reference : Plant responses to increasing CO2 reduce estimates of climate impacts on drought severity

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/reference/b673e746-6eca-4b77-8a62-e1ae9ed6380a
Bibliographic fields
reftype Journal Article
Abstract Rising atmospheric CO2 will make Earth warmer, and many studies have inferred that this warming will cause droughts to become more widespread and severe. However, rising atmospheric CO2 also modifies stomatal conductance and plant water use, processes that are often are overlooked in impact analysis. We find that plant physiological responses to CO2 reduce predictions of future drought stress, and that this reduction is captured by using plant-centric rather than atmosphere-centric metrics from Earth system models (ESMs). The atmosphere-centric Palmer Drought Severity Index predicts future increases in drought stress for more than 70% of global land area. This area drops to 37% with the use of precipitation minus evapotranspiration (P-E), a measure that represents the water flux available to downstream ecosystems and humans. The two metrics yield consistent estimates of increasing stress in regions where precipitation decreases are more robust (southern North America, northeastern South America, and southern Europe). The metrics produce diverging estimates elsewhere, with P-E predicting decreasing stress across temperate Asia and central Africa. The differing sensitivity of drought metrics to radiative and physiological aspects of increasing CO2 partly explains the divergent estimates of future drought reported in recent studies. Further, use of ESM output in offline models may double-count plant feedbacks on relative humidity and other surface variables, leading to overestimates of future stress. The use of drought metrics that account for the response of plant transpiration to changing CO2, including direct use of P-E and soil moisture from ESMs, is needed to reduce uncertainties in future assessment.
Author Swann, Abigail L. S.; Hoffman, Forrest M.; Koven, Charles D.; Randerson, James T.
DOI 10.1073/pnas.1604581113
Date September 6, 2016
Issue 36
Journal Proceedings of the National Academy of Sciences of the United States of America
Pages 10019-10024
Title Plant responses to increasing CO2 reduce estimates of climate impacts on drought severity
Volume 113
Year 2016
Bibliographic identifiers
.reference_type 0
_record_number 21010
_uuid b673e746-6eca-4b77-8a62-e1ae9ed6380a