loading page

CO2-plant effects do not account for the gap between dryness indices and projected dryness impacts in CMIP5 or CMIP6
  • +1
  • Jacob Scheff,
  • Justin S Mankin,
  • Sloan Coats,
  • Haibo Liu
Jacob Scheff
UNC Charlotte

Corresponding Author:[email protected]

Author Profile
Justin S Mankin
Dartmouth College
Author Profile
Sloan Coats
University of Hawaii
Author Profile
Haibo Liu
columbia university
Author Profile


Recent studies have found that terrestrial dryness indices like the Palmer Drought Severity Index, Standardized Precipitation Evapotranspiration Index, and Aridity Index calculated from climate model projections are mostly negative, implying a drier land surface with future warming. Yet, the same models’ prognostic runoff and bulk soil moisture projections instead feature regional signals of varying sign, suggesting that the dryness indices could overstate climate change’s direct impacts. Observed trends also show this “index-impact gap.” Most 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 model experiments that switch off CO2 effects on plants. In these simulations, mean PDSI, Aridity Index, and SPEI still decline broadly with warming, while mean runoff and bulk soil moisture still respond more equivocally. This implies that CO2-plant effects are not the dominant or sole reason for the index-impact gap.
01 Mar 2021Published in Environmental Research Letters volume 16 issue 3 on pages 034018. 10.1088/1748-9326/abd8fd