Changes in Seasonality in China under Enhanced Atmospheric CO2 Concentration

Seasonality changes in China under elevated atmospheric CO2 concentrations were simulated using nine global climate models, assuming a 1% per year in- crease in atmospheric CO2. Simulations of 20th century experiments of season changes in China from the periods 196180 to 19812000 were also assessed using the same models. The results show that the ensemble mean simula- tion of the nine models performs better than that of an individual model simulation. Compared the mean clima- tology of the last 20 years in the CO2-quadrupling ex- periments with that in the CO2-doubling ones, the ensem- ble mean results show that the hottest/coldest continu- ous-90-day (local summer/winter) mean temperature in- creased by 3.4/4.5°C, 2.7/2.9°C, and 2.9/4.1°C in North- east (NE), Southwest (SW), and Southeast (SE) China, respectively, indicating a weakening seasonal amplitude (SA), but by 4.4/4.0°C in Northwest (NW) China, indi- cating an enlarging SA. The local summer lengthened by 37/30/66/54 days in NW, NE, SW, and SE China, respec- tively. In some models, the winter disappeared during the CO2-quadrupling period, judging by the threshold based on the CO2-doubling period. The average of the other model simulations show that the local winter shortened by 42/36/61/44 days respectively, in the previously men- tioned regions.