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Evaluating a 1981 temperature projection

Guest commentary from Geert Jan van Oldenborgh and Rein Haarsma, KNMI

Sometimes it helps to take a step back from the everyday pressures of research (falling ill helps). It was in this way we stumbled across Hansen et al (1981) (pdf). In 1981 the first author of this post was in his first year at university and the other just entered the KNMI after finishing his masters. Global warming was not yet an issue at the KNMI where the focus was much more on climate variability, which explains why the article of Hansen et al. was unnoticed at that time by the second author. It turns out to be a very interesting read.

They got 10 pages in Science, which is a lot, but in it they cover radiation balance, 1D and 3D modelling, climate sensitivity, the main feedbacks (water vapour, lapse rate, clouds, ice- and vegetation albedo); solar and volcanic forcing; the uncertainties of aerosol forcings; and ocean heat uptake. Obviously climate science was a mature field even then: the concepts and conclusions have not changed all that much. Hansen et al clearly indicate what was well known (all of which still stands today) and what was uncertain.

Next they attribute global mean temperature trend 1880-1980 to CO2, volcanic and solar forcing. Most interestingly, Fig.6 (below) gives a projection for the global mean temperature up to 2100. At a time when the northern hemisphere was cooling and the global mean temperature still below the values of the early 1940s, they confidently predicted a rise in temperature due to increasing CO2 emissions. They assume that no action will be taken before the global warming signal will be significant in the late 1990s, so the different energy-use scenarios only start diverging after that.

The first 31 years of this projection are thus relatively well-defined and can now be compared to the observations. We used the GISS Land-Ocean Index that uses SST over the oceans (the original one interpolated from island stations) and overlaid the graph from the KNMI Climate Explorer on the lower left-hand corner of their Fig.6.

Given the many uncertainties at the time, notably the role of aerosols, the agreement is very good indeed. They only underestimated the observed trend by about 30%, similar or better in magnitude than the CMIP5 models over the same period (although these tend to overestimate the trend, still mainly due to problems related to aerosols).

To conclude, a projection from 1981 for rising temperatures in a major science journal, at a time that the temperature rise was not yet obvious in the observations, has been found to agree well with the observations since then, underestimating the observed trend by about 30%, and easily beating naive predictions of no-change or a linear continuation of trends. It is also a nice example of a statement based on theory that could be falsified and up to now has withstood the test. The “global warming hypothesis” has been developed according to the principles of sound science.


  1. J. Hansen, D. Johnson, A. Lacis, S. Lebedeff, P. Lee, D. Rind, and G. Russell, "Climate Impact of Increasing Atmospheric Carbon Dioxide", Science, vol. 213, pp. 957-966, 1981.

86 Responses to “Evaluating a 1981 temperature projection”

  1. 51
    KiwiCM says:

    Thanks for the response Gavin, and others.

    @Hank – don’t worry, I assumed it was garbage, I was just looking for the best explanation. Gavin gave it to me.

  2. 52
    Schrodinger's Cat says:

    It seems that NASA scientists do not approve of Hansen’s version of science.

    [Response: Love the way that 49 retired astronauts and administrators (and one meteorologist) suddenly become some all-encompassing ‘NASA scientists’. Especially since they haven’t actually provided any specific example of what they are complaining about, and despite the fact they are calling for the bureaucracy to censor the ability of real NASA scientists to talk about their work. This is ably dissected here. – gavin]

  3. 53

    #52–It seems that Gavin (and Skeptical Science) were the ones who actually “opened the box” and took a look…

  4. 54
    tokodave says:

    If you check in at WTFUWT and look at the comments you’d think they’d died and gone to heaven….actual science or scientists….not so much

  5. 55
    Tietjan Berelul says:


    I dont understand your reply to #52, why would you imply that astronauts are not scientists ? I guarantee you that most Americans believe the people involved in the Apollo missions have done more for science than all of todays climate scientists together.


