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The geographical distribution of fossil fuels unused when limiting global warming to 2 °C


Policy makers have generally agreed that the average global temperature rise caused by greenhouse gas emissions should not exceed 2 °C above the average global temperature of pre-industrial times1. It has been estimated that to have at least a 50 per cent chance of keeping warming below 2 °C throughout the twenty-first century, the cumulative carbon emissions between 2011 and 2050 need to be limited to around 1,100 gigatonnes of carbon dioxide (Gt CO2)2,3. However, the greenhouse gas emissions contained in present estimates of global fossil fuel reserves are around three times higher than this2,4, and so the unabated use of all current fossil fuel reserves is incompatible with a warming limit of 2 °C. Here we use a single integrated assessment model that contains estimates of the quantities, locations and nature of the world’s oil, gas and coal reserves and resources, and which is shown to be consistent with a wide variety of modelling approaches with different assumptions5, to explore the implications of this emissions limit for fossil fuel production in different regions. Our results suggest that, globally, 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. 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 exploit rapidly and completely their territorial fossil fuels are, in aggregate, inconsistent with their commitments to this temperature limit. Implementation of this policy commitment would also render unnecessary continued substantial expenditure on fossil fuel exploration, because any new discoveries could not lead to increased aggregate production.

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Figure 1: Supply cost curves for oil, gas and coal and the combustion CO2 emissions for these resources.
Figure 2: Cumulative production between 2010 and 2050 from a range of long-term energy scenarios.
Figure 3: Oil, gas and coal production in the TIAM-UCL 2 °C scenario (with CCS) and comparison with all other 2 °C scenarios in the Intergovernmental Panel on Climate Change Fifth Assessment Report (AR5) database5.

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We thank I. Keppo at the UCL Energy Institute, E. Trutnevyte at ETH Zurich, and A.-M. Lyne at the UCL Department of Statistical Science. This research formed part of the programme of the UK Energy Research Centre and was supported by the UK Research Councils under Natural Environment Research Council award NE/G007748/1.

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Both authors contributed equally to this work.

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Correspondence to Christophe McGlade.

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The authors declare no competing financial interests.

Extended data figures and tables

Extended Data Figure 1 Cumulative fossil fuel production under a range of sensitivity scenarios run using TIAM-UCL.

Scenario names and characteristics are given in Extended Data Table 2.

Extended Data Figure 2 The auxiliary energy inputs for natural bitumen production in Canada by in situ technologies in the 2 °C scenario and the CO2 intensity of these.

bbl SCO, a barrel of synthetic crude oil, the oil that results after upgrading the natural bitumen.

Extended Data Table 1 Best estimates of remaining reserves and remaining ultimately recoverable resources from 2010
Extended Data Table 2 Labels and description of the sensitivity scenarios modelled in this project
Extended Data Table 3 Regional distribution of resources unburnable before 2050 in absolute terms and as a percentage of current resources under the 2 °C scenario that allows CCS
Extended Data Table 4 Principal data sources used to derive reserve and resource estimates and estimates at the global level for each category of production
Extended Data Table 5 Global aggregated oil, gas and coal reserve and resource estimates from a selection of data sources
Extended Data Table 6 Regions included in TIAM-UCL and their aggregation to the regions given in the main text
Extended Data Table 7 Labels and description of the four core scenarios modelled in this project

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McGlade, C., Ekins, P. The geographical distribution of fossil fuels unused when limiting global warming to 2 °C. Nature 517, 187–190 (2015).

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