The American public has multiple personality disorder when it comes to the issue of climate change, a Yale study has found.

Yale Project on Climate Change Director Anthony Leiserowitz and his team identified the six types of Americans — the alarmed, the concerned, the cautious, the disengaged, the doubtful and the dismissive — by conducting a national survey in fall 2008. The researchers said they hope to use the results of the survey to more effectively motivate Americans to take political and personal action against climate change.

“The key is to know thy audience, where the public is [on the issue] and who the public is,” Leiserowitz said.

Because the objective of the Yale Project on Climate Change is to better galvanize the public to act against climate change, it was important to the nuances of what Americans think about the topic, he said.

According to the study, alarmed Americans, which represent 18 percent of the population, are convinced of the reality and seriousness of climate change and are already taking action by reducing their greenhouse gas emissions and lobbying their legislators. Concerned Americans, who make up 33 percent of the public, have similar beliefs but have not taken action yet. Cautious Americans (19 percent), disengaged Americans (12 percent) and doubtful Americans (11 percent) represent decreasing stages of understanding and acceptance of the topic, while dismissive Americans (7 percent) are certain there is no climate change and are actively opposing efforts to reduce greenhouse gas emissions.

The six types of Americans will help researchers better understand what they should attempt to achieve with different segments of the public, said co-researcher Edward Maibach, the director of George Mason University’s Center for Climate Change Communication. Alarmed Americans should be urged to act politically because it is the only group willing to do so, Maibach said. While concerned Americans are a large segment and are unlikely to act politically, he added that they should be encouraged to use their purchasing power to motivate corporations to become more environmentally conscious.

The results of the study follow another Yale Project on Climate Change survey that indicates that Americans’ beliefs in the reality of global warming has decreased. The other survey found that only 50 percent of Americans are somewhat or very worried about global warming, a 13-point decrease since 2008. The number of Americans who think global warming is happening also dropped from 71 percent to 57 percent.

“I did strongly suspect [the drop],” Leiserowitz said. “I was just surprised by how steep the drop had become.”

Leiserowitz said he was optimistic that once the United States emerges from its economic slump, people will have the time and space to pay more attention to climate change. His team will continue to survey Americans each quarter for the next 12 months to track public opinion on the topic, he added.

It is important for Americans and the rest of the world to act now on climate change, Leiserowitz said.

“If we continue to delay [significantly reducing greenhouse gas emissions] another decade then we’re really starting to push our boundaries,” he said.

The study was funded by the Yale Center for Environmental Law and Policy, The Betsy and Jesse Fink Foundation, The Eleventh Hour Project, The Pacific Foundation and the Robert Wood Johnson Foundation.