    [Response: Some astronauts are scientists, some are not. None of the ’49’ have any climate expertise, however capable they might be in other fields. They are of course entitled to their opinions, but the vague and unsourced accusations they level at NASA and GISS, and in particular their call for scientists to be censored for talking about their research is unbecoming, and not compatible with the high regard that many of them retain for their impressive actions in the manned space flight program. My respect for those achievements is very strong, but that doesn’t make their opinion about NASA’s climate research valid. I presume you are not taking the position that authority should be granted to an argument purely on the basis of the past history of the arguer? – gavin]

  6. 56
    Ray Ladbury says:

    Tietjan Berelul: “I guarantee you that most Americans believe the people involved in the Apollo missions have done more for science than all of todays climate scientists together.”

    And that right there might be the sorriest indictment of the American education system ever uttered. Why do you hate America, Tietjan?

  7. 57
    dhogaza says:

    I dont understand your reply to #52, why would you imply that astronauts are not scientists ?

    The early astronauts were all jet fighter pilot jocks from the miliary.

    Not scientists.

    Even today, 60% have military backgrounds.

    Only 36% have doctorates, and many of those are in engineering or other fields, not science, certainly not climate science.

    So what made *you* assume that astronauts are “scientists”? After all, each bird needs a pilot and co-pilot. Do you think commercial airline pilots are “scientists”? Fighter pilots?

    I guarantee you that most Americans believe the people involved in the Apollo missions have done more for science than all of todays climate scientists together.

    Yes, we’re all aware that most Americans are sadly lacking in scientific knowledge.

    One can “do for science” without being a scientist, as any working scientist will tell you when asked about their lab technicians if they’re involved in experimental science, or field techs if they’re doing field research. So even if your statement’s true, it doesn’t make astronauts “scientists”. The landing targets for the Apollo flights were chosen by scientists on earth in conjunction with NASA engineers (who had to decide whether or not the areas of scientific interest included safe landing zones) – *NOT* the astronauts themselves. At best, the astronauts were field techs when walking on the moon. Those working on the space station spend a lot of time being glorified construction workers, bolting this, duct-taping that, yanking on the other, sometimes a good kick or two.

    But the unmanned space exploration program has done far, far more to push forward scientific knowledge than those missions that include astronauts, which mostly have been limited to earth orbit, other than a few jaunts to the moon that brought back a few rocks, so valuable to science that some have ended up as souvenirs. Hubble alone dwarfs the entire scientific output of every astronaut or cosmonaut that’s ever entered space.

    On the other hand astronauts acting as lab/engineering techs saved the Hubble from a serious manufacturing flaw, and later upgraded the camera system. They weren’t doing science, though, and the skills required weren’t those of a scientist.

    It takes guts to blast off into orbit with a giant rocket strapped to your tail. That doesn’t make those who do so scientists.

  8. 58
    David B. Benson says:

    Well, one geologist
    went to the moon. I suppose he did some lunology while he was there.

  9. 59
    GSW says:


    “None of the ’49’ have any climate expertise, however capable they might be in other fields.”

    I think this is a bit cheap, the achievements of this remarkable group of people speak for themselves.

    Their criticism is based on an understanding of what does, and does not, constitute “Science” – a discipline constrained by imperical evidence, objectively determining what you can and cannot say. It is not based on the emotional fears for the well-being of one’s grandchildren, how cuddly polar bears are, or an eagerness to support the prevailing political “will”. This is obvious surely.

    The first part “None of the ’49’ have any climate expertise” is particularly galling. Science is science. No doubt homeopathists would feel equaly justified in dismissing challenges from the medical profession on the grounds that they had no “Homeopathy expertise”.

  10. 60
    dhogaza says:

    David B Benson:

    Well, one geologist
    went to the moon.

    Yep, and apparently the experience drove Harrison Schmitt … looney!

  11. 61
    gerben says:

    one ought to read the paper by Svante Arhhenius written in 1896. Talking about early warnings… :’)

  12. 62
  13. 63
    Chris Vernon says:

    “…the concepts and conclusions have not changed all that much.”
    I think this rases an interesting point. Despite dramatic increases in model complexity and computation power over the last 30 years, conclusions haven’t changed that much. Our understanding of zero order results such as climate sensitivity, mean global surface temperature haven’t advanced much from the relatively simply models Hansen was using then. I suggest we’ve been overly focused on increasing model complexity and resolution, an approach that isn’t delivering good returns on the investment.

