Temperature increase of 21st century mitigation scenarios

Abstract

Estimates of 21st Century global-mean surface temperature increase have generally been based on scenarios that do not include climate policies. Newly developed multigas mitigation scenarios, based on a wide range of modeling approaches and socioeconomic assumptions, now allow the assessment of possible impacts of climate policies on projected warming ranges. This article assesses the atmospheric CO 2 concentrations, radiative forcing, and temperature increase for these new scenarios using two reduced-complexity climate models. These scenarios result in temperature increase of 0.5–4.4°C over 1990 levels or 0.3–3.4°C less than the no-policy cases. The range results from differences in the assumed stringency of climate policy and uncertainty in our understanding of the climate system. Notably, an average minimum warming of ≈1.4°C (with a full range of 0.5–2.8°C) remains for even the most stringent stabilization scenarios analyzed here. This value is substantially above previously estimated committed warming based on climate system inertia alone. The results show that, although ambitious mitigation efforts can significantly reduce global warming, adaptation measures will be needed in addition to mitigation to reduce the impact of the residual warming.

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Affiliated Institutions

• National Institute for Environmental Studies JP
• NSF National Center for Atmospheric Research US
• ETH Zurich CH
• Massachusetts Institute of Technology US
• Graz University of Technology AT
• Potsdam Institute for Climate Impact Research DE
• University of Bern CH
• Manchester Metropolitan University GB
• Energy Research Institute CN
• Netherlands Environmental Assessment Agency NL
• Oeschger Centre for Climate Change Research CH
• Pacific Northwest National Laboratory US
• Electric Power Research Institute US
• International Institute for Applied Systems Analysis AT
• Joint Global Change Research Institute US

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