Over 99.9% of the published science agrees: climate change is caused by humans

The reality of anthropogenic climate change is no more in contention among scientists, with over 99.9% of them agreeing that the climate crisis is being driven by human activities, according to a new study. The degree of certainty is similar to the level of agreement on evolution, the authors said, after reviewing almost 90,000 studies.

There’s no doubt among climate scientists that burning fossil fuels (such as coal, natural gas, and oil) and clearing out forests for agriculture is warming up the planet and causing extreme weather phenomena. And that we need to scale up our actions to reduce emissions and avoid even worse consequences of the climate crisis.

“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,” Mark Lynas, a visiting fellow at the Alliance for Science and the paper’s first author, said in a statement. 

A debate that doesn’t exist

Despite the overwhelming scientific evidence, a large number of politicians still seems to not understand — and while climate is not really a scientific debate anymore, it’s still a political debate for some reason.

A survey published earlier this year showed that there’s a deepening of the partisan divide in US politics on whether global warming since the industrial revolution is caused mainly by humans. This divide is similar among elected US politicians, according to a study among officials now sitting in Congress. 

Previously, a study from 2013 quantified the level of scientific consensus on human responsibility behind global warming. Researchers went through peer-reviewed papers published between 1991 and 2012 and found a consensus among 97% of the world’s science over man-made climate change. This had a big impact on global awareness of the level of scientific consensus

Now, a group of researchers from Cornell University wanted to re-examine the literature published since 2012 to establish whether any change in the scientific consensus on climate change is discernible. This was in fact the case, showing the minority of skeptical voices has diminished to almost nothing as evidence of human responsibility behind climate change piles up. 

First, they looked at a random sample of 3,000 climate-related studies from their 88,125 studies database and found only four that expressed doubts over the climate crisis being caused by humans. Then they searched for keywords linked to climate skepticism such as “cosmic rays” in the larger database and found only 28 papers published in minor journals.

This follows the views expressed back in August by the Intergovernmental Panel on Climate Change (IPCC), a leading group of climate experts. In their Sixth Assessment report, they wrote that it’s “unequivocal” that human actions have warmed the atmosphere, ocean, and land, something they have been reiterating over the years across their reports.

“It’s critical to acknowledge the principal role of greenhouse gas emissions so that we can rapidly mobilize new solutions, since we are already witnessing in real time the devastating impacts of climate related disasters on businesses, people and the economy,” Benjamin Houlton, a co-author of the study, said in a statement.

In the Paris Agreement, a landmark climate agreement signed in 2015 by almost every government, countries committed to doing everything in their power to limit global warming to 2ºC by the end of the century. As it turns out, we are still very far from that target. Based on the pledges so far presented, the world is heading to a global warming of 2.7ºC.

The study was published in the journal Environmental Research Letters. 

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