CO2-plant effects do not account for the gap between dryness indices and projected dryness impacts in CMIP6 or CMIP5

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Scheff, J., Mankin, J. S., Coats, S., & Liu, H. (2021). CO2-plant effects do not account for the gap between dryness indices and projected dryness impacts in CMIP6 or CMIP5. Environmental Research Letters. https://doi.org/doi:10.1088/1748-9326/abd8fd
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Faculty, Recent studies have found that terrestrial dryness indices like the Palmer Drought Severity Index (PDSI), Standardized Precipitation Evapotranspiration Index (SPEI), and Aridity Index calculated from future climate model projections are mostly negative, implying a drying land surface with warming. Yet, the same models’ future runoff and bulk soil moisture projections instead show regional signals of varying sign, and their vegetation projections show widespread greening, suggesting that the dryness indices could overstate climate change’s direct impacts. Most modeling studies have attributed this gap to the indices’ omission of CO2-driven stomatal closure. However, here we show that the index-impact gap is still wide even in future-like model experiments that switch off CO2 effects on plants. In these simulations, mean PDSI, Aridity Index, and SPEI still decline broadly with strong warming, while mean runoff, bulk soil moisture, and vegetation still respond more equivocally. This implies that CO2-plant effects are not the dominant or sole reason for the simulated index-impact gap. We discuss several alternative mechanisms that may explain it.

Details
Title

CO2-plant effects do not account for the gap between dryness indices and projected dryness impacts in CMIP6 or CMIP5

Author(s)

Scheff, Jacob
Mankin, Justin S.
Coats, Sloan
Liu, Haibo

UNC Charlotte Affiliate Type

Faculty

Extent

1 online resource

Date Created

2021

Genre

articles

Resource Type

text

Abstract

Recent studies have found that terrestrial dryness indices like the Palmer Drought Severity Index (PDSI), Standardized Precipitation Evapotranspiration Index (SPEI), and Aridity Index calculated from future climate model projections are mostly negative, implying a drying land surface with warming. Yet, the same models’ future runoff and bulk soil moisture projections instead show regional signals of varying sign, and their vegetation projections show widespread greening, suggesting that the dryness indices could overstate climate change’s direct impacts. Most modeling studies have attributed this gap to the indices’ omission of CO2-driven stomatal closure. However, here we show that the index-impact gap is still wide even in future-like model experiments that switch off CO2 effects on plants. In these simulations, mean PDSI, Aridity Index, and SPEI still decline broadly with strong warming, while mean runoff, bulk soil moisture, and vegetation still respond more equivocally. This implies that CO2-plant effects are not the dominant or sole reason for the simulated index-impact gap. We discuss several alternative mechanisms that may explain it.

Subjects--Topics

Climatic changes
Earth sciences

Is Part Of

Environmental research letters

Language

English

Published Version (Please cite this version)

doi:10.1088/1748-9326/abd8fd

Publisher's Version

https://doi.org/10.1088/1748-9326/abd8fd

Permalink

http://hdl.handle.net/20.500.13093/work:1041

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