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Thursday, 2 October 2014

John Cook in Bristol: The consensus gap

As a biologist, the fact that anthropogenic climate change is occurring has been explained to me throughout my education. We are interested in how crops might respond to global warming or what might happen to bees or coral reefs, not the basic question of whether or not it is happening at all.  So that is why I was keen to attend John Cook’s talk at the Cabot Institute and learn a bit more about climate science and how it is perceived both within and outside the climate change science community

John Cook is the Climate Communication Fellow for the Global Change Institute at the University of Queensland, Australia. He runs the popular Skeptical Science blog, with the aim of explaining the scientific consensus on global warming. As he pointed out, his website has received a lot of criticism from people who do not agree that climate change is significantly driven by human effects.

The climate consensus

97% of climate scientists agree that humans are responsible
 for climate change. Image credit: Skeptical Science 
Several studies, including John’s own (Cook et al., 2013), have shown that 97% of climate scientists agree that humans are significantly contributing to global warming. Doran and Zimmermann (2009) asked earth and climate scientists whether they thought that humans are significantly impacting global climate change and found that 97.4% agreed we are, while Anderegg and colleagues (2010) found that 97-98% of climate scientists agreed with the Intergovernmental Panel on Climate Change finding that anthropogenic greenhouse gases have been responsible for most of the Earth’s global warming.

Public perception of consensus

John described how the public does not seem to realise the extent of scientific agreement. When asked to estimate “how many climate experts agree that the global warming we are witnessing is a direct consequence of the burning of fossil fuels by humans”, the average response was 55%, a marked underestimate of the 97% consensus.

John is working to improve public understanding of
the scientific consensus around global climate change.
Image credit: Skeptical Science 
John showed a video from comedian John Oliver, who insisted that the only reason there was still an ongoing debate about climate change is because it is always portrayed with an “inherently misleading” 50:50 divide in representation. He goes on to hold a “mathematically fair” debate with three sceptics and 97 climate scientists, which ends with the immortal line, “I can’t hear you over the weight of scientific evidence”.

John Cook tried to bridge the consensus gap with a more balanced approach in his latest project, entitled “97 hours of consensus”. A total of 97 experts were asked to address the topic of humans causing global warming. Cabot’s own director, Professor Rich Pancost, was one of the scientists included.
Cabot Institute Director Professor Rich Pancost was a featured
climate expert in the 97 Hours of Consensus project.
Image credit: Skeptical Science 
John said that there is a lot of misinformation out there, causing confusion for the public who put their trust in scientific experts. He highlighted one particular website, the Global Warming Petition Project, which as of today [10 February 2014] had been signed by 31,487 American scientists urging their government to reject any limits on greenhouse gas emissions. As John pointed out, only 39 of these people are actually climatologists, therefore 99.9% of them are simply people with science degrees. As I mentioned earlier, I’m a biologist, but that doesn’t give me the expertise needed to decide whether anthropogenic climate change is occurring or what the causes are. I leave that to the experts. Instead, I focus my intellectual energy on ecosystems and how global warming (and other factors) will affect them.

Dr. Tamsin Edwards is a climate scientist who actively engages with people who differ in their opinions on what the science shows. In her blog, she states, “We can’t avoid scientific uncertainty, because we can’t perfectly measure or understand the universe. So we need to be very clear about what we know, what we don’t know, and the surprises we might face”. It can be tempting to avoid discussing difficult topics, but Tamsin inspires me (and hopefully her fellow climate scientists) to explain the science behind the conclusions and hopefully enable the public to make informed decisions too.

Do we need to close the consensus gap?

John said that he fears that if people don’t realise there is 97% scientific consensus about anthropogenic climate change, they won’t accept that it is happening and/or care enough to do anything about it. In the video abstract for his 2013 paper, John states that, “This misperception has real world consequences. When people correctly understand that the scientists agree, they are more likely to support policy that mitigates climate change”.

In the UK, several polls over the past five years have looked at what people consider the main cause of global climate change. Where two options (humans versus natural causes) were given, 43-71% of respondents chose humans as the main driver of global warming. These results were diluted when a third option (both human and natural causes) was given, however it is encouraging to note that only around 10-15% blamed natural processes alone.

Carbon Brief compared UK participants’ opinions on what
causes climate change. Image credit: Carbon Brief
The weekend following John’s talk was a perfect example of a possible change in public opinion of climate change globally. Hundreds of thousands of people marched in cities across the world in the People’s Climate March, including a couple thousand locally in Bristol.  This was the largest climate march in history. The biggest turnout was in New York, where over 300,000 people called for action from the UN climate summit, which convened in the city on Tuesday 23 September 2014. UN Secretary General Ban Ki-moon marched with the crowd, an unusual move highlighting the importance of the event. He said, “Action on climate change is urgent. The more we delay, the more we will pay in lives and in money”.

I think Joel Pett’s cartoon sums up my thoughts pretty well on the subject of climate change... 

This blog is written by Sarah JoseCabot Institute, Biological Sciences, University of Bristol
Sarah Jose


  1. @Sarah
    You may want to poke about at bit to see whether Cook's claims really stand up. Dan Kahan's work, for instance, contradicts much of what he says, and Cook's analyses are not uncontested.

    Your final cartoon suggests you may want to have a read of Tinbergen (the brother). These things may be worthwhile, but is climate policy really the best way to achieve them?

  2. Sarah

    Does the repeated appearance of the magic number 97 not ring any alarm bells for someone with scientific training?

    Opinion polls of various groups of people, for political or sociological research, routinely come up with with a fairly wide spread of results - even for similar groups presented with identical propositions.

    The idea that several studies of different groups of scientists, carried out at different times would produce an identical result to one significant figure is frankly preposterous.

    The endless PR activities of Cooks activist group, intended to push the number 97 into public consciousness, should also make it obvious to an objective observer that they are being exposed to a fairly crude marketing exercise.

    Additionally, the whole idea of choosing members of an activist group to rate data from the subject area of their activism is pure scientific nonsense - as social scientist Jose Duarte makes eloquently clear in this blog:-

    I think the take-home message for anyone tempted to believe any "climate science" including the magic number 97 is best expressed by the original 17th century motto of the Royal Society - "Nullius in Verbia".

  3. Sarah
    Good blog. Looking at the numbers differently, the different surveys suggest that between 2 and 3% of climate scientists don't think that humans are contributing to climate change - a spread of 50%. Given our knowledge of the physics of radiation transmission through gas, it is implausible that we could double the amount of CO2 in the atmosphere (at current levels) without messing with the earth's radiation balance - and given the risks and uncertainties it is not an experiment that any ethics committee would allow you to conduct! So the "consensus gap" is a big problem if it prevents us having a proper discussion about appropriate mitigation and adaptation measures - which as Ban Ki Moon correctly says, will cost more the longer they are delayed.

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