  14. 64
    Ray Ladbury says:

    Chris Vernon,
    Well, that would be one rather bizarre interpretation. Another would be that we have understood such concepts as sensitivity for a long time now and that none of the advances made (and they are advances) has changed that understanding.

    The models have allowed us to understand a great many other things–prompt response to volcanic eruptions, the build-up of ice inland in Antartica even as ice shelves disappear, and so on. If you only look at Anthropogenic climate change, you are missing half the circus.

  15. 65
    Chris Vernon says:

    But, Ray, we don’t have a very good understanding of climate sensitivity today, nor of global mean surface temperature. That’s my point, the dramatic improvement in computer power and model complexity hasn’t narrowed the uncertainty on sensitivity nor, brought all the AR4 models, for example, into agreement when recreating 20th C. mean surface temperature.

  16. 66
    Ray Ladbury says:

    Chris Vernon,
    Say what? We’ve nailed computer sensitivity down to between 2 and 4.5 degrees per doubling–reduced from 1.5-5.5 a decade ago. That is significant progress. The current range is sufficient to establish that we have a serious problem at best and a civilization-threatening problem if the upper end turns out to be true.

    Perhaps you should read up on the problem, and then you might understand why smaller grid size is not necessarily going to answer all questions and why getting all the models to agree on everything is neither necessary nor sufficient for them to be useful.

  17. 67
    Ric Merritt says:

    GMW: “…remarkable achievements speak for themselves…” and finding straightforward, relevant, factual statements “particularly galling”.

    Contentless trolling. Go away.

  18. 68
    Ray Ladbury says:

    GSW, these “49” wouldn’t know science if it bit their peckers off. Anyone who knows anything about science realizes that expertise matters. I do not opine about brain surgery or string theory, because I am do not possess professional level competence in them.

    The facts are that 97% of experts say we are changing the climate. This is not just the NAS study, it’s consistent with the results from Bray and von Storch, no great advocates of the consensus. The consensus has been vetted and vindicated by countless independent reviews by national scientific academies from around the globe, by professional organizations of scientists.

    The rules in science: You don’t publish in the field, you don’t get to play.

  19. 69
    Gator says:

    GSW: “It is not based on the emotional fears for the well-being of one’s grandchildren, how cuddly polar bears are, or an eagerness to support the prevailing political “will”. This is obvious surely.”

    You are correct that this is not science. Neither is science based on the emotional fear that taxes will go up if climate change happens to be true. This should be obvious but has obviously been the one connecting thread between all of the denialists I have seen. They have no coherent scientific story, but they all think climate change will hit their pocket book so it must be wrong.

  20. 70
  21. 71

    I would like to post your figure in my blog on the CBI web site. Is it proprietary or can I just take it? I will of course be glad to give you and Hansen credit for the graphics and the paper.
    Please let me know as I would like to post it next week.
    Our blog page is:
    Thank you

    [Response: Please contact Geert for permission. – gavin]

  22. 72
    David Lewis says:

    After I saw that Hansen cited his 1981 paper in his recent TED talk I read it. One thing I’ve thought about often since I read the paper is the first line in the third paragraph:

    “The major difficulty in accepting this theory has been the absence of observed warming coincident with the historic CO2 increase.”

    I’ve only been observing climate change debate and considering the issues involved since 1988. I wonder if this sentence counts as a prediction Hansen got wrong. I am still astonished that so many who would count themselves as leaders of this civilization still reject the theory even as the observations pile up.
    Maybe Hansen in 1981 was referring to his colleagues?

  23. 73
    Walt Finerman says:

    Ray Ladbury @68: “The rules in science: You don’t publish in the field, you don’t get to play.”

    That’s just ridiculous. Free inquiry is open to anyone. It is a bit frightening that you would say or believe otherwise. Personally, it’s completely obvious to me that these astronauts probably don’t have a lot of facts or well-founded arguments to back up their cases, but you shouldn’t just be a jerk and shut them out completely. Just address their arguments and if anyone says “They’re astronauts”, you say, “So what” and turn back to the arguments. Now that’s science.

