Climate Change Projections over East Asia with BCC_CSM1.1 Climate Model under RCP Scenarios

We study climate change projections over East Asia under various representative concentration pathway (RCP) scenarios using simulations performed with the Beijing Climate Center Climate System Model version 1.1 (BCC_ CSM1.1) for the Coupled Model Intercomparison Project phase 5 (CMIP5). Under all RCPs (including RCP2.6, RCP4.5, RCP6.0, and RCP8.5), East Asian climate is found to be warmer and wetter in the 21st century than the present climatology (1986-2005). For 2080-2099, East Asian mean surface air temperature (precipitation) is higher than that for the present climatology by 0.98 C (4.4%) under RCP2.6, 1.89 C (7.7%) under RCP4.5, 2.47 C (7.1%) under RCP6.0, and 4.06 C (9.1%) under RCP8.5. Such changes in East Asia are all larger than the corresponding global changes, with greater differences under the higher RCPs. In the simulation of RCP4.5, which is extended to the late 23rd century (2280-2299), further warming of 0.34 C relative to 2080-2099 is found in East Asia; this is lower than the global mean warming (0.56 C). Under mitigation scenario RCP2.6, East Asia experiences greater cooling than that experienced globally throughout the 22nd and 23rd centuries. In the late 21st century, East Asian summer mean precipitation increases prominently (by 10-15%) with respect to the present climatology under all RCPs. This increase in precipitation occurs primarily in southern China and northern East Asia and is associated with anomalous southerly flow in the lower troposphere. Drought occurs in the Yangtze River valley for the middle and high RCPs; we attribute this to anomalous subsidence around 30 N associated with the northward shift of the East Asian jet stream. Under the high scenario (RCP8.5), the western Pacific subtropical high extends westward and northward to southern China and is partly responsible for the deficient precipitation in regions to the south of the Yangtze River.