Projected Temperature and Precipitation Changes over Major Land Regions of the Belt and Road Initiative under the 1.5°C and 2°C Climate Targets by the CMIP6 Multi-Model Ensemble

Surface air temperature and precipitation changes over major land regions of the Belt and Road Initiative under the 1.5°C and 2°C climate targets are projected by the multi-model ensemble (MME) method based on the 16-member CMIP6. The MME mean simulations of 16-member CMIP6 can capture observed spatial structures in surface air temperature and precipitation for the period of 1995−2014. Relative to the pre-industrial levels (1850−1900), the global warming of 1.5°C and 2°C will occur in the middle and late 2020s and around 2040, respectively, for the Shared Socioeconomic Pathways 2-Representative Concentration Pathways 4.5 (SSP2-4.5), SSP3-7.0 and SSP5-8.5. Under the 1.5°C and 2°C climate targets, the MME mean projections show that averaged over major land regions of the Belt and Road Initiative, annual average surface air temperature will increase significantly by 1.84°C and 2.43°C with a difference of 0.59°C; for the standard deviations between 16-CMIP6 models, they are 0.18°C and 0.21°C. Annual precipitation will increase significantly by 20.14 mm/a and 30.02 mm/a, with a difference of 9.88 mm/a; and the standard deviations between 16-CMIP6 models are 10.79 mm/a and 13.72 mm/a. Spatially, annual mean surface air temperature are projected to generally have significant increases over the whole study areas compared with the pre-industrial levels under the two global warming targets with the stronger warming magnitudes at high latitudes than at low latitudes. Future precipitation variations are projected to show clear spatial differences: Annual mean precipitation will decrease over the Mediterranean and Black Sea regions, yet increase over most of the remaining areas. The aridity represented by P-E index will reach the maximum in Europe, Southern China to Indochina Peninsula, South Asia, Eastern India, Southeast Asia and Central Africa.