Global precipitation-related extremes at 1.5 °C and 2 °C of global warming targets: projection and uncertainty assessment based on the CESM-LWR experiment

To avoid more severe impacts from climate change, the Paris Climate Agreement strives to limit global warming to below 1.5 °C above the pre-industrial level. The large socioeconomic costs of extreme weather events make this target crucial for the impact assessments of 1.5 °C warming. Using four extreme precipitation indices, this study presents a global assessment of precipitation extremes projections under 1.5 and 2 °C warming targets based on the Community Earth System Model low warming (CESM-LWR) experiment. The uncertainties in precipitation extremes projections due to model internal variability (IV) and warming scenario (WS) are quantified by using the variance-based hierarchical uncertainty analysis. Results indicate that both warming targets are expected to exacerbate the extreme wetness events (RX1day and RX5day) and precipitation intensity (SDII) in most global regions, and to intensify the consecutive dry days (CDD) in tropical regions. The additional 0.5 °C warming will increase RX1day, RX5day and SDII over many global regions (e.g., northern high latitudes and central Africa), while decrease (increase) the frequency of CDD in northern high latitudes, central Africa, and eastern South America (in some arid regions and Amazon). Our uncertainty analysis indicates large spatio-temporal variability in the uncertainties of IV and WS. Overall, IV contributes to >80% of the uncertainties in all projected precipitation extremes and this contribution tends to diminish towards the end of this century at the interannual scale, while WS contributes to <20% of the uncertainties. IV (WS) uncertainty is the lowest (largest) in Greenland, northern Europe, Australia, northeastern and southeastern Asia, and Amazon.