High-resolution simulations reveal positive global warming feedback from Pacific low clouds.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 42497251.
- Also identified by DOI 10.1126/sciadv.aec8488 and PMC identifier 13398498.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Uncertainty in marine low-level cloud feedbacks limits accurate climate projections. Using 7083 high-resolution simulations of tropical Pacific low clouds, we separated the impacts of sea surface warming from direct carbon dioxide (CO<sub>2</sub>) effects. Surface warming alone drives a positive low-cloud feedback of [Formula: see text]. While this changes little with doubled CO<sub>2</sub>, the total cloud radiative response strengthens markedly to [Formula: see text] under quadrupled CO<sub>2</sub>, revealing a strong nonlinear interaction. Surface warming alone modifies the boundary layer through increased inversion strength and weakened subsidence, which buffers clouds by promoting higher liquid water content while cloud fraction decreases. Rapid adjustments to high CO<sub>2</sub> concentrations counteract this protective cloud thickening. Consequently, a pronounced reduction in cloud fraction is no longer offset by an increase in cloud brightness, markedly strengthening the total radiative response under quadrupled CO<sub>2</sub>. Ultimately, our results suggest that climate sensitivity is more state-dependent than often assumed.