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Apr 12, 2012

Global warming projections from 1981 prove tellingly accurate

A seminal article by climate scientists back in 1981 has proved eerily accurate at predicting global temperature rises over the last three decades, with its lead author James Hansen telling Crikey that his early research on global warming "seems to hold up remarkably well".

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A seminal article by climate scientists in 1981 has proved eerily accurate at predicting global temperature rises over the past three decades, with its lead author James Hansen telling Crikey that his early research on global warming “seems to hold up remarkably well”.

Hansen, now one of the world’s leading experts on climate science and the head of the NASA Goddard Institute for Space Studies, was one of seven scientists who wrote the 10-page report in Science in 1981 that examined the impact of increased carbon dioxide in the atmosphere.

The New York Times ran a front-page story on it at the time, noting that “the seven atmospheric scientists predict a global warming of ‘almost unprecedented magnitude’ in the next century.”

Dutch scientists Geert Jan van Oldenborgh and Rein Haarsma recently dug up the old report and compared Hansen et al’s projections of global mean temperatures to the actual temperatures of the past three decades and found the 1981 projections to be surprisingly close.

Here’s the original graph from Science, which projects global mean temperatures until 2100. It also takes in to account the phasing out of coal at different times, since coal is a cheap and plentiful resource and the scientists were aware that use of synthetic fuels or renewable energies would take a while.

Here is Oldenborgh and Haarsma’s graph, which has overlaid Hansen et al’s graph with the data from the past 31 years.

“Given the many uncertainties at the time, notably the role of aerosols, the agreement is very good indeed,” write Oldenborgh and Haarsma at Real Climate. “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).”

Why was it slightly underestimated? “Assumed climate sensitivity to doubled CO2, for our primary simulation then, was 2.8C. We now suggest 3C, so it may have been slightly low,” explained Hansen. “Overall it should be quite accurate, if observed climate forcings are used.”

Hansen told Crikey that he’d made mention of the Science article in his recent TED talk — titled “Why I must speak out about climate change” and he assumes that’s why Oldenborgh and Haarsma investigated it.

Not that the 1981 report was Hansen’s first look at climate models. “I became involved in climate calculations for Earth in the middle 1970s, publishing a paper on the effect of Mount Agung on global temperature in 1978, I believe, and a paper on the effect of several trace gases in 1976, and working on a 3-D climate model, providing results to the famous Charney study in 1979,” he said.

Climate science has developed significantly since 1981, says Australian palo-climate scientist Andrew Glikson from the Australian National University. These include a clearer understand of the role of the oceans and the magnitude of their feedbacks, the role of aerosols, projecting tipping points, the connection between climate change and extreme weather events, the study of ice cores and the development of paleoclimate science.

“An awful lot has been learnt since then but the principles and projections of the system have been determined quite accurately by Hansen and his group,” Glikson told Crikey.

Hansen has been an outspoken member of the climate science community for many years, and has even been arrested several times for his involvement in environmental protests. His activist attitudes have come under attack from his own NASA colleagues in recent days. A letter released overnight, signed by 49 former NASA scientists and astronauts, criticises NASA’s public crusading on climate change. The letter was sent late last month to NASA administrator Charles Bolden. It reads in part:

“We believe the claims by NASA and GISS, that man-made carbon dioxide is having a catastrophic impact on global climate change are not substantiated, especially when considering thousands of years of empirical data. With hundreds of well-known climate scientists and tens of thousands of other scientists publicly declaring their disbelief in the catastrophic forecasts, coming particularly from the GISS leadership, it is clear that the science is NOT settled.

“The unbridled advocacy of CO2 being the major cause of climate change is unbecoming of NASA’s history of making an objective assessment of all available scientific data prior to making decisions or public statements.”

But Glikson said he did not recognise any of the 49 names from the list as climate scientists and instead said most appeared to be astronauts, engineers and various technical specialists, and therefore from a scientific point of view their arguments were not based in peer review-based science.

He did note however that astronauts are powerful public figures and he expected that media outlets would pick up the story.

The final lines from Hansen et al’s 1981 research seem particularly prophetic:

“Political and economic forces affecting energy use and fuel choice make it unlikely that the CO2 issue will have a major impact on energy policies until convincing observations of the global warming are in hand. In light of historical evidence that it takes several decades to complete a major change in fuel use, this makes large climate change almost inevitable. However, the degree of warming will depend strongly on the energy growth rate and choice of fuels for the next century. Thus, CO2 effects on climate may make full exploitation of coal resources undesirable. An appropriate strategy may be to encourage energy conservation and develop alternative energy sources, while using fossil fuels as necessary during the next few decades.

