Eastern equatorial Pacific warming delayed by aerosols and thermostat response to CO₂ increase

Ulla K. Heede (1) , Alexey V. Fedorov (2, 1)

1 Department of Earth and Planetary Sciences [New Haven]
2 VARCLIM - Océan et variabilité du climat

Understanding the tropical Pacific response to global warming remains challenging. Here we use a range of Coupled Model Intercomparison Project Phase 6 greenhouse warming experiments to assess the recent and future evolution of the equatorial Pacific east-west temperature gradient and corresponding Walker circulation. In abrupt CO₂-increase scenarios, many models generate an initial strengthening of this gradient resembling an ocean thermostat, followed by a small weakening; other models generate an immediate weakening that becomes progressively stronger, establishing a pronounced eastern equatorial Pacific warming pattern. The initial response in these experiments is a strong predictor for the intensity of this pattern simulated in both abrupt and realistic warming scenarios, but not in historical simulations showing no multi-model-mean warming trend in this region. The likely explanation is that the recent CO₂-driven changes in the tropical Pacific are masked by aerosol effects and a potential ocean-thermostat-related delay, while the eastern equatorial Pacific warming pattern will emerge as greenhouse gases overcome aerosol forcing.

Domaines: Planète et Univers [physics]

Ulla K. Heede, Alexey V. Fedorov. Eastern equatorial Pacific warming delayed by aerosols and thermostat response to CO₂ increase. Nature Climate Change, 2021, 11, pp.696-703. ⟨10.1038/s41558-021-01101-x⟩. ⟨insu-03747042⟩