US President Donald Trump said on Monday he doesn't believe his own government's report warning of massive economic losses if carbon emissions continue to feed climate change unchecked.

The National Climate Assessment, quietly unveiled on Friday, warns that natural disasters are worsening in the United States because of global warming.

It projected that climate change will "cause growing losses to American infrastructure and property and impede the rate of economic growth over this century". The effects will spill over into global trade, affecting import and export prices and US businesses with overseas operations and supply chains, it added.

Responding to questions about the economic impacts of climate change, Trump said it doesn't think they will be devastating.

"I don't believe it," he told reporters on Monday.

"I've seen it, I've read some of it, and it's fine," he said.  

The report, written with the help of more than a dozen US government agencies and departments, said the effects of climate change would harm human health, damage infrastructure, limit water availability, alter coastlines and increase costs in various industries.

The assessment also said projections of damage could change if greenhouse gas emissions were curbed, although many of the impacts of climate change, like powerful storms, droughts and flooding, have already begun.

The report supplements a study issued last year that concluded humans are the main driver of global warming and warned of catastrophic effects to the planet.

Trump on climate change

Trump's comments on Friday were not all that surprising given the president's past rhetoric on climate change.

Last year, Trump announced his intent to withdraw the United States from the 2015 Paris Agreement to combat climate change, though the country cannot do so until after the 2020 presidential election. 

Trump has also rolled back Obama-era environmental and climate rules such as the Clean Power Plan, while seeking to boost output of oil, gas and coal for domestic use and for shipping to allies and partners.

US output of crude oil is already the highest in the world, above Saudi Arabia and Russia.

During the 2016 presidential election, Trump called climate change a "hoax", although he has since said he does not believe that to be the case.

The president often falsely cites cold weather as proof global warming is not as bad as scientists say. Scientists, however, are quick to point out that weather is a short-term event and climate science looks at weather patterns over an extended period of time. 

Agencies