Model spread in tropical low cloud feedback tied to overturning circulation response to warming

Kathleen A. Schiro, Hui Su, Fiaz Ahmed, Ni Dai, Clare E. Singer, Pierre Gentine, Gregory S. Elsaesser, Jonathan H. Jiang, Yong Sang Choi, J. David Neelin

Research output: Contribution to journalArticlepeer-review

12 Scopus citations

Abstract

Among models participating in the Coupled Model Intercomparison Project phase 6 (CMIP6), here we show that the magnitude of the tropical low cloud feedback, which contributes considerably to uncertainty in estimates of climate sensitivity, is intimately linked to tropical deep convection and its effects on the tropical atmospheric overturning circulation. First, a reduction in tropical ascent area and an increased frequency of heavy precipitation result in high cloud reduction and upper-tropospheric drying, which increases longwave cooling and reduces subsidence weakening, favoring low cloud reduction (Radiation-Subsidence Pathway). Second, increased longwave cooling decreases tropospheric stability, which also reduces subsidence weakening and low cloudiness (Stability-Subsidence Pathway). In summary, greater high cloud reduction and upper-tropospheric drying (negative longwave feedback) lead to a more positive cloud feedback among CMIP6 models by contributing to a greater reduction in low cloudiness (positive shortwave feedback). Varying strengths of the two pathways contribute considerably to the intermodel spread in climate sensitivity.

Original languageEnglish
Article number7119
JournalNature Communications
Volume13
Issue number1
DOIs
StatePublished - Dec 2022

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© 2022, The Author(s).

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