About Hansen’s powerful demo that climate models work!

Summary: This is a revealing tale of climate science in action. We are told that a 30-year old paper demonstrates that models can accurately predict climate change. A closer look reveals a different story.

“‘We’re toast if we don’t get on a very different path,’ Hansen, director of the Goddard Institute of Space Sciences who is sometimes called the godfather of global warming science told the Associated Press. …This is the last chance. …We see a tipping point occurring right before our eyes …The Arctic is the first tipping point and it’s occurring exactly the way we said it would.’ Hansen, echoing work by other scientists, said that in five to 10 years, the Arctic will be free of sea ice in the summer.”
In the AP ten years ago, on 23 June 2008. The arctic is still not free of ice in the summer.

Crystal ball in hand, seeing the world
©creativecommonsstockphotos via Dreamstime.

On 29 March 2017 the House Science, Space, and Technology Committee held a hearing on “Climate Science: Assumptions, Policy Implications, and the Scientific Method“. The star witness was climate scientist Michael Mann. He gave a confident statement that climate models work.

“While we’re at it, let me address another favorite talking point of the critics, the claim that climate models we use to project future climate change are unreliable and untested. The reality is that the models have been tested vigorously and rigorously in numerous ways, and have passed a number of impressive tests in the past, such as James Hansen’s famous successful predictions from the 1980s and 1990s.”

The supporting citation Mann gave to Congress was a ten year old blog post: “Hansen’s 1988 projections” by Gavin Schmidt at RealClimate. He discussed “Global climate changes as forecast by Goddard Institute for Space Studies three-dimensional model” by Hansen et al. in the Journal of Geophysical Research, 20 August 1988. That paper is probably the most-often cited evidence that climate models can make accurate long-term predictions of weather. It was the basis for Hansen’s testimony to the Senate that ignored the campaign for public policy action to fight climate change.

On its thirtieth anniversary, we have a burst of excited congratulations in the media.

  • Warned 30 years ago, global warming ‘is in our living room’” by Seth Borenstein and Nicky Forster at AP. They misinterpret Hansen’s study as a prediction of that the world would warm, ignoring that the world has been warming since the end of the Little Ice Age in the mid-19th century. Hansen provided a quantitative prediction of the effect of increased CO2 on global temperature. The AP does not even attempt to assess its accuracy.
  • Listening to James Hansen on Climate Change, Thirty Years Ago and Now” by Elizabeth Kolbert in The New Yorker. She conflates natural weather with results of anthropogenic climate change (the alarmists’ mantra: if it’s bad weather, its climate change). She also trots out zombie climate myths. To debunk just one, western US wildfires are a natural phenomenon exacerbated by a century of fire suppression (see details here and here).

An endless list of other stories echo these, such as “James Hansen’s legacy: Scientists reflect on climate change in 1988, 2018, and 2048” by Eric Holthaus at Grist — “Hansen’s warning was prescient and his predictions were scarily accurate.” He cites only the YaleClimate and AP stories as evidence.

These are propaganda of the crudest kind. Like most modern propaganda, it has a big lie: that the debate about climate policy is existence of global warming. If CO2 warms the world, massive and expensive measures must be taken. But for a century we have been bombarded with the products of modern propaganda and such crude programs no longer work.

The debate is, like most in science and public policy, about “how much” and “when.” All four of the scenarios used in AR5, the IPCC’s most recent report, expect warming. But the most optimistic (RCP2.6) warrants only mild action while the worst (RCP8.5) would warrant severe and immediate action. Analysis of these pathways requires science, which ruins the simple narrative preferred by click-hungry and alarmist journalists.

A second oddity

“{T}here is another special kind of boldness …the boldness of a conjecture which takes a real risk – the risk of being tested, and refuted; the risk of clashing with reality. Thus my proposal was …that it is this second boldness, together with the readiness to look out for tests and refutations, which distinguishes ‘empirical’ science from non-science, and especially from pre-scientific myths and metaphysics.”
— Karl Popper in “Replies to my critics” (1974).

A more sophisticated analysis reveals the big oddity of this interest in Hansen 1988: “30 years after Hansen’s testimony” by Gavin Schmidt at RealClimate (he is a climatologist and Director of the NASA Goddard Institute for Space Studies) — “The first transient climate projections using GCMs are 30 years old this year, and they have stood up remarkably well.” Zeke Hausfather of Berkeley Earth provided additional insights on Twitter.

