OSLO, NORWAY — World powers are running out of time to slash their use of high-polluting fossil fuels and stay below agreed limits on global warming, a draft U.N. study to be approved this week shows.

Government officials and top climate scientists will meet in Berlin from April 7-12 to review the 29-page draft that also estimates the needed shift to low-carbon energies would cost between two and six percent of world output by 2050.

It says nations will have to impose drastic curbs on their still rising greenhouse gas emissions to keep a promise made by almost 200 countries in 2010 to limit global warming to less than 2 degrees Celsius (3.6 Fahrenheit) over pre-industrial times.

Temperatures have already risen by about 0.8 C (1.4F) since 1900 and are set to breach the 2 C ceiling on current trends in coming decades, U.N. reports show.

“The window is shutting very rapidly on the 2 degrees target,” said Johan Rockstrom, head of the Stockholm Resilience Centre, and an expert on risks to the planet from heatwaves, floods, droughts and rising seas.

“The debate is drifting to ‘maybe we can adapt to 2 degrees, maybe 3 or even 4’,” Rockstrom, who was not among authors of […]