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Why we care about the 97% expert consensus on human-caused global warming

Posted on 24 June 2014 by dana1981

Three distinct studies using four different methods have independently shown that the expert consensus on human-caused global warming is 97 ± 1%. The result is the same whether we ask the experts’ opinions, look at their public reports and statements, or examine their peer-reviewed science. Even studies that quibble about the precise percentage have accidentally reinforced the 97 ± 1% consensus.

The evidence is crystal clear that humans are the main cause of the current global warming, and the expert consensus reflects the strength of that body of evidence. It’s not easy to convince 97% of scientific experts about anything – that requires some powerful scientific evidence.

And yet public opinion is a very different story. Americans think experts are evenly split on the causes of global warming. The public is likewise split on the cause of global warming, with just over half understanding that humans are primarily responsible. As a result, Americans don’t see global warming as an urgent issue, putting climate policy low on the list of priorities.

The sources of this disparity and how it can be corrected are the subjects of an intense debate amongst social scientists. One school of thought says that we have a problem with ‘information deficit’ as well as what climate scientist Michael Mann calls ‘misinformation surplus.’

For example, experimental evidence shows that if people are presented with a basic explanation of how global warming works, they’re more likely to accept the reality of human-caused global warming. Other research has shown that if people are told about the expert consensus, they’re also more likely to accept the science. In both cases, presenting people with certain pieces of information trims the gap between what the scientific evidence and experts say, and what the public believes.

The other school of thought, led by Dan Kahan at Yale, argues that the problem boils down to cultural biases. In essence, liberals feel as though they’re on Team ‘global warming is a problem caused by humans’ while conservatives identify with Team ‘no it’s not.’ Kahan feels that people will take any new information and pass it through their cultural filter; if it conforms to their cultural identity, they’ll accept it, or otherwise they’ll just reject it. In fact, Kahan argues that giving people information that doesn’t conform to their cultural identity (like the 97% consensus) may just act to polarize them further.

In a recent editorial for The Guardian, Adam Corner made a similar argument, asking 'who cares about the climate change consensus?'. Corner suggested that climate information is ineffective if it’s not coming from “communicators whose cultural credentials are congruent with the audience they are speaking to.” Both Kahan and Corner have also argued that if consensus messaging could work, then it should have worked by now, whereas American public acceptance of human-caused global warming in 2014 is lower than in 2003.

Gallup poll results on the perceived causes of global warming. Gallup poll results on the perceived causes of global warming.

So if the ‘information deficit’ model is right, why hasn’t consensus messaging led to an increase in public acceptance of the science? Adam Corner identifies the problem in his Guardian piece.

In response, 'merchants of doubt' have tried to muddy the waters by exaggerating scientific uncertainty.

This is the ‘misinformation surplus’ that’s also been in play for several decades. For as long as the expert consensus on human-caused global warming has existed, there’s been a campaign to convince the public that the experts remain divided. This was articulated in a leaked 2002 memo from Republican political strategist Frank Luntz, which said,

“Voters believe that there is no consensus about global warming in the scientific community. Should the public come to believe that the scientific issues are settled, their views about global warming will change accordingly. Therefore, you need to continue to make the lack of scientific certainty a primary issue in the debate, and defer to scientists and other experts in the field.”

We don’t have a second America to use as a control group, but without the consensus messaging that’s happened over the past decade, my guess is that the public would be even more misinformed about global warming than it is now. The problem isn’t consensus messaging itself; the problem is that it’s fighting against a misinformation surplus.

Another key point is that while ‘expert consensus’ is vague, ‘97% expert consensus’ is concrete and memorable (a.k.a. ‘sticky’ messaging). While Naomi Oreskes first identified the consensus on human-caused global warming in the peer-reviewed literature in 2004, the first study to quantify it at 97% came in 2009, reinforced by 97% studies in 2010 and 2013. The above graph shows that the public became increasingly accepting of human-caused global warming during 2010–2014, so perhaps 97% consensus messaging is moving the dial after all.

Most social scientists believe that both information deficit/misinformation surplus and cultural biases contribute to the problem. Research by John Cook supports this idea. He asked a representative sample of Americans across the political spectrum what percentage of scientific experts agree on human-caused global warming.

Not surprisingly, the perceived consensus decreased from left to right across the political spectrum. However, even liberals believed the consensus is below 70%, in stark contrast to the actual 97%. Cook calls this the 'liberal consensus gap.' Cultural filters can't explain it, because liberals are supposed to be on Team ‘global warming is a problem caused by humans.’

These data come from research by John Cook, taken from a survey of a US representative sample (N=200). These data come from research by John Cook, taken from a survey of a US representative sample (N=200).

As the above figure indicates, the difference in perceived consensus between the left and right can be explained by Kahan's preferred cultural bias explanation, but the 'liberal consensus gap' can't. That's due to the information deficit/misinformation surplus. Both factors are partially responsible for public misconceptions about the causes of global warming.

Another team of social scientists from George Mason and Yale Universities explained why the global warming consensus is important in a recent paper,

Click here to read the rest

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Comments 1 to 9:

  1. This is a question for John Cook regarding the graph labelled "These data come from research by John Cook, taken from a survey of a US representative sample (N=200)."

