Remembering Hansen’s Congressional Testimony


…there is only a 1 percent chance of an accidental warming of this magnitude….[T]he greenhouse effect has been detected, and it is changing our climate now.

James Hansen, 23 June 1988


With the Greenhouse scare turning thirty this summer, we remember the Congressional testimony that launched it in the USA.

Thirty years ago, on 23 June 1988, James Hansen testified to a Congressional committee that anthropogenic global warming has been detected—he claimed a 99% statistical certainty that greenhouse warming is happening now. Later, surrounded by reporters, Hansen urged an immediate policy response, thereby launching the greenhouse warming scare in the United States.


James Hansen testifying to the US Senate Committee on Energy and Natural Resources, June 23, 1988.

James Hansen testifying to the US Senate Committee on Energy and Natural Resources, 23 June 1988

The committee hearings were called to promote a climate bill introduced by the Democrats and to promote responses to the greenhouse threat in the environmental policy platform of the Dukakis presidential campaign. There had been a number of previous attempts to promote the issue at Congressional hearings—particularly persistent was Al Gore—so it does pay to ask why this one was so spectacularly successful.

Bold claims by a scientist

Global Temperature Trend, Testimony, James Hansen, 23 June, 1988

Click to enlarge and notice how the running 5-year mean climbs through 1987 and then seems to continue steeply up to a point for the first five months of 1988.

Undoubtedly important was the strength and confidence of the claims Hansen made under solemn oath. Where previously scientists were guarded and qualified and they avoided policy advice, Hansen made a strong and confident ‘detection’ claim followed by an unreserved call for action.

Hansen backed up his detection claim with startling new evidence. Already in April he had published a new graph of the global temperature trend, which showed how the recent warming had shot past the late-1930s peak. In that paper he quoted the 99% confidence level (i.e., that 1987 is abnormally warm at 3 standard deviations from the 1951-80 mean) but rejected any ‘causal connection’ with ‘the greenhouse effect’. In his testimony Hansen extended the graph by including incomplete trend data for 1988 (collected up to the previous month). This suggested that 1988 will be warmer than ever, and its inclusion created a striking visual effect. The 5-year running mean seems to continue on a steep rise into 1988 so that it looked like the line is about to burst through the top of the graph. (See testimony here.)

Extreme weather

Weather also played a part in the success of Hansen’s performance. The hearing followed a warm spring and a widely reported drought, which would continue through that long hot North American summer. In Washington summer opened with a stifling heatwave. The day before the hearing the thermometer topped 100o F and the following day was not much cooler. The 22nd of June 1988 was the warmest 22nd of June on record. The day of the hearing also set the record for the 23rd of June.

False claims of human intervention

Human intervention had accentuated the influence of the weather conditions in the crowded meeting room. At least, that claim was made on the good authority, but it has since been withdrawn.

The senator presiding over the hearing was Tim Wirth. In 2007 he told an interviewer how they had purposefully scheduled the hearing for a date that the Weather Service told them is likely to be the hottest day of summer. Then, the night before, they opened all the windows of the hearing room so that the air-conditioning would not be able to cope. With all the TV lights warming the room, this meant that ‘the wonderful Jim Hansen’, was ‘wiping his brow’ when he gave his ‘remarkable testimony’.

When skeptics first heard this story they were amazed as much at the audacity of  the stratagem as at the boldness of this admission. Nevertheless, the story was accepted and widely repeated on the authority of Senator Wirth. This writer certainly accepted it and repeated it, even while holding reservations on two points. One was that the third day of summer is unlikely to be its statistical peak. The other was that the video footage in the news reports do not show Hansen or anyone else mopping sweat, or, indeed, noticeably uncomfortable with excessive perspiration. A recent fact check by The Washington Post has challenged every part of the story. Wirth himself even withdrew the claim about the opening of the windows and excused himself for repeating a boastful mythology. So, while the hot weather certainly served to fortify Hansen’s message, it now seems this was mostly fortuitous, with no one giving it a helping hand.

The response of the research community

The media and public response to the Hansen testimony is widely known, but not so the response of the research community. The overwhelming reaction was outrage and condemnation of the detection claim.

'Hansen vs. the World on the Greenhouse Threat' by Richard Kerr, Science; 2 June 1989, p. 1041

Tremendous hostility was directed towards James Hansen following his testimony. An article in Science by Richard Kerr reveals the acrimony that persisted one year later [2 June 1989, p. 1041].

