Review of influential 2013 paper that produced ‘97%’ figure reaches same conclusion: which the authors say shows “consensus on consensus”
By Alex Pashley
Over nine out of ten relevant scientists believe human activity is warming the planet, a new review of multiple studies confirmed on Tuesday.
The findings reach the same conclusion as a widely-cited 97% figure from a 2013 study compiled by the University of Queensland’s John Cook, who was involved in the new study.
“We have shown that the scientific consensus on [anthropogenic global warming] is robust, with a range of 90–100% depending on the exact question, timing and sampling methodology,” say the authors in the journal Environmental Research Letters.
Cook said the outcome was “not unexpected” because the level of consensus is related to the level of expertise scientists have in climate science.
The level of scientific consensus is deemed critical, influencing the public’s perception of climate change and their desire to embrace policies to curb emissions.
Last December 195 countries signed a UN-backed pact to curb greenhouse gas emissions in recognition of the threat.
The original 2013 study analysed the abstracts of around 12,000 peer-reviewed papers between 1991-2011. From the 4,000 abstracts stating a position on climate change it judged 97.1% to endorse the consensus of human-caused climate change.
That finding was disputed by Sussex University economist Richard Tol, who released research claiming that as few as 7% of scientists believed humans cause climate change, contesting Cook’s sample size and methods of people determining consensus.
“Cook’s 97% nonsensus paper shows that the climate community still has a long way to go in weeding out bad research and bad behaviour,” he wrote in a 2015 blog post.
“If you want to believe that climate researchers are incompetent, biased and secretive, Cook’s paper is an excellent case in point.”
The latest study directly tackles this claim, and accuses Tol of misrepresenting the results by citing non-experts and determining non-affirmation to be dissent.
“Tol (2016) obtains lower consensus estimates through a flawed methodology, for example by conflating nonexpert and expert views, and/or making unsupported assumptions about sources that do not specifically state a position about the consensus view,” it says.
When contacted, Tol told Climate Home the new paper “duck[s] my other critiques”.
“As to the consensus on the consensus, if you carefully pick results from the various studies, then you see agreement. If, on the other hand, you look at all the data, then the various consensus studies strongly disagree with each other,” he said.