Articles | Volume 18, issue 12
Research article
19 Dec 2014
Research article |  | 19 Dec 2014

Climate change and sectors of the surface water cycle In CMIP5 projections

P. A. Dirmeyer, G. Fang, Z. Wang, P. Yadav, and A. Milton

Abstract. Results from 10 global climate change models are synthesized to investigate changes in extremes, defined as wettest and driest deciles in precipitation, soil moisture and runoff based on each model's historical 20th century simulated climatology. Under a moderate warming scenario, regional increases in drought frequency are found with little increase in floods. For more severe warming, both drought and flood become much more prevalent, with nearly the entire globe significantly affected. Soil moisture changes tend toward drying, while runoff trends toward flood. To determine how different sectors of society dependent on various components of the surface water cycle may be affected, changes in monthly means and interannual variability are compared to data sets of crop distribution and river basin boundaries. For precipitation, changes in interannual variability can be important even when there is little change in the long-term mean. Over 20% of the globe is projected to experience a combination of reduced precipitation and increased variability under severe warming. There are large differences in the vulnerability of different types of crops, depending on their spatial distributions. Increases in soil moisture variability are again found to be a threat even where soil moisture is not projected to decrease. The combination of increased variability and greater annual discharge over many basins portends increased risk of river flooding, although a number of basins are projected to suffer surface water shortages.

Short summary
Climate change simulations project drought to increase even under moderate warming scenarios; both droughts and floods increase sharply with severe warming. Over 20% of the globe is projected to experience reduced rainfall but greater year-to-year variability. The vulnerability of growing regions for many types of crops are assessed based on soil moisture, and rivers using runoff projections. Increased water cycle variability is found to be a threat to agriculture and river systems as well.