“The climate change induced by anthropogenic release of CO2 is likely to be the most fascinating global geophysical experiment that man will ever conduct. The scientific task is to help determine the nature of future climatic effects as early as possible. The required efforts in global observations and climate analysis are challenging, but the benefits from improved understanding of climate will surely warrant the work invested.”

Crikey asked Hansen how he felt that despite all the “convincing observations of the global warming” from scientists in the last 30 years, there has been little impact on major global energy policies.

“We assumed that governments would act in the best interests of the public. So far they have acted in the best interests of the fossil fuel industry,” he replied. “Money talks in Washington and other capitals, and, unfortunately, the people profiting from business-as-usual have the money.”

Amber Jamieson —

Amber Jamieson

Freelance journalist in New York

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32 thoughts on “Global warming projections from 1981 prove tellingly accurate

  1. Fran Barlow

    Ebanks Sen


    Let’s see if there’s a single sentence without an error or meaningless claim above:

    [While the Nostradami are being typically self congratulatory for spraying wild predictions around, ignoring the 99% that crashed and burned …]

    No wild predictions are cited. That’s just as well because then we could discuss whether they are in fact “wild”. The then (unspecified) “wild predictions are compared with an equally unspecified “99%” that “crashed and burned”. With no specification for either data pool, the calim is meaningless and it would be right to ignore them. For all we know, Ebanks Sen is talking about people betting on horses or declaring the end of the world or predicting that global warming will turn out to be a scam.

    [and claiming Messianic status for those that survived reality tests]

    Predictions can’t be “messiahs” or annointed by god. This is just a lead into denier projection. Deniers are largely religious and are offended by truth claims based on science. Since they are religious they iterate scientific truth claims as an alternative religion and thus blasphemy — but because that would give the game away amongst secfular fiolk they accuse it of being a religion or flath. Classic and hypocritical projection!

    [remind you that the NASA Prophet of doom Hansen was proselytizing for grant money in the ’70′s for the onrushing anthropogenic global ICE AGE!]

    This is another old troll as even a cursory reading of the link will reveal. Hansen said nothing there that wasn’t defensible. had aersols continued to rise at the rate he hypothesised it might well have been the case that cooling would have continued. It didn’t of course and by the late 1970s better measures of Charney sensitivity were available to Hansen changing his views. Did this mean that reserarch into the impact of aerosols on climate was unwarranted? Not at all. On the contrary, if there was a plausible possibility of any disruption to basic ecosystem services on a large scale then grant money would have been called for. It’s absolutely risible for deniers to claim that “the science isn’t settled” and to scream that “science should question assumptions” and then claim that research should not be undertaken to prove or disprove a hypothesis merely on the basis of what one thinks one might find. Actually, it’s not merely risible, but damning of them — for it shows that they don’t even think through the consequences of their talking points but merely grasp at anything that some barely literate dimwit might think casts science they don’t like in a poor light.

    [I don’t actually expect any of the self-anointed (sic) … to read anything that contradicts their articles of faith.]

    Ah the projection again … As noted though, the link doesn’t contradict anything of interest to science. I did read it and it revelaed the poster to be a dimwit. One needs no more than basic literacy to see that. Faith is optional.

    [What I do expect is the same sort of ad hominem attacks]

    The deniers discovered a while back that using Latin-style phrases sounds impressive — at least to them. Sciencey people love latin precisely because your average illiterate — their main audience — doesn’t understand it and is copwed. A bit of post coc ergo propter hoc and ex nihilo nil fit or mutatis mutandum and people reckon you must be an intellect. Ad hominem here is merely being used as a synonym for abuse of vituperation. That’s quite wrong. Argumenta ad hominem are objections based on the character or standing of the person to make a claim. A judge who has a conflict of interest in ruling a case may be objected to, and thatb would be ad hominem but legitimate. Ebanks sen tried it himself when claiming that Hansen’s speculation on a potential ice age driven by aerosols such as SO2 precluded him from later claiming CO2-driven warming. Presumably, (s)he thought this argumentum ad hominem was legitimate. That it was absurd on the face of it was neither here nor there.

    [claims that we know so *very* much more now than we did then]

    That’s not an argumentum ad hominem. That’s a statement of observable reality. If this chap weren’t a buffoon, he’d realise he needed to refute it to begin to make his ad hominem claim against Hansen.

