A global assessment of the effects of climate policy on the impacts of climate change


This study presents the first global-scale multi-sectoral regional assessment of the magnitude and uncertainty in the impacts of climate change avoided by emissions policies. The analysis suggests that the most stringent emissions policy considered here—which gives a 50% chance of remaining below a 2 °C temperature rise target—reduces impacts by 20–65% by 2100 relative to a ‘business-as-usual’ pathway which reaches 4 °C, and can delay impacts by several decades. The effects of mitigation policies vary between sectors and regions, and only a few are noticeable by 2030. The impacts avoided by 2100 are more strongly influenced by the date and level at which emissions peak than the rate of decline of emissions, with an earlier and lower emissions peak avoiding more impacts. The estimated proportion of impacts avoided at the global scale is relatively robust despite uncertainty in the spatial pattern of climate change, but the absolute amount of avoided impacts is considerably more variable and therefore uncertain.

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Figure 1: Global annual and cumulative CO2-equivalent emissions, CO2-equivalent concentrations, average global temperature change and global sea-level rise under the emissions pathways.
Figure 2: Global-scale impacts of climate change under different emissions pathways, using the HadCM3 climate model geographical and seasonal patterns of change.
Figure 3: Global-scale impacts avoided by climate policy in 2050 and 2100, relative to two plausible no-policy climate futures, using the HadCM3 climate model patterns of change.
Figure 4: Uncertainty in global-scale avoided impacts in 2050 and 2100 due to using different climate model patterns for A1B-2016-5-L emissions compared with the A1B no-policy pathway.
Figure 5: Regional variation in a selection of impacts avoided by climate policy in 2100, for A1B-2016-5-L emissions compared with the A1B no-policy pathway.


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The research presented in this paper was funded under the UK Department of Energy and Climate Change (DECC) AVOID programme (www.avoid.uk.net), and builds on the QUEST-GSI project funded by NERC (grant number NE/E001890/1). P.S. is a Royal Society-Wolfson Research Merit Award holder. The authors thank S. Raper (Manchester Metropolitan University) for her contribution to the development of the probabilistic parameterization of MAGICC. The authors thank the reviewers for their helpful comments.

Author information

N.W.A. developed the experimental design, led the analysis, performed some of the simulations and wrote the paper. J.A.L. led the AVOID project, developed the emissions and (with S.B.) the sea-level scenarios. T.J.O. developed and applied the ClimGEN climate scenario program. S.B. and J.H. ran the DIVA model, S.N.G. ran the hydrological models, P.G. ran the soil organic carbon model, B.L-H. ran the drought model and T.M.O. and G.A.R. ran the GLAM crop model. J.H. and R.J.N. contributed to the analysis of the coastal results, and P.S. contributed to the analysis of soil organic carbon results. R.F.W. contributed to the experimental design.

Correspondence to N. W. Arnell.

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Arnell, N., Lowe, J., Brown, S. et al. A global assessment of the effects of climate policy on the impacts of climate change. Nature Clim Change 3, 512–519 (2013). https://doi.org/10.1038/nclimate1793

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