Earth’s energy imbalance has increased markedly over the past two decades, reaching a record in 2023. Both the long-term trend and year-to-year variations are linked to reduced reflection of sunlight by low-level clouds, which is pronounced over Northern Hemisphere oceans. However, the causes of these cloud changes and their implications for future Earth system evolution are unknown, raising concerns about a stronger-than-expected cloud feedback. Here we quantify the meteorological factors behind interannual cloud-radiative anomalies, several of which aligned to produce the extreme 2023 value. These meteorological variations are superposed on a background of declining sulfate aerosol concentrations, contributing to a sustained decrease in cloud reflection over the past 22 years. The resulting constraints on cloud feedback and aerosol forcing are consistent with previous studies, supporting an equilibrium climate sensitivity near 3∘C (likely range 2.7–4.1∘C). Thus, recent observations do not indicate an emerging stronger cloud feedback or underestimated future warming. Cloud feedback does not exceed prior expectations, given the evidence that the cloud-radiative anomalies can be explained by meteorological variations and aerosol emission reduction, according to quantifications based on observations.
Zelinka et al. (2026) studied this question.