Climate Change: What’s the Worst Case?

by Judith Curry

My new manuscript is now available.

A link to my new paper ‘Climate Change: What’s the Worst Case?’ is provided here [worst case paper final (1)]

A few words on the intended audience and motivation for writing this:

First and foremost, this is written for the clients of Climate Forecast Applications Network who are interested in scenarios of future climate change [link]

Second, this paper is written as a contribution to my series of academic papers on the topic of uncertainty in climate science:

Third, the paper is written to inform the public debate on climate change and policy makers.  I am ever hopeful that some sanity can be interjected into all this.

This paper is particularly relevant in light on the preceding post on consensus, and Gavin’s desire for a better way to treat the extreme tails.

Overview of contents

I’m reproducing the Abstract, Introduction and Conclusions in this blog post, I encourage you to read the entire paper.

Abstract. The objective of this paper is to provide a broader framing for how we assess and reason about possible worst-case outcomes for 21st century climate change. A possibilistic approach is proposed as a framework for summarizing our knowledge about projections of 21st century climate outcomes. Different methods for generating and justifying scenarios of future outcomes are described. Consideration of atmospheric emissions/concentration scenarios, equilibrium climate sensitivity, and sea-level rise projections illustrate different types of constraints and uncertainties in assessing worst-case outcomes. A rationale is provided for distinguishing between the conceivable worst case, the possible worst case and the plausible worst case, each of which plays different roles in scientific research versus risk management.

1.Introduction

The concern over climate change is not so much about the warming that has occurred over the past century. Rather, the concern is about projections of 21st century climate change based on climate model simulations of human-caused global warming, particularly those driven by the RCP8.5 greenhouse gas concentration scenario.

The Intergovernmental Panel on Climate Change (IPCC) Assessment Reports have focused on assessing a likely range (>66% probability) for projections in response to different emissions concentration pathways. Oppenheimer et al. (2007) contends that the emphasis on consensus in IPCC reports has been on expected outcomes, which then become anchored via numerical estimates in the minds of policy makers. Thus, the tails of the distribution of climate impacts, where experts may disagree on likelihood or where understanding is limited, are often understated in the assessment process, and then exaggerated in public discourse on climate change.

In an influential paper, Weitzman (2009) argued that climate policy should be directed at reducing the risks of worst-case outcomes, not at balancing the most likely values of costs and benefits. Ackerman (2017) has argued that policy should be based on the credible worst-case outcome. Worst-case scenarios of 21st century sea level rise are becoming anchored as outcomes that are driving local adaptation plans (e.g. Katsman et al. 2011). Projections of future extreme weather/climate events driven by the worst-case RCP8.5 scenario are highly influential in the public discourse on climate change (e.g. Wallace-Wells, 2019).

The risk management literature has discussed the need for a broad range of scenarios of future climate outcomes (e.g., Trutnevyte et al. 2016). Reporting the full range of plausible and possible outcomes, even if unlikely, controversial or poorly understood, is essential for scientific assessments for policy making. The challenge is to articulate an appropriately broad range of future scenarios, including worst-case scenarios, while rejecting impossible scenarios.

How to rationally make judgments about the plausibility of extreme scenarios and outcomes remains a topic that has received too little attention. Are all of the ‘worst-case’ climate outcomes described in assessment reports, journal publications and the media, actually plausible? Are some of these outcomes impossible? On the other hand, are there unexplored worst-case scenarios that we have missed, that could turn out to be real outcomes? Are there too many unknowns for us to have confidence that we have credibly identified the worst case? What threshold of plausibility or credibility should be used when assessing these extreme scenarios for policy making and risk management?

This paper explores these questions by integrating climate science with perspectives from the philosophy of science and risk management. The objective is to provide a broader framing of the 21st century climate change problem in context of how we assess and reason about worst-case climate outcomes. A possibilistic framework is articulated for organizing our knowledge about 21st century projections, including how we extend partial positions in identifying plausible worst-case scenarios of 21st climate change. Consideration of atmospheric emissions/concentration scenarios, equilibrium climate sensitivity, and sea-level rise illustrate different types of constraints and uncertainties in assessing worst-case outcomes. This approach provides a rationale for distinguishing between the conceivable worst case, the possible worst case and the plausible worst case, each of which plays different roles in scientific research versus risk management.

2. Possibilistic framework

3. Scenarios of future outcomes

     3.1 Scenario justification

     3.2  Worst-case classification

     3.3  Alternative scenarios

4. Is RCP8.5 plausible?

5. Climate sensitivity

6. Sea level rise

     6.1 Worst-case scenarios

    6.2 Possibility distribution

    6.3 Alternative scenarios    

7. Conclusions

The purpose of generating scenarios of future outcomes is that we should not be too surprised when the future eventually arrives. Projections of 21st century climate change and sea level rise are associated with deep uncertainty and rapidly advancing knowledge frontiers. The objective of this paper has been to articulate a strategy for portraying scientific understanding of the full range of possible scenarios of 21st century climate change and sea level rise in context of a rapidly expanding knowledge base, with a focus on worst-case scenarios.

A classification of future scenarios is presented, based on relative immunity to rejection relative to our current background knowledge and assessments of the knowledge frontier. The logic of partial positions allows for clarifying what we actually know with confidence, versus what is more speculative and uncertain or impossible. To avoid the Alice in Wonderland syndrome of scenarios that include too many implausible assumptions, published worst-case scenarios are assessed using the plausibility criterion of including only one borderline implausible assumption (where experts disagree on plausibility).

The possibilistic framework presented here provides a more nuanced way for articulating our foreknowledge than either by attempting, on the one hand, to construct probabilities of future outcomes, or on the other hand simply by labeling some statements about the future as possible. The possibilistic classification also avoids ignoring scenarios or classifying them as extremely unlikely if they are driven by processes that are poorly understood or not easily quantified.

The concepts of the possibility distribution, worst-case scenarios and partial positions are relevant to decision making under deep uncertainty (e.g. Walker et al. 2016), where precautionary and robust approaches are appropriate. Consideration of worst-case scenarios is an essential feature of precaution. A robust policy is defined as yielding outcomes that are deemed to be satisfactory across a wide range of plausible future outcomes. Robust policy making interfaces well with possibilistic approaches that generate a range of possible futures (e.g. Lempert et al. 2012). Partial positions are of relevance to flexible defense measures in the face of deep uncertainty in future projections (e.g. Oppenheimer and Alley, 2017).

Returning to Ackerman’s (2017) argument that policy should be based on the credible worst-case outcome, the issue then becomes how to judge what is ‘credible.’ It has been argued here that a useful criterion for a plausible (credible) worst-case climate outcome is that at most one borderline implausible assumption – defined as an assumption where experts disagree as to whether or not it is plausible – is included in developing the scenario. Using this criterion, the following summarizes my assessment of the plausible (credible) worst-case climate outcomes, based upon our current background knowledge:

  • The largest rates of warming that are often cited in impact assessment analyses (e.g. 4.5 or 5 oC) rely on climate models being driven by a borderline implausible concentration/emission scenarios (RCP8.5).
  • The IPCC AR5 (2013) likely range of warming at the end of the 21st century has a top-range value of 3.1 oC, if the RCP8.5-derived values are eliminated. Even the more moderate amount of warming of 3.1oC relies on climate models with values of the equilibrium climate sensitivity that are larger than can be defended based on analysis of historical climate change. Further, these rates of warming explicitly assume that the climate of the 21st century will be driven solely by anthropogenic changes to the atmospheric concentration, neglecting 21st century variations in the sun and solar indirect effects, volcanic eruptions, and multi-decadal to millennial scale ocean oscillations. Natural processes have the potential to counteract or amplify the impacts of any manmade warming.
  • Estimates of 21st century sea level rise exceeding 1 m require at least one borderline implausible or very weakly justified assumption. Allowing for one borderline implausible assumption in the sea level rise projection produces high-end estimates of sea level rise of 1.1 to 1.6 m. Higher estimates are produced using multiple borderline implausible or very weakly justified assumptions. The most extreme of the published worst-case scenarios require a cascade of events, each of which are extremely unlikely to borderline impossible based on our current knowledge base. However, given the substantial uncertainties and unknowns surrounding ice sheet dynamics, these scenarios should not be rejected as impossible.

The approach presented here is very different from the practice of the IPCC assessments and their focus on determining a likely range driven by human-caused warming. In climate science there has been a tension between the drive towards consensus to support policy making versus exploratory speculation and research that pushes forward the knowledge frontier (e.g. Curry and Webster, 2013). The possibility analysis presented here integrates both approaches by providing a useful framework for integrating expert speculation and model simulations with more firmly established theory and observations. This approach demonstrates a way of stratifying the current knowledge base that is consistent with deep uncertainty, disagreement among experts and a rapidly evolving knowledge base. Consideration of a more extensive range of future scenarios of climate outcomes can stimulate climate research as well as provide a better foundation for robust decision making under conditions of deep uncertainty.

Publication status

Since I resigned my faculty position, there has been little motivation for me to publish in peer reviewed journals. And I don’t miss the little ‘games’ of the peer review process, not to mention the hostility and nastiness of editors and reviewers who have an agenda.

However, one of my clients wants me to publish more journal articles.  This client particularly encouraged me to publish something related to my Special Report on Sea Level and Climate Change. I submitted a shorter version of this paper, in a more academic style,  for publication in a climate journal.  It was rejected.  Here is my ‘favorite’ comment from one of the reviewers:

“Overall, there is the danger that the paper is used by unscrupulous people to create confusion or to discredit climate or sea-level science. Hence, I suggest that the author reconsiders the essence of its contribution to the scientific debate on climate and sea-level science.”

You get the picture.  I can certainly get some version of this published somewhere, but this review reminded me why I shouldn’t bother with official ‘peer review.’  Publishing my research on Climate Etc.  and as Reports ‘published’ by my company  allows me to write my papers in a longer format, including as many references as I want.  I can also ‘editorialize’ as I deem appropriate.  In summary, I can write what I want, without worrying about the norms and agendas of the ‘establishment.’  Most of my readers want to read MY judgments, rather than something I think I can get past ‘peer reviewers.’

This particular paper is titled as a ‘Working Paper’, in the tradition often used by economists and legal scholars in issuing their reports.  It is publicly available for discussion, and I can revise it when appropriate.  I hope it will stimulate people to actually think about these issues and discuss them.  I look forward to a lively review of this paper.

And finally, it is difficult to see how this paper could be categorized at ‘contrarian.’  It is not even ‘lukewarm.’ It discusses worst-case scenarios, and how to think about their plausibility.  In fact, in one of the threads at WUWT discussing one of my previous ‘worst-case’ posts, commenters thought that this was way too ‘alarmist’ to be posted at WUWT.

Bottom line:  we need to think harder and differently about climate change.  This paper helps provide a framework for stepping beyond the little box that we are currently caught in.

199 responses to “Climate Change: What’s the Worst Case?

  1. Pingback: Climate Change: What’s the Worst Case? — Climate Etc. – Climate- Science.press

  2. “It has been argued here that a useful criterion for a plausible (credible) worst-case climate outcome is that at most one borderline implausible assumption – defined as an assumption where experts disagree as to whether or not it is plausible – is included in developing the scenario.”

    An excellent framewwork for bringing order to grapplings with this topic.

    • Projections of future extreme weather/climate events driven by the worst-case RCP8.5 scenario are highly influential in the public discourse on climate change (e.g. Wallace-Wells, 2019).

      Much of the problem with what is “highly influential in the public discourse” is the press, who consistently pick just the worst case numbers because they make more dramatic headlines. While the usual “may be as much as” claims are not technically lying they are highly misleading as a statement of
      the state of knowledge of the content of papers or IPCC reports.

      It is these headline numbers which the public retain, they do not read and absorb the full range including the “may be as little as” figures and do not realise that the high end numbers are right out on the end of a long fat tail of probability.

      Part of this is click-bait and selling newspapers but a lot of it misguided ‘save the world’ zealotry on the part of journalists who seem to consider themselves on a mission from God ( or Gaia ) and are perfectly happy to distort, misrepresent and mislead.

      If ” at most one borderline implausible assumption” is included , that is the number which will hit the headlines and be retained in the public mind and public discourse.

      There is also the army of climate “scientists” who see no problem in Schneider’s “dilemma” of whether to be honest or effective”, where the effective bit has nothing to do with science. These folks have abandoned the basic tenants of science and should be removed, however they are always the go-to guys for evangelical climate journalists.

      • The legacy media publishes the worst case scenarios, as they’re encouraged to do so.
        The Climascientologists like Mann (I see Dr Tim Ball’s won his case against that charlatan!) push them on social media & his blog.

    • Projections of future extreme weather/climate events driven by the worst-case RCP8.5 scenario are highly influential in the public discourse on climate change (e.g. Wallace-Wells, 2019).

      Much of the problem with what is “highly influential in the public discourse” is the press, who consistently pick just the worst case numbers because they make more dramatic headlines. While the usual “may be as much as” claims are not technically lying they are highly misleading as a statement of
      the state of knowledge of the content of papers or IPCC reports.

      It is these headline numbers which the public retain, they do not read and absorb the full range including the “may be as little as” figures and do not realise that the high end numbers are right out on the end of a long fat tail of probability.

      Part of this is click-bait and selling newspapers but a lot of it misguided ‘save the world’ zealotry on the part of journalists who seem to consider themselves on a mission from God ( or Gaia ) and are perfectly happy to distort, misrepresent and mislead.

      If ” at most one borderline implausible assumption” is included , that is the number which will hit the headlines and be retained in the public mind and public discourse.

      There is also the army of climate “scientists” who see no problem in Schneider’s “dilemma” of whether to be honest or effective”, where the effective bit has nothing to do with science. These folks have abandoned the basic tenants of science and should be removed, however they are always the go-to guys for evangelical climate journalists.

  3. My understanding was that carbon wasn’t actually causing warming but that it was the other way around. Maybe I’m just not keeping up …

    “There are some things about climate change that we know for sure. For example, we are certain that increasing atmospheric carbon dioxide will act towards warming the planet.”

    • I think Dave, it is very clear that greenhouse gases cause warming. There is a feedback loop in that warming will cause a secondary increase in CO2, but that’s a secondary effect. The more interesting question is how much warming.

    • “The hypothesis of a Greenhouse Effect is obviously false.” gm…: and why do we see a blue sky when it’s cloudless and the sun is shining? The rayligh scattering is very similiar to the infrared scattering of GHG in the atmoshere. And it seems to me not appropriate to discuss Judy’s paper with this lack of fundamental knowledge. The antropogenic forcing is a fact, the question is: how sensitive is our climate system to the forcing. Judy tried to find out the upper bound. All the best!

  4. Pingback: CLimate Change | Transterrestrial Musings

  5. Typo at “And finally, it is difficult to see how this paper could be categorized at ‘contrarian.’ Should be “as”.

  6. Judith, Your observations about peer review particularly resonate with me and mirror my experience. The process of peer review instantiates the perceived interests of the research community in a particularly field. In my field, that involves making sure that uncertainty is minimized (or not discussed) and negative results are not highlighted. As I’ve gotten older and my experience with CFD has broadened, I’ve come to realize how deep the structural problems in science are.

