The scientific community disagrees about plenty of things. But according to a sweeping new survey of 12,000 peer-reviewed climate studies, global warming isn't one of them.
Published this week in the journal Environmental Research Letters, the analysis shows an overwhelming majority of climate scientists agree that humans are a key contributor to climate change, while a "vanishingly small proportion" defy this consensus. Most of the climate papers didn't specifically address humanity's involvement — likely because it's considered a given in scientific circles, the survey's authors point out — but of the 4,014 that did, 3,896 shared the mainstream outlook that people are largely to blame.
"This is significant because when people understand that scientists agree on global warming, they're more likely to support policies that take action on it," says lead author John Cook, a research fellow at the University of Queensland in Australia, in a statement. "For example, if 97 percent of doctors told you that you had smoking-induced cancer, you'd take action: Quit smoking and start chemotherapy to get rid of the cancer."
Confirming such an established consensus may seem redundant, but the public is often misled about where scientists stand on climate change and its causes. This has bred widespread confusion, seen in a recent Gallup poll that showed only 58% of Americans agree with 97% of scientists. That's up from 51% in 2011 but down from 72% in 2000, a turbulence of opinion that's unmatched among experts.
"There is a gaping chasm between the actual consensus and the public perception," Cook says. "Making the results of our paper more widely known is an important step toward closing the consensus gap and increasing public support for meaningful climate action."
Cook and his colleagues built on several previous analyses, including a 2004 survey by science historian Naomi Oreskes that found no disputes of manmade climate change in 928 climate papers published between 1993 and 2003. The new survey, which covers 10 more years and reviews 12 times more papers, supports Oreskes' 2004 finding as well as her later prediction that such a broad consensus will grow less explicit over time.
Scientists "generally focus their discussions on questions that are still disputed or unanswered," Oreskes wrote in 2007, "rather than on matters about which everyone agrees." Just as few papers bother to tout the existence of gravity or atoms anymore, the scientific need to re-explain humanity's role in climate change seems to be fading. Of the 12,000 studies examined in the new analysis, nearly 8,000 "simply accept this fact and go on to examine the consequences," co-author Dana Nuccitelli writes in the Guardian.
More than 4,000 papers did express a stance on human involvement, though, and the survey's authors took a conservative approach in classifying those positions. "[I]f a paper minimized the human contribution, we classified that as a rejection," they explain on the website Skeptical Science. "For example, if a paper were to say 'the sun caused most of the global warming over the past century,' that would be included in the less than 3% of papers in the rejection categories."
Yet their analysis still shows a crushing consensus that humans are fueling climate change, and it comes at an especially relevant time. Not only have political debates stalled climate-change action in the U.S. and many other countries — leaving little room for progress at United Nations climate talks — but the Earth also recently reached a bleak milestone. Atmospheric levels of carbon dioxide, a potent and durable greenhouse gas emitted by burning fossil fuels, have hit 400 parts per million for the first time in human history.