Global warming is on track to breach the toughest limit set in the Paris climate agreement by the middle of this century unless governments make unprecedented economic shifts from fossil fuels, a draft U.N. report said.

The draft, of a report due for publication in October, said governments will also have to start sucking carbon dioxide from the air to achieve the ambition of limiting temperatures to 1.5 degrees Celsius above pre-industrial times.

"There is very high risk that ... global warming will exceed 1.5 degree Celsius above pre-industrial levels," the U.N. panel of experts wrote, based on the current pace of warming and current national plans to limit their greenhouse gas emissions.