Increase in seasonal precipitation over the Tibetan Plateau in the 21st century projected using CMIP6 models

Precipitation changes over the Tibetan Plateau (TP) substantially impact the downstream river runoff. However, future precipitation variation over the TP remains unclear. Here, we evaluated the historical (1961-2014) precipitation of 25 CMIP6 models based on the observations. The multi-model ensemble mean of the five best models (BMME) was in stronger agreement with observations than the single model. Then, seasonal precipitation changes in 2015-2099 were projected using the BMME under four Shared Socioeconomic Pathway (SSP) scenarios. The results showed that seasonal precipitation would increase over the TP in the 21st century, with a higher rate of precipitation increase under the higher emission scenarios. Precipitation is projected to increase by 29.3% (11.5%), 27.1% (12.7%), 23.2% (9.4%), and 16.7% (2.9%) in spring, summer, autumn, and winter by end of the 21st century relative to 1995-2014 under the high-emission SSP5-8.5 (low-emission SSP1-2.6) scenario, respectively. The largest precipitation increases in summer and autumn during 2040-2059 and 2080-2099 will occur in the southeastern TP, whereas the largest increases in winter and spring will appear in the Pamirs, where precipitation will increase by >40% during 2080-2099 relative to 1995-2014. The spatial discrepancy in seasonal precipitation changes indicates a potential glacier expansion over the Pamirs and increased flood risks over the southeastern TP.