It’s probably the most famous study ever conducted about how climate scientists, themselves, think about the subject they examine. According to a gigantic 2013 literature review, 97.1 percent of published scientific studies that took a position on the matter “endorsed the consensus position that humans are causing global warming.”
This “97 percent” figure has since gone everywhere — triggering debates and discussions around the world. It has been celebrated, pilloried, attacked — and most of all, heralded as the key to explaining climate change to the public.
Indeed, public opinion scholars have been trying to measure, in controlled experiments, whether simply telling people about the existence of the “97 percent” consensus can make them think more in the way that scientists do — and knock off the all too common practice of doubting the reality of climate change.
A new study, just out in PLOS One from researchers at Princeton, Yale, and George Mason University, presents some results on this inquiry. In the study — part of the findings were previously reported in a 2014 paper — 1,104 research subjects (save for those in a control group) were presented with the following message: “97% of climate scientists have concluded that human-caused climate change is happening.”
Sometimes, they received the message in the form of simple text or a simple pie chart. In other cases, the message was conveyed through various metaphorical explanations — for instance, “If 97% of doctors concluded that your child is sick, would you believe them? 97% of climate scientists have concluded that human-caused climate change is happening.”
But it was always the same message: 97 percent, people. 97 percent. 97 percent.
The new PLOS One paper hypothesized that receiving such a message would make people worry more about climate change, and would render them more likely to believe it’s real and caused by humans. “We posit perceived scientific agreement as a ‘gateway belief’ that either supports or undermines other key beliefs about climate change, which in turn, influence support for public action,” the authors wrote.
They provide this figure, showing how they expect the “gateway belief” model to work:
So did it work out that way? The answer, says the study, is yes.
After being presented with the consensus message, people on average increased their estimate of the percentage of scientists who agree about climate change by 12.8 percent. And the paper further found that when people up their estimate of the percentage of scientists who accept that global warming is caused by humans, they also increase their own belief in the science, and their own worry about it, becoming more likely to want the world to take climate action.
“Perceived scientific consensus acts as a key gateway belief for both Democrats and Republicans,” wrote the authors. Interestingly, the paper found that the consensus message was particularly effective with Republicans — a group that, in general, is not easily swayed on the climate issue.
The authors concluded by suggesting that this finding could be the basis for a public information campaign. “Repeated exposure to simple messages that correctly state the actual scientific consensus on human-caused climate change is a strategy likely to help counter the concerted efforts to misinform the public,” they wrote.
It’s important to note, however, that not every researcher agrees with this approach. Indeed, Yale public opinion researcher Dan Kahan has already blogged a response to the new study, and it’s pretty critical.
“I gotta say, I just don’t see any evidence in these results that the ‘97% consensus msg’ meaningfully affected any of the outcome variables that the authors’ new writeup is focused on (belief in climate change, perceived risk, support for policy),” he wrote. Kahan objected that while statistically significant, the changes were relatively small and may not have “practical” significance.
More broadly, Kahan questions whether, in light of how politicized the climate debate has become, mere statements about fact like the “97 percent” claim can successfully depolarize matters. Kahan himself recently published research suggesting that a wildly different approach — telling people about the subject of geoengineering — actually has a depolarizing effect.
So in sum — 97 percent of scientists may agree about climate change, but scientific agreement about how to get people to accept that is significantly lower.