Update — see a detailed analysis: “The Hansen forecasts 30 years later” by Ross McKitrick and John Christy at Climate Etc. Lots of problems found with it in the comments.

These provide analysis by climate scientists. Yet from a public policy perspective they miss several key points. First, neither Schmidt nor the journalists looking at Hansen 1988 cite any peer-reviewed papers documenting Hansen’s successful prediction. This displays remarkable amnesia. For 30 years we have been told that skeptics’ writings, no matter how imminent the author, are dismissed (correctly, imo) as irrelevant to the policy debate because the peer-reviewed literature is the “gold standard.” Accept no substitutes! But now the evidence about one of the great threats of our time is based on blog posts and scientists cheers to journalists.

Other blog posts have discuss this forecast, such as “Evaluating Jim Hansen’s 1988 Climate Forecast” by Roger Pielke Jr. (2006) and “A detailed look at Hansen’s 1988 projections” by Dana Nuccitelli at Skeptical Science (2010).

If the evidence for this prediction was strong, why has Hansen — or anybody — not published peer-reviewed confirmation? It would be headline news.

I have found one (only one) published paper evaluating the predictions of Hansen 1988 vs. actual temperatures: “Skill and uncertainty in climate models” by Julia C. Hargreaves at WIREs: Climate Change, July/Aug 2010 (ungated copy). She attempted to input the actual emissions data since 1988 and compare the resulting forecasts with actual temperatures. That is the essential means of validation. Models can be tuned so that they accurately predict the past (which is why hindcasts are low-grade evidence for validation). Only data from after publication provide effective tests. The result: “efforts to reproduce the original model runs have not yet been successful.” Hargreaves has a PhD from Cambridge in astrophysics. See her publications, job history, and website.

The dog ate my model. Case closed. Now, let’s save the world by spending trillions of dollars and changing our economic and political systems (as advised by Naomi Klein and Pope Francis). /sarcasm.

Fun fact: none of the cheerleaders for Hansen 1988 that I have seen mention Hargreaves’ paper (update: the propaganda cited in the first section above). When I point it out to them, chaos reigns as they explain why there is no need to replicate it. My fav, from a PhD candidate in climate science (the next generation has drank the Kool-Aid):

“Why don’t you do it then? I want to but it’s a big chunk of work and will probably take me years to do it properly.”

If only we had followed such advice in the past! I believe we should build Hoover Dam. “Why don’t you do it? I want to, but don’t have the time.” I believe we should fight the Nazi’s. “Why don’t you do it? I don’t have the time.” Too bad, world. Neither of us can do it! The other explanations are even more daft.

That these climate scientists show so little interest in investigating Hansen 1988 is a tell. A robust successful test of Hansen’s multi-decade prediction — validation of his results by an independent multidisciplinary team of experts — would be the biggest evidence ever that models can accurately predict climate change. That would be more significant since Hansen’s 1988 model is a toy compared to present models, which are built with far deeper knowledge of climate dynamics, running with vastly superior data, on machines with several orders of magnitude more computing power.

This might have been a game-changer in the climate policy debate. It might be possible for a team to reconstruct Hansen’s code. The cost would be a trivial fraction of the world’s climate science budget. That none even propose doing so tells us how serious they are about the wonders of Hansen 1988.

Nobel Prize

A sad moment in time

What if Hansen had retained the full code for his model, so that today he was able to prove a 30 year successful forecast of global temperatures? He would be getting a Nobel Prize in physics 2018.

At what point in the past 30 years did Hansen realize that his model could be vital evidence in the policy debate? It was discussed as important in 2006 – 2008 (eight to ten years after publication). Probably then he could have still archived the code and updated it for modern systems. As the famous James Hansen, he could have easily found the money for this research. His decision not to do so had severe consequences for both him and the world. We can only guess at why he choose not to do so.


The intense focus and cheers about Hansen 1988 shows the absence of strong evidence that climate models can successfully predict climate change. Scientists’ long disinterest in validation of these models, from Hansen’s 1988 model to the ones used in the most recent three IPCC reports (TAR, AR4, AR5) tells us something. Each of us must draw his or her own conclusions about that.

Let’s end on a positive note. See Climate scientists can restart the climate policy debate & win: test the models! This describes one way to restart the climate policy debate, putting it on a stronger foundation. Also see the list of papers about model validation in the For More Info section at the end. It is pitifully sparse. Mostly boastful hindcasts, which tell us almost nothing (e.g., too vulnerable to tuning the model to accurately predict the past). Climate science can do better, but chooses not to do so.