Consider only the reported response of two scientist who were then drafting the ‘detection’ chapter of the IPCC report, Tom Wigley and Tim Barnett. Of Hansen’s 99% certainty on detection, Wigley said that all Hansen had shown was that there had been some recent warming. Exceptional though this warming might be, Hansen’s crude statistical method had not established ‘attribution’—as Hansen himself had said in his scientific paper, natural causation had not been ruled out. The problem of establishing long-range background natural variability was something that Tim Barnett was always keen to emphasis. In response to Hansen’s detection claim, he is quoted saying:

The [natural] variability of climate from decade to decade is monstrous. . .To say that we’ve seen the greenhouse signal is ridiculous. It’s going to be a difficult problem.

Hansen’s grandstanding in Washington made him a pariah among researchers, and his alienation was only exacerbated by avoidance of forums for discussion and debate. Yet there is no doubt about one positive effect of Hansen’s intervention: with fears abroad of dangerous climate change, long sought funding for climate-related research would now surely flow. Thus, a moral conflict arose among scientists—Does the end justify the means?—and this explains many of the varied responses to Hansen, from public condemnation to quiet grudging support.

A few months after Hansen’s testimony, an extended article in Discover magazine gave a taste of the conflict it had provoked in the US research community. One quoted scientist-activist summed it up well, if in his own terms. On the one hand, Stephen Schneider said, scientists are ‘ethically bound…to tell the truth, the whole truth, and nothing but [the truth]’, which means scientists should include ‘all doubts, the caveats, the “ifs”, “ands” and “buts”’. Yet, this would not win ‘broad-based support’. And so, on the other hand, to ‘capture the public imagination’ with ‘loads of media coverage’, scientists must ‘offer up scary scenarios, make simplified, dramatic statements, and make little mention of any doubts we might have’.

For Schneider, this broad-based support is required ‘to reduce the risk of potentially disastrous climate change’. But, of course, however so much one considered this risk real, still the same distortions, omissions and exaggerations would generate and maintain climate research funding. To point out this fact is often taken as little more than the portraying of scientists as motivated solely by greed. But can we blame scientists for wanting to do their science while avoiding the politics that permits them to do so? Moreover, for a scientist to publicly question the likes of Hansen’s ‘dramatic statements’ was for them to risk not only their own job but the careers of their students and peers.

There are many ways to understand the resilience of the warming scare. But the great career cost to any scientist who dares to speak out against it does go a long way towards explaining why the myth of its science has persisted across the thirty years since Hansen made his stand.

For more detail and comprehensive referencing see Searching for the catastrophe signal. Next week we remember the conference in Toronto that launched the greenhouse scare on the global stage.

2 thoughts on “Remembering Hansen’s Congressional Testimony

  1. Three decades of rancorous handwavium debate over evidence for and the physics behind the Radiative Greenhouse House Effect and man-caused climate change, aka CAGW.

    What a waste since none of it is real.

    The earth being 33 C warmer with an atmosphere is based on the difference between two completely unrelated made up numbers: 288 K, a wild ass guess pulled straight out of WMO’s butt and 255 K, a theoretical S-B BB ideal calculation for the 240 W/m^2 Long Wave Infrared Radiation leaving the top of the atmosphere.

    Furthermore, the lunar studies by Volokin/Nikolov and Kramm clearly conclude that without an atmosphere the earth would be much like the moon, a barren rock with the lit/hot side maybe 390 K, the dark/cold side maybe 150 K and not even colder by 33 C.

    The LWIR up/down/”back” GHG energy warming loop is a theoretical S-B BB ideal baseline calculation for any surface at 288 K and likewise not real. Contiguous participating media, i.e. atmospheric molecules, render impossible any BB emission from the surface.

    No 33 C warmer + No GHG energy loop = No RGHE & No CAGW.

    Am I wrong?
    Always possible – for all of us.
    ’cause if I’m not wrong decades of research, “evidence,” publications and billions of dollars goes straight in the dumper and the entire trillion dollar global climate change industry is suddenly unemployed.

  2. Bernie, thanks for the painstaking research necessary to explain how the idea of, ‘warming caused by man’, came to so dominate the minds of the liberal intelligentsia in western democracies. You provide a thoroughly credible account of the process by which mankind can be led up the garden path by a small group of enthusiastic and self seeking individuals in love with an idea.

    Adolph Hitler and James Hansen………. what charisma..

    Without ‘the observation necessary to the scientific method’, or in other words ‘history’, we are doomed to repeat the same mistakes.. ‘Insanity’ is very much part of the human condition.

    The most cursory examination of how the globe warms and cools by location, according to latitude and season indicates that natural processes are at work. The ‘warming caused by man’, since the composition of the atmosphere is invariable, should impact all latitudes across all seasons and show evidence of a relentless increase. In fact the entire southern hemisphere has not warmed in the month of January over seventy years, about the length of time for which we have an admittably sketchy record of the Earths climate.

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