    Generally, science is infected with cultural biases and positive narratives about scientists and science itself that are more about self-promotion than about facts and data. One of the most pernicious is the marketing of more and more complex and costly simulations based on the “more physics must be more accurate” idea. This focus is an easy and perhaps even lazy one for scientists in that no fundamental advances are required, but it virtually guarantees a lack of focus on fundamental theoretical (and much more risky) work. Unfortunately this fundamental work is what we really need.

    • “As I’ve gotten older and my experience with CFD has broadened, I’ve come to realize how deep the structural problems in science are. ”

      Maybe it’s been done (several times), but some historian/anthropologist should do a study of modern natural science as a sociocultural/anthropological phenomenon. One crucial facet such a study should notice and explore is how natural science has become deeply & broadly enmeshed in the complex of industry/technology/economics/politics(geopolitics)/media/bureaucracy.

      Certainly there probably always was some degree of nexus between scientific endeavors that above-mentioned complex. The point is the extent; and such a profound extent as has become internationally institutionalized would likely explain many of the signs of corruption of the scientific ethos. The the protracted debacle of the politico-scientific global warming issue, whatever else it manages to wreak in the coming decades, will make clearer the extent of this corruption.

      Greater efforts should be made to segregate science & scientists from the above-mentioned complex, institutionally and pedagogically, if not also on a cultural level. Such segregation would help foster more neutrality, of which the aforementioned corruption shows serious signs of compromise. This neutrality is much like how expert witnesses in legal trials work best when they are not shilling for one side or the other, defense or plaintiffs. If a defense lawyer or plaintiff prosecutor can show that his expert witness is truly impartial, his expert witness becomes that much more effective for the lawyer’s case (if, of course, the conclusions of the expert witness support the lawyer’s case).

    • Frank, There is a broad understanding of what is happening. As science has become big business funded by soft money, its become involved in selling the work and the incentives have grown perverse. Universities have adopted an entrepreneurial business model that has also proven disastrous. In the past scientists were mostly gentlemen with free time to spend on their interests. Now its become a “career.”

  7. We have about 78 years of experience with rising CO2 levels and mild, intermittent global warming (from roughly 1940 through 2018).

    No one was hurt.

    Our planet is ‘greening’.

    There is no logical reason to expect the next 78 years of climate change to be much different than the past 78 years, which were 100% good news !

    In fact, the most likely worst case concerning climate change would be the Green New Deal, or similar policies — gross overreactions to a non-existent climate problem.

    The coming climate catastrophe is fiction — it exists ONLY in overactive imaginations, and in computer games that have made grossly inaccurate climate predictions for the past 30+ years.

    One of my favorite “philosophers” understood the problem many decades ago, and I am afraid, Ms. Curry, that you have completely missed the real worst possible case (a Green New Deal).

    The coming climate change catastrophe, that is not coming, and the gross
    overreactions to it, are 99% politics and 1% real science.

    Groucho understood politics, along with H. L. Mencken:

    “Politics is the art of looking for trouble, finding it everywhere, diagnosing it incorrectly, and applying the wrong remedies.” Groucho Marx

    ” … the whole aim of practical politics is to keep the populace alarmed (and hence clamorous to be led to safety) by menacing it with an endless series of hobgoblins, most of them imaginary.”
    — From H. L. Mencken’s In Defense of Women (1918).

    • Richard
      You’re right. The worst case is a hard-green hard-left power grab. It’s beginning. Once it is established the climate issue will be quietly forgotten.

    • Thanks for the Mencken quotation. I did not realise it was that old. We are so slow to catch on.

    • “…the most likely worst case concerning climate change would be the Green New Deal”. Exactly.

      But besides worst case, what’s the best case scenario from a “do no harm” perspective? This is also a part of risk assessment. It’s been discarded, scientifically speaking, which has always been subservient to “politically speaking”. And there’s little stomach in the media to actually argue about which is the better, warming, or cooling. How to redistribute US capital trumps everything, and we know where most media advocacy swings. But if human behavioral modification could facilitate more shoreline and cooling, is this a superior outcome to more greening and warming? There’s virtually no expressed confidence that technology will render AGW concerns obsolete, that’s because it’s not the point whether technology can or will resolve anything. The desire to motivate people a particular way is decidedly mostly a political ambition, not an environmental one.

      We know from science that the earth has greened 14% from presumably mostly human contributions of CO2, not because of a continuation of natural warming since the LIA ended. But when listening to the drumbeat of worst case scenarios from the media we must surmise that the best case scenario must include reversing the greening effect of the planet as a consequential outcome. It’s not a Green New Deal “or” bust, it’s the Green New Deal “and” bust.

    • Richard writes: “We have about 78 years of experience with rising CO2 levels and mild, intermittent global warming (from roughly 1940 through 2018). No one was hurt. Our planet is ‘greening’. There is no logical reason to expect the next 78 years of climate change to be much different than the past 78 years, which were 100% good news!”

      Today, CO2 levels are rising at about 2.5 ppm/yr. They haven’t been rising at this rate for the past 78 years. CO2 isn’t the only GHG and rising aerosols associated with burning of fossil fuels have negated some of the forcing from rising GHGs. However, aerosols peaked around 2000 and are now falling. Let’s be a little more honest in our extrapolations: For the past half-century, anthropogenic forcing has increased roughly linearly at a rate of 0.4 W/m2/decade and surface temperature has risen at an average rate of slightly less than 0.2 K/decade. That is 0.5 K/(W/m2).

      This is transient warming. ARGO shows about 0.7 W/m2 of today’s 2.5 W/m2 forcing is still being taken up by the ocean (leaving an additional 1.8 W/m2 for radiative cooling to space in response to roughly 1 K of surface warming). So we have experienced only about 70% of the equilibrium warming associated with today’s forcing. That brings us to 0.7 K/W/m2.

      The RCP6.0 W/m2 emissions scenario (which no one calls alarmist and includes serious reductions in emissions in the second half of the 21st century) projects another 3.5 W/m2 of anthropogenic forcing by the end of the century. That would be an additional 2.5 K on top of the 1 K we have already experienced. (RCP8.5 would be an addition 6 W/m2 of forcing and 4.2 K of warming). Lewis and Curry provide estimates for ECS which are somewhat less than this ballpark estimate, while the IPCC’s AOGCMs are higher.


      Figure 8.18. Forcing vs time.

      Now that you recognize that SIMPLE EXTRAPOLATION shows that future change is likely to be much larger than past change, you are welcome to express your opinion that climate change will be will be 100% good news – or not, as the case might be. Before doing so, however, it it worth pointing out that the most productive and successful area of our planet today are in the temperate zone, some of which is likely become arid sub-tropics with this much warming. And worth pointing out that saturation vapor pressure increases 7%/K, a 5.6 W/m2/K increase in latent heat flux if overturning of the atmosphere is unchanged. However, the climate sensitivities discussed above are consistent with only 1-2 W/m2/K escaping to space in response to warming. The rate of atmospheric overturn must slow. The increase in precipitation (typically estimated to be 2%/K can’t keep up with the increase in evaporation on land (7%/K). CO2 can fertilize plant growth only when there is enough precipitation.

      • frank too
        The global average temperature has barely changed from the early 2000’s through 2018.

        A linear trend line does not show that well because is captures the large 2015 / 2016 El Nino — a temporary heat increase NOT caused by CO2.

        Linear trend lines are also not acceptable for honest reporting of non-linear temperature data.

        But a glance at the UAH LT chart makes it clear.

        CO2 rose about +100 ppm from 1940 through 2018 — I had not mentioned in my prior comment that the next +100 ppm increase in CO2 levels is EXPECTED to have a smaller warming effect than the prior +100 ppm increase.

        If the global average temperature happens to increase +0.1 degree C. in the next ten years, and the same amount in each of the following nine decades, for +1.0 degree C. warming in the next 100 years = ho him, so what !

        Would you have us believe 4.5 billion years of natural climate change suddenly stopped in the 20th century, then CO2 mysteriously took over as the “climate controller”, and the “proof” of that is some scientists say so ?

        Since 1910, the CO2 – Average Temperature Correlation has changed repeatedly … but you would have us believe that YOU “know” what the future climate will be. Grow up !

        https://elonionbloggle.blogspot.com/2019/08/the-co2-global-average-temperature.html

        Your comment is climate scaremongering, based on wild guesses of the future climate, that no one is capable of predicting — in scientific terms, your comment is a steaming pile of farm animal digestive waste products.

        You can believe your fairy tale scenarios and computer games.

        I’ll study reality — the past 325 years of global warming — it’s been 100% good news all the way … and there is no evidence that CO2 is, or will ever be, the “climate controller”.

      • Richard writes: “The global average temperature has barely changed from the early 2000’s through 2018.”

        Wrong. If I go to Nick Stokes trendviewer and look at any period ending now (6/2019), for HADCRUT, the lowest trends are 1.33 (+/-0.65) K/century beginning in 5/1997 and 1.38 (+/-0.72) K/century beginning in 4/2001. Given the fluctuations (mostly associated with ENSO) in global temperature, there is no significant difference between these warming rates and the long-term warming rate since forcing began rising at about 0.40 W/m2/decade around 1970: 1.73 (+/- 0.18) K/century for 1/1970 to 6/2019. So, even when I cherry-pick from hundreds of possible starting months, I can’t find any period ending right now where WARMING TO PRESENT has been statistically slower than the better defined long-term trend. The reason for this is that the temperature has never returned to the plateau seen during the Pause. Since the 15/16 El Nino ended, temperature has averaged roughly 0.2 K higher than during the Pause and never been less than 0.1 K above that plateau.

        You cited UAH. Given the massive problems recently associated with orbital drift, the increased variability in satellite temperature, and the shorter record, I find UAH less meaningful that the surface temperature records. However, here are the trends for UAH and RSS beginning:
        1/1979: 1.38+/-0.37 and 2.04+/-0.36
        5/1997: 0.85+/-0.99 and 1.72+/-0.91
        4/2001: 1.21+/-1.08 and 1.78+/-1.01
        The conclusion is the same: there is no clear evidence that the recent warming rate has been significantly different from the long-term trend. The higher uncertainty in the trends in satellite records makes it harder to detect a change.

        If one cherry-picks both the starting date and ending date (from among thousands of possibilities), you can identify periods with significantly slower warming and no warming. And in any normal distribution of more a thousand data points, about 50 points would be expected to lie outside the 95% confidence interval.

        Richard writes: “A linear trend line does not show that well because is captures the large 2015 / 2016 El Nino — a temporary heat increase NOT caused by CO2. Linear trend lines are also not acceptable for honest reporting of non-linear temperature data.”

        The proper way to deal with the noise associate with ENSO is to include confidence intervals (95%) properly adjusted for the autocorrelation in the temperature data along with the central estimate for the trend. I have done so.

        Forcing has been increasing roughly linearly since 1970. There are good physical reasons to expect transient warming to vary in proportion with forcing. For this reason, it make sense to apply a linear fit to the temperature data since 1970. A linear fits to the data since 1900 doesn’t make since because forcing hasn’t been linear over that period.

        Richard wrote: “CO2 rose about +100 ppm from 1940 through 2018 — I had not mentioned in my prior comment that the next +100 ppm increase in CO2 levels is EXPECTED to have a smaller warming effect than the prior +100 ppm increase.”

        That is why I discussed the long-term trend in FORCING (0.4 W/m2/decade) rather than the change in CO2. I didn’t need to deal with logarithms and I have properly accounted for other smaller forcings.

        Richard continued: “Would you have us believe 4.5 billion years of natural climate change suddenly stopped in the 20th century, then CO2 mysteriously took over as the “climate controller”, and the “proof” of that is some scientists say so?”

        Of course, natural climate change didn’t stop in the 20th-century. Going back 4.5 billion year would be nonsense: the atmosphere didn’t contain oxygen and plants were not growing on land. You can go back 300 million years, but the continents and ocean currents weren’t in the same places and periods of intense volcanic activity released GHGs. You can go back a million years ago, but then climate was swinging from glacial to interglacial due to orbital mechanics. So I look back over the past 70 centuries of natural climate change after conditions stabilized in the early Holocene and compare the 20th century to the 69 or so preceding centuries. Isn’t that the best comparison? Yes, you can see the MWP, RWP and Minoan warm periods in the Greenland ice core record, but temperature swings in Greenland are doubled by Arctic amplification. There is no evidence for those warm periods in Antarctica or in the global record of ocean sediment cores. The warmest recent period in Greenland lasted long past the end of the MWP elsewhere. Climate change in Greenland appears to be a regional, rather than global, phenomena. The depths of the LIA currently appear to be less than 1 degK colder than the 1860-1960 average, and we know that solar activity was clearly weaker in parts of the LIA. (There were also some volcanos about 10X more powerful than Pinatubo during the LIA.) The 0.9 K of warming since 1970 clearly hasn’t been influenced by an increase in solar activity or large volcanic eruptions.

        The clearest example of UNFORCED climate variability I know of is the warming that ended in 1945 that can’t be explained by forcing. That warming lasted half as long involved a change half as big, and developed at a rate comparable to warming since 1970. That means that the current unforced warming is unprecedented by a factor of 2, but we have only a few centuries of precedent for unforced variability and 70 centuries of variability that might be naturally forced or unforced.

        Richard continues: “Since 1910, the CO2 – Average Temperature Correlation has changed repeatedly … but you would have us believe that YOU “know” what the future climate will be. Grow up!”

        OK, LET’S GROW UP. It is idiotic for anyone to say that warming over the past half-century or lack of warming during the Pause proves or disproves that CO2 is causing warming. Climate can change chaotically – without obvious cause. Of course, it is far more idiotic to use a short Pause for disproof and fail to recognize that the Pause has ended. A half century trend is far more substantial, but not “proof”. NEVERTHELESS, the well understood theory of the interactions between radiation and matter (QM), careful laboratory study of the absorption of IR by GHGs, AND thorough testing of radiation transfer calculations in our atmosphere leave no room for doubt that rising GHGs will slow radiative cooling to space – by about 3.5 W/m2 for a doubling of CO2. The law of conservation of energy demands that the retained energy show up as “internal energy” – higher temperature somewhere in our climate system. And COE demands continued warming until a higher temperature restores balance between incoming and outgoing radiation. 3.5 W/m2 is a massive amount of power: Simple calculations show that much power would warm the top 50 m of the ocean (the part that warms seasonally) and the atmosphere at a rate of 0.7 K/year (!) – if none of that extra power escaped to space or were taken up by the deep ocean.

        The key unknowns are how much heat will be transported into the deep ocean (slowing warming at the surface) before balance is restored and how fast radiative cooling to space increases with surface warming (W/m2/K). ARGO shows that recently the ocean has been taken up about 0.8 W/m2 of the current forcing of 2.5 W/m2, meaning that more 1.7 W/m2 are reaching space in response to the roughly 1 K of transient warming. Nevertheless, I can’t say for sure whether chaos ADDED TO or SUBTRACTED FROM that 1 K of warming. The satellites monitoring Earth from space show that LWR cooling to space increases about 2.2 W/m2/K as the planet seasonally warms and cools every year. And there is some other observational evidence consistent with the idea that chaos hasn’t had a big effect in the last half century.

