The scientific consensus that humans are altering the climate has passed 99.9%, according to research that strengthens the case for global action at the Cop26 summit in Glasgow.
The degree of scientific certainty about the impact of greenhouse gases is now similar to the level of agreement on evolution and plate tectonics, the authors say, based on a survey of nearly 90,000 climate-related studies. This means there is practically no doubt among experts that burning fossil fuels, such as oil, gas, coal, peat and trees, is heating the planet and causing more extreme weather.
A previous survey in 2013 showed 97% of studies published between 1991 and 2012 supported the idea that human activities are altering Earth’s climate.
This has been updated and expanded by the study by Cornell University that shows the tiny minority of sceptical voices has diminished to almost nothing as evidence mounts of the link between fossil-fuel burning and climate disruption.
The latest survey of peer-reviewed literature published from 2012 to November 2020 was conducted in two stages. First, the researchers examined a random sample of 3,000 studies, in which they found only found four papers that were sceptical that the climate crisis was caused by humans. Second, they searched the full database of 88,125 studies for keywords linked to climate scepticism such as “natural cycles” and “cosmic rays”, which yielded 28 papers, all published in minor journals.
The authors said their study, published on Tuesday in the journal Environmental Research Letters, showed scepticism among experts is now vanishingly small.
“It is really case closed. There is nobody of significance in the scientific community who doubts human-caused climate change,” said the lead author, Mark Lynas, a visiting fellow at Cornell University.
This echoed the view expressed in August by the world’s leading scientific body, the United Nations Intergovernmental Panel on Climate Change, which said: “It is unequivocal that human influence has warmed the atmosphere, ocean and land.”
The general public does not yet understand how certain experts are, nor is it reflected in political debate. This is especially true in the US, where fossil fuel companies have funded a disinformation campaign that falsely suggests the science is not yet settled, similar to the campaign by tobacco industries to cast doubt on the link between smoking and cancer.
The paper cites a 2016 study by the Pew Research Center that found only 27% of US adults believed that “almost all” scientists agreed the climate emergency was caused by human activity.
Many senior Republicans continue to cast doubt on the link between human activity and the climate crisis as market researchers have advised them to do since at least the presidency of George W Bush. According to the Center for American Progress, 30 US senators and 109 representatives “refuse to acknowledge the scientific evidence of human-caused climate change”. Several big media organisations and social networks also promote climate-sceptical views that have little or no basis in science.
Lynas said the study should encourage them to review their policies. “This puts the likes of Facebook and Twitter in a quandary. It is pretty similar to vaccine misinformation; they both lack a basis in science and they both have a destructive impact on society. Social networks that allow climate misinformation to spread need to look at their algorithms and policies or to be forced to do so by regulators.”
Some commentators have challenged the significance of a scientific consensus, saying it is a distraction from more pressing concerns. However, they say it is important for media organisations to avoid giving a false sense of balance by giving equal weight and coverage to for-and-against arguments. Most important, a consensus is seen as vital for a concerted international response to the climate crisis.