Since the late 1980s, governments and policy makers have worked to develop policy to mitigate climate change. At the same time, opponents have worked to delay and prevent climate action—not just by attacking policy solutions, but also by attacking climate science. A key focus in this decades-long campaign has been to cast doubt on the scientific consensus that humans are causing global warming.
Why attack the consensus? In recent years, social scientists have started to put the pieces together. A study published in the journal Nature Climate Change in 2011, replicated by a 2013 study published in the journal Climatic Change, found that public perceptions about scientific agreement are linked to support for policy to mitigate climate change. When people think that scientists are still debating about what’s causing climate change, they’re less likely to support climate action.
Social scientists were not the first to come to this realization. Political consultant Frank Luntz advised Republicans in the 2000 presidential election to cast doubt on the consensus, arguing “should the public come to believe that the scientific issues are settled, their views about global warming will change accordingly.” More than a decade before social scientists observed the link between perceived consensus and support for climate policy, opponents of climate action understood this link and implemented communication strategies designed to erode public support for climate policy.
In fact, attacks on the consensus date back to the early 1990s. In 1991, the Western Fuels Association spent more than $500,000 on a campaign to “reposition global warming as theory (not fact).” More recently, an analysis of conservative columns published from 2007 to 2010 found that the most repeated climate myth was “there is no scientific consensus.”
These strategies have been effective. To this day, there is a significant “consensus gap” between public perception and the actual scientific consensus. A 2012 poll conducted by the Pew Research Center for the People & the Press found 43 percent of Americans thought climate scientists were still in disagreement about whether the Earth is getting warmer because of human activity. I have conducted similar research, measuring perceived consensus in the United States and Australia. When Americans were asked what percentage of climate scientists agree on human-caused global warming, the average answer was 55 percent. When repeating this survey with Australians, I found that my own country doesn’t perform much better, with an average answer of 58 percent.
The misperception of a scientific community in disagreement is in stark contrast with reality. A 2009 study found that 97 percent of actively publishing climate scientists agree that humans are significantly changing global temperature. A 2010 analysis of public statements by climate scientists found the same 97 percent consensus. Science historian Naomi Oreskes did the seminal work on consensus in 2004; she analyzed the abstracts of 928 climate papers published between 1993 and 2003 and found none rejecting the consensus.
I recently led a citizen science effort, The Consensus Project, to continue and extend Oreskes’ analysis. We analyzed 21 years’ worth of climate research, resulting in the most comprehensive analysis yet done. We identified more than 4,000 peer-reviewed climate papers stating a position in their abstract on whether humans were causing global warming. Among these papers, 97 percent endorsed the consensus. To independently check our results, we asked the scientists who wrote the climate papers to rate their own research. Among papers self-rated by the authors as stating a position on human-caused global warming, 97 percent endorsed the consensus.
Our research went further than earlier studies and found that the consensus had already formed by the early 1990s. Agreement continued to strengthen over the 21-year period. While our sample was admittedly a small portion of the global climate science community, we nevertheless found more than 10,000 scientists in more than 80 countries publishing climate papers that endorse the consensus.
Although President Obama tweeted our research to more than 31 million followers on the day after it was published, and later mentioned the 97 percent consensus in his landmark speech calling for climate action, public perception has not yet caught up with the science. Many psychological barriers to climate action remain in place, and opponents continue to focus intensely on attacking the scientific consensus—which is indicative of its importance. Closing the consensus gap would remove a significant roadblock that has for two decades inhibited public support for climate action.