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Early benefits of mitigation in risk of regional climate extremes


Large differences in climate outcomes are projected by the end of this century depending on whether greenhouse gas emissions continue to increase or are reduced sufficiently to limit total warming to below 2 °C (ref. 1). However, it is generally thought that benefits of mitigation are hidden by internal climate variability until later in the century2. Here we show that if the likelihood of extremely hot seasons is considered, the benefits of mitigation emerge more quickly than previously thought. It takes less than 20 years of emissions reductions in many regions for the likelihood of extreme seasonal warmth to reduce by more than half following initiation of mitigation. Additionally we show that the latest possible date at which the probability of extreme seasonal temperatures will be halved through emissions reductions consistent with the 2 °C target is in the 2040s. Exposure to climate risk is therefore reduced markedly and rapidly with substantial reductions of greenhouse gas emissions, demonstrating that the early mitigation needed to limit eventual warming below potentially dangerous levels benefits societies in the nearer term not just in the longer-term future.

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Figure 1: Definition of the halving of probability in extremes date (HOPE date).
Figure 2: HOPE dates for four selected regions.
Figure 3: The early benefits of mitigation as represented by regional HOPE dates.


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This work was supported by the Joint UK BEIS/Defra Met Office Hadley Centre Climate Programme (GA01101) and by the EUCLEIA project funded by the European Union’s Seventh Framework Programme [FP7/2007–2013] under grant agreement no. 607085. We acknowledge the World Climate Research Programme’s Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modelling groups (listed in Supplementary Table 1) for producing and making available their model output. For CMIP the US Department of Energy’s Program for Climate Model Diagnosis and Intercomparison provides coordinating support and led development of software infrastructure in partnership with the Global Organization for Earth System Science Portals.

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A.C. conducted the research and wrote the first draft of the paper. P.S. initially suggested a study concerning changing extremes under mitigation. Both P.S. and J.L. contributed to discussion of the results and revisions of the paper.

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Correspondence to Andrew Ciavarella.

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The authors declare no competing financial interests.

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Ciavarella, A., Stott, P. & Lowe, J. Early benefits of mitigation in risk of regional climate extremes. Nature Clim Change 7, 326–330 (2017).

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