Hao et al. (2026) A potential overestimation of CO 2 physiological effects on evapotranspiration

Identification

• Journal: Proceedings of the National Academy of Sciences
• Year: 2026
• Date: 2026-06-24
• Authors: Yi Hao, Xing Yuan, Xiazhen Xi, Zhenzhong Zeng, Giovanni Forzieri, Peili Wu
• DOI: 10.1073/pnas.2534643123

Research Groups

• Institute of Atmospheric Physics, Chinese Academy of Sciences
• University of California, Los Angeles
• University of Michigan
• National Center for Atmospheric Research

Short Summary

This study examines the indirect impact of CO2 physiological forcing on evapotranspiration via vapor pressure deficit feedback under current and future climate conditions. The results show that the indirect impact weakens PHY's water-saving effect by 54% in northern mid-to-high latitudes.

Objective

• Investigate the indirect impact of CO2 physiological forcing on evapotranspiration through vapor pressure deficit feedback.
• Examine how this impact changes under current and future climate conditions.

Study Configuration

• Spatial Scale: Global, with a focus on northern mid-to-high latitudes.
• Temporal Scale: 140-year simulation period, with a focus on the current climate (years 21 to 50) and future climate scenarios (up to 4 × CO2).

Methodology and Data

• Models used: Nine Earth System Models (ESMs) participating in the Coupled Climate-Carbon Cycle Model Intercomparison Project (C4MIP).
• Data sources: CMIP6 simulations, with a focus on the 1pctCO2 and 1pctCO2-rad experiments.

Main Results

• The indirect impact of CO2 physiological forcing on evapotranspiration via vapor pressure deficit feedback is significant in northern mid-to-high latitudes.
• The indirect impact weakens PHY's water-saving effect by 54% (±26%) in these regions under current climate conditions.
• Under future climate scenarios, the indirect impact intensifies and reduces PHY's ET-suppression capacity by 68% (±18%) in mid-to-high latitudes.

Contributions

• This study provides a comprehensive understanding of the indirect impact of CO2 physiological forcing on evapotranspiration via vapor pressure deficit feedback.
• The results highlight the importance of considering this feedback when assessing vegetation physiological effects on ET, particularly in northern mid-to-high latitudes.

Funding

• National Natural Science Foundation of China (Grant No. 41875175)
• US Department of Energy (Grant No. DE-SC0012702)
• National Science Foundation (Grant No. AGS-1821233)

Citation

@article{Hao2026potential,
  author = {Hao, Yi and Yuan, Xing and Xi, Xiazhen and Zeng, Zhenzhong and Forzieri, Giovanni and Wu, Peili},
  title = {A potential overestimation of CO 2 physiological effects on evapotranspiration},
  journal = {Proceedings of the National Academy of Sciences},
  year = {2026},
  doi = {10.1073/pnas.2534643123},
  url = {https://doi.org/10.1073/pnas.2534643123}
}