Uncertainties in historical changes and future projections of drought. Part II: model-simulated historical and future drought changes

摘要: While most models project large increases in agricultural drought frequency and severity the 21st century, significant uncertainties exist these projections. Here, we compare model-simulated changes with observation-based estimates since 1900 examine model projections from both Coupled Model Inter-comparison Project Phase 3 (CMIP3) 5 (CMIP5). We use self-calibrated Palmer Drought Severity Index Penman-Monteith potential evapotranspiration (PET) (sc_PDSI_pm) as a measure of drought. Results show that estimated long-term global hemispheric areas to 2014 are consistent CMIP3 CMIP5 response historical greenhouse gases other external forcing, short-term variations within spread internal variability, despite regional still dominated by variability. Both continued (by 50–200 % relative sense) century area even under low-moderate emissions scenarios, resulting decrease mean flattening probability distribution functions (PDFs) sc_PDSI_pm. This is especially pronounced over Northern Hemisphere land, leading increased increasing Large differences model-projected precipitation Sahel northern Australia due simulating African Inter-tropical convergence zone (ITCZ) subsidence Australia, while wetting trend East Africa reflects robust Indian Ocean ITCZ seen models. warming-induced PET all latitudes decreases subtropical land responsible for sc_PDSI_pm decreases, exact cause its PDF needs further investigation.