There is a general consensus among policymakers that the average temperature rise caused by greenhouse gas emissions must not exceed two degrees Celsius in relation to pre-industrial times. It is further assumed that in order to have at least a 50 percent chance of keeping warming below this level throughout the 21st century, cumulative carbon emissions between 2011 and 2050 must be limited to around 1,100 gigatonnes (Gt).
However, this notion is set to come under new scrutiny in the months leading up to the 2015 UN Climate Summit in Paris at the end of the year. A new study, conducted by scientists at University College London’s Institute for Sustainable Resources (UCL) and published in the journal Nature, offers ample evidence to suggest that limiting cumulative carbon emissions to 1,100 Gt might prove illusory as the emissions contained in present day estimates of global fossil fuel reserves are around three times higher than this.
Unabated use of all current fossil fuel reserves is therefore incompatible with a warming limit of 2 degrees, the UCL scientists conclude. Using an integrated assessment model comprising estimates of the quantities, locations and nature of the world’s oil, gas and coal reserves and resources to explore the implications of this emissions limit for fossil fuel production in different regions, the authors claim 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.
On a practical level, the study offers regional and country-bycountry suggestions with respect to the share of fossil fuel reserves that should stay in the ground. For Australia, Russia and the United States these would require 90, 94 and 92 percent of their respective domestic coal reserves to remain untouched. The Middle East would have to forfeit 38 percent of its oil reserves, while Canada would have to cease oil extraction from tar sands immediately. Lead author Dr Christophe McGlade, Research Associate at the UCL Institute for Sustainable Resources, said: “Policymakers must realise that their instincts to completely use the fossil fuels within their countries are wholly incompatible with their commitments to the 2°C goal.”