Are unprecedented climate extremes unavoidable with temperature overshoot pathways?

According to climate and socioeconomic projections, a global development based on high-emission scenarios is likely to see a progressive increase in magnitude of climate extremes, resulting in large impacts who can lead to devastating impacts and hinder the stability of ecosystems. To minimize the risk of such events, the Paris Agreement recommended pursuing the strongest efforts to keep the global temperature increase – compared to pre-industrial level – to 1.5°C or, at least, well below 2°C. Considering the global temperature tendency of the last decades, it is likely that the World would exceed the 1.5°C threshold, and so the efforts to limit the temperature increase, and possibly revert it, fit into the 1.5°C (or 2°C) overshoot pathways. However, if the World will follow low-emission scenarios, will such overshoot trajectory prevent us from unprecedented climate extremes or are we unavoidably bound to experience new record-breaking events? To answer this question, we used the bias-adjusted multi-model ISIMIP3b data, we constructed a dataset of 12 hazards (including heat and cold waves, droughts, precipitation extremes, fire danger, snowfall, and compound events), and we evaluated – for each hazard – whether, where, and when the most severe event recorded in the past is likely to be exceeded in the future. The results are presented at grid point scale (0.5°) and separately for the SSP1-1.9 and SSP1-2.6 scenarios. To expand the analyses, we coupled the integrated assessment model WITCH with a climate emulator to create multiple overshoot curves (still at 1.5°C, but with different timing and duration), and we again estimated the possible occurrence of such unprecedented events. In this presentation, we also discussed the population and land-use shares exposed to such events, depending on the scenario and the shape of the temperature overshoot.