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8th November 2021

99.9% of studies agree: humans caused climate change

More than 99.9% of peer-reviewed scientific papers have concluded that climate change is mainly caused by human activity, according to a new survey of 88,125 climate-related studies.


99-9 percent of studies agree humans caused climate change


The research updates a similar 2013 paper that revealed 97% of studies published between 1991 and 2012 supported the idea that human activities are altering Earth's climate. The current survey examines the literature published from 2012 to November 2020 to explore whether the consensus has changed.

"We are virtually certain that the consensus is well over 99% now and that it's pretty much case closed for any meaningful public conversation about the reality of human-caused climate change," said Mark Lynas, a visiting fellow at the Alliance for Science at Cornell University and the paper's first author.

"It is critical to acknowledge the principal role of greenhouse gas emissions, so that we can rapidly mobilise new solutions. We are already witnessing in real time the devastating impacts of climate-related disasters on businesses, people and the economy," said Benjamin Houlton, Dean of the College of Agriculture and Life Sciences at Cornell and a co-author of the study, which appears in the journal Environmental Research Letters.

Despite the near-unanimous view among climate scientists that global warming is the result of human activity, public opinion polls show that this belief is significantly weaker among the general population. Politicians and public representatives have also made it a highly partisan issue in some countries. However, concern about climate change is growing over time. Last year, the Pew Research Center found that 76% of people it surveyed now believe that climate change is a major threat to their country, up from a median average of 55% in 2013.


climate change future timeline


"To understand where a consensus exists, you have to be able to quantify it," said Lynas. "That means surveying the literature in a coherent and non-arbitrary way in order to avoid trading cherry-picked papers, which is often how these arguments are carried out in the public sphere."

Lynas and his team began by examining a random sample of 3,000 studies from the dataset of 88,125 English-language climate papers published between 2012 and 2020. They found only four out of the 3,000 papers to be sceptical of human-caused climate change.

"We knew that [sceptical papers] were vanishingly small in terms of their occurrence, but we thought there still must be more in the 88,000," said Lynas.

Co-author Simon Perry, a UK-based software engineer and volunteer at the Alliance for Science, created an algorithm that searched out keywords from papers the team knew were sceptical – such as "solar," "cosmic rays," and "natural cycles." The algorithm was then applied to all 88,000-plus papers, and the program ordered them, so the sceptical ones came higher in the order. They found many of these dissenting papers near the top, as expected, with diminishing returns further down the list. Overall, the search yielded 28 papers that were implicitly or explicitly sceptical, all published in minor journals.

If the 97% result from the 2013 study still left some doubt on scientific consensus on the human influence on climate, the current findings go even further to allay any uncertainty, said Lynas: "This pretty much should be the last word," he added.


global warming future timeline
Efbrazil, CC BY-SA 4.0, via Wikimedia Commons


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