Fifty-four percent said the warming was caused by human behavior. “Man has ruined the earth,” said Laura Fort, 27, from Lexington Park, Md. “We need renewable energy that won’t hurt the environment.”

By contrast, 31 percent considered warming to be a natural phenomenon, and 10 percent did not accept the idea that global warming existed at all.

Fifty-seven percent of those surveyed said they did not think global warming would cause any harm to them personally. But 42 percent saw it as an imminent threat.