Regional And Seasonal Temperature Characteristics Under The Background Of Global Warming Slowdown

Global surface air temperature (TAS) raised rapidly after mid-1970s with a heating rate of0.30℃/10a. However, the heating rate has slowed down to0.14℃/10a which has decreased by more than50%since2000. Using the monthly mean Climatic Research Unit surface air temperature high-resolution gridded datasets, and sets of CMIP5historical experiments and representative concentration pathways (RCPs) of33models, this paper discusses the characteristics of annual average TAS in different areas and seasons under the period of global warming slowdown and different periods of20th century, and estimates temperature in the future. The main conclusions are as follows:(1) The results point out that the mid-high latitudes of Eurasia (40-65°N,45-150°E) is the region which has the largest contribution to global warming slowdown, and the temperature of autumn and winter show inverse variation in this region since2000, which means interdecadal warming in autumn, and cooling in winter. Judging from configuration of the atmospheric circulation, in lower troposphere, the intensity of Siberian High weakens interdecadally in autumn, while enhances in winter; In upper troposphere, the geopotential height presents a "high-low-high" anomaly distribution from Western Europe to Northeast Asia, with zonal circulation strengthened and meridional circulation weakened, while in winter, the geopotential height presents a dipole pattern between polar and Lake Baikal region, with East Asian trough deepened and meridional circulation strengthened.(2) Within20th century, annual global TAS increased from1911to1940, decreased between1941and1958, and accelerated after1976.4models out of33models of CMIP5historical experiments have familiar simulation results of TAS in decadal timescales, which are bcc-csm1.1, IPSL-CM5A-MR, MRI-ESM1and CESM1(WACCM). From1901to2005, MRI-ESM1model has the similar simulation result of heating rates for globe and each region compared with CRU observation, and the mid-high latitudes of Eurasia is the region which has the largest contribution to global warming, but the seasonal variation of heating rate cannot be simulated by the4models. For the transition of warming period to cooling, the heating rates of globe and seasons have all decreased among4models. For the transition of cooling period to accelerating, bcc-csm1.1can reflect the fact that the mid-high latitudes of Eurasia is the region which has the largest contribution. In the period of warming, temperature raised in spring, summer and autumn, while decreased in winter in the mid-high latitudes of Eurasia; in the cooling period, temperature of winter raised, and only IPSL-CM5A-MR model has the simulation ability of this characteristics.(3) In the period of global warming slowdown, MRI-ESM1model in RCP8.5scenario can simulate the characteristics that temperature decreased in the mid-high latitudes of Eurasia and the interdecadal warming in autumn and cooling in winter after2000. The spatial distribution of TAS linear trend is also consistent with observation. The results of bcc-csm1.1in RCP4.5scenario and RCP2.6can reflect cooling trend in the mid-high latitudes of Eurasia, but the opposite phase of autumn and winter only exists in the RCP2.6scenario. After2012, MRI-ESM1in RCP8.5scenario shows that the temperature amplitude of variation does not change significantly before2025, and the heating rate is only0.07℃/10a. While temperature rises rapidly after2025, the heating rate is0.66℃/10a in2025-2050, far greater than any heating rate of period in the past one hundred years. Characteristics of temperature in the future simulated by bcc-csm1.1model in RCP2.6scenario are distinct from the results of MRI-ESM1, the temperature changes abruptly around2020, and then oscillates near the average value of2℃.