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Abstract:
The East Asian Monsoon (EAM) dominates the climate over the densely populated region of eastern China and adjacent regions and therefore influences a fifth of the world's population. Thus, it is highly relevant to assess the changes in the central characteristics of the East Asian Summer Monsoon (EASM) under future warming in the latest generation of coupled climate models of the Coupled Model Intercomparison Project Phase 6 (CMIP6). We apply a set of selection criteria to 34 CMIP6 models to identify the six best performing (TOP6) models that best capture the EASM in the reference period 1995–2014. All of these models project an increase in June–August rainfall independent of the underlying emission scenario. The multi-model mean increase is 16.5 % under SSP5-8.5, 11.8 % under SSP3-7.0, 12.7 % under SSP2-4.5 and 9.3 % under SSP1-2.6 in the period 2081–2100 compared to 1995–2014. For China, the projected monsoon increase is slightly higher (12.6 % under SSP1-2.6 and 18.1 % under SSP5-8.5). The EASM rainfall will particularly intensify in southeastern China, Taiwan and North Korea. The multi-model mean indicates a linear relationship of the EASM rainfall depending on the global mean temperature that is relatively independent of the underlying scenario: per degree of global warming, the rainfall is projected to increase by 0.17 mm d−1, which refers to 3.1 % of rainfall in the reference period. It is thus predominately showing a “wet regions get wetter” pattern. The changes in the wind fields in the region are relatively small indicating the minor importance of dynamic factors, while pointing towards thermodynamic factors as responsible for the rainfall increase. The interannual variability is also robustly projected to increase between 17.6 % under SSP1-2.6 and 23.8 % under SSP5-8.5 in the multi-model mean between 2051–2100 and 1965–2014. Comparing the same periods, extremely wet seasons are projected to occur 7 times more often under SSP5-8.5.