        Climate science doesn’t need rising surface temperature in a chaotic climate system to prove that rising CO2 causes warming. Radiative forcing and COE – simple sound physics – is all one needs! The public doesn’t understand the physics, so the alarmists have misled you by focusing far too much attention on warming. If you don’t understand the physics, learn it:

        https://en.wikipedia.org/wiki/Schwarzschild%27s_equation_for_radiative_transfer

        I merely corrected YOUR misleading extrapolations from the past to the future. Physics suggests my extrapolation is reasonable.

  8. “Overall, there is the danger that the paper is used by unscrupulous people to create confusion or to discredit climate or sea-level science. Hence, I suggest that the author reconsiders the essence of its contribution to the scientific debate on climate and sea-level science.”

    How ironic the reviewer recommended a self-censorship policy based on a perceived worst case scenario rather than on the merits of the paper.

    • The reviewer is Inquisitor Cardinal Bellarmine who was instrumental in sentencing Giordano Bruno to burning at the stake. Old good times are returning.

  9. There are some things about climate change that we know for sure. For example, we are certain that increasing atmospheric carbon dioxide will act towards warming the planet.

    For sure they are wrong. Here’s the view from outside ‘the little box’:

    The fact is the carbon dioxide trend is driven from the Nino4 region which has been warmer than 26.5C, the transient CO2 equilibrium temperature, for all but 2 months since at least 1870, pumping out CO2 the whole time following Henry’s Law of Solubility of Gases.

    CO2 doesn’t cause warming, it is a natural predictable response to warm tropics which follows a natural annual temperature cycle and the ocean’s solar-driven upward temperature trend, unfazed by puny human emissions.

    The obsession over human CO2 emissions needs to stop. It’s unscientific.

  10. Judith,

    You question how your paper could be construed as contrarian.

    To my mind there are five key methodological issues to be considered within risk management:

    1) The highly subjective nature of risk analysis and the extent to which this is not recognised.

    2) The widespread application of additive (probabilistic) techniques for the quantification of likelihoods, notwithstanding the extent to which evidential ambiguity underpins the uncertainties.

    3) The insistence that decision-making is still risk-based, long after the levels of uncertainty have precluded reliable calculation of likelihoods.

    4) The dominant role in the determination of policy that is ceded to mere plausibility, once high impact / low likelihood scenarios start to feature in risk assessment.

    5) The failure to appreciate the importance of risk efficiency and attendant risks when deciding upon risk management strategies.

    I see no reason why climatology should be granted immunity from the above. And yet, in my experience, any attempt to discuss such areas of controversy within the context of climate science leads to accusations of contrarianism. In particular, those who are satisfied that uncertainty may be adequately modelled with nothing more than a probability density function are unlikely to be otherwise persuaded by someone with ‘denialist’ credentials. Probability theory is so entrenched in our way of thinking about uncertainty, you will find it a difficult enough paradigm to overcome outside of climatology – within it, you will definitely have your work cut out!

  11. “Overall, there is the danger that the paper is used by unscrupulous people to create confusion or to discredit climate or sea-level science.”

    This. This is why some people distrust scientists. A scientists job is to do science. Yes, that’s overly simplistic, but it’s also the truth. So, there’s not only an replication crisis in science, but an integrity crisis, as well. We shouldn’t care that someone would take this paper and spin it to their purpose, whatever that may be. Truth and facts should be transcendent to fear of how someone will spin this paper. This person cares more about what someone will think of this paper or how they’ll use it than advancing science and understanding. This is a cargo cult scientist at work. Is it too late for this scientist to come around? It’s hard to say. If he’s more worried about what people will think of a particular study, it seems he would be less likely to do a study pushing the knowledge boundaries of science due to peer fear. This is exactly the type of person we don’t need in science.

  12. Rich countries certainly won’t passively watch a worst case scenario. So the real worst case would be that (cheap) geoengineering/solar radiation management does not work or has very bad side effects.

    • Completely agree that geoengineering will be deployed because anything else would require personal sacrifice. Not going to happen.
      Daniel Kahneman theories of behavioral economics make it pretty clear we lack the ability to deal with distant threats like climate change (or 450 trillion $ in global debt).

      • If geoengineering’s deployed, it’ll be because somebody’s making money out of it.

      • Geoengineering will be done because technology will makes it possible. There may be some profit for the organizations that create and deploy it.
        It might not be because we want to counteract AGW but for the betterment of humanity. I would much rather see us turn the Sahara or Gobi deserts green than put humans on lifeless planets.

  13. Dr Judy Curry
    Thanks so much for continuing to work on these issues, irrespective of your company needs.

    You remain an inspiration to science respecting observers.

    From the time I first became aware of you in Scientific American discussing with Dr Mann these issues I followed you with growing respect.

    Please never get discouraged by the slander thrown your way.

    With deep respect,
    Scott

  14. When considering scenarios there is an issue with everyone using words like “credible” and “plausible” The dictionary definition is “:adjective
    able to be believed; convincing.
    synonyms: acceptable, trustworthy, reliable, dependable, sure, good, valid; ”

    It begs the question: credibility to whom? What one is able to believe is largely subjective. If something is believed it must be because it is believable to the people who believe it Thus I see “credibility” as being psychological and perhaps even tribal rather than scientific. All the media stories about having only 12 years to save all life on Earth are credible to and believed by millions of readers. The wider the consensus (for right or wrong scientific reasons) the more credible is the story about which there is a consensus. We may just be reasoning in circles.

    I don’t have the solution to this issue, but perhaps other readers can suggest better words or concepts for assessing risk and likelihood of harm than “consensus”.

  15. The overwhelming majority of “climate scientists” and their published papers are narrowly defined within a specialty of science related to climate. Such specialists might be developing an instrument, or deriving historical data from proxies, or whatever. That does not give them the broad perspective on the “system engineering” of climate change. That makes the notion of a “consensus” ludicrous because most of these people are in no way qualified to be expert on the big picture issues of climate. At the same time, those few climate scientists who are concerned with the big picture, face herculean challenges in trying to understand the technical and economical and social issues that are so fraught with the uncertainty monster. The peer-reviewed literature has become essentially irrelevant as it continues to focus on narrow reports on this or that, which make it through the political review process. The interesting discussions occur in the blog world, although that discussion realm is diluted by the endless silly stuff where bloggers can’t stick to the issue and continue to argue incessantly for alarmism or total denialism

  16. Denis Rushworth

    See https://www.jcronline.org/doi/full/10.2112/03-0123.1. Dr. Larson concludes sea level has been rising at 1.3 to 2 mm/yr for the past 6000 years.

  17. The worst case for warming would be if solar activity returned to SC21-24 levels and stayed there indefinitely as that would drive continuous warming and provide the necessary power for severe extreme events experienced such as happened during that time.

    I think this happened many times in the past, as well as the opposite, that lead to long-term cooling. The worst case for cooling would be if solar activity returned to Dalton or Maunder Minimum levels for many decades.

    Once it becomes clear the magnitude of sea surface change which defines real climate change is bounded by the maximum solar energy via TSI changes and ocean thermal inertia, there is nothing to worry about. Humans are not part of this equation, so climate change is 100% natural, solar-driven, along with CO2.

    There is nothing we can do about limiting future temperatures. No 1.5 or 2C human political limit will matter to dear old Sol and the great ocean.

    • The worst case for cooling would be if solar activity returned to Dalton or Maunder Minimum levels for many decades.
      Cold times correlated with ice extent max, read what you also wrote!

      I think this happened many times in the past, as well as the opposite,
      REPEAT AS WELL AS THE OPPOSITE!!!!!
      I think this happened many times in the past, as well as the opposite,

      REPEAT AS WELL AS THE OPPOSITE!!!!!

      Right! solar minimum or max sometimes correlates and does not cause anything long term, the ice extent is the major cause of long term warming and cooling.

      REPEAT AS WELL AS THE OPPOSITE!!!!! Ice extent is cause of longer term warming and cooling and not result!

      • What happened recently happened in the past I think, that is a long stretch of high solar activity that leads to warming. The opposite has happened too, meaning a long stretch of low solar activity that leads to cooling happened before, many times, back and forth, sequentially, over and over – the lesson of history.

        Sea ice extent is connected to the tropics with a lag. The Pacific NW warm pool lags Nino4 by 6-7 months.

        NH & SN sea ice extent is significantly governed by tropical warmth:

        Since Nino4 peaked in March, we’ve got a few months to go before the northern ocean regions peak. After that its all downhill, and because of that and the continuation of low solar activity, I predict very strong ice growth for Greenland and the Arctic by spring 2020.

      • What happened recently happened in the past I think, that is a long stretch of high solar activity that leads to warming. The opposite has happened too, meaning a long stretch of low solar activity that leads to cooling happened before, many times, back and forth, sequentially, over and over – the lesson of history.

        long cold periods had warm and cold solar periods. long warm periods had warm and cold solar periods. Every cold period had more ice extent and every warm period had less ice extent. You have clearly not studied the data an you do not understand, you do not even suspect.

      • After that its all downhill, and because of that and the continuation of low solar activity, I predict very strong ice growth for Greenland and the Arctic by spring 2020.

        Ice core data shows that the ice accumulation rates are highest in warmest times. Colder times do not thaw sea ice, do not promote evaporation and snowfall. When you promote ice growth in the times that sea ice covers the oceans and prevents evaporation and snowfall, you prove you do not understand.

      • Ice extent is cause of longer term warming and cooling and not result!

        The cross-correlations are clear evidence your idea is backwards.

        Ice extent change is a result of a yearly tropical influence and also long-term ocean warming or cooling, both depending on solar activity trends and averages on two different timescales, the current influence and the cumulative influence over a decade or more.

        If you argue without any data again I’ll know you’re just trolling me.

  18. Imo, reality is RCP4.5. Climate “crisis” at this moment, should be stricken from the record.

  19. Projections of 21st century climate change and sea level rise are associated with deep uncertainty

    BS it is snowing more and sea level will begin to drop.

    and rapidly advancing knowledge frontiers.

    BS consensus prevents advancing Knowledge

  20. Thanks, Judith.

    Regards,
    Bob

  21. Further to the point I just made, IIRC, the RCP8.5 scenario is an extreme high solar SC23 projection out to 2100. SC23 has the top 3 PMOD TSI years, and 4 of the top ten. No wonder that model runs hot.

    What matters is what’s coming up in SC25, whether the solar energy maintains or diminishes, and how the climate follows:

    To be updated upon official solar minimum determination. The prediction is based on Leif Svalgaard’s sunspot prediction for SC25 being between SC20 and SC24. Note the high-range SC21-23 model predicts positive net warming for the next cycle, just as RCP8.5 does.

    Imagine the temperature climb resulting from the cumulative effect of 6 or 7 such high cycles out to 2100 – the root of alarmism is right there.

    • What matters is what’s coming up in SC25, whether the solar energy maintains or diminishes, and how the climate follows:

      Solar cycles have repeated the same cycles in nearly the same, slightly increasing bounds over fifty million years. There are immediate response to what the sun does but climate cooled over fifty million years while the sun got hotter. You have nothing that works for longer term changes.

      • That is vague conjecture. I think for the best data we have my system works from the top of the Holocene to today. The well-known historically repetitive CO2 lagged responses to temperature with correlated linear trends and then the similar rates of temperature change seen during the Holocene to the present indicate similar processes to today’s climate, where now we have high enough resolution data to determine and show what causes what in real-time, as I show in my sun-climate work, CO2 is the by-product of solar-warmed tropics, and global warming is from higher global ocean energy storage over time from higher solar activity driven absorbed solar energy in the tropics.

  22. Climate Change: What’s the Worst Case?

    The worst case is that action is taken without even trying to understand natural causes of climate change. That has been the case so far.

    A change in CO2 from nearly 300 parts per million to 400 parts per million is one more molecule of CO2 per ten thousand other molecules.

    Quit pretending to believe that is causing dangerous temperature rise and any sea level rise.

    Worst Case is that more dumb stuff is done that makes many rich and does not influence climate.

  23. In Section 6.2, two of the bullet points under “possible worst case” refer to sea-level rises of “3.39 cm” and “2.97 cm”– surely the units here should be meters?

  24. The concern over climate change is not so much about the warming that has occurred over the past century. Rather, the concern is about projections of 21st century climate change based on climate model simulations of human-caused global warming, particularly those driven by the RCP8.5 greenhouse gas concentration scenario.

    The concern is all based on claiming to predict the weather decades into the future. It may well turn out to be concern about nothing.

    • The concern is all based on claiming to predict the weather decades into the future. It may well turn out to be concern about nothing.

      Business and government and people will be impacted by future climate changes and it is way more than nothing. It is natural and normal and we have not caused climate change and we cannot, but it is much more important than nothing. Where will we grow which crops and where will we do winter sports and where will we do summer sports? What will our heating or cooling needs be?

    • popes
      Policy makers need to understand the concept of the opportunity cost.
      The opportunity cost is the sum of all the opportunities and possibilities for humanity that are forfeit, that disappear, that otherwise would have been available, because you have chosen economic self-flagellation in response to a dystopian virtual climate model.
      What else could all that money have been spent on?
      By households as well as governments, both with 2-5 times smaller energy bills and transport costs.
      What could the world’s plants have done with all that CO2?
      Grow I guess.
      We humans can also choose to shrink – or grow.
      Those two alternative futures lie before us but it is increasingly clear which one we and our children are now committed to.
      “Honey I shrank the human race!”

  25. Projections of 21st century climate change and sea level rise are associated with deep uncertainty and rapidly advancing knowledge frontiers.

    Dear be understands the goodwill behind the last part of this sentence but is it true? In 1985 predicted warming per CO2 doubling was 1.5-4.5 C. Today, 2019, it is still 1.5-4.5. What advancing knowledge?

    They chatter on and on. No one really knows what is going to happen; no one can predict the future. Ecclesiastes 10: 14.

  26. Hindsight is going to tell people a lot 50 years from now… hindsight also tells us models of the future, 50 years out, are works of fiction and belief in scary predictions says more about ourselves today than what’s possible tomorrow.

  27. It may be positively impossible to respond to a worst case scenario but entirely possible to respond negatively.

    • Natural cycles that repeat what has happened before in the past ten thousand years is 97% likely to happen next. A worst case scenario is 3% or less, likely to happen. That is how this stuff works. All they need to scare people into paying for expensive cures for false problems is a 3% fear factor that they multiply into a 97% fear factor. They are not responding to worst case scenario but they are responding negatively to normal scenario.

      • Like turning the precautionary theory on its head- turning a quest for knowledge into a judgement day proclamation instead of a tool for coping for use by the living.

  28. Dr Curry

    “Bottom line: we need to think harder and differently about climate change.”

    I am all for thinking about climate change including: What is the worst thing that could possibly happen?” After that, in various gradations from that perspective to the “forget about it” viewpoint, we can think about: What is likely to happen in the future? And there in lies the rub for me.

