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Cloud feedback uncertainty in the equatorial Pacific across CMIP6 models
  • Peter Gordon Hill,
  • Declan Luke Finney,
  • Mark D. Zelinka
Peter Gordon Hill
University of Reading
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Declan Luke Finney
University of Leeds

Corresponding Author:[email protected]

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Mark D. Zelinka
Lawrence Livermore National Laboratory (DOE)
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Abstract

Cloud feedback is the largest uncertainty in estimating Equilibrium Climate Sensitivity. In this study we focus on the equatorial Pacific, where CMIP6 model cloud feedback spread is notably large. Cloud radiative effects in this region are relevant for the global climate. Our findings show that models predict a consistent shift towards the ascent regime in response to El Nino-like sea surface warming. Models diverge in terms of the radiative impact due to differences in cloud morphology in ascent and subsidence regimes. Using the observed relationship between circulation regime and cloud radiative effect, we find a reduction in the regional mean cloud feedback estimate from 0.77 to 0.22 Wm-2K-1, though this does not substantially lessen the model spread in total feedback. Pathways to reduce this spread include: improving confidence in the regional ocean warming pattern, and using observations and models to understand cloud morphology and circulation interactions.
02 Oct 2024Submitted to ESS Open Archive
04 Oct 2024Published in ESS Open Archive