The link between a global 2 °C warming threshold and emissions in years 2020, 2050 and beyond

Huntingford, Chris; Lowe, Jason A.; Gohar, Laila K.; Bowerman, Niel H.A.; Allen, Myles R.; Raper, Sarah C.B.; Smith, Stephen M.. 2012 The link between a global 2 °C warming threshold and emissions in years 2020, 2050 and beyond. Environmental Research Letters, 7 (1), 014039. 8, pp.

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In the Copenhagen Accord, nations agreed on the need to limit global warming to two degrees to avoid potentially dangerous climate change, while in policy circles negotiations have placed a particular emphasis on emissions in years 2020 and 2050. We investigate the link between the probability of global warming remaining below two degrees (above pre-industrial levels) right through to year 2500 and what this implies for emissions in years 2020 and 2050, and any long-term emissions floor. This is achieved by mapping out the consequences of alternative emissions trajectories, all in a probabilistic framework and with results placed in a simple-to-use set of graphics. The options available for carbon dioxide-equivalent (CO2e) emissions in years 2020 and 2050 are narrow if society wishes to stay, with a chance of more likely than not, below the 2 °C target. Since cumulative emissions of long-lived greenhouse gases, and particularly CO2, are a key determinant of peak warming, the consequence of being near the top of emissions in the allowable range for 2020 is reduced flexibility in emissions in 2050 and higher required rates of societal decarbonization. Alternatively, higher 2020 emissions can be considered as reducing the probability of limiting warming to 2 °C. We find that the level of the long-term emissions floor has a strong influence on allowed 2020 and 2050 emissions for two degrees of global warming at a given probability. We place our analysis in the context of emissions pledges for year 2020 made at the end of and since the 2009 COP15 negotiations in Copenhagen.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Topics & Objectives 2009 - 2012 > Biogeochemistry > BGC Topic 2 - Biogeochemistry and Climate System Processes > BGC - 2.3 - Determine land-climate feedback processes to improve climate model predictions
UKCEH and CEH Sections/Science Areas: Reynard
ISSN: 1748-9326
Additional Information. Not used in RCUK Gateway to Research.: This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Additional Keywords: climate change, global warming, two degrees, carbon dioxide, greenhouse gases
NORA Subject Terms: Meteorology and Climatology
Atmospheric Sciences
Date made live: 17 Apr 2012 11:19 +0 (UTC)

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