    Posts by Tomas Milankovic introduced me to climate having a special kind of chaos: Spaciotemporal chaos (belonging to both time and space). By his suggestions, I believe, he did not think that we have at present the tools to address probabilistic projections of future climate. Indeed, such exercises can not account for all possible outcomes. Decision making as to what to do if anything about the future; ie, mitigation or adaptation then falls to people interested in public policy, these individuals having various political intents as well.

    My understanding is that current climate computer models make probabilistic projection on some linear basis. I can understand computer models making probabilistic projections of a tropical storm forming in the Gulf of Mexico in the next month or three. It is just, that I find it hard to believe that current computer climate models deal with “wicked problems” with any certainty; let alone that they should form long faced judgements. Instead, I propose climate model outputs form a basis for idle speculation, while sitting by the shore, on a warm summer day, with a cold beer in your hand.

  29. See http://climatesense-norpag.blogspot.com/2017/02/the-coming-cooling-usefully-accurate_17.html
    Here is the abstract:
    “This paper argues that the methods used by the establishment climate science community are not fit for purpose and that a new forecasting paradigm should be adopted. Earth’s climate is the result of resonances and beats between various quasi-cyclic processes of varying wavelengths. It is not possible to forecast the future unless we have a good understanding of where the earth is in time in relation to the current phases of those different interacting natural quasi periodicities. Evidence is presented specifying the timing and amplitude of the natural 60+/- year and, more importantly, 1,000 year periodicities (observed emergent behaviors) that are so obvious in the temperature record. Data related to the solar climate driver is discussed and the solar cycle 22 low in the neutron count (high solar activity) in 1991 is identified as a solar activity millennial peak and correlated with the millennial peak -inversion point – in the RSS temperature trend in about 2003. The cyclic trends are projected forward and predict a probable general temperature decline in the coming decades and centuries. Estimates of the timing and amplitude of the coming cooling are made. If the real climate outcomes follow a trend which approaches the near term forecasts of this working hypothesis, the divergence between the IPCC forecasts and those projected by this paper will be so large by 2021 as to make the current, supposedly actionable, level of confidence in the IPCC forecasts untenable”

    • Sorry for the typo . Should be Norman Page. Also – here are links to other pertinent Blog-posts and the published paper:
      From
      https://climatesense-norpag.blogspot.com/2019/01/the-co2-derangement-syndrome-millennial.html
      “The reality is that Earth’s climate is the result of resonances and beats between various quasi-cyclic processes of varying wavelengths.
      It is not possible to forecast the future unless we have a good understanding of where the earth is in relation to the current phases of these different interacting natural quasi-periodicities which fall into two main categories.
      a) The orbital long wave Milankovitch eccentricity,obliquity and precessional cycles which are modulated by
      b) Solar “activity” cycles with possibly multi-millennial, millennial, centennial and decadal time scales.
      When analyzing complex systems with multiple interacting variables it is useful to note the advice of Enrico Fermi who reportedly said “never make something more accurate than absolutely necessary”. The 2017 paper proposed a simple heuristic approach to climate science which plausibly proposes that a Millennial Turning Point (MTP) and peak in solar activity was reached in 1991,that this turning point correlates with a temperature turning point in 2003/4, and that a general cooling trend will now follow until approximately 2650.
      The establishment’s dangerous global warming meme, the associated IPCC series of reports ,the entire UNFCCC circus, the recent hysterical IPCC SR1.5 proposals and Nordhaus’ recent Nobel prize are founded on two basic errors in scientific judgement. First – the sample size is too small. Most IPCC model studies retrofit from the present back for only 100 – 150 years when the currently most important climate controlling, largest amplitude, solar activity cycle is millennial. This means that all climate model temperature outcomes are too hot and likely fall outside of the real future world. (See Kahneman -. Thinking Fast and Slow p 118) Second – the models make the fundamental scientific error of forecasting straight ahead beyond the Millennial Turning Point (MTP) and peak in solar activity which was reached in 1991.These errors are compounded by confirmation bias and academic consensus group think.
      See the Energy and Environment paper The coming cooling: usefully accurate climate forecasting for policy makers.http://journals.sagepub.com/doi/full/10.1177/0958305X16686488
      and an earlier accessible blog version at http://climatesense-norpag.blogspot.com/2017/02/the-coming-cooling-usefully-accurate_17.html See also https://climatesense-norpag.blogspot.com/2018/10/the-millennial-turning-point-solar.html
      and the discussion with Professor William Happer at http://climatesense-norpag.blogspot.com/2018/02/exchange-with-professor-happer-princeton.html

  30. “What’s the worst case?”

    The worst case is global cooling.

    Any global warming that might occur this century will be beneficial.

    Another bad case is mitigation policies that reduce global warming.

  31. If you want to know why the media has increased its attack and or coverage look at this. https://www.cjr.org/the_media_today/covering-climate-change-now.php . I hope you will have something to say about the Forbes censorship of the Israeli astrophysicist solar theory. V.V Zharkova recent paper in Nature also seems to be totally ignored. Thank you, Bruce Zeitlin

    >

  32. “Returning to Ackerman’s (2017) argument that policy should be based on the credible worst-case outcome, the issue then becomes how to judge what is ‘credible.’ It has been argued here that a useful criterion for a plausible (credible) worst-case climate outcome is that at most one borderline implausible assumption – defined as an assumption where experts disagree as to whether or not it is plausible – is included in developing the scenario.”

    What appears to be forgotten in these policy discussions is the other side of the science based worst case outcome and that is the worst case outcome for the implementation of government based policy. What are the unintended consequences of the implementation and what is the government’s track record in matters such as these? Cost for programs that government implements have historically been dramatically underestimated and sold to the public based on those estimates. Two examples that come immediately to mind are the Iraq war and the student loan program. Another problem with government programs is that the momentum is always such as to never significantly change course and instead calling for more funds for failing programs.

  33. So what have we observed so far that might confirm their worst CAGW claims?
    Dr John Christy recently gave a presentation to the GWPF and listed all their CAGW claims and provided the observations so far.
    There certainly doesn’t seem much room for panic at all and anyway future concerns should be presented to the developing countries and definitely not the OECD.
    Since 1990 the developing country’s co2 emissions have soared and the OECD countries have flat-lined.
    Emissions over that time have increased by about 60 ppm and China India etc continue to build coal fired stations, with little evidence of a slow down before 2030.
    Here’s Dr Christy’s presentation.

    https://www.thegwpf.com/putting-climate-change-claims-to-the-test/

    • François Riverin

      That is a very valuable document. If my understanding is corrected, Mr Christy has a preview of cimp6 models, and it shows that the same mistake regarding equator hot spot still there. Incredible!

  34. Here’s what the alarmist scientists project for the climate even if we STOP ALL CO2 EMISSIONS TODAY. This is via the Royal Society & NAS report and this is their question 20 Q&A.

    Nic Lewis has applied his maths skills to this claim and still has a very long lag for temp, but not as long as the claims made by them. Thousands of years is a long time even if we stopped all emissions today.

    https://royalsociety.org/topics-policy/projects/climate-change-evidence-causes/question-20/

    20.” If emissions of greenhouse gases were stopped, would the climate return to the conditions of 200 years ago”?
    Climate change: evidence and causes

    “No. Even if emissions of greenhouse gases were to suddenly stop, Earth’s surface temperature would not cool and return to the level in the pre-industrial era for thousands of years”.

    fig9-smallFigure 9.” If global emissions were to suddenly stop, it would take a long time for surface air temperatures and the ocean to begin to cool, because the excess CO2 in the atmosphere would remain there for a long time and would continue to exert a warming effect. Model projections show how atmospheric CO2concentration (a), surface air temperature (b), and ocean thermal expansion (c) would respond following a scenario of business-as-usual emissions ceasing in 2300 (red), a scenario of aggressive emission reductions, falling close to zero 50 years from now (orange), and two intermediate emissions scenarios (green and blue). The small downward tick in temperature at 2300 is caused by the elimination of emissions of short-lived greenhouse gases, including methane”. Source: Zickfeld et al., 2013 (larger version)

    “If emissions of CO2 stopped altogether, it would take many thousands of years for atmospheric CO2 to return to ‘pre-industrial’ levels due to its very slow transfer to the deep ocean and ultimate burial in ocean sediments. Surface temperatures would stay elevated for at least a thousand years, implying extremely long-term commitment to a warmer planet due to past and current emissions, and sea level would likely continue to rise for many centuries even after temperature stopped increasing (see Figure 9). Significant cooling would be required to reverse melting of glaciers and the Greenland ice sheet, which formed during past cold climates. The current CO2-induced warming of Earth is therefore essentially irreversible on human timescales. The amount and rate of further warming will depend almost entirely on how much more CO2 humankind emits”.

    • If emissions of CO2 stopped altogether, it would take many thousands of years for atmospheric CO2 to return to ‘pre-industrial’ levels due to its very slow transfer to the deep ocean and ultimate burial in ocean sediments.

      The ocean can cool as fast as it did before within the last few hundred years, naturally, as long as maximum solar cycle activity is low or falling, taking outgassed CO2 down with it, possibly to the point where there is no net annual CO2 production, and the CO2 curve declines until the ocean sinks much of it while cooling, or until ocean warms enough under a resurgent and sufficiently active sun so outgassing can resume.

      It would likely take a few hundred years not thousands to sink 100ppm, but will the ocean cool down significantly and long enough for that to happen?

      The ocean cooled twice under low or declining solar activity in the last 170 years, and it will cool again from it without any support from CO2. It could take as long or longer to sink out all the outgassed CO2, but why want that when it greens the earth? Reversing or capturing CO2 is an evil wasteful counter-productive societal goal with no climate benefit.

      The amount and rate of further warming will depend almost entirely on how much more CO2 humankind emits

      CO2 was at record levels in 2016 when the ocean temperature peaked, but even while natural CO2 increased since then, it hasn’t maintained or increased the temperature, so obviously neither will human emissions.

      The increasing risk in this discussion is to climate scientists for being dead wrong about solar forcing vs CO2, and to the public and policymakers for believing the wrong climate scientists and their wrong theory.

      The wrong side of this argument does everything they can now to avoid and forestall their impending public reckoning by sabotaging open public discussion, muddying the waters with repetitive propaganda, and by priming politicians and children with tall tales of extreme fears.

  35. ashleys9@bigpond.com

    Hello

    Please note the change of my e-mail address

    Old e-mail address ashleys9@bigpond.com

    New e-mail address ashleysaies320@gmail.com

    Thank you

    Ashley Saies

  36. Those budgeting for worst-case RCP8.5 scenario should equally allocate money for preventing a small meteor hitting Earth, as that is also a rare catastrophic possibility.
    A full out nuclear missile exchange is also possible, specially from an unstable country as Pakistan, where religious extremists rule the roost.
    Why is the US still giving them $ 4 billion this year? To make more over their 160?

  37. The largest rates of warming that are often cited in impact assessment analyses (e.g. 4.5 or 5 oC) rely on climate models being driven by a borderline implausible concentration/emission scenarios (RCP8.5).

    The IPCC AR5 (2013) likely range of warming at the end of the 21st century has a top-range value of 3.1 oC, if the RCP8.5-derived values are eliminated.

    Point on baselines.

    The impact assessment analyses temperature increases referred to are likely to be vs pre-industrial – that’s the usual baseline and certainly is for the Bamber paper heavily relied on in the report. The 3.1 degrees is however, presumably taken from the synthesis report “The increase of global mean surface temperature by the end of the 21st century (2081–2100) relative to 1986–2005 is likely to be 0.3°C to 1.7°C under RCP2.6, 1.1°C to 2.6°C under RCP4.5, 1.4°C to 3.1°C under RCP6.0”. Additionally, the “end of century” is actually 2080-2100 mean.

    So this is probably not an apples vs apples comparison, and the 3.1 actually corresponds to close to 4.5 degrees for a like – for like, taking into account both the differing baseline and the endpoint not being truly end of century.

  38. Dr Curry could you tell us what conclusions your research reached regarding the worst case plausible scenario. What is it and what does it lead to by 2100? E.g the forcing, temperature rise, sea level rise by 2100, rate of sea level rise, rate of temperature rise, rate of CO2 emissions.

  39. Note on assignment of possibilities. From the report:

     ECS ≤ 0: inconsistent with theory and observations (impossible; ≤ 0)
     0 > ECS < 1oC: implies negative feedback (unverified possibility; 0.1 ≤  < 0.5)
     1.0 ≤ ECS ≤ 1.2oC: no feedback climate sensitivity (strongly verified, based on theoretical analysis and empirical observations;  = 1).
     1.05 ≤ ECS ≤ 2.7oC: empirically-derived values (5-95%) based on energy balance models from the instrumental period with verified statistical and uncertainty analysis methods (Lewis and Curry, 2018) (corroborated possibilities; 0.8 ≤  < 1)
     2.1 ≤ ECS ≤ 4.1oC: derived from climate model simulations with TCR ≤ 2oC. (Table 9.5, IPCC AR5) (verified possibilities; 0.5 ≤  < 0.8)
     4.5 < ECS ≤ 6 oC: consistency with relevant background knowledge is disputed; multiple implausible inputs, assumptions or parameterizations (borderline implausible; 0 <  6oC: refuted by observations or without physical justification; generated by pure speculation or statistically-manufactured fat tail (impossible or unjustified; ≤ 0)

    This is pretty simple: it’s preferring the author’s own results from EBMs rather than other approaches. Which is fine, as far as it goes, everyone is entitled to their opinons. It’s however unlikely to convince anyone else of the possibilities ascribed, given there are as many reasons if not more to doubt EBM appraisal of ECS as the other methodologies.

    As an aside, I’ve no idea why ECS is used rather than TCR, given that the impacts are only discussed up to end of this century.

  40. Climatologists should be aware of anaphylaxis – a situation when the reaction of the human organism to certain poison becomes more dangerous than the poison itself. A climatologist who does not warn against both denialism and alarmism is guilty in case of anaphylactic shock.

    • A climatologist who does not warn against both denialism and alarmism is guilty in case of anaphylactic shock.

      You desire to smear people like me who see through the CO2 smokescreen, those of us who you disparagingly call ‘denialists’.

      You wish to engage in the same exact exclusionary shunning behavior Michael Mann and Greta and now Nature Communication demand.

      Congratulations for being Mann’s tool, doing his work for him.

      This entire thing is sick because you can’t understand natural variability.

      You are now asking Judith to carry on Mann’s crusade. Are you self-aware?

      I challenge you and all others who think like you to actually refute what I’ve said on this blog post without resorting to a smear.

      The fact is you’re afraid. You’d rather hang with Mann than get real.

  41. Judith,

    I’ve been thinking about your paper for a short while now and, with the greatest respect, there are a couple of things that are still troubling me.

    As I see it, the most important distinction between probability theory and possibility theory is that the former is additive and the latter isn’t. This is as a direct consequence of the potential ambivalence inherent in an evidential case, i.e. evidence can simultaneously support more than one proposition. To my mind this means that the possibility of a proposition is less important than the difference between its possibility and necessity. However, this is a quantitative consideration, so I’m not convinced, therefore, that your qualitative approach to possibility theory could fully capture this important aspect. Indeed, I am unable, at present, to convince myself that what you are doing with possibility couldn’t just as readily be achieved using probability theory. In the extreme, by taking a qualitative approach there is a danger that the distinction between possibility and probability is rendered essentially semantical, since, at the end of the day, likelihood seems to be the common conceptual framework.

