The challenge of accurately quantifying future megadrought risk in the American Southwest

Abstract 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...

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Main Authors: Sloan Coats, Justin S. Mankin
Format: Article
Language:English
Published: Wiley 2016-09-01
Series:Geophysical Research Letters
Subjects:
Online Access:https://doi.org/10.1002/2016GL070445
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author Sloan Coats
Justin S. Mankin
author_facet Sloan Coats
Justin S. Mankin
author_sort Sloan Coats
collection DOAJ
description Abstract 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.
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spelling doaj-art-ce537f9011774fa2aebaba4c7163f6cf2025-08-20T03:49:45ZengWileyGeophysical Research Letters0094-82761944-80072016-09-0143179225923310.1002/2016GL070445The challenge of accurately quantifying future megadrought risk in the American SouthwestSloan Coats0Justin S. Mankin1Cooperative Institute for Research in Environmental Sciences University of Colorado Boulder Boulder Colorado USAOcean and Climate Physics Lamont‐Doherty Earth Observatory of Columbia University Palisades New York USAAbstract 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.https://doi.org/10.1002/2016GL070445hydroclimatedroughtNorth Americaclimatemegadroughtprojections
spellingShingle Sloan Coats
Justin S. Mankin
The challenge of accurately quantifying future megadrought risk in the American Southwest
Geophysical Research Letters
hydroclimate
drought
North America
climate
megadrought
projections
title The challenge of accurately quantifying future megadrought risk in the American Southwest
title_full The challenge of accurately quantifying future megadrought risk in the American Southwest
title_fullStr The challenge of accurately quantifying future megadrought risk in the American Southwest
title_full_unstemmed The challenge of accurately quantifying future megadrought risk in the American Southwest
title_short The challenge of accurately quantifying future megadrought risk in the American Southwest
title_sort challenge of accurately quantifying future megadrought risk in the american southwest
topic hydroclimate
drought
North America
climate
megadrought
projections
url https://doi.org/10.1002/2016GL070445
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