The vast majority of scientists—by most measures, well over 90 percent—accept the evidence that humans are driving our current climate change. Among the public, however, that figure is much lower. One possible explanation for this discrepancy is that the public doesn't understand just how strong the scientific consensus is. If people think scientists are divided on this issue, they could be more likely to feel that their own opinion is justified, even if it goes against the conclusions of the people with the most relevant expertise.

Researchers have now looked at how people in the US respond to being told about the scientific community's near unanimity on the topic. They found that the results vary geographically, with a stronger response in states that are more politically conservative. This roughly balances the lower acceptance in the states initially, meaning that all states more or less end up looking about the same.

Consensus messaging

The issue here is typically called "consensus messaging." The idea is that many members of the public don't fully realize just how unified scientific opinion—the consensus—currently is. If they did, members of the public might be more likely to accept scientists' conclusions and perhaps demand policies that address climate change. And there's room for a lot of improvement here, as only about 10 percent of the US public correctly recognizes that the scientific consensus on climate change is over 90 percent.

There's some evidence to support the idea that consensus messaging can be valuable. The researchers behind the new work cite studies showing that people who don't accept the scientific reality of climate change also don't seem to know that scientists are nearly unanimous that it's real. In addition, awareness of scientific dissent about environmental issues tends to make people less likely to accept policy solutions. Still, a direct connection between consensus messaging and support for policy solutions hasn't been shown, and it's unclear if knowing what scientists think changes personal opinions significantly, so the concept remains controversial.

The researchers weren't trying to address this controversy; instead, they were just looking at whether consensus messaging stuck. To do this, they generated a series of poll questions designed to get at the issue. The study involved asking people about two additional issues so they wouldn't recognize that the real subject was climate change. As part of a series of questions, people were asked to move a slider along a one-to-100 scale to reflect what percentage of scientists thought that human-caused global warming was happening.

Shortly after, they were told the actual figure (along with some other climate facts); later, they were asked the same questions. That may sound more like a test of short-term memory, but it does get at whether the mention of the existing consensus made it through the filters that people use to reject information they don't like.

State by state

Overall, the consensus messaging did have an effect, increasing its acceptance among those polled by 16 percentage points. But the researchers polled enough people (over 6,000) to break down the results geographically. And here, they got some unexpected results.

You might think, for example, that consensus messaging would resonate in California, a state with extensive public support for climate policy action. But California came in last, with only a 12.2 percentage-point shift in response to the consensus messaging. In contrast, the places where opinion shifted the most were Wyoming and West Virginia, two coal-dependent states where acceptance of climate change is low to start with. This was a general trend, with states where acceptance of climate change was low to start with showing the biggest gains in recognizing the consensus.

At its least interesting, the data simply suggests that you see bigger changes when there are more people around that need convincing. But there's an indication that something more is going on here. After the consensus messaging, every state ended up in the range of 81-87 percent acceptance that the consensus exists. This suggests that it's relatively easy to reach a saturation point, where everyone who can be convinced is.

There are also some oddities in the details that suggest this effect isn't simply a matter of politics. For example, relatively liberal states like Minnesota and Oregon saw larger shifts than states like Nevada and Wisconsin, which tend to be more conservative.

Will it stick?

Overall, the results indicate that most people are willing to accept information about the scientific consensus. But the results are extremely limited and need a lot of follow-up. To begin with, it's not clear whether the knowledge of the scientific consensus that these researchers saw will persist. In the long term, people tend to adapt their views to conform to those of their community, and polls suggest that up to 30 percent of the US doesn't even believe the climate is warming, much less that humanity is driving that change.

There's also the issue of whether people will end up believing the scientists. While the researchers behind the new results cite studies indicating that conservatives tend to defer to authorities, this is a case where their scientific and political authorities are telling them opposing things. In other words, it's still not clear whether consensus messaging is enough to convince people that climate change is real, much less a problem that demands a policy solution.

Still, the paper shows a valuable piece of the puzzle. Many have tended to treat the public as a monolithic thing when it comes to the public understanding of science. But the clear indication of regional differences drives home that there's no single message that will work for everyone.

Nature Climate Change, 2018. DOI: 10.1038/s41558-018-0122-0 (About DOIs).