By Tim Radford for Climate News Network, part of the Guardian Environment Network

Available carbon budget is half as big as thought if global warming is to be kept within 2C limit agreed internationally as being the point of no return, researchers say. Climate News Network reports

Climate scientists have bad news for governments, energy companies, motorists, passengers and citizens everywhere in the world: to contain global warming to the limits agreed by 195 nations in Paris last December, they will have to cut fossil fuel combustion at an even faster rate than anybody had predicted.

Joeri Rogelj, research scholar at the International Institute for Applied Systems Analysis in Austria, and European and Canadian colleagues propose in Nature Climate Change that all previous estimates of the quantities of carbon dioxide that can be released into the atmosphere before the thermometer rises to potentially catastrophic levels are too generous.