Regional climate signals in overshoot scenarios

Global warming levels are politically relevant targets, and therefore, in public discussion and in climate science, these global warming levels are often taken as a reference for climate states. While the focus on global warming levels is a useful simplification in many cases, it becomes misleading when looking at temperature overshoot (or stabilization) scenarios. In temperature overshoot scenarios, greenhouse gas concentrations are eventually reduced leading to a decrease in global mean temperatures. In such scenarios, lagged effects, feedback mechanisms, and tipping points can result in considerably different climate states after the overshoot as compared to before at the same global warming level.

Here we assess to what extent changes in regional climate signals are reversed in the period after peak warming when global mean temperature decreases. We analyze a multi-model ensemble of CMIP6 simulations of two overshoot scenarios, SSP5-34-OS and SSP119. In many regions, climate signals are decoupled from global mean temperatures in the decades after peak warming, leading to differences in regional climate signals between before and after the overshoot at the same global warming level.

More dedicated climate simulations of overshoot scenarios would be required to better evaluate how long the influence of the overshoot would affect regional climate signals and to better understand the mechanisms behind these changes. The presented overview of regional climate signals in overshoot scenarios until 2100 already suggests that considerable implications of temperature overshoots for climate impacts are to be expected and that these implications need to be considered for adaptation planning and policy making.