Meeting two degree climate target means 80 per cent of world’s coal is unburnable, study says
Posted on 6 February 2015 by Guest Author skepticalscience.come This is a re-post from Roz Pidcock at Carbon Brief
More than 80 per cent of the world’s known coal reserves need to stay in the ground to avoid dangerous climate change, according to new research. Thirty per cent of known oil and 50 per cent of gas reserves are unburnable and drilling in the Arctic is out of the question if we’re to stay below two degrees, the new research notes. That vast amounts of fossil fuels must go unused if we’re to keep warming in check isn’t a new idea. What’s novel about today’s paper is that it pinpoints how much fuel is unburnable in specific regions of the world, from Canadian tar sands to the oil-rich Middle East.
…In its most recent report, the Intergovernmental Panel on Climate Change (IPCC) calculated how much carbon we can emit and still keep a decent chance of limiting warming to two degrees above pre-industrial levels. This is known as a carbon budget. Two degrees is the internationally-accepted point beyond which climate change risks become unacceptably high. As of 2010, we could release a maximum of about 1000 billion more tonnes of carbon dioxide and still have a 50:50 chance of staying below two degrees, according to the IPCC. Today’s paper compares this allowable carbon budget with scientists’ best estimate of how much oil, gas and coal exist worldwide in economically recoverable form, known as “reserves”. Were we to burn all the world’s known oil, gas and coal reserves, the greenhouse gases released would blow the budget for two degrees three times over, the paper finds.
The implication is that any fossil fuels that would take us over-budget will have to be left in the ground. Globally, this equates to 88 per cent of the world’s known coal reserves, 52 per cent of gas and 35 per cent of oil, according to the new research. The University College London team used a complex energy system model to investigate the fraction of “unburnable” fossil fuel reserves in 11 specific regions worldwide. The results suggest the Middle East holds half of total global unburnable oil and gas reserves, with more than 260 billion barrels of oil and nearly 50 trillion cubic metres of gas needing to remain untouched if we’re to stay within budget. This “unburnable” fraction equates to two thirds of the region’s gas and 38 per cent of oil reserves. Russia accounts for another third of the world’s total unburnable gas …. It’s worth noting, the numbers above relate to known “reserves”. These are fossil fuels that have already been discovered and have a high probability of being recovered under current economic conditions. This is different from fossil fuel “resources”. These are all the fossil fuels thought to exist which are potentially recoverable irrespective of economic conditions.Today’s research suggests 25 per cent of Europe’s unconventional gas resources could feasibly be exploited while still remaining below two degrees. This includes shale gas, tight gas and coal-bed methane. How much of this is economically viable to recover remains to be seen, however….…According to today’s research, technology to capture greenhouse gas emissions before they reach the atmosphere would only have a limited impact on the proportion of fossil fuels that can be burned. Carbon Capture and Storage (CCS) would allow just six per cent more of the world’s known coal reserves to be burned, with an even lower figure for oil and gas. The paper explains:
“Because of the expense of CCS, its relatively late date of introduction (2025), and the assumed maximum rate at which it can be built, CCS has a relatively modest effect on the overall levels of fossil fuel that can be produced before 2050 in a two-degree scenario”. The new research paints a stark picture of the compromises in fuel use necessary in a climate-constrained world. The researchers say it raises the question of how we divvy up the winners and losers, and that’s one we should all now be asking of our policymakers.
McGlade, C & Ekins, P. (2015) The geographical distribution of fossil fuels unused when limiting global warming to 2C. Nature, http://dx.doi.org/10.1038/nature14016