Belief among Americans that global warming is a reality is now at 70 per cent, its highest level since the United States entered a deep recession five years ago, according to researchers.
In a report released on Thursday by the Yale Project on Climate Change Communication, authors wrote that America's concern about global warming is also at its highest level since 2008, and that 58 per cent of Americans expressed worries about it.
"Historically Americans have viewed climate change as a distant problem ... and perceived that it wasn't something that involved them," said environmental scientist and lead author Anthony Leiserowitz. "That gap is beginning to close, however. We're seeing a jump in the number of people who believe it will affect them or their families."
American attitudes on climate change shifted remarkably during the recession. While 71 per cent of Americans said they believed that global warming was real just prior to the recession in late 2008, the number of believers had plummeted to 57 per cent by 2010, according to the study. By the same token, the share of Americans who did not believe in global warming before the recession stood at 10 per cent, whereas today it is 12 per cent.
Many climate scientists said they believed public perception changed dramatically after the start of the recession - in part because economic worries took precedence in people's minds.
In recent years, however, the number who say that global warming is real has grown steadily, according to study authors.
"Additional analysis is required to determine why Americans increasingly believe that global warming is happening, but it is likely due to a number of factors, including the record number of extreme weather events that have occurred over the past two years, including heat waves, widespread drought, floods, wildfires and violent storms," said Leiserowitz.
He said he expected the trend to continue. While this summer was the third hottest in the US since record-keeping began in 1895, the entire year is on track to be the nation's hottest, according to the National Oceanic and Atmospheric Administration.
For the first time since 2008, more than half of Americans believe global warming is caused mostly by human activities. The proportion who say it is caused mostly by natural changes has declined to 30 per cent.
A growing number of Americans also believe global warming is already harming people both at home and abroad.
The study conclusions were based on an online survey of 1,061 American adults that took roughly 25 minutes to complete. The sampling was random and respondents who needed a computer were provided with one.