CMIP5-based threshold-crossing times of 1.5℃ and 2℃ global warming above pre-industrial levels

doi:10.12006/j.issn.1673-1719.2017.230

Abstract

Abstract:

Based on the outputs of CMIP5 models, 1.5℃ and 2℃ global warming threshold-crossing time above pre-industrial levels are evaluated under different Representative Concentration Pathways (RCPs) scenarios. The results of multi-model ensemble showed that relative to the pre-industrial levels, the global warming would exceed 1.5℃ threshold in 2029, 2028 and 2025 in the RCP2.6,RCP4.5 and RCP8.5 scenarios, respectively. Under RCP2.6 scenario, the global warming would be kept below 2℃ until the end of the 21st century while the 2℃ global warming would occur around 2048 and 2040 in the RCP4.5 and RCP8.5 scenarios. The time required from 1.5℃ to 2℃ global warming threshold is cut down in RCP8.5 compared with RCP4.5. On the regional scales, the threshold-crossing times over the land are earlier than those over the ocean and show little difference among scenarios whereas the time can be advanced in stronger emission for the ocean. Regarding global warming, the times crossing 1.5℃ and 2℃ warming threshold in China are both earlier, especially for Northeast China and Northwest China.

Key words: CIMP5, 1.5℃warming, 2℃warming, Threshold-crossing time, Geographical variations

Meng-Zi ZHOU,Guang-Sheng ZHOU,Xiao-Min LYU,Li ZHOU,Yu-He JI. CMIP5-based threshold-crossing times of 1.5℃ and 2℃ global warming above pre-industrial levels[J]. Climate Change Research, 2018, 14(3): 221-227.

Figures/Tables 5

Table 1 Basic information of global climate models from CMIP5

Fig. 1 The time series of global mean surface temperature relative to the reference period (1861-1990) under RCP2.6 (a) RCP4.5(b) RCP8.5 (c) scenarios

Fig. 2 Equivalent CO2 concentration of greenhouse gases under RCP2.6, RCP4.5 and RCP8.5 scenarios

Fig. 3 The proportion of climate models in which the temperature change exceeds the 1.5℃ and 2℃ thresholds in each particular year. The vertical black lines indicate the mean expected 1.5℃and 2℃threshold-crossing time. The red and blue vertical lines refer to 90% confidence intervals

Fig. 4 The spatial distribution of 1.5℃ and 2℃ threshold-crossing times. The white refers to the regions which are below the corresponding threshold by the end of the 21st century

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