For More Information

For another perspective on Hansen 1988, see “Thirty Years On, How Well Do Global Warming Predictions Stand Up?” by Pat Michaels and Ryan Maue, an op-ed in the WSJ — “James Hansen issued dire warnings in the summer of 1988. Today earth is only modestly warmer.” The Guardian fired with “30 years later, deniers are still lying about Hansen’s amazing global warming prediction” by Dana Nuccitelli – “Koch paychecks seem to be strong motivators to lie.” It is mad that we are supposed to change the world economy on the basis of this chatter.

Ideas! For shopping ideas see my recommended books and films at Amazon.

If you liked this post, like us on Facebook and follow us on Twitter. For more information see The keys to understanding climate change, all posts about computer models, and especially these …

  1. How climate scientists can re-start the public policy debate about climate change.
  2. We can end the climate policy wars: demand a test of the models.
  3. Milton Friedman’s advice about climate models, & how to win the policy debate.
  4. Save the world from climate threats, myths and fears. – Presentation by Prof. Demetris Koutsoyiannis.

18 thoughts on “About Hansen’s powerful demo that climate models work!”

  1. Pingback: About Hansen’s powerful demo that climate models work! – Michael Jackson

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  4. I looked at the IPCC report of 2013, particularly chapter 11. My impressions of climate science are unchanged before and after reading some of the report. It’s a lot of money and intellect spent on something that’s going to happen anyway on time-scales that allow humans to adapt. Looking at figure 1 in chapter 11, it’s not at all clear that near-term simulations are matching observations well (red line versus black line). Also, why does the forecast line (green) not extend to 2013? To the extent that I’m wrong about this claim, it’s the fault of IPCC scientists for failing to caption their figures clearly.

    Here’s the problem I have: climate temperature “data” before the era in which we directly measured it using traceable thermometers is an INFERENCE from other measured things such as the content of ice cores judged dated through radiocarbon. No one was around to record climate temperatures thousands of years ago because Celsius hadn’t been invented yet. The observations (direct measurements) you do have appear to date to the 1960s which is extremely recent for climate time scales. Running IPCC simulations backwards on historic data doesn’t even give a great correlation to the historic data.

    This should encourage modesty and humility amongst climate scientists. Maybe it does. Maybe climate scientists are being made into a political football against their will. The Summary for Policy Makers suggests climate scientists are the opposite of modest. FIgure SPM 5 is of particular concern. They have high confidence in significant human radiative forcing by comparing 2011 data to data from the 1750s (inclusive?) Anders Celsius didn’t even invent Celsius until somewhere around the 1750s, did he? Was there a robust system of tracing individual thermometer readings back to international standards like we have today? Weren’t standards bodies themselves just getting off the ground? Then they make claims about CO2 concentration dating back to the 1750s. Obviously, carbon wasn’t identified as an element until 1789, so when were CO2 concentrations first directly measured (traceably)? Why is the writing in the “Summary for Policy Makers” so jargon-heavy and unclear when it’s supposed to be for laymen?

    1. Larry Kummer, Editor


      (1) “Here’s the problem I have: climate temperature “data” before the era in which we directly measured it using traceable thermometers is an INFERENCE”

      Science takes place on the edge of our measuring capability. That’s just life, to be considered when evaluating confidence for public policy purposes.

      (2) “The observations (direct measurements) you do have appear to date to the 1960s which is extremely recent for climate time scales.”

      There is decent global temp data going back to 1900, except for the poles.

      (3) “Running IPCC simulations backwards on historic data doesn’t even give a great correlation to the historic data.”

      There are many papers that disagree with you. I don’t believe that is even in dispute. See the links in my “Test the Models” post (link in the Conclusions section).

      (4) “This should encourage modesty and humility amongst climate scientists.”

      You are asking too much. Moses was humble. He was the last leader of whom that could be said. That’s why we have systems to test evidence, so we don’t have to rely on the personal attributes of scientists and other experts.

    1. Larry Kummer, Editor


      Anthony Watts publishes almost all my articles about climate change public policy. Since there is no longer a middle in this debate, the comments are mostly hostile. Anthony publishes them despite his audience’s displeasure because he is a prince.

