Abstract
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.
Highlights
The suite of climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) offers a wealth of information about the potential for future climate change across a range of emission/mitigation scenarios
The CMIP5 simulations have suggested that hydrologic feedbacks of the land surface to the atmosphere are likely to intensify and the spatial and temporal extent of the regions of strong feedbacks will expand in the 21st century (Dirmeyer et al, 2013, 2014)
We focus on the median value and the value of the lowest decile (50 and 10 % of the cumulative distributions, respectively) in the historical case, and find what fraction of the crop areas lie below those values in the future climate cases
Summary
The suite of climate model simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5) offers a wealth of information about the potential for future climate change across a range of emission/mitigation scenarios. Recent studies have used the output of a small number of CMIP5 models to drive an additional suite of sector models to assess changes in the likelihood of flood (Dankers et al, 2014), drought (Prudhomme et al, 2014), significant water resource impacts (Schewe et al, 2014) and agriculture (Rosenzweig et al, 2014). In such a two-step modeling approach, versions of the same land surface model are sometimes employed twice (once in the CMIP5 climate model and again as a sector model) or different land surface models are convolved where inconsistencies can amplify errors (cf Koster et al, 2009)
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