    [Response: Some vaguely interesting background has come to light. Apparently the genesis of the letter was a meeting of the NASA Alumni League at JSC in September, where Cunningham and Steward gave some heavily contrarian talks. Their slides (linked) are remarkable only in how bad they are. For instance, they use multiple figures that have simply made up data on them – purported temperature reconstructions that are two different series with different baselines plotted together, inconsistent measures of solar forcing to get better fits with different data, and most bizarrely of all, multiple slides all claiming that only ~3%’ of atmospheric CO2 is anthropogenic and that this is “0.12%” of the greenhouse effect. This is nonsense of the highest order (CO2 is up over 40% because of human activities, and CO2 as a whole is roughly 20% of the greenhouse effect when judged by the effect it has on upwelling longwave radiation). The lack of understanding in what they are showing is evident and that is a little sad. – gavin]

  24. 74
    Walt Finerman says:

    From an interested layperson: the complexity and opacity of contemporary climate models cause me to be skeptical of the anthropogenic hypothesis. Although it deals with purely physical, chemical, and maybe a few biological processes, the flavor of the models and their statistical analysis seems to be quite different from other branches of the natural sciences. There seem to be free parameters floating around (“climate sensitivity”) that are not well-understood. (Or if they are well-understood, we can’t really know they’re well-understood, since so few precise predictions can be made and verified in a convincing way in less than a few decades.) Knowledge of the basic physical processes seems to be in flux as well: how long ago was the importance of the ozone layer and aerosols discovered? Really, not long at all. Many of the basic physical processes involved also seem to be approximated with plausible dynamics, but again, they are only indirectly based on foundational first principles, which everyone agrees on. (There are no deniers of quantum physics that I know of.)

    That said, this chart does sway me. It is precisely this type of longer-term, non-trivial prediction that I’ve been looking for. If it withstands scrutiny, my assessment of the likelihood of the anthropogenic hypothesis being correct will grow considerably.

    Can someone respond to Roger Pieilke’s critique of the Atlantic article?

    [Response: Roger Pielke’s critique doesn’t make much sense. He appears to be claiming that a single month anomaly with respect to the last 30 year baseline (0.11ºC) should be compared to a trend from 1979 onwards. That isn’t correct at all. Instead one should use the trend in the UAH TLT data, which is 0.144ºC per decade (Pielke’s graph of the trend is possibly out of date). That gives an overall increase of 3.2*0.144 deg C from 1979-2011 i.e. 0.46ºC, which is a pretty good match to the roughly 0.45ºC change in that period in the Hansen figure. Of course there is uncertainty in the trends (both from fitting the OLS line, +/-0.6ºC, and structurally, since RSS has slightly different numbers), and there is no expectation that TLT and surface air temperature should have identical trends (overall, TLT should be increasing a little faster than SAT – but this is also subject to noise over relatively short periods). Overall, I see no way in which either Geert or Fallows are guilty of ‘cherry-picking’ or that there is any biased presentation here. There was a prediction of surface air temperatures and the comparison was made against that same metric for the entirety of the period predicted. A much better critique would examine questions of the net forcing used in the 1981 paper versus what really happened – but that gets complicated quickly because of the uncertain changes in aerosol. – gavin]

  25. 75

    #73–“Just address their arguments and if anyone says “They’re astronauts”, you say, “So what” and turn back to the arguments. Now that’s science.”

    Yes, but in any scholarly pursuit the only place where arguments can be meaningfully ‘addressed’ is in the professional literature. That’s the case primarily in order that all contributions to the ‘conversation’ can be readily ‘found’ and so taken into account. (Secondarily, it’s to weed out arguments that aren’t up to snuff–this may sound like elitism, but it’s very important because the rates at which new knowledge is being generated are such that it’s really, really time-consuming to keep up, and there really aren’t enough hours to waste on junk. Preferentially presenting the best work is a service that journals do (or at least, should) provide their readers.)

    It’s in that sense that Ray says “You don’t publish, you don’t get to play,” not the sense you seem to take from it–ie., that because somebody says something in an ‘out of bounds’ place, one should arbitrarily cut off consideration of their point of view.

    Of course ‘side conversations’ are possible; in this sense all of RC is ‘side conversation.’ But if you want to ‘play’ at scholarship–whether it’s climate science, comparative literature, pitch-class set theory or what have you–the only places to do that are in the journals that collectively form the relevant professional literature. That’s where the scholarly ‘game’ takes place.