    Also, when I look at the IPCC’s qualitative approach to the expression of confidence, it seems markedly similar to your proposed possibilistic approach, i.e. it too is founded upon strength of evidence and degree of agreement between experts. Once again, the degree of ignorance that results from inconclusive and conflicting evidence is not being properly captured because their approach basically adopts the additive logic of probability theory.

    In conclusion, your paper includes one seemingly throw-away line to the effect that the quantitative difference between possibility and necessity represents a degree of ignorance. Since it is this degree of ignorance that has to be measured and tackled, might I suggest that what followed should have been based upon that throw-away, i.e. since possibility is less important than the difference between possibility and necessity, it is that difference that should have formed the basis of your classification scheme. Possibility theory allows this calculation of ignorance in a way that probability theory cannot. If you are not going to focus upon it, you might as well stick with probability theory.

    It is still early days and so I might be able to reconcile my misgivings with a more careful reading of your paper. In the meantime, any comments you might have regarding my initial observations would be most helpful to me, I am sure.

    • Thx the possibility-necessity argument is a good point, I will think about this.

      Several issues with the IPCC: they emphasize RCP8.5; their ECS determination heavily weights climate models; their confidence measures (low, med, high) don’t have objective criteria.

      • Dr Curry,

        Thank you for your response. I think part of my difficulty is that I am not too familiar with the qualitative approach to possibility theory, and so I am struggling to see the essential difference between it and qualitative approaches to probability theory. It is only when a quantitative approach is taken that the differences become clearly apparent to me. Developing the possibility/necessity complementarity angle seems to me like a good way of pushing in that direction. And it may be a means of avoiding the congruence bias that I feel is invited by the IPCC approach.

        As for the IPCC, please do not take anything I say as tacit support of its approach towards the handling of uncertainty. By focusing only upon the parts of your paper that currently trouble me I may be giving the false impression that I am largely in disagreement with it. This is certainly not the case. For example, another of the cognitive biases that concerns me is the pseudo-certainty effect, as featured in Kahneman and Tversky’s prospect theory. I have always thought that pseudo-certainty is involved in the evaluation of climate model ensembles whenever fidelity with observation is cited without regard to the plausibility of the chosen parameter/inputs that led to such fidelity. I think that your proposed classification of worst case scenarios highlights this problem nicely.

      • John, I greatly appreciate your comments.

    • John Ridgway: As I see it, the most important distinction between probability theory and possibility theory is that the former is additive and the latter isn’t.

      What do you mean by probability is additive. Formally, the probability of the union of two events (the probability that at least one happens) is the sum of the probabilities of the two events if the probability of their intersection (the probability that both happen) is 0. But what are you writing about?

      • John Ridgway

        “What are you writing about?”

        The same thing, I believe.

        By Additivity, I mean that:

        P(A∪B) =P(A) +P(B) −P(A∩B).

        This does not hold with regard to possibility. Instead, Possibility measures and Necessity measures follow the max\min rules:

        Π(A∪B) =max[Π(A), Π(B)] and

        η(A∪B) =min[η(A), η (B)]

        With regard to probability functions and possibility functions, the area under the former is always 1, whereas the maximum height of the latter is always 1.

      • John Ridgway

        With regard to my previous response, I appreciate that the final paragraph was with regard to normalisation rather than additivity. So I guess, I am drawing two important distinctions rather than just one.

      • John Ridgway: So I guess, I am drawing two important distinctions rather than just one.

        Thank you for the reply.

  42. One contra high forcing feedback that I haven’t seen mentioned is that if global temperatures do rise 5 or 10C substantial geoengineering would undoubtedly be undertaken. Unwanted side-effects would result, but I can’t imagine they would prevent it.

  43. The ONE TRUE REALITY and ONLY that is Earth’s Climate is absolutely, truly, and DEFINITELY changing beyond any doubt and not for the “cool!” Now I don’t give a squat “who” or “what” is causing it because that is completely irrelevant and will not help or reverse it’s course. I am an Investigative Research Analyst and have been studying this very issue for 50 years. Do not tell me that I don’t know what I’m talking about. I’m sick and tired of this ridiculous debate that is not doing anyone a damn bit of good on either side!
    In my findings the sad and unfortunate truth is that there is no fixing this. What’s done is done and that is final. There will be no reversal of time, no magic wand, no amount or form of new technology that will change the sequence of events that led to this point in our evolution. Humanity will continue to suffer the consequences of it’s own existence and creation. There is no arguing that and this subject is concluded.
    Very Sincerely,
    Officer Alton Cook
    U.S.O.
    G4S North American Division

    • Rob Johnson-taylor

      An appeal to authority is always a poor attempt to shut down debate. Science always requires debate, it is essential to challenge ideas, especially “scientific sacred cows”. As one writer puts, forgotten who, “Consensus is the first refuge of liars”.
      “there is no fixing this.” – this presupposes that something is wrong, and needs fixing. I don’t think there is. The Earth is just progressing through its natural cycles.
      I blame “Star Trek”, people have watched to much of it, and think that a planet can be transformed, or a star created, during a 1hr broadcast.

      • Rob Johnson-taylor

        Sorry that was a miss quote it shoudl have read
        “the claim of consensus has been the first refuge of scoundrels; it is a way to avoid debate by claiming that the matter is already settled.”
        by Michael Crichton.

    • Don’t panic Officer. Natural solar variability is in control as always.

      You’re right there’s no fixing a non-problem. CO2 causes greening not warming.

      The problem is that you Officer Cook are a victim of propaganda.

      I’m sorry sir but emoting like that puts you on the same level as Greta.

      You appear to have an authoritarian disposition, not surprising:

      There is no arguing that and this subject is concluded.

      Natural solar variability is cooling the earth now, and this NH winter will be every bit as cold and hard as the last one because of the ongoing low solar activity. The climate changes with variable solar energy.

      The climate changed from a solar regime change called the Solar Modern Maximum, where sunspots averaged 65.6% higher from 1935-2004 compared to the previous 70 years. The sun got hotter.

      The military was used nefariously by Obama. Rear Admiral Titley installed the mental program of natural climate change is counter-factual.

      Tell me, can you even imagine the climate is 100% natural? It is.

      So it’s a top-down authoritarian enforced science based on using various human hierarchies like the military to push the propaganda. You are expected to follow your leaders without question. Climateers are working hard to achieve the same level of authoritarianism.

      What is ridiculous about this debate is how language has been used like Orwell predicted, complete with newspeak like “counter-factual” and “human-caused _________”, and ECS and TCS, things that really are counter-factual.

      Ironic how things that are really counter-factual are being held up as real.

      Now how many of you after all my comments have had the feeling that you wish someone would shut me up or shout me down, or get me off the page…

      If you did, you have succumbed to their current programming efforts. They want you to self censor skeptics to the point where we can only agree with them.

    • Alton Squat: Now I don’t give a squat “who” or “what” is causing it because that is completely irrelevant and will not help or reverse it’s course.

      If you do not know “who” or “what” is causing it, then you can not know that the knowledge would be irrelevant.

  44. Judith, I was particularly interested in section 2, Possibility Framework. It has been some years (late 1990’s) since I was professionally involved in related issues. So that framework was new and most interesting. It is a logical extension of frequentist probability theory.

    For some years, I have thought that a Bayes theorem approach achieves similar ends on matters like ECS and SLR. In fact, wrote a Bayesian framework recognition chapter section, and then applied it to ECS in the climate chapter in my 2012 ebook The Arts of Truth. For example, the 2011 Annan and Hargreaves ECS paper in Climate Change (TAoT fn 81) used informed Bayesian priors to eliminate the high ECS tail in climate models and derive a central estimate of 1.9.

    Put more generally, as evidence accumulates that ECS cannot be high (Lindzen rate of temperature change) and SLR is not accelerating, ever more informed priors and Bayesian analysis suggest that the warmunist worst cases (heck, even their typical scenarios) are ever more improbable.

    And then you can go to alternate physical science approaches (such as you and Nic Lewis did using energy budget methods for ECS, or I did in my guest posts here on SLR and closure) to show Bayes ‘right’ and simple frequentist scenarios (not your possibility framework) ‘wrong’.

    • Bayes approach in principle works ok for ECS (where you can reasonably bound things), but not for SLR. Way too much ignorance re SLR for Bayes approach to be meaningful. Bayes isn’t so helpful when you are trying to clarify ‘worst case’

  45. Eco-colonialism is back with a vengeance.
    This is part of the worst case.
    The new France-Ireland axis threaten to block trade unless Brazil submit to extreme climate policies.

    https://www.bbc.com/news/world-latin-america-49450495

    Green climate hysteria pushes the world backwards in every possible sense.
    A deeply misanthropic nostalgia for the worst aspects of the past.

    • Phil

      I ‘own’ an acre of amazon rain forest as part of a much larger charity holding to try to deter the fires.

      its a difficult one, many of the fires are in order for farmers to clear land at the edge of the forest in order to grow soya, beef and palm oil for guess who? Yes, us over here in the west.

      The irony of course is that the EU are trying to punish the UK because we want to leave this ridiculous organisation and they are refusing a deal, even though our trade dwarfs that of Brazil and is there for the asking.

      The EU is a quasi empire and I hope Brazil resists the bullying and they would find a ready market in the UK for much of their fruit and agricultural products.

      Having said that I obviously want Brazil to be responsible but this fire business is very complex and we bear a good proportion of the blame for it

      tonyb

      • Tonyb
        Hi.
        Good for you. Save your acre of rain forest for 80 years to 2100.

        Good luck on Brexit.

        I look forward to germany destroying its auto industry on the alter of climate correctness. Mercedes Benz, BMW and Audi will do well with reduced energy prices and no tariffs in USA.

        In the meantime forests reclaim farmlands in NE US and Great Plains tall prairie grasses sequester carbon.

        This is an interesting time.
        Scott

    • It is difficult indeed, Europe was as forested over as Brazil before we paved it over. Your efforts at conservation in the Amazon are to be applauded none the less.

      A lot of contradictions in play but a souring of relations between the EU and Brazil couldn’t come at a better time for Britain.

      Some people seem to forget that crops and grasses also photosynthesise. It’s not just a choice between trees and concrete.

  46. Policy makers need to understand the concept of the opportunity cost.
    The opportunity cost is the sum of all the opportunities and possibilities for humanity that are forfeit, that disappear, that otherwise would have been available, because you have chosen economic self-flagellation in response to a dystopian virtual climate model.
    What else could all that money have been spent on?
    By households as well as governments, both with 2-5 times smaller energy bills and transport costs.
    What could the world’s plants have done with all that CO2?
    Grow I guess.
    We humans can also choose to shrink – or grow.
    Those two alternative futures lie before us but it is increasingly clear which one we and our children are now committed to.
    “Honey I shrank the human race!”

  47. Robert Francis Lyman

    I spent my entire career working in the realm of public policy, with a heavy focus on policies related to the economy, energy and the environment. Fortunately, there are are very few areas of public policy where governments have to weigh heavily the potential consequences of “worst cases”. In the event of major uncertainty, the political decision maker is likely to ask, “Then what do we need to do to increase the certainty?”, as the most immediate question is often, “How much of taxpayers’ dollars must we spend now?” Making allowances for the fact that the current generation of decision makers in OECD countries has relatively little regard for the harm done by over-spending, they still must decide how to trade off among the many different spending priorities. Those that are both high in cost and intended to avoid a very unlikely outcome would, in almost every other field of public policy, be immediately rejected. The proponents of the global warming catastrophe thesis have done their greatest damage to the public policy process related to climate by reinforcing the media’s acceptance of worst cases as though they are “most likely” cases and by propounding the myth that the costs of the “energy transition” are low. Ms. Curry’s analysis is insightful and intelligent; it would take a great deal, however, to move it to the centre of the public policy considerations regarding climate.

    • Robert,

      ” Ms. Curry’s analysis is insightful and intelligent; it would take a great deal, however, to move it to the centre of the public policy considerations regarding climate”

      Imo, politically speaking, climate policy is front and center here in the US and has been since the 2016 election.

      The Trump administration’s energy, environmental, and climate policies are more in line with Dr. Curry’s fine work. The “C” in “CAGW” has been removed (RCP8.5) from Obama’s global climate agenda, we are out of the Paris accords. His executive orders went out the door with him.

      A sane, rational climate policy ratified by Congress would be in order…that’s the great deal it would take.
      The “green new deal” is not the deal for me.

    • The issue is that the public perception of ‘most likely’ includes RCP8.5 scenarios and climate model simulations with unrealistically high CO2 sensitivity and impacts that are poorly justified. What is presented as driving emissions and adaptation policy is in the borderline implausible category. Extreme tail values have driven calculations of the social cost of carbon. Adaptation to sea level rise in some locations is using 10 feet by 2100; planning for managed retreat (e.g. Pacifica, California)

  48. …Here is my ‘favorite’ comment from one of the reviewers:

    “Overall, there is the danger that the paper is used by unscrupulous people to create confusion or to discredit climate or sea-level science. Hence, I suggest that the author reconsiders the essence of its contribution to the scientific debate on climate and sea-level science.”

    VERY depressing! 😪😵😤

  49. Stewart Trickett

    “Overall, there is the danger that the paper is used by unscrupulous people to create confusion or to discredit climate or sea-level science. Hence, I suggest that the author reconsiders the essence of its contribution to the scientific debate on climate and sea-level science.”

    If I received a comment of that nature from a reviewer — not likely since climatology is not my field — I would contact the journal editor to say that the comment was unprofessional and unscientific, and ask that the reviewer be replaced.

    In your case, the journal editor might have sided with the reviewer. But you never know. Miracles sometimes happen, and certainly the editor deserves to know what is going on. It would have been worth a try.

    • The editors clearly did not want to publish my paper. That comment was only the most egregious one; there were others that belied astonishing ignorance by the reviewers of climate change and what is included in climate models. These were people that the editors regarded as ‘experts’ on sea level rise.

  50. Stewart Trickett

    There are many good sides to peer review. It can definitely improve papers by providing another set of eyes. Reviewers can often point out errors and show where the writing can be improved. They can also find weaknesses in your arguments, not to tear down your logic but to strengthen it.

    So the question is, how can you get the benefits of peer review without being subjected to its gate keeping?

  51. I am not persuaded that the main focus should be on worst case scenarios. I believe the main focus should be on the most likely scenarios, and then equally on the best and worst case scenarios with their likelihood of occurrence.

    It is essential that a substantial proportion of the resources and effort be focused on objectively estimating the costs and benefits of each scenario – and the risk (i.e. consequence x probability).

    Before allocating resources to mitigation to avoid or reduce the negative consequences of scenarios, we need to weigh up the benefits of positive consequences.

    However, even more important before allocating resources to climate change mitigation, we need to fully estimate the consequences and probabilities of all other worst case scenarios – such as nuclear war, major diseases, malnutrition, power failure, energy disruption etc. We then need to apportion our response appropriately between all the risks, not just focus on climate change – especially since the evidence seems to suggest that global warming is beneficial, not harmful.

