By just about every measure, the vast majority of scientists in general—and climate scientists in particular—have been convinced by the evidence that human activities are altering the climate. However, in several countries, a significant portion of the public has concluded that this consensus doesn't exist. That has prompted a variety of studies aimed at understanding the large disconnect between scientists and the public, with results pointing the finger at everything from the economy to the weather. Other studies have noted societal influences on acceptance, including ideology and cultural identity.

Those studies have generally focused on the US population, but the public acceptance of climate change is fairly similar in Australia. There, a new study has looked at how societal tendencies can play a role in maintaining mistaken beliefs. The authors of the study have found evidence that two well-known behaviors—the "false consensus" and "pluralistic ignorance"—are helping to shape public opinion in Australia.

False consensus is the tendency of people to think that everyone else shares their opinions. This can arise from the fact that we tend to socialize with people who share our opinions, but the authors note that the effect is even stronger "when we hold opinions or beliefs that are unpopular, unpalatable, or that we are uncertain about." In other words, our social habits tend to reinforce the belief that we're part of a majority, and we have a tendency to cling to the sense that we're not alone in our beliefs.

Pluralistic ignorance is similar, but it's not focused on our own beliefs. Instead, sometimes the majority of people come to believe that most people think a certain way, even though the majority opinion actually resides elsewhere.

As it turns out, the authors found evidence of both these effects. They performed two identical surveys of over 5,000 Australians, done a year apart; about 1,350 people took the survey both times, which let the researchers track how opinions evolve. Participants were asked to describe their own opinion on climate change, with categories including "don't know," "not happening," "a natural occurrence," and "human-induced." After voicing their own opinion, people were asked to estimate what percentage of the population would fall into each of these categories.

In aggregate, over 90 percent of those surveyed accepted that climate change was occurring (a rate much higher than we see in the US), with just over half accepting that humans were driving the change. Only about five percent felt it wasn't happening, and even fewer said they didn't know. The numbers changed only slightly between the two polls.

The false consensus effect became obvious when the researchers looked at what these people thought that everyone else believed. Here, the false consensus effect was obvious: every single group believed that their opinion represented the plurality view of the population. This was most dramatic among those who don't think that the climate is changing; even though they represent far less than 10 percent of the population, they believed that over 40 percent of Australians shared their views. Those who profess ignorance also believed they had lots of company, estimating that their view was shared by a quarter of the populace.

Among those who took the survey twice, the effect became even more pronounced. In the year between the surveys, they respondents went from estimating that 30 percent of the population agreed with them to thinking that 45 percent did. And, in general, this group was the least likely to change its opinion between the two surveys.

But there was also evidence of pluralistic ignorance. Every single group grossly overestimated the number of people who were unsure about climate change or convinced it wasn't occurring. Even those who were convinced that humans were changing the climate put 20 percent of Australians into each of these two groups.

In the end, the false consensus effect is swamped by this pluralistic ignorance. Even though everybody tends to think their own position is the plurality, those who accept climate change is real still underestimate how many people share their views. Meanwhile, everyone overestimates the self-labelled "skeptic" population.

The authors suggest that this could, in part, be a result of the media's tendency to always offer two opposing opinions, even on issues where one is a fringe belief. They also point out that it would be good to perform a similar study in other nations where the dynamics of public belief are different.

Nature Climate Change, 2012. DOI: 10.1038/NCLIMATE1743 (About DOIs).