Christophe McGlade; Paul Ekins (2015). “The geographical distribution of fossil fuels unused when limiting global warming to 2 °C”. Nature517: 187–190. doi:10.1038/nature14016. "a third of oil reserves, half of gas reserves and over 80 per cent of current coal reserves should remain unused from 2010 to 2050 in order to meet the target of 2 °C."