Thomson Reuters Foundation

The proportion of Americans found to be "alarmed" by climate change has doubled in five years, the pollsters behind a nationwide survey revealed on Tuesday.

Twenty-nine percent of respondents to the poll conducted last December by Yale and George Mason universities were in the alarmed category - an all-time high - and twice the percentage of those surveyed in 2013.

"It's an incredibly important shift in the political climate of climate change," said Anthony Leiserowitz, director of the Yale Program on Climate Change Communication.

More than 1,100 adults across the United States were asked about their beliefs, attitudes and behaviors toward climate change.

The answers were then used to classify respondents into six groups, from dismissive, or least worried about climate change, to alarmed, for those most worried.

Those dismissive of climate change represented nine per cent of respondents, a drop of five points compared to 2013.

The findings come amid a growing polarisation of the political debate over the issue of global warming in the United States.

The decision by US President Donald Trump to pull out of the Paris climate deal has fired up his base, while opponents have championed a "Green New Deal" that seeks to virtually eliminate US greenhouse gas emissions within a decade.

The 2015 Paris accord, agreed to by nearly 200 nations, seeks to wean the global economy off fossil fuels in the second half of this century, limiting the rise in average temperatures to "well below" two degrees Celsius above pre-industrial times.

The increased visibility of global warming debates could explain Americans' rising concern, said Kenneth Sherrill, a political science professor emeritus at Hunter College in New York City.

"The more information you get, the more interested that you are," he said.

Academic research has further shown that growing exposure to bouts of extreme weather may also change minds, he added.

"And it results in higher concern," said Sherrill.

Climate change will cost the US economy hundreds of billions of dollars by the end of the century, hitting everything from health to infrastructure, according to a 2018 government report.