    I believe that focusing so much resources on researching and trying to reduce GHG emissions is wasting massive resources that could be much better used to improve the wellbeing of humanity. Bjorn Lomborg frequently reports the cost-benefit of other uses of resources and highlights where resources could be best deployed. Climate change is way down the list.

    I suspect and honest appraisal would show that the return on investment in climate research and mitigation policies is negative.

    • I suspect and honest appraisal would show that the return on investment in climate research and mitigation policies is negative.

      There has been NO INVESTMENTS in actual climate research. There has only been investments in climate alarmism. CO2 has not and is not and will not cause measurable changes to temperature or sea level. There have been no investments in learning what really does cause climate change.

      There is more evaporation and snowfall in cold places where ice is sequestered that advances and causes colder during the warmest times when the oceans are warmer and more thawed. Understanding this does not require expensive climate research, it only requires looking at ice core data we already have.

    • But Peter, that approach requires replacing alarmism with commonsense! Unfortunately, the former has become entrenched with little resistance from governments.

  52. A few questions arise regarding the risk of substantial sea level rise:

    1. What is the probability of 0.2, 0.3, 0.4, 0.5, 0.7, 1.0 1.5 m seal level rise during this century?
    2. What is the economic cost of each?
    3. What is the cost of preventing such sea level rise?
    4. What is the probability that climate mitigation policies would actually prevent such seal level rise?
    5. What is the cost of dealing with rapid sea level rise if and when it occurs?
    6. How does this cost of dealing with it compare with the cost of trying to prevent it and almost certainly failing?
    7. What would be the net benefit of redirecting the funds to programs that will certainly deliver much greater benefit for humanity?

    • What would be the net benefit of redirecting the funds to programs that will certainly deliver much greater benefit for humanity?

      That is the “opportunity cost”.

      • Yep.

      • As a 30 yr practicing environmental industry professional who studies climate science out of intellectual interest, this has been my beef since 2001.

        Over $150 BILLION spent just by the U.S. govt. on “climate policy” since 1999.

        I haven’t bothered to try and ascertain the cost to the rest of the developed world, but it easily tops a quarter trillion dollars since 2000.

        What good could have been done for the lot of humanity in terms of clean water, basic sanitation, adequate food, basic healthcare, distributed electricity, etc. that wasn’t b/c this quarter trillion dollars was wasted on “climate policy” instead?

        Answer: a lot of good. for a lot of people facing more immediate risks than “climate change”.

        EcoLeftism owns that outcome

  53. Stewart Trickett

    I agree that the MAIN focus should be on the most likely scenario, but the best- and worst-case scenarios should also be studied and reported on. Knowing what the worst thing that can happen is very useful. .

  54. “Are some of these outcomes impossible?”

    With strong negative cloud feedbacks, all of them are impossible.

    “On the other hand, are there unexplored worst-case scenarios that we have missed, that could turn out to be real outcomes?”

    Yes the only real worst case, the inevitable return of a super solar minimum. Which sees increased cold shots to the mid latitudes, and a sharp increase in El Nino conditions driving regional aridity and heatwaves.

    “Are there too many unknowns for us to have confidence that we have credibly identified the worst case?”

    Fundamental elements of what is considered as known are completely backwards. Low indirect solar drives a warm AMO, and the warm AMO phase reduces cloud cover and increases lower troposphere water vapour. If rising CO2 forcing projects onto natural variability, it will do the reverse of that, like the stronger solar wind in the 1970’s did.
    The popular view of global change driving changes in weather extremes is backwards. The solar forcing of short term anomalies to decadal regimes in the annular modes and the inverse responses of the major ocean modes is the major agent of regional and global change. We can state that Atlantic hurricanes are more intense when the AMO is warm, but we cannot state that global heating made the AMO warm when weaker indirect solar is the cause.

    And then there’s the issue of how much net surface warming the standard 3.7W/m2 actually drives. It would warm something at 255K by 1.2°C, but for a surface at 288K it would warm it by only 0.68°C.

  55. Geoff Sherrington

    Judith,
    Thank you once more for a reasoned approach to addressing several contemporary problems. I cannot understand why any experienced scientist would object to your conclusions unless there was a dominant belief system at work in the person’s brain. Level discussion of the main conclusions is how progress should be made.
    It is always disconcerting when the conclusions involve semantics like likely or unlikely, probable or improbable, expert subjective judgement and so on.
    I have a broad question. Much of my career work used fairly straightforward numerical terms like standard deviation, 2 or 3 sigma estimates of variability often based on an assumed normal distribution for statistical analysis. We did not venture (formally, at least) into expert judgement. The broad question is, can your problems like rate of ocean level rise be treated purely by old fashioned established statistics, or does each problem demand this subjectivity?
    Are we all becoming too contemplative, too sophisticated, too nuanced when the answers are already there?
    Is this sophistication used to give an answer to a problem, or is it to convince others that one is more clever? Geoff S

    • There is no unique pdf for 21st century sea level rise. E.g. many have been constructed from the IPCC likely range, each of which disagrees with each other. The problem is particularly acute on the extreme high end, where the knowledge frontier is rapidly advancing.

      Fuzzy probabilistic methods require that you at least know the upper and lower bound – there is deep uncertainty associated with the upper bound. Another problem with probabilistic methods is that very high tail values are manufactured by the pdf, which have no physical justification.

      Expert judgment is unavoidable here. The challenge is to include a sufficiently broad range of expert opinion and allow space for experts to disagree

      • Geoff Sherrington

        Thank you Judith,

        My response is rather primary and not meant to sound impudent to you.
        I suggest that expert judgement should be applied to the past before we get too concerned about the future. You cannot surmise about the future until you understand quite fully what happened in the past, in terms of possible mechanisms, their probabilities and their magnitudes.
        Using sea level change as an example, there are several popular papers about (past) global tide gauge data. Authors have failed to agree. Some deduce linear responses in time series, others claim acceleration. Time trends differ one author to another. Clearly, some authors are more expert than others; and some might not be expert enough to deal with the future. When I mentioned resort to classical numerical statistics, I was implying that IF the classical stats had been done properly on past data, we should be free of disagreement. Unworthy sites would have been culled. I would see this current disagreement as meaning that the science about the topic is poorly understood. Authors on their way to becoming ‘expert’ tend to repress data that causes them problems. For the sea level change example, we have unanswered or underanswered questions about the past. Some examples – tide gauge data does not show ocean masses acting as thermometers, with quantified expansion with warmth, as intuition suspects. There is a shortage of math relating sea level change quantitatively to temperature change, of water and air. How many mm of sea level change do we predict from a 1 deg C temperature change? What is the role of the coefficient of thermal expansion of sea water?Ultimately, we get back to how much temperature change is induced by CO2, but that gets us back to sensitivities like ECS where I do not want to tread just now.
        In short, there is plenty of quantitative uncertainty about the past, before we worry about the future. We need to show that our implements work well on past data before turning to the future. They do not, yet. Part of that further understanding is implicitly tied to proper error analysis.
        There are other fields where proper error analysis needs another look. One is TOA radiation balance. The primary data could have trucks driven through its adjustments. Another is selective rejection of ocean buoy data like Argo on the premise that some buoys were defective. These are classic examples that need detailed, objective error analysis, of which there is a little, but IMHO, not enough.
        So, let us be confident of past climate science findings before we look much into the future. Once we work out the past pattern of sea level change, we can discard some current hypotheses about the future. We can also sort authors, to reject those who should be kept well away from future expert judgement, especially when their selection is based on poor science but loud words; and on a lack of understanding of how errors work.
        Maybe I am too simplistic, but I think not. Geoff S.

      • Judy: Even in the absence of a pdf for 21st-century SLR, scientists could provide better information to policymakers. Right now, sea level is rising at a rate of about 1 inch/decade and fluctuations in this linear rate make it difficult to detect and quantify acceleration. However, an average acceleration of 1 inch/decade/decade is needed to produce sea level rise greater than 1 m by 2100. At some point in the future, the rate of sea level rise could increase to 2 and then 3 inches/decade, providing us with a more accurate idea of how fast SLR is accelerating. Today, however, we are positive that any acceleration in the rate of SLR is far smaller than 1 inch/decade/decade. The average rate of SLR over the 20th century was only 2/3 inch/decade and the average rate for the last quarter century is 1 inch/decade according to satellite altimetry.

        Furthermore, if we ever detect an acceleration in the rate of SLR of 1 inch/decade/decade, we will still have more than half a century to prepare for a coming sea level rise of a meter or more. Therefore, though we can’t eliminate the (remote?) possibility that SLR might be greater than 1 m by 2100, we can be confident that society will have plenty of warning and time to respond if the IPCC’s current central estimate turns out to be to low.

        FWIW, after the nth reprocessing of data from the first satellite altimetry mission (Topex/Poseiden) recently reduced its reported rate of SLR by 50%, the first claim to detection of statistically significant acceleration of SLR of was reported: 0.084+/-0.025 mm/yr^2. That rate is 8.4 mm/decade/decade or about 1/3 inch/decade/decade. This much acceleration is consistent with AR5’s central estimates of 0.5 m (RCP6.0) and 0.65 m (RCP8.5) of sea level rise by 2100.

        https://doi.org/10.1073/pnas.1717312115

        In short, uncertainty in acceleration of SLR will have a trivial impact on SLR by mid-century. By then, we will have a much clearer understanding of acceleration and a half-century to prepare for the consequences.

        Policymakers would benefit from reporting the rate and acceleration of SLR in tangible and relevant units of rise/decade and rise/decade/decade. Since the current rate is near 1 inch/decade and acceleration near 1 inch/decade/decade is needed produce a rise of 1 m in a century, I personally find inches extremely convenient.

  56. Pingback: Autoentrevista climática | Loretta Enfurecida

  57. I think it is worth remembering that the main thrust of Dr Curry’s paper is concerned with methodological issues, i.e. the proposal that a possibilistic approach towards evaluation of worst case scenarios would be a more useful and dependable one than the traditional probabilistic approach. Anyone sharing such interests would benefit from consulting papers such as the following:

    https://pdfs.semanticscholar.org/befb/1b3f2e96673ec2367016a6618c4f820b3425.pdf

    One particular quote taken from the above paper that I feel is particularly germane:

    “Possibility can be less conservative than probability in risk assessment with many failure modes. In many reliability assessment problems, one can easily determine the most conservative possibilistic model that is consistent with the available information. On the other hand, it is difficult to choose the most conservative probabilistic model if little information is available. This is an advantage of possibility because in design of high consequence systems, for example nuclear power plants, designers prefer to err on the conservative side.”

    Given that there is an understandable appetite for conservatism in regard to climate risk, one would have thought that the climate science community would welcome Dr Curry’s paper with open arms. The fact that it did not speaks volumes regarding their general level of ignorance on such matters.

    The question was: How can this paper possibly be categorized as ‘contrarian’?

    Answer: By simply noting the reputation of the person who wrote it.

    • [T}he main thrust of Dr Curry’s paper is concerned with methodological issues…

      Indeed that is the thrust! And the reference you provide places that in the context of semantics. Yet pure logic exercised even in a sophisticated context can only elucidate what we mean by our words, without providing a shred of actual evidence concerning the physical process that we’re talking about. The hazards of such an approach to reasoning were pointed out centuries ago by Kant, well before the fruits of empiricism were harvested by modern science. I fear that recourse to mere possibilistic approaches to physical risk assessment is more an act of imagination than of science. There has to be a point at which responsible scientists admit that they simply don’t have reasonable answers to all questions.

      • John Ridgway

        John321s,

        I wouldn’t want to get dragged into a philosophical debate on this subject lest I quickly find myself out of depth. However, I will say the following: theories such as probability theory and possibility theory are mathematical, albeit set within a philosophical context (I, for one, have used probability in my deliberations all my professional life, but I couldn’t tell you for sure exactly what probability is – though I am in good company here since even Laplace conceded as much). Nevertheless, these theories are internally consistent mathematical formalisms, each based upon a set of axioms that can be compared to related theories. Indeed, both probability theory and possibility theory are, mathematically speaking, special cases of Dempster-Schafer theory (aka evidence theory). There are plenty of papers out there that will demonstrate this for you, though you are a better man than I if you can follow them all.

        So where does the semantics come in? Well, it certainly becomes a problem when qualitative approaches are taken. But even with a full-blown quantitative approach, you still have to wonder whenever problems are amenable to analysis using a range of competing theorems, each having different conceptual bases that are reflected in frustratingly ambivalent terminologies. And, perhaps more importantly, once the conclusions are offered up for public consideration and political debate, one can expect an ensuing semantic bun fight that drowns out any mathematical rigour that may have been previously exercised.

  58. Dr Curry, thank you as always for your paper. And thank you for your responses to comments.

  59. Michael Mann’s ‘hockey stick’ graph became Penn State’s, UN-IPCC- approved and Al Gore’s favorite pin-up model for the fake science of the AGW (human-caused global warming) alarmism because, it was just what the teacher ordered in the new world of ill-informed, overcredulous consumers.

  60. In figure 2 the heading “global surface air temperature anomaly (vs 1880-1909) I assume the 1909 is a type and should be 2009?

    That hockey stick curve should be taken not with a pinch of salt but a salt-mine full of salt. I guess the salt mines is where many of us will be going before long.

    The 1930’s were as warm as today. All difference is fraud by the activist data custodians.

  61. “Projections of future extreme weather/climate events driven by the worst-case RCP8.5 scenario are highly influential in the public discourse on climate change”

    Major heatwaves are discretely solar driven, without which they wouldn’t exist. They drive climate change. You can predict them for your great grandchildren.

    https://www.linkedin.com/pulse/major-heat-cold-waves-driven-key-heliocentric-alignments-ulric-lyons/

  62. The best policy to deal with sea level rise is to adapt to it as and when it happens. Reducing GHG emissions will make no significant difference to the rate of sea level rise.

    Policies should focus on maximising global economic growth – including by funding developments that will give the greatest return on investment. Examples are health, education and infrastructure.

    If a sudden sea level rise does occur, we have no idea when it will happen. Therefore, we should do all we can to increase economic growth so we are best able to deal with it if and when it does occur. If it doesn’t occur then the world will be richer and better able to deal with whatever events do occur.

    • Peter, fears of sea level rise are laughable. (and that’s the biggest fear talking point that alarmists have) A far bigger known threat to infrastructure has been, is, and will be demographic changes. Here in the good ol’ U.S. of A., white flight is commonly thought to be a relic of the sixties. What the general public doesn’t realize is that these demographic changes never end. Here in the new orleans area we are actually experiencing a second wave of white flight out of jefferson (west of the city) to st tammany north of lake ponchartrain. These are relatively rapid changes that everyone well notes, the city of detroit being the poster child. Sea level rise will be a very slow creep that nobody would ever have noticed were it not for the shrill voices of the left leaning greens. (kings tides, kings tides!!!) And that’s assuming that the greens will even have a voice by the time we get there…

  63. This is a very interesting paper and collection of comments.
    I come from a different – highly applied – discipline: managing and innovating in large, complex, industrial/commercial/social networks – like industries, energy systems, governments, etc.

