Impacts of anthropogenic activities on climate change in arid and semiarid areas based on CMIP5 models

Based on all (ALL) forcing and single-forcing runs from CMIP5 (Coupled Model Intercomparison Project Phase 5) simulations, the present paper examines the anthropogenic influence of greenhouse gases (GHG), anthropogenic aerosols (AA), land use (LU) and combined anthropogenic (Ant) effects on climate change in global arid and semiarid regions. Significant warming is a robust feature over the global land as a response to Ant and GHG forcings, and the warming rate from the latter forcing is two to three times that of ALL forcing results over the past 60 years. AA produces remarkable cooling over the global land surface, whereas LU leads to slight cooling in most arid and semiarid areas. GHG- and Ant-driven increases of precipitation are found in most land areas, especially in arid and semiarid regions. AA and LU produce substantial variation of precipitation over various areas, and current uncertainties are relatively great in AA and LU forcing runs. Ensemble Empirical Mode Decomposition (EEMD) is used to analyze temporal scales of annual temperature and precipitation. The results show that interdecadal and multidecadal variations of temperature and precipitation are attributable to combined natural and anthropogenic forcings in most arid and semiarid regions, where AA dominates variations of both temperature and precipitation on multidecadal timescales. Both GHG and LU have positive effects on multidecadal changes of precipitation over arid and semiarid regions globally. However, the latter significantly prevents multidecadal changes of temperature over arid and semiarid regions of Australia.