A study published in this week's issue of Nature is the first to identify the quantity and geographical distribution of fossil fuels that must remain unused in order to keep global temperature rise below 2°C.
Write study authors Christophe McGlade and Paul Ekins, both of University College London's Institute for Sustainable Resources:
Our results suggest that, globally, a third of oil reserves, half of gas reserves, and over 80 percent of current coal reserves should remain unused from 2010 to 2050 in order to meet the target of 2 °C. We show that development of resources in the Arctic and any increase in unconventional oil production are incommensurate with efforts to limit average global warming to 2 °C. Our results show that policy makers' instincts to exploid rapidly and completely their territorial fossil fuels are, in aggregate, inconsistent with their commitments to this temperature limit.
In a nuthsell: The carbon dioxide emissions contained in global fossil fuel reserves is estimated to be several times greater than 1,100 gigatonnes – the cumulative carbon emission limit from 2011 through 2050 that estimates predict must be adhered to, if we want a better than 50% chance at limiting global warming due to greenhouse gas emission below 2 °C.
"If the world's nations keep their pledge to combat climate change, the analysis finds the prospects are bleakest for coal, the most polluting of all fossil fuels," writes Damian Carrington for The Guardian. He continues, with additional geographical information:
Globally, 82% of today's reserves must be left underground. In major coal producing nations like the US, Australia and Russia, more than 90% of coal reserves are unused in meeting the 2C pledge. In China and India, both heavy and growing coal users, 66% of reserves are unburnable.
While the prospects for gas are better, the study still found 50% of global reserves must remain unburned. But there are stark regional variations, with the giant gas producers in the Middle East and Russia having to leave huge quantities underground, while the US and Europe can exploit 90% or more of their reserves to replace coal and provide local power to their large cities. Some fracking for shale gas is consistent with the 2C target, according to the study, but is dominated by the existing industry in the US, with China, India, Africa and the Middle East needing to leave 80% of their potential shale gas unburned.