Projected temperature and precipitation changes on the Tibetan Plateau: results from dynamical downscaling and CCSM4

The regional climate of the Tibetan Plateau (TP) was simulated by dynamically downscaling reanalysis data and the Community Climate System Model version 4 (CCSM4) and comparing trends of temperature and precipitation with gridded observations. Then, future CCSM4 projections under high and low emission scenarios were downscaled and compared with CCSM4 projections. Observations showed a marked upward trend in temperature and precipitation since 1979. The spatiotemporal distribution of temperature and precipitation in the TP were well represented by the reanalysis data. Downscaled simulations of ERA-Interim and CCSM4 were able to reproduce the spatial distribution of temperature in the TP; however, a cold bias was apparent in the central and western regions. Compared with precipitation observations, the downscaled CCSM4 simulation showed markedly different precipitation trends. Future climate projections indicated that temperatures will increase markedly in the TP, especially under the high emission RCP8.5 scenario. Under RCP4.5, both CCSM4 and the downscaled simulation projected a 1.5 °C increase in annual temperatures during 2006–2050, while under RCP8.5, the downscaled simulation projected an increase greater than 2.5 °C, and CCSM4 projected an increase of 2.0 °C. Emission scenarios had no apparent impact on projections of future precipitation. Therefore, to mitigate warming over the TP, reducing greenhouse gas emission should be a priority.