  5. Global Warming’s Worst-Case Projections Look Increasingly Likely” by James Temple at MIT Technology Review, 6 December 2017 — “A new study based on satellite observations finds that temperatures could rise nearly 5 °C by the end of the century.”

    Based on “Greater future global warming inferred from Earth’s recent energy budget” by Patrick T. Brown & Ken Caldeira in Nature, 7 December 2017. Abstract:

    Climate models provide the principal means of projecting global warming over the remainder of the twenty-first century but modelled estimates of warming vary by a factor of approximately two even under the same radiative forcing scenarios. Across-model relationships between currently observable attributes of the climate system and the simulated magnitude of future warming have the potential to inform projections.

    Here we show that robust across-model relationships exist between the global spatial patterns of several fundamental attributes of Earth’s top-of-atmosphere energy budget and the magnitude of projected global warming. When we constrain the model projections with observations, we obtain greater means and narrower ranges of future global warming across the major radiative forcing scenarios, in general. In particular, we find that the observationally informed warming projection for the end of the twenty-first century for the steepest radiative forcing scenario is about 15% warmer (+0.5 degrees Celsius) with a reduction of about a third in the two-standard-deviation spread (−1.2 degrees Celsius) relative to the raw model projections reported by the Intergovernmental Panel on Climate Change. Our results suggest that achieving any given global temperature stabilization target will require steeper greenhouse gas emissions reductions than previously calculated.

    1. Larry Kummer, Editor


      I added full citations to that article, and added the paper it was based on.

      Climate scientists have too much invested in RCP8.5 to easily give it up. This paper makes no effort whatsoever to explain how the scenario in RCP8.5 might happen. That is a massive slowdown in the rate of technological progress, so that in the late 21st century coal is the dominant fuel — as it was in the late 19th century, and how the decline in fertility observer in every society that industrializes will not happen in Africa and other under-developed nations.

      Instead we get “fun with models”. That’s nice, but irrelevant to the objections.

      This shows, much like the emphasis on Hansen 1988, the weakness of the case predicting extreme climate change. They rely on their control of the news media to conceal this weakness from the public. as the polls show, this tactic has failed for 30 years.

      As they say in AA, “insanity is repeating your actions …”

      1. Larry Kummer, Editor


        A follow-up comment — the MIT Tech Review headline is wrong. The Brown-Caldeira paper in Nature did not discuss the liklihood of the “worst case projection” being “more likely.” It discussed the projected temperature increase in that scenario.

        Also note that the headline correctly calls RCP8.5 the “worse-case” projection (actually it is a forecast or scenario, not a projection). In the body they repeat the zombie lie of RCP8.5 being a “business as usual” scenario.

        It’s another example of the news media’s capture by climate alarmists. Liquidating their credibility, one story at a time.

    1. Larry Kummer, Editor


      “Or am I missing something?”

      Write it up and publish in a peer-reviewed journal. Then it becomes evidence in the public policy debate. That is the point of this 2000 word post.

    1. Larry Kummer, Editor


      Let’s stay on topic here. Let’s esp not try to refight “the hockey stick.” From memory (which is unfortunately getting less reliable each year), it’s not even cited in AR5.

  6. “The intense focus and cheers about Hansen 1988 show the absence of strong evidence that climate models can successfully predict climate change.”

    Can you link that conclusion of yours to a peer-reviewed journal article?

    1. Larry Kummer, Editor


      I need a peer-reviewed paper to show that peer-reviewed papers are the basis of modern science?

      Good try, but that’s nuts.

  7. I looked at Dr Hansen’s projections and the actual temperature plot and they match to an astonishing degree. Smooth ENSO and the actual global temperature average match Hansen’s projections very closely. I understand that Free Market Justice Warrior fascists hate this fact since it goes against your political ideologies and tribalism, but demonstrable fact does not go away when you cultists just say it doesn’t exist. Try putting some ice on it.

    1. Larry Kummer, Editor


      (1) “I looked at Dr Hansen’s projections and the actual temperature plot and they match to an astonishing degree.”

      Model validation is a bit more complex than overlaying two lines, esp for a brief period (climatologically speaking) of 30 years. There are well-established methods for doing this.

      (2) “I understand that Free Market Justice Warrior fascists hate this fact”

      Thank you for telling us that your amateur observation is a “fact” in cutting edge science! However, please excuse the rest of the world if we wait for peer-reviewed research to confirm it.

      Also, congrats on your extraordinary self-esteem. The California Task Force to Promote Self-Esteem would be proud of you.

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