Climate change could cost US 'hundreds of billions' a year: study

Climate change is already hurting the global economy and will cost the US hundreds of billions of dollars annually by century's end unless drastic action is taken to cut carbon emissions, a major US government report warned on Friday.

"With continued growth in emissions at historic rates, annual losses in some economic sectors are projected to reach hundreds of billions of dollars by the end of the century -- more than the current gross domestic product (GDP) of many US states," the latest edition of the National Climate Assessment said.

"Without substantial and sustained global mitigation and regional adaptation efforts, climate change is expected to cause growing losses to American infrastructure and property and impede the rate of economic growth over this century," it added.

The effects will spill over into global trade, affecting import and export prices and US businesses with overseas operations and supply chains, it added.

Some of these impacts are already being felt in the United States, the report said, and recent extreme weather and climate-related events can now be attributed "with increasingly higher confidence to human-caused warming."

Compiled by more than 300 scientists, the Fourth National Climate Assessment Volume II is a congressionally mandated report that spans more than 1,000 pages.

US President Donald Trump dismissed last year's report, and just this week appeared to confuse weather with climate when he tweeted: "Brutal and Extended Cold Blast could shatter ALL RECORDS - Whatever happened to Global Warming?"

Trump also yanked the United States out of the landmark 2015 Paris climate accord, signed by more than 190 nations to limit carbon emissions.

David Easterling, director of the technical support unit at the National Oceanic and Atmospheric Administration's National Centers for Environmental Information, said there had been "no external interference" in the report.

Scientists found "clear and compelling evidence that global average temperature is much higher and is rising more rapidly than anything modern civilization has experienced," he told reporters.

"And this warming trend can only be explained by human activities, especially emissions of greenhouse gases into the atmosphere."

Reporters questioned the timing of this year's release, which came on the Friday after Thanksgiving, a national holiday when many people are traveling and shopping.