Numerical simulation of climate change in 21 century under two different mitigation scenarios.

The climate system model BCC_CSM1.0, newly developed by National Climate Center, is used to simulate climate influences of two mitigation scenarios (De90 and De07) on global and China climate compared to the B1 emissions scenario. The mitigation scenarios De90 and De07 represent CO2 emissions are linearly decreased during 2012-2050, and mitigated to half of that in 1990 and 2007 by 2050, respectively. Results show that the global mean surface air temperature simulated by the model under the two mitigation scenarios has been lower than that under the B1 scenario since 2040s. This is twenty years later than when the concentrations of the mitigation scenarios are less than that of the B1 scenario. Although the stabilization emission level of De90 scenario is lower than De07 after 2050, the global warming amplitude under De90 scenario has been lower than that under De07 scenario since 2070. Such delay effect may be related to the inertia of the coupled system (mainly the ocean). By the end of 21 century, the warming amplitudes of De90 and De07 are lowered by 0.4℃ and 0.2℃, respectively. Globally, the warming amplitude during 2070-2099 under B1 scenario is largest in the high amplitudes of the North Hemisphere and the North Pole. The mitigation scenarios significantly mitigate the warming in those regions. In China, regional mean warming amplitude by the end of 21 century is higher than the global mean by about 1.2℃. This is lowered by De90 and De07 scenario about 0.4℃ and 0.3℃, respectively. Northern China is warmer than that in southern China and the southern coasts during 2070-2099. The mitigation emission scenarios significantly decrease the warming amplitude in western China. Seasonally, the global warming during 2070-2099 is largest in winter. De90 and De07 can mitigate the warming in each season by about 17% and 10%, respectively.