    This includes environmental regulation, new global product introductions, innovations in technology systems – like global telecom, scientific innovations like modern genomic sciences, etc.

    I’ve built large-scale forecasting models like those projecting the economic and financial effects of national and global environmental regulations (CAFE and fuel pricing, etc) So have made the sausage.

    I traveled the world for 10 years to the “edge of electricity” observing first hand, and online how 7 billion people obtained mobile communications and how that built the global “cloud” that is now changing almost everything on Earth.

    Those of us who work in these areas of innovation, entrepreneurship, and similar areas know two things:

    1. Every forecast made for any purpose is always partly right, and partly wrong. Always. Forecasts that seek to include wide numbers of variables and long time frames are mostly wrong. Even quarterly corporate earnings forecasts, which are like shooting fish in a barrel, are often wrong by factors, not percentages.

    2. The only way to successfully innovate in large systems is to ask, “what is the smallest, MOST FLEXIBLE thing we can do now with the largest, most flexible, most pervasive positive social and commercial benefit, to the largest number of members in an unpredictable ecosystem?” Google, mobile phones, etc are excellent examples.

    In cases – like climate change – where skilled *practitioners* know most long term forecasts will have large, unpredictable errors – because science and technology IMPROVE in surprising ways…

    ….we use a group process to have all the “experts” EXPERIENCE humility, and to therefore seek more inclusive, experimental, collaborative ways to improve an un-forecastable future.

    We don’t allow projections.

    We break groups into small teams, including diverse practitioners and scientists – and then we ask each group to paint a simple 10-bullet point SCENARIO of the future anywhere from 10 to several hundred years out, depending on the scale of the innovation contemplated.

    A future “scenario state” might be: everyone in the world has a phone that can test their blood for genetic diseases. And a world health organization has finances and enough skilled physicians to radically reduce death rates and improve infant survival.

    Really. That simple.

    Then – here’s the key.

    We ask each team to pick one element of this future (enough physicians to help everyone in the world)

    We do this for five or so teams.

    And then we ask them: STARTING WITH THE SINGLE FUTURE REALITY YOU HAVE ENVISIONED, WORK BACKWARD TO DEFINE IN GREAT PRECISION HOW EVERY MAIN ELEMENT OF YOUR SCENARIO WILL HAPPEN – FROM YOUR ASSUMED FUTURE BACK TO THE PRESENT.

    This ALWAYS quickly brings every forecaster “to their knees” because it forces everyone from the “Nobel” level to the CEO, to the factory manager, to the “street-sweeper” to EXPERIENCE the impossibility of forecasting the future with any single-point precision.

    And – while doing this, the groups discover MANY WONDERFUL, SMALLER COLLABORATIVE EXPERIMENTS THAT CAN BE DONE ACROSS DISCIPLINES AND MANAGEMENT HIERARCHIES – TO INCREASE THE PROBABILITIES THAT PEOPLE CAN WORK TOGETHER TO IMPROVE THE LIVES OF EVERYONE.

    From a management perspective THE IPCC PROCESS IS THE EXACT OPPOSITE OF THIS – IT TRIES TO FORCE DIVERSE PARTS OF SOCIETY TO AGREE ON THINGS THAT PROJECT FORWARD IN TIME TO SINGLE-POINT TYPE FORECASTS (TEMPERATURE) – so its ability to build global consensus for COLLABORATIVE INNOVATION FOR ALL…is pretty low.

    Just sayin’…

    • Thank you for your excellent comment – which is clearly based on a wealth of highly relevant experience.

    • Reading this post has triggered something from my past; buried memories.
      I spent all my career life in power generation, deeply involved at the ‘action’ level. Seen several rough spots where the outcome could have had devastating effect on the whole country. Like the running out of fuel, less than 24 hours supply. The total destruction of the generating plant that has always been taken for granted, because of the held belief that a system can be too big to fail (I can say this because it is now all a brown site, and moved on to newer plant). To a very few of us it was an eye opener; to build resilience in the system at the foundations. Where failure at one point will not cascade, nor bring down a large edifice that was built upon and around it.
      Question: how will mobile based infrastructure work with loss of power? What happened in UK recently was also an earlier experience. Then you find that the emergency setups in critical places don’t work. People not trained. No fuel; low reserve. Diesel fuel in emergency generators needs to be replaced annually if not consumed. And a host of other things. Integrated systems collapse together.
      A civilisation moves from day to day on its belly. In a globally integrated system there are a myriad ways how that can be effected and interfered with. (So what’s the worst case?). Have we lost sight of the trees for the woods?
      A case in point, but in reverse. Durham is introducing an ancient lore. https://www.thenorthernecho.co.uk/news/local/northdurham/17333313.medieval-tradition-of-plough-sunday-set-to-return-to-durham/
      We should keep clear in mind where our bread comes from. (I don’t see a replacement today for the diesel tractor – and its supporting services). Then we have this: https://www.telegraph.co.uk/news/earth/agriculture/farming/6047467/Farmers-use-combine-harvesters-with-satnav.html

      • Marty Anderson

        You make great points.

        One unintended consequence of global cellular dependence is that it might decrease the threat of nuclear attack…

        ….because it makes it much easier for hostile regimes to take down billions of mobile communication devices with a cheap bomb or radiation source.

        Not only should forecasting be taken as – only – a very helpful way to think about and anticipate an uncertain future – but “big bang”, centrally-commanded, large-scale solutions always have unintended consequences

        The petrol fired motorcar was seen as an environmental savior that would eliminate piles of horse manure in NY and London, for example.

        For several years a small group of us have been traveling the entire life cycle of electric vehicles – from mine, through production, use, recycling and scrap.

        At the scale of a Tesla-size batteries and about 1/8 of the current volume of global motor vehicles, the mining of lithium (etc) and the scrapping of batteries at end of life – will both likely be significant environmental insults.

        Lithium mining is now cheap because it takes from seasonally flooded salars

        Soon it will require hard rock mining. Just as damaging as any other mine.

        Despite happy-talk articles, no one really knows how to recycle solar panels and Tesla-size batteries in massive quantities.

        One discovery on our travels is that fire-fighters often hate fighting fires in buildings with rooftop solar. With water on the fire there is always risk of electrocution. It takes time to find the cut off switch, during which time the fire intensifies. And the rooftop solar panels hold in near-explosive heat and gasses and ventilating the roof with an axe can be a near-blast furnace episode.

        Notice the mini-industry of fire-fighter training for this “green” innovation.

        A “Physics Principle” of System Implementation:

        For every action, in a loose network, there is always another reaction, sometimes opposite, mostly unpredictable until tested at scale.

  64. Pingback: Climate Change: What’s the Worst Case? | Watts Up With That?

  65. Pingback: Local weather Trade: What’s the Worst Case? – All My Daily News

  66. Judith: Were more substantial criticisms of your paper than the one below?

    “Overall, there is the danger that the paper is used by unscrupulous people to create confusion or to discredit climate or sea-level science. Hence, I suggest that the author reconsiders the essence of its contribution to the scientific debate on climate and sea-level science.”

    Almost every climate science paper warrants the following comment:

    “Overall, there is the danger that the paper is used by unscrupulous people to create confusion and force society impose an absurd price on CO2 emissions that will vastly exceed the discounted cost of the damage they are likely to cause. Hence, I suggest that the author reconsiders the essence of its contribution to the scientific debate on climate science.”

    Alice Dreger, a champion of the scientific method who works in a vastly different field, wrote in her semi-autobiography “Galileo’s Middle F….”:

    “Good scholarship had to put the search for truth first and the quest for social justice second… The world needed that of us, to maintain – by our example, by our very existence – a world that would keep on learning and questioning, that would remain free in thought, inquiry and word.”

  67. Way to go, Judy.

    Galileo and Copernicus are smiling.

  68. This just in: Climate Petition – call for support

    A petition being prepared by hundreds of independent climate scientists and professionals from numerous countries for submission to heads of the European Council, Commission and Parliament declares: “There is No Climate Emergency.”
    They welcome more signatures from all over the world.

    Here is the petition: https://saltbushclub.com/wp-content/uploads/2019/08/european-petition.pdf

    And some media comment:
    https://www.thegwpf.com/dutch-climate-intelligence-foundation-challenges-belgian-climate-alarmists/
    Petitioning Against Climate Alarmism Goes Global | Newsmax.com
    We invite individuals with suitable qualifications or experience to advise the organisers who will add their names. Please circulate the declaration to appropriate colleagues.

    Supporters are requested to send their name and brief qualifications/experience to
    Prof Guus Berkhout at the Climate Intelligence Foundation (Clintel) —

  69. “After the flight, Willis, wearing Ray Bans, a leather jacket with the collar turned up and a guitar, gave a performance of his Elvis-inspired “Climate Rock” to diners and visiting journalists in the village’s hotel, explaining the difference between the weather and climate.”

    https://phys.org/news/2019-08-high-greenland-glaciers-nasa-ocean.html?fbclid=IwAR3I999NEUyHwMbLGj9maabDHb-8XYuzHc-Ck2oOd0BlBYJD8m_Bn0C7oGM

    When you read what they’re doing, it’s primitive. Why weren’t we doing this 5 years ago?

    “”We’re looking at probably metres of sea level rise in the next hundred years and that’s a huge threat to hundreds of millions of people around the world, so a bit of alarm and OMG is probably warranted,” he said.”

    We are looking at 2.3 inches per decade through about 2090 under the two middle emission scenarios. The IPCC says that. Metres is two or more as I see it.

    Oceans Melting Greenland—or OMG. Branding fail. Initial traction good. Long term fail. No sustain.

    We should buy Greenland. Or just take it. They say there is a threat.

  70. (I haven’t read the comments.) “Returning to Ackerman’s (2017) argument that policy should be based on the credible worst-case outcome, the issue then becomes how to judge what is ‘credible.’” Ackerman’s argument is untenable. There are many possible adverse events in the future, some may be known now, others will arise later. If we base policy on the CWCO across the board, we will be directing vast amounts of resources to probably useless ends, impoverishing ourselves in the process and reducing our capacity to deal with whatever crises do arise. That bad policy would be amplified by the near-certainty that two of the world’s largest and fastest-growing economies, China and India, are most unlikely to fall in line with the Western countries. The West would be shooting itself in the foot to ensure Asian dominance. As I’ve said many times, the future will always surprise us, it’s better to pursue policies which increase our capacity to deal with whatever befalls – across the whole range, not just climate – such as fostering innovation, enterprise and resilience, rather than risk-specific responses to remote possibilities. If a particular issue does become more threatening, we will have more resources available to deal with it as it becomes more likely. As for acting on 67% (two out of three) as being “very likely,” in economic modelling we regard 95% (19 out of 20) as “probable,” rejecting anything below that, and 98% (49 out of 50) as more or less proven (though not proven).

    • + millions.

      This is excellent. This is what the debate should be about. But it seems everyone dodges discussing what’s important for policy and would prefer to discuss anything but what is relevant.

      Thanks Michael. We really do need many more comments from people who are well versed policy analysis, as you are.

  71. “Overall, there is the danger that the paper is used by unscrupulous people to create confusion or to discredit climate or sea-level science. Hence, I suggest that the author reconsiders the essence of its contribution to the scientific debate on climate and sea-level science.”

    Frankly put… if some research could be discredited, then it also should.

  72. A small comment:
    Quote “— this review reminded me why I shouldn’t bother with official ‘peer review.’”
    ‘Trail-blazers’ , especially the maverick ones, have no peers. In my ‘eventful career’, when things were going right, my work/projects had many mothers. But when something pooped I was always alone in the hot searchlight. That’s the way it is.

    • melitamegalithic. My Fig 2 identifies the Millennial cycles post the Younger Dryas northern hemisphere cooling event which was caused by a comet strike on the Ice Cap near the Great Lakes about 12900. The Antarctic was not much affected by this event. For the comparative temperatures see
      https://www.ncdc.noaa.gov/abrupt-climate-change/The%20Younger%20Dryas

      • Dr Norman Page. In my post I just wanted, primarily, to point out that the Gisp2 trace is probably shown 1100 yrs late timewise.
        A spinoff from that: Once aligned to Vostok and Kilimanjaro it will become evident that from the end of the YD both poles reacted together in sync, but opposite to equatorial Kilimanjaro. Your link above mentions the 8k2 abrupt event. But there were more. The 8k2BP (6150bce), 4375bce and 2345bce. All were abrupt events, and similar. A recent clue from others linked the events to the near millennial Eddy Cycle. In all three there is abrupt increase in polar temp; the reverse in equatorial.
        Data has been gathered over 5+yrs and is correlating. I don’t think it can be attributed to chance any more. See link https://melitamegalithic.wordpress.com/2019/03/15/searching-evidence-update-2/
        The abrupt end of the YD is a global event and serves as a point of correlation of dates. It was greater than the 8k2 event. This is what the NOAA says of the latter, “Climate changed globally during the 8.2 ka event. There is clear evidence from lake and ocean sediments —“. There is, too, the repeating near coincidence -trigger?- with the Eddy root (even the end of the YD).

  73. Judith. The worst and most plausible case is that we have global cooling while spending trillions and destroying the world economy in a futile, and misguided attempt to control CO2 levels.
    Your possibilistic analyses don’t allow for what is ,in my opinion, a very plausible forecast based on identifying the millennial peak and turning point in solar “activity” at about 1991.Forecasts which do not honour this obvious event will fall well outside long term real world outcomes.
    see Dr Norman Page | August 29, 2019 at 11:50 am above

    • I agree with you. The worst case is we have GLOBAL ICE MAKING BEGINNING IN THE NEAR FUTURE. According to my interpritation of the Ice Core we began that 18,000 years ago.

    • Norman: No one has identified a “millennial peak” and turning point in solar activity. No one has a clear idea supported by evidence of how any aspect of “solar activity” besides TSI changes our climate. Nor can they be sure that aspect of solar activity is going to change – in the colder direction – in the next few centuries. Finally, no global climate change experienced in the past 70 centuries of the Holocene compares in magnitude with even the best cast scenario for the 21st century. The MWP, RWP and other warm periods seen in Greenland – which were likely enhanced by Arctic amplification don’t appear to be global events: The don’t appear in Antarctic ice cores nor in a global composition of ocean sediment cores. Natural variability added about 0.3 K of unforced warming in 1920-1945. The LIA appears to be an extreme example of naturally-forced variability. Such variability could moderate a “worst case”, but it will still be bad. Even worse, the variability could work in the wrong direction.

      About 3.5 W/m2 of radiative forcing from doubled CO2 is unavoidable. If all of that power remained in a 50 m mixed layer of the ocean and the atmosphere, simple mathematics says that the temperature would be rising at a rate of 0.7 K/yr. Some of that power temporarily will be going into the deep ocean (0.8 W/m2 if you believe ARGO) and the rest must be emitted to space as LWR or reflected by clouds in response to rising surface temperature. The efficiency of that cooling response – the climate feedback parameter (W/m2/K) – is critical. Given the positive feedback expected for WV+LR, plus a hopefully small surface albedo feedback, a climate feedback parameter of 2 W/m2/K (ECS 1.7) is about the best we can hope for.

