listen to RG next time.

    • “That is, over 99% of the earth’s heat capacity is carried by the oceans.”

      Webby, you believe in Hollow Earth? Joking aside, I agree, most of the Earth’s climate system heat capacity is carried by the oceans. What’s your point?

    • Maks,

      You miss the point about heat gain in the S. Ocean around Antarctica. Warming is leading to warming. It a positive feedback of the kind that can lead to rapid climate shifts. Some of this heat is going into the latent heat of fusion melting glacial ice from the bottom where it is a tidewater glacier, and some is being advected elsewhere. The important part is the positive feedback. More ice in winter means less heat escape from the ocean, but, unlike what some would posit, that increased OHC is not just harmlessly diffused, but being put to work melting glacial ice.

    • Rob Starkey


      Where do you believe the NORSEX ice area minimum will be this summer? Do you still think it will be like 2011 or more like 2013?

    • “Gates

      Where do you believe the NORSEX ice area minimum will be this summer? Do you still think it will be like 2011 or more like 2013?”
      I would say more like 2011, but such predictions are essentially crap shoots at this point. Overall, the dynamic of the slow “death spiral” in Arctic sea ice is the most important thing. As it spirals down to an ice-free condition in this century, any individual year has too much natural variability to be useful for anything other than gambling. One big cyclone at the right time (early August, for example) can now chew up so much ice and bring up so much warmer water that is can alter the final ice extent greatly, as it did in 2012.

    • @R Gates – the potential for Toba or Yellowstone to erupt exists. The potential for an ELE meteor hitting the planet exists. However, Man cannot stop either or cause either. Abrupt climate change has happened and man did not cause it nor can he stop it.

      You can live in fear all your life on events that are possible with probabilities below 1% of occurring. Most people do not care to waste their life on such activities.

  48. Interesting theory. So how would we fight it ? Thorium power plants round the edge of Greenland pumping their heat into the surrounding waters ?

  49. This is one of the best posts ever. Thanks Dr. Curry and others for the links to papers and other info.

  50. Reblogged this on Tallbloke's Talkshop and commented:
    A very important topic indeed, thanks for raising it.

  51. Non Calor Sed Umor

    But what if the D-O events were not about warm versus cold but instead arid versus moist? What evidence is supporting the ‘cold-warm’ pendulum? To my knowledge only the isotopes in the ice cores and nothing from Arctic paleobiological records.

    The isotope proxy thermometer is -with all due respect to Willy Dansgaard- still an affirming-the-consequent fallacy. If it’s cold, the isotopes are low. The isotopes are low, hence it was cold.

    But what if it was arid instead, would the isotopes also be low?

    You bet, they would.

    An attempt to explain that here:


  52. Ian Wilson

    For what it’s worth, here is another possible explanation for DO events: :

    1. Are the Dansgaard-Oeschger (D-O) Warm Events driven by Lunar Tides?

    2. DO Events Cause Rapid Warming Events in the Last Glacial Period


  53. Reblogged this on CRIKEY !#&@ …… IT'S THE WEATHER CYCLES and commented:
    Reblogged from JUDITH CURRY
    and Tallbloke has a lively forum going on this as well

  54. Pingback: Dansgaard-Oeschger events | CRIKEY !#&@ ...... IT'S THE WEATHER CYCLES

  55. Pingback: State of the blog discussion thread | Climate Etc.

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