    Could you provide some more background on the research?

    I am particularily interested in how you ascertained the measure of your subjects "Public perception of scientific consensus of climate change".

    Could you tell us how you did this exactly?

    If it was via a questionnaire, could you tell us the form and wording of that questionnaire?


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  2. "[Convincing conservatives that AGW is serious]... can be achieved with informed messages... coming from sources that conservatives can trust."  Think about that: 'that conservatives can trust'.  This clearly does not include scientists.  We need to ask 'why' it doesn't, because this is a serious problem moving forward.  Science denial can doom a nation for a century or more.  Consider Asia between the 18th and 20th centuries.  The truth may be inconvenient, but not as inconvenient as Admiral Perry steaming into Tokyo Harbor, or the indignities that culminated in the Boxer rebellion.  Paulson's article is welcome, but he's a Banker who oversaw the finance system bailout of 2008.  Is he really 'what it takes' for a conservative to change his mind on climate?  For some of us, since 2008, bankers have got credibility issues of their own when speaking on Finance, much less Climate.  

    A deep suspicion of Science has been growing in Western Nations for several decades.  It's conclusions conflict with unrestrained commerce on several fronts, not just on Climate, and a concerted effort undertaken to paint Scientists as untrustworthy. Religion has often been enlisted to support this effort.  We need to keep in mind that Asia learned its lessons of the past, and will gleefully surpass us if we discourage the Science-minded among us.

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  3. This is all very well and of course important, but only underlines how ludicrous it is to quibble about the exact scale of the overwhelming scientific consensus telling us we have to act now to mitigate a terrible risk.

    Sensible people hit the brake before they hit the wall, even when they are unsure what they have seen is a wall. And especially when they have a car full of children. To deliberately undermine attempts to protect against risks at either of these scales is beyond my comprehension.

    Ask these quibblers at what level of consensus they would join the general call for action.

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  4. In New York, Oct. 2-Oct 26, Theater Three Collaborative will be producing a play "Extreme Whether" that tells the story of the attacks on American climate scientists, in an engaging fictional way. Can art help? I'm not so sure.

    It feels more and more to me that Naomi Klein is correct.  The deniers understand that free-market capitalsim may be at stake here, and are perfectly willing to sacrifice a liveable climate for $.

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  5. ubrew12 @#2:

    Paul Krugman's take on Henry Paulson Jr.'s New York Times Op-ed, The Coming Climate Crash is instructive:

    "Given the state of U.S. politics today, climate action is entirely dependent on Democrats, With a Democrat in the White House, we got some movement through executive action; if Democrats eventually regain the House, there could be more. If Paulson believes that he can support Republicans while still pushing for climate action, he’s just delusional."

    The Loneliness of the Non-Crazy Republican by Paul Krugman, Conscience of a Liberal, New York Times, June 22, 2014

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  6. Maybe I'm wrong, but my conservative friends aren't distrustful of science, but rather of scientists, and they have a point. If an intelligent, analytical conservative is more likely to go with his or her crowd, then who is to say that (regardless of political affiliation) scientists wouldn't be victims of their own cultural biases?

    Before you say that scientific method is designed to short-circuit that kind of behavior I recommend reading this article:

    which shows just how easy it is to taint the scientific method with preconceptions — even unconsciously.

    By the way I believe global warming is human-created.

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  7. troyvit...  Don't you think it would be hard to get to a 97% consensus if scientific results were biases along political lines?

    I think what you do find is, when scientists express their opinion outside their specific area of expertise, that opinion is going to be far more influenced by their political views over research.

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  8. troyvit academics have very little to gain by following the crowd, we are generally a rather disagreeable lot that spend our time finding fault with the work of others (and more importantly trying to do better).  To get highly cited papers, you need to find out something that people don't already know, and the best way to do that is to be different.

    The reason that we have a consensus is not because we are all following the crowd, but because reality places constraints on which hypotheses are plausible.  The reason that there is a consensus on, for example that the rise in CO2 is anthropogenic, is not because we all agree with eachother, but because the alternative hypothesis is inconsistent with the observations.  Of course that doesn't mean there are not still some scientists that disagree, and even the occasional one that manages to get something published in a journal, despite it being incorrect.  That is why it is 97% not 100%.

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  9. troyvit @6.

    Your linked item "The Control Group Is Out Of Control" is mainly about parapsychology and the examples it looks at in wider science are still pretty soft psychology (eg social priming) plus the odd reference to pharma research. The argument offered by your linked item is that a subject that is so obviously crackpot like parapsychology must then be subject to much more suspicion, and thus much higher levels of checking, if parapsychology can fail to spot so much unreplicable work, what of other sciences where suspicion and checking would be less? Is it valid to conclude as the item quotes "It just means that the standard statistical methods of science are so weak and flawed as to permit a field of study (parapsychology) to sustain itself in the complete absence of any subject matter."?

    Well, the level of defense in psychology/psychiatry literature appears to be the problem and one that doesn't extend to geosciences & enviro-eco science, as this graphic from a subsequently-linked Nature article illustrates. (The position of Material Sciences second from bottom may be to do with initial results being far more strongly based in such a physical area of study.)

    Nature - accentuate the positive


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