EARTH In the literature: partially resolved

How strongly do low marine clouds amplify warming?

In plain words

Low clouds over the oceans reflect sunlight and cool the planet. If warming thins them, the planet absorbs more sunlight and warms further, and how much is the largest single uncertainty.

Precise statement

Determine the global low-cloud feedback parameter (stratocumulus and trade cumulus over the subtropical oceans) in erg/(s cm^2 K); current assessments center near $+2e2\,\mathrm{erg}/(\mathrm{s}\,\mathrm{cm}^{2}\,\mathrm{K})$ with large uncertainty. An answer is a value with uncertainty below about $1e2\,\mathrm{erg}/(\mathrm{s}\,\mathrm{cm}^{2}\,\mathrm{K})$ supported by large-eddy simulations and observed cloud-controlling-factor relations.

What would settle it

Large-eddy simulations across regimes validated by field campaigns and satellite cloud-controlling-factor analyses.

Status in the literature

Field data from the 2020 EUREC4A campaign were interpreted (Vogel and coauthors, Nature 2022) as indicating a weak trade-cumulus feedback; stratocumulus feedback remains uncertain.