In a paper in the journal Science Advances, they said the actual range could be between 4.78C to 7.36C by 2100, based on one set of calculations.
Some have dismissed the idea that the world would continue to burn fossil fuels despite obvious global warming, but emissions are still increasing despite a 1C rise in average thermometer readings since the 1880s.
And US President-elect Donald Trump has said he will rip up America’s commitments to the fight against climate change.
Professor Michael Mann, of Penn State University in the US, who led research that produced the famous “hockey stick” graph showing how humans were dramatically increasing the Earth’s temperature, told The Independent the new paper appeared “sound and the conclusions quite defensible”.
“And it does indeed provide support for the notion that a Donald Trump presidency could be game over for the climate,” he wrote in an email.
“By ‘game over for the climate’, I mean game over for stabilizing warming below dangerous (ie greater than 2C) levels.
“If Trump makes good on his promises, and the US pulls out of the Paris [climate] treaty, it is difficult to see a path forward to keeping warming below those levels.”
Greenpeace UK said the new research was further evidence that urgent action was needed.
Climate change may be escalating so fast it could be ‘game over’, scientists warn