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The challenge of accurately quantifying future megadrought risk in the American Southwest
Author(s) -
Coats Sloan,
Mankin Justin S.
Publication year - 2016
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1002/2016gl070445
Subject(s) - forcing (mathematics) , environmental science , term (time) , climatology , scale (ratio) , current (fluid) , risk assessment , climate change , natural (archaeology) , geology , geography , oceanography , computer science , cartography , paleontology , physics , computer security , quantum mechanics
American Southwest (ASW) megadroughts represent decadal‐scale periods of dry conditions the near‐term risks of which arise from natural low‐frequency hydroclimate variability and anthropogenic forcing. A large single‐climate‐model ensemble indicates that anthropogenic forcing increases near‐term ASW megadrought risk by a factor of 100; however, accurate risk assessment remains a challenge. At the global‐scale we find that anthropogenic forcing may alter the variability driving megadroughts over 55% of land areas, undermining accurate assessments of their risk. For the remaining areas, current ensembles are too small to characterize megadroughts' driving variability. For example, constraining uncertainty in near‐term ASW megadrought risk to 5 percentage points with high confidence requires 287 simulations. Such ensemble sizes are beyond current computational and storage resources, and these limitations suggest that constraining errors in near‐term megadrought risk projections with high confidence—even in places where underlying variability is stationary—is not currently possible.