Twenty-first century hydroclimate: A continually changing baseline, with more frequent extremes

Journal Article · Mon Mar 14 00:00:00 EDT 2022 · Proceedings of the National Academy of Sciences of the United States of America

DOI:https://doi.org/10.1073/pnas.2108124119· OSTI ID:1904229

Stevenson, Samantha ^[1]; Coats, Sloan ^[2]; Touma, Danielle ^[3]; Cole, Julia ^[4]; Lehner, Flavio ^[5]; Fasullo, John ^[6]; Otto-Bliesner, Bette ^[6]

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1. Univ. of California, Santa Barbara, CA (United States); OSTI
2. Univ. of Hawaii at Manoa, Honolulu, HI (United States)
3. Univ. of California, Santa Barbara, CA (United States)
4. Univ. of Michigan, Ann Arbor, MI (United States)
5. Cornell Univ., Ithaca, NY (United States); National Center for Atmospheric Research (NCAR), Boulder, CO (United States); Eidgenoessische Technische Hochschule (ETH), Zurich (Switzerland)
6. Cornell Univ., Ithaca, NY (United States)

Variability in hydroclimate impacts natural and human systems worldwide. In particular, both decadal variability and extreme precipitation events have substantial effects and are anticipated to be strongly influenced by climate change. From a practical perspective, these impacts will be felt relative to the continuously evolving background climate. Removing the underlying forced trend is therefore necessary to assess the relative impacts, but to date, the small size of most climate model ensembles has made it difficult to do this. Here we use an archive of large ensembles run under a high-emissions scenario to determine how decadal “megadrought” and “megapluvial” events—and shorter-term precipitation extremes—will vary relative to that changing baseline. When the trend is retained, mean state changes dominate: In fact, soil moisture changes are so large in some regions that conditions that would be considered a megadrought or pluvial event today are projected to become average. Time-of-emergence calculations suggest that in some regions including Europe and western North America, this shift may have already taken place and could be imminent elsewhere: Emergence of drought/pluvial conditions occurs over 61% of the global land surface (excluding Antarctica) by 2080. Relative to the changing baseline, megadrought/megapluvial risk either will not change or is slightly reduced. However, the increased frequency and intensity of both extreme wet and dry precipitation events will likely present adaptation challenges beyond anything currently experienced. In many regions, resilience against future hazards will require adapting to an ever-changing “normal,” characterized by unprecedented aridification/wetting punctuated by more severe extremes.

• Research Organization: Georgia Institute of Technology, Atlanta, GA (United States); University Corporation for Atmospheric Research, Boulder, CO (United States)
• Sponsoring Organization: National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); Swiss National Science Foundation; USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: SC0019418; SC0022070
• OSTI ID: 1904229
• Journal Information: Proceedings of the National Academy of Sciences of the United States of America, Journal Name: Proceedings of the National Academy of Sciences of the United States of America Journal Issue: 12 Vol. 119; ISSN 0027-8424
• Publisher: National Academy of Sciences
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
climate change
drought
extreme events
hydroclimate
large ensembles