      • franctoo See the 3 Figures in
        http://climatesense-norpag.blogspot.com/2018/10/the-millennial-turning-point-solar.html
        and Figs 2 -11 at http://climatesense-norpag.blogspot.com/2017/02/the-coming-cooling-usefully-accurate_17.html
        For the Millennial and 60 year quasi cycles. These seem glaringly obvious to me and are at least more highly plausible interpretations than the “consensus” bottom up model pipe-dreams.

      • franktoo: If all of that power remained in a 50 m mixed layer of the ocean and the atmosphere, simple mathematics says that the temperature would be rising at a rate of 0.7 K/yr.

        Is it possible for all of that energy (power is the rate, energy is accumulated) to remain in a 5m mixed layer of the ocean and atmosphere? The increased temp in that layer would produce an increase in the rate of transfer of energy from that layer to the middle and upper troposphere, radiative and nonradiative transfer, would it not? If so, that would throw off your calculation. Water vapor, for example, does not merely reside in the troposphere, but rises to the cloud condensation layer, freezes, and falls back to earth; increased near surface temperature should increase the rate of the process.

      • Dr Norman Page | August 29, 2019 at 7:37 pm |
        Gisp2 in Fig 2, in the second link, may not be correct chronologically. Some years ago I needed to compare ice core data from Greenland and Antarctica with equatorial. This site provided all three, all from same isotope. See https://commons.wikimedia.org/wiki/File:Holocene_Temperature_Variations.png
        It appears that Gisp2 is shown lagging behind Vostok and Kilimanjaro by some 11000 yrs. At 11500 Vostok and Kilimanjaro show sudden increase – end of YD-. A global event; unlikely Greenland was that retarded.

        I had adjusted that and found what I wanted; polar and equatorial behave opposite. I have updated with your pic in link below showing your fig2 trace in two positions (at bottom fig)
        https://melitamegalithic.wordpress.com/2017/12/15/comparing-proxies/

        Aim was to find polar compared to equatorial temp changes. They reflect earth orientation changes; as seen in archaeology.

      • Mat asked: “Is it possible for all of that energy (power is the rate, energy is accumulated) to remain in a 5m mixed layer of the ocean and atmosphere?”

        50 m is the average depth seasons changes in ocean temperature penetrate each year. Locally, that depth depends on local average wind speed. So, you can think of the top 50 m of the ocean as that part that is physically stirred by the wind within a month or so. So, heat does not remain in a 5 m mixed layer.

      • franktoo: Mat asked: “Is it possible for all of that energy (power is the rate, energy is accumulated) to remain in a 5m mixed layer of the ocean and atmosphere?”

        50 m is the average depth seasons changes in ocean temperature penetrate each year.

        Oh nuts, I wrote another typo: I dropped a 0.

        I meant to ask : Is it possible for all of that energy (power is the rate, energy is accumulated) to remain in a 50m mixed layer of the ocean and atmosphere?

        Following up your calculation.

        Bother. I am sorry for the mistake.

      • Norman: Two 60 cycles (mostly associated with the AMO) is not reliable evidence for a cyclic process. Chaotic phenomena often show seemingly regular behavior for a few oscillation and then the pattern stops.

        The MWP, RWP and Minoan warm periods are not observed in Greenland ice cores or a global composite of ocean sediment cores. They appear to be regional, not global climate change. The is good evidence for a warmer period before the LIA, but it does not appear to be globally synchronous.

        The observed changes in TSI and extrapolated TSI are much smaller that future forcing from GHGs. (Remember to divide TSI by 4 to get solar forcing.)

      • The observed changes in TSI and extrapolated TSI are much smaller that future forcing from GHGs.

        GHGs produce no power, hence are incapable of forcing the climate in any rigorous dynamical sense. They’re merely instrumental in changing stored-energy concentrations within the system. Alas, such amateurish misconceptions permeate the CAGW tropes of “climate science,” rendering them of dubious scientific value.

      • Franctoo. First thanks for your comments at 2:27 It is refreshing to find someone who actually checks the data in the links rather than attacking the messenger. Re your TSI comments
        The Turning Point link says “This Lean figure shows an increase in TSI of about 2 W/m2 from the Maunder minimum to the 1991 activity peak . This TSI and solar magnetic field variation modulates the earths albedo via the GR flux and cloud cover. From the difference between the upper and lower quintiles of Fig 4 (in link below) a handy rule of thumb a la Fermi would conveniently equate this to a Northern Hemisphere temperature millennial cycle amplitude of about 2 degrees C with that amount of cooling probable by 2,650+/-.The MTP in cloud cover was at about 2000.”
        In other words the TSI difference of 2W/m2 + the associated change in the Solar magnetic filed strength together modulate the GR flux and cloud cover to produce a Millennial temperature cycle variation of about 2 degrees C. This is cannot be calculated from the bottom up. See Section 1 of second link.”Climate forecasts are made by the IPCC using analytic numerical models called General Circulation Models (GCMs) which attempt to describe the climate dynamics using sets of differential equations. This modelling approach is of limited value for predicting future temperature with any calculable certainty because of the difficulty of sampling or specifying the initial conditions of a sufficiently fine grained spatio-temporal grid of a large number of variables with sufficient precision. In addition, Essex 2013 (1) proved that models with the number of variables in the GCMs are simply incomputable.
        The same thing goes for ECS – See same link
        “The IPCC AR4 SPM report section 8.6 deals with forcing, feedbacks and climate sensitivity. It recognizes the shortcomings of the models. Section 8.6.4 concludes in paragraph 4 (4): “Moreover it is not yet clear which tests are critical for constraining the future projections, consequently a set of model metrics that might be used to narrow the range of plausible climate change feedbacks and climate sensitivity has yet to be developed”
        What could be clearer? The IPCC itself said in 2007 that it doesn’t even know what metrics to put into the models to test their reliability. That is, it doesn’t know what future temperatures will be and therefore can’t calculate the climate sensitivity to CO2. This also begs a further question of what erroneous assumptions (e.g., that CO2 is the main climate driver) went into the “plausible” models to be tested any way. The IPCC itself has now recognized this uncertainty in estimating CS – the AR5 SPM says in Footnote 16 page 16 (5): “No best estimate for equilibrium climate sensitivity can now be given because of a lack of agreement on values across assessed lines of evidence and studies.” Paradoxically the claim is still made that the UNFCCC Agenda 21 actions can dial up a desired temperature by controlling CO2 levels. This is cognitive dissonance so extreme as to be irrational. There is no empirical evidence which requires that anthropogenic CO2 has any significant effect on global temperatures.”
        The 60 year +/ cycle is clearly present during the last century and it is one of the fundamental astronomical cycles. 3 X the Saturn/Jupiter lap cycle is 3 X 19.859 = 59.6.

      • john321s: They’re merely instrumental in changing stored-energy concentrations within the system.

        Isn’t that the gist of AGW theory? Changing the temperature gradients changes the weather, hence the climate. Clearly, changing the stored-energy concentrations can change the net rate of cooling/warming because the energy transfer processes are nonlinear in temperature.

        Did you mean to write something else?

      • I wrote what I intended to write about: a basic misuse of technical terms that reveals a chronic lack of scientific mastery prevalent in “climate science.”

        While you may consider that such lack of scientific clarity nevertheless captures “the gist of AGW theory,” it creates the misconception that direct CO2 effects upon climate are inevitable and strong. Inasmuch as radiative heat transfer is but a minor factor in Earth’s surface climate, which is dominated by moist convection, the notion of “GHG forcing” is misleading.

  74. Making computer simulations of future weather/climate based on lots of assumptions.

    Paying minimal attention to such real world data as yet survives intact, the simulations are believed implicitly.

    Basing future industrial, technological and macroeconomic policy not on the most likely but on the worst conceivable outcome of the computer models.

    To me this is something close to collective suicide. It is putting a madman behind the wheel with all humanity on board. What insanely misanthropic rhetoric has put out elites on this genocidal path?

  75. Looking at projections for the putative path of hurricane Dorian shows that just two days ahead of an expected landfall, even heading south of the tip of Florida is a possibility. It’d be great ‘climate’ forecasts were as honest when it comes to the certainty of the forecasting.

    • The dishonesty is built into the UNFCCC Agenda 21 approach see

      “the Intergovernmental Panel on Climate Change was set up to select from the evidence and from time to time produce reports which would show that CO2 was the main driver of dangerous climate change and a second recommendation resulted in a meeting in Rio in 1992 chaired by Maurice Strong himself which produced the United Nations Framework Convention on Climate Change , later signed by 196 governments.

      The objective of the treaty is to keep greenhouse gas concentrations in the atmosphere at a level that they guessed would prevent dangerous man made interference with the climate system.

      This treaty is really a comprehensive, politically driven, political action plan called Agenda 21 designed to produce a centrally managed global society which would control every aspect of the life of every one on earth.
      See http://climatesense-norpag.blogspot.com/2015/08/the-epistemology-of-climate-forecasting.html
      It says :
      “…………The Parties should take precautionary measures to anticipate, prevent or minimize the causes of climate change and mitigate its adverse effects. Where there are threats of serious orirreversible damage, lack of full scientific certainty should not be used as a reason for postponing
      such measures”
      In other words if the models show there is even a small chance of very bad things happening the Governments who signed the treaty should act now to stop it. But how good are the computer Models?
      The successive five reports of the IPCC in the Summaries for Policymakers written by Government representatives have claimed increasing certainty for the outcomes of their Model based projections of future temperature which is not supported by the Science sections of the reports or the actual data.
      Remember the Villach meeting said
      “in the first half of the next century a rise of global mean temperature could occur which is greater than any in man’s history.”
      All the models and projections made since 1985 were built in the assumption that CO2 was the main climate change driver- for that and for many other reasons they are in reality useless for forecasting future temperatures.”

    • Good grief Wagathon, you should know by now that it is much easier to accurately forecast 100 years hence than 2 days because…oh computer projections and other clever stuff, which works better the more inaccurate or vague the input. Its the next step up from GIGO

      Its SNGETBG

      Stuff not garbagy enough to be garbage

      tonyb

      • True, true… it’s not like we have an easier time predicting what the world will be like in 3000 compared to people in 1900 predicting life in 2000, just because we have computers so now, anyone can simply ‘google’ the answer.

  76. Talk about “worst case”, the academic post-modern shepherds of our post-souls have come up with a new social construct-busting radical dietary suggestion to help save the climate: cannibalism.

    https://www.rt.com/news/467685-cannibalism-promoted-by-academics/

    Yes – cannibalism. No meat – veganism – that’s old hat already. Where to go for the truly trend setting moral signaller? Denier and ale pie?

  77. I love your approach and admire your courage, expertise and demeanor. I saw some typo-level issues in your (excellent, important) paper. Do you want that kind of feedback?

  78. Pingback: Spotlight on green news & views: Regenerative agriculture; missing sharks; starving orcas | Patriots and Progressives

  79. Pingback: Spotlight on green news & views: Regenerative agriculture; missing sharks; starving orcas | NoPartySystem.Com

  80. Pingback: Spotlight on green news & views: Regenerative agriculture; missing sharks; starving orcas – Headlines

  81. Reblogged this on Quaerere Propter Vērum.

  82. “Overall, there is the danger that the paper is used by unscrupulous people to create confusion or to discredit climate or sea-level science. Hence, I suggest that the author reconsiders the essence of its contribution to the scientific debate on climate and sea-level science.”
    – unnamed consensus enforcer.

    This well illustrates the endemic deviousness, dishonesty, intolerance and blinkered bias that characterises the bulk of the present-day government-funded climate science profession. A deep anti-science ethic much like that revealed by Climategate, especially in the ensuing official coverups.

    In plain English : we will not publish anything that differs from or criticises the alarmist view. To be published you must stick to the consensus brief and not ever question or doubt its conclusions.

    Further proof that there is no peer-review in climate science, only pal-review. This profession is quite simply not qualified to include the word “science” in its name.

  83. CMIP ensembles are not technically probabilistic. This is probabilistic.

    bom.gov.au/climate/enso/wrap-up/archive/20190820.sstOutlooks_nino34.png

    The difference is between a collection of solution trajectories from different models – as opposed to multiple solutions of a single model that diverge from imprecisely known initial conditions. The former is arbitrary the latter allows for probabilities to be calculated.

    How reliable these probabilities are is another question. Models lack internal variability – as do so called observational estimates of climate sensitivity. Sensitivity is itself a problematic concept in a nonlinear system with thresholds and climate shifts.

    Geophysics and its mathematical representations are not advanced enough to dispel ‘deep uncertainty’.

  84. In your “Worst Case” paper you say:
    “The IPCC assessments of ECS have focused on a ‘likely’ (> 66% probability) range to be between 1.5 and 4.5oC, which has mostly been unchanged since Charney et al. (1979).”

    When Arrhenius published the relevant paper in 1896 his value for what we now call the “ECS” was ~4.5 degrees Centigrade/doubling of [CO2]. One hundred and twenty three years later the IPCC claims (AR5) that the ECS is 3.0 +/- 1.5 degrees per doubling. This is way too squishy to qualify as “Science”.

    The Arrhenius theory is simply wrong. It fails a bunch of sanity tests. For example you can use the IPCC’s figures to estimate the surface temperature of Mars and Venus based on an average temperature of 287.4 K @ 300 ppm of CO2 for planet Earth:

    Mars has 6 mbar of CO2 which means 4.4 doublings……..multiply by 0.810 to adjust for the TSI (586.2 W/m^2). The predicted temperature range is 238-249 K. Even though this is a wide range, the observed value of 210 K does not fall within it. FAIL!

    It gets much worse with Venus where the pressure is 92 bar, equivalent to 18.2 doublings. Multiply by 1.176 to adjust for TSI (2601.3 W/m^2). The predicted temperature range is 363-412 K. According to NASA the temperature is ~737 K. ABSURD FAIL!

    The theory is wrong because it only considers radiation (incoming & outgoing) and trace gases on the assumption that the “Bulk of the Atmosphere” has no effect. The theory should have been abandoned years ago.

    Today there are theories that include the effect of radiation, convection, conduction, oceans, trace gases and bulk gases. Not too surprisingly they do a pretty good job predicting atmospheric temperatures in some detail. For example:
    https://faculty.washington.edu/dcatling/Robinson2014_0.1bar_Tropopause.pdf
    https://arxiv.org/pdf/1608.08620.pdf

  85. Pingback: ‘Alarmism enforcement’ on hurricanes and global warming | Climate Etc.

  86. Pingback: Climate activists attack climate science – Ubuntu News

  87. Pingback: ‘Alarmism enforcement’ on hurricanes and global warming — Judith Curry | Climate etc. | Taking Sides

  88. Pingback: Climate deniers vs hurricanes (guess who blows harder) | Red, Green, and Blue

  89. “Worst Case Scenario” does not mean that we should discard the ‘editorialized’ idea of “borderline implausible concentration/emission scenarios” if it means rejecting the effect of the methane bomb in the Arctic. Sea level rise of 10 meters, warming of +5oC – those are MEDIAN projections, and very possible if the methane bomb goes off . It is currently bubbling up in the Arctic oceans….

Leave a Reply to John Prince Cancel reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s