    So when the ’49’ chose to publish where they did, they were choosing not to ‘play climate science.’ Instead, they were playing politics.

  26. 76

    #74–“(There are no deniers of quantum physics that I know of.)”

    You’d be surprised, Walt; I could name one vociferous commenter on a prominent Canadian news site who is just that. In addition to climate change and quantum physics denial, he also contests that HIV causes AIDS, (IIRC) the Big Bang, and the utility of OLS for calculating trends.

    Yes, he’s deeply ignorant–an ignorance directly proportional to his cock-sureness. (Cf., Dunning-Kruger.)

    But he can be convincing for the unwary, because he doesn’t superficially sound ‘stupid’ or ‘illiterate’ unless you already know a bit about the subject.

  27. 77
    Dan H. says:

    I think deny is the wrong choice of word here. There are astrophysicists who disagree with the Big Bange theory(Fred Hoyle comes to mind), but denial gives the impressions that they are closing their mind to the truth, as opposed to having other ideas. BTW, Einstein disagreed with the quantum physics theory.

    In reference to your Canadian, you might want to add that his hot air is increasing faster than the atmospheric changes due to CO2.

  28. 78
    dhogaza says:

    From an interested layperson: the complexity and opacity of contemporary climate models cause me to be skeptical of the anthropogenic hypothesis.

    Were you also skeptical of the Boeing 787 before it was built and flown? The models used to develop it (skilled enough that Boeing built the simulator to train the test pilots long before the plane was built, and skilled enough that when the plane was finally flown, the pilots found virtually no difference between the real plane and the pre-built simulator) are easily as opaque as climate models.

    And, of course, you’re stating a strawman in the first place, climate models help with the understanding of various details of climatology, but the basic understanding that CO2 is a GHG, that warming temps increases the absolute humidity leading to a positive feedback, etc etc would stand even if the complex climate models you disparage didn’t exist.

    And lastly, you’re arguing from personal ignorance – you’re not capable of understanding the models, therefore you’re skeptical.

  29. 79
    Ray Ladbury says:

    Walt Finerman,
    Anyone is welcome to learn about climate science,just as anyone is welcome to watch pro football on television or in the stands. However, should you decide to suit up for a game, I think your career would be brief, painful and followed by surgery and a long recuperation.

    Climate scientists study for decades before they contribute significantly to the field. It is simply silly to assume your opinion will contribute anything to the understanding of a complex technical field unless you devote your life to understanding it.

  30. 80
  31. 81

    #77–Dan, trust me–“deny” is precisely the right word. And as far as I can tell, his ‘hot air’ is pretty much steady-state (speaking of Fred Hoyle.)

  32. 82
    Walt Finerman says:

    dhogaza @78:
    I find your comparison between climate models and aerodynamic flight simulations deeply misleading. (1) The fundamental physics of flight and aerodynamics is understood to a vastly, incomparably larger extent than climate dynamics. (2) The leap from first principles (e.g., Navier-Stokes) through to a full-fledged flight simulation is really not a great conceptual leap. Completely new, important mechanisms significantly affecting flight are not discovered very often. That doesn’t seem to be the case in climate science: there is a gigantic gap between first principles and the climate modeling equations, and rather fundamental new mechanisms are being discovered every decade or two it seems. This suggests the models may still be incomplete. (3) It is much easier to validate aerodynamic models: experiments can be performed, parameters tweaked and responses noted and compared to predicted behavior. None of this is possible with planetary climate. (4) The learning feedback loop is much, much shorter with aerodynamics: experimental results confirming or refuting a model’s accuracy are available within a few months to a few years. With climate science, most predictions will take decades to validate with much certainty. (5) Even with the relatively simple dynamics of flight (simple compared to climatology), enormous and catastrophic simulation failures are certainly not uncommon:

    Oh, and I am not “disparaging” climate models. I am skeptical. There’s a big difference.

    And as for the comment about “arguing from ignorance”: do not make your statements personal. It makes you look weak and as if you have a hidden agenda based on emotion. I may not know all the specific details of climate models, but the basic ideas are quite clear. Also, I’ve had a lot of experience with simulations and complex statistical analysis in other contexts. The experience taught me to be very skeptical of very complex simulations. Parameter tweaking and seemingly innocuous tweaks of dynamics can have profound impacts on simulation outcomes.