    [Science is *never* “settled.” ]

    No, but the reverse {science is impossible} doesn’t follow. Insight is provisional and with careful corroboration or refinement we can derive useful information about the world. We know as the saying goes that all models are wrong (or at least ought be deemed so) — but some are useful. Hansen’s model above turned out to be inaccurate, but it was also very useful because it showed that his methodology was sound as it closely represented observed reality in advance.

    Taken to its logical extreme, in the mouths of deniers, the mantra “the science is never settled” is an argument for intellectual nihilism and as the Latin goes ex nihilo nil fit — nothing can come from nothing. If they really believe that, they ought to remain silent because they can make no claims at all. There could be no “real science”. Every sceintist climbs onto the shoulders of those who have gone before, flawed as they were and strengthens science in the process.

    So as it turns out there was no line in ebanks sen that was not incorrect and as a corpus, it was also internally incoherent.

    Nice …

  2. Ebanks Sen

    While the Nostradami are being typically self congratulatory for spraying wild predictions around, ignoring the 99% that crashed and burned, and claiming Messianic status for the couple that survived reality tests, may I remind you that the NASA Prophet of doom Hansen was proselytizing for grant money in the ’70’s for the onrushing anthropogenic global ICE AGE!


    Of course, I don’t actually expect any of the self-anointed to read anything that contradicts their articles of faith. What I do expect is the same sort of ad hominem attacks, claims that we know so *very* much more now than we did then and the standard appeal, “Everyone else is doing it!”

    Science is *never* “settled.” Real science is *always skeptical of its own results, always challenging it’s own assumptions. Only religion takes the personal pronouncements of fallible humans and claims they are direct statements of Truth, correct and invariate.

  3. Michael Wilbur-Ham (MWH)


    You hit the nail on the head with saying that the tipping points all have lots of uncertainty involved. That is why they have not been included in the IPCC reports.

    The problem is that just because they are uncertain does not mean that they will not happen. And if one or more do happen then things are likely to be much worse than the IPCC predict.

    Now if I were to make you wear earplugs and a blindfold, and take you to a busy road, and ask you to cross it, what happens next is clearly very uncertain. There is a chance that you will get across the road with no injury. Does this mean that you think it is safe to cross a road this way? Ignoring the dangers of tipping points due to uncertainty is as silly as ignoring the very real risks involved in crossing a road without vision and hearing.

    Both you and Frank also ignore my main point that by the time the evidence is good enough to convince you both that it will be far too late to prevent significant warming.

    If you ask a creationist what scientific evidence is needed to convince them that evolution is true you will find, that even though they have been discussing how science proves that evolution is false, when it comes down to it they will admit that nothing will convince them that their interpretation of the bible is wrong.

    Similarly the reason that I feel justified to call those on Crikey who post against climate change ‘deniers’ is that if climate change were true, nothing would convince them of this until it was far too late.

    We are already at the stage where major action is needed now. So what further science could reasonable be available now to convince the deniers?

  4. Michael Wilbur-Ham (MWH)

    I wonder what the graph will look like in 30 years time?

    Unless there is some major world wide economic collapse, the growth of China and India (which I doubt was fully factored in way back in 1981), and the way that climate change has become a political issue where rational argument makes little difference (as shown by the astronauts letter) and thus real action to prevent climate change is becoming less likely, means that the most likely scenario is now the Fast Growth scenario.

    It is also worth remembering that the 1981 paper, and the IPCC reports, all ignore possible flipping points. If we reach one of these in the next thirty years then things might be much worse than even the predictions of the Fast Growth scenario.

    As Hansen says, we are conducting an experiment on the climate. Certainly in thirty years it will be clear whether it is the deniers or acceptors of climate change that are right.

    Because the deniers do not accept the science, they are also ignoring the reality of what happens if climate change is real and the effects are as bad, or worse, than predicted. I suspect that the deniers all think that if this ends up being the case we can take some action in the future and undo the damage.

    The reality is that the carbon we emit now will be in the atmosphere for hundreds of years. If, for example, in 2030 we suddenly took action and stopped all emissions, the damage will have been done, and though this action will stop things from getting even worse, the high temperatures will be locked in.

    And if we reach a tipping point, once again when the deniers accept that something bad has happened, I don’t think that the yet realize that once one (or more) of these tipping points is reached that once again there is nothing that can be done.

    It is all very sad.

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