A global-scale, multi-sectoral, regional assessment of the impacts of climate change that may be avoided by emissions policies is reported this week in Nature Climate Change.
Although a number of studies have looked at the effects of proposed mitigation policies on global average temperature, there have been few assessments of the global or regional scale impacts of climate change that will be avoided by climate policy. Those studies that do exist have examined only a small set of climate models and scenarios, and it has therefore been difficult to provide policy-relevant evidence on the effect of different proposed emissions policies and targets on the impacts of climate change. Nigel Arnell and colleagues evaluate the regional and global impacts avoided by a set of climate mitigation policies across a range of sectors. They report that although a policy with emissions declining at 5% per year after 2030 reaches a similar temperature by 2100 to a policy with emissions declining at 2% per year from 2016, it has a smaller effect on impacts. This suggests that 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 team also reports that there is considerable variability in the impacts avoided between sectors. For example, an emissions pathway peaking in 2016 and declining at 5% per year, avoids between 58 and 66% of the adverse impacts of climate change on coastal flood risk, but only 30-40% of the adverse impacts on crop suitability.
They conclude that while the impacts avoided by climate policy are negligible by 2030 and remain small at the global scale by 2050, they are clear at 2100. Their findings indicate that emissions policies can delay by decades the impacts that would occur in 2050 in the absence of policy.