    Do not take my skepticism personally. If I had to put a probability on it, I’d say the “climate scare mongers” (probably such as yourself) are essentially right with probability ~70%. That’s mainly based on two things: (1) the fundamental plausibility of their assertions based directly on first principles (rather than complex climate models) and (2) the mainstream climatologic opinion does not seem to have varied much in 20-30 years.

  33. 83
    Walt Finerman says:

    Gavin @74: I’ve looked more closely at Pielke’s critique. I agree with your comment, and I have to say, I’m a little amazed that Pielke would have made that critique in the first place. As with most things I have encountered in climate science, even the esoteric, really-super-big-brain-required-to-understand stuff turns out to be pretty darn elementary. I’d only add: Pielke compares the +0.11 C UAH figure for the temperature anomaly above 30 year average observed in March 2012 with Hansen’s (1981) prediction of ~+0.5 C change over the whole 30 years. The first figure is departure from a mean, the second is expected difference between the start and end points. The later should be roughly twice the former for a linearly increasing time series. So Pielke should really be comparing ~0.22 C with ~0.5 C. And as you say, that ~0.22 C is just one noisy data point in a rather noisy time series that proves very, very little.

  34. 84
    Ray Ladbury says:

    Walt Finerman says: “(1) The fundamental physics of flight and aerodynamics is understood to a vastly, incomparably larger extent than climate dynamics.”

    This is utter bullshit–as one might guess by the piling on of adjectives. They physics of climate change is pretty fundamental as well. It is basically conservation of energy and molecular/electomagnetic interactions. Yes, there are subtleties, but what we do not know does not invalidate what we do.

    Walt: ” there is a gigantic gap between first principles and the climate modeling equations, and rather fundamental new mechanisms are being discovered every decade or two it seems. This suggests the models may still be incomplete.”

    Again, bullshit. Where are you getting this crap? Global Circulation Models are first-principles, physics driven models. New mechanisms, huh? Care to name one?

    Walt: ” It is much easier to validate aerodynamic models.

    Wrong. It takes a while to do so is all. However, you also have millions of years of climate data the models must explain–that is a pretty strong test. You have the occasional volcanic eruption–every one of which is different.

    As to the rest of your screed, all I can suggest is that “argument from ignorance” is a perfect description. You do not know of the validation studies that have been done, so you assume they don’t exist. I suggest you read the following and the references therein:

    Walt, ignorance is not a sin. This is not your day job. It isn’t a simple field. Everything now depends on how you respond to criticisms of ignorance. You can actually look at what people have said, read the resources they’ve supplied and learn, or you can become a Dunning-Kruger Jedi.

    All of us started out there. I have a PhD in physics and had to work about 2-3 years before I really felt comfortable with even the basics.

  35. 85
    jdey123 says:

    I think RealClimate would be best advised to pull this article. If the author actually bothered to read the paper rather than fixating on a single graph, he’d understand that Hansen acknowledges a huge number of unknowns at the time. The reason why the term Synfuels is used because Hansen assumed that oil and gas would rapidly become uneconomic to produce and would be replaced by synthetic equivalents. Hansen also includes a graph showing that the capacity of the ocean to absorb increased heat was unknown, as indeed it remains unknown at this time. Hansen also makes the claim in this paper that the CO2 signal will have overcome all natural variability factors by the 1990s, whereas natural variability is still trotted out by warmists including Hansen himself as the reason why global temperatures haven’t appeared to have increased significantly since 1998. The author of this article needs to at the very least provide a graph showing a comparison between actual growth in energy usage since 1980 and the scenarios that Hansen provided, so we can see which line on the graph we’re supposed to be comparing observed temperature with.

    Really, this paper provides a whole arsenal of evidence to tear the credibility of climatologists apart. Hansen has never associated himself to this paper, but his 1988 model is compared on an annual basis by his co-author on a number of papers Dr Sato of Columbia university, a link to which can be found from Hansen’s GISS website (see page 2).

  36. 86
    Hank Roberts says:

    > author of this article needs to at the very least provide ….
    International and United States Total Primary Energy Consumption, Energy Intensity, and Related-Data Tables