Guendelman et al. (2026) The role of atmospheric fast adjustment in the distinct precipitation response between increase and decrease of CO2 concentrations

Identification

• Journal: npj Climate and Atmospheric Science
• Year: 2026
• Date: 2026-07-23
• Authors: Ilai Guendelman, Ivan Mitevski, Gabriel Vecchi
• DOI: 10.1038/s41612-026-01488-4

Research Groups

• Department of Earth and Environmental Sciences, Ben Gurion University of the Negev, Israel
• Geoscience Department, Princeton University, NJ, USA
• High Meadows Environmental Institute, Princeton University, NJ, USA

Short Summary

This study examines the global mean precipitation response to different CO2 perturbations using idealized climate model experiments. The results show that the apparent hydrological sensitivity is asymmetric when comparing increases (doubling) and decreases (halving) of CO2 concentrations from pre-industrial conditions.

Objective

• Investigate the role of fast atmospheric adjustments in shaping the hydrological response to CO2 forcing across different experimental designs

Study Configuration

• Spatial Scale: Global mean precipitation response
• Temporal Scale: Abrupt doubling and halving experiments with a duration of 150 years, as well as transient CDR simulations with a period of 140 years of increase and subsequent 140 years of decrease of CO2 concentration

Methodology and Data

• Models used: CESM1, GFDL-CM2, CanESM5, CESM2, CNRM, GISS, IPSL, MIROC6, MRI, TaiESM
• Data sources: CMIP simulations, NonLinMIP simulations

Main Results

• The apparent hydrological sensitivity is larger for halving than for doubling CO2 concentrations from pre-industrial conditions.
• The asymmetry in the fast adjustments between the doubling and halving of CO2 from PI arises almost entirely from changes in clear-sky longwave radiative cooling.
• Fast adjustments contribute directly to the CDR hysteresis beyond the slow, ocean-mediated component.

Contributions

• This study highlights the role of fast atmospheric adjustments in shaping the hydrological response to CO2 forcing across different experimental designs.
• The results provide new insights into the mechanisms driving the precipitation response asymmetry between increasing and decreasing CO2 concentrations.

Funding

• Cooperative Institute for Modeling the Earth System
• Guilford Glazer Foundation
• HESS Postdoctoral Fellowship
• Simons Foundation (MPS-SRM-00006584)

Citation

@article{Guendelman2026role,
  author = {Guendelman, Ilai and Mitevski, Ivan and Vecchi, Gabriel},
  title = {The role of atmospheric fast adjustment in the distinct precipitation response between increase and decrease of CO2 concentrations},
  journal = {npj Climate and Atmospheric Science},
  year = {2026},
  doi = {10.1038/s41612-026-01488-4},
  url = {https://doi.org/10.1038/s41612-026-01488-4}
}