The Occurrence of Global Drought Under Future Climate Scenarios

GCM predictions of future climate change indicate substantial changes in globally averaged precipitation and other water balance variables. The distribution of these changes in space is predicted to be quite variable however, with some regions predicted to experience increases and others regions decreases. These combined changes may manifest themselves locally through the impact of natural hazards such as droughts and floods. The assessment of how these changes translate into actual levels of impact is useful in planning and mitigation in the face of potential change. In this study we generate scenarios of drought occurrence under potential future climates. The occurrence of drought is determined from a physically based drought index using soil moisture fields from simulations using the Variable Infiltration Capacity (VIC) land surface model. Future climate simulations are compared with historic simulations using probability density functions of soil moisture. The historic simulations are driven by a 50-yr forcing dataset based on the NCEP/NCAR Reanalysis, corrected for biases in precipitation totals and rain day statistics, air temperature, and radiation. The future climate forcings are based on data from two GCM simulations of future climates scaled to remove systematic biases. We show the predicted development of drought over the next 100 years and changes in the occurrence and intensity of drought events at regional scales.