STOCKHOLM (AP) — The U.N.'s scientific panel on climate change will write a special report on how to limit global warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit) compared with pre-industrial times.

The Intergovernmental Panel on Climate Change agreed Thursday to explore the issue after a request by world governments in Paris last December.

Many scientists say it will be virtually impossible to keep warming below that level without removing vast quantities of heat-trapping greenhouse gases from the atmosphere.

Temperatures have already risen almost 1 degree C (1.8 F) since humans started burning fossil fuels — the biggest source of greenhouse gases — on an industrial scale in the 19th century.

Meeting in Nairobi, the IPCC also said it will release its sixth assessment of global warming in 2020-2022.