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A recent study, published in Geophysical Research Letters, combines historical satellite observations with atmospheric reanalysis data to construct a multidecade record of low-cloud cover in the hope of improving current climate models.
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The study reveals that low-cloud cover has historically had a protective effect against warming, but climate models still show a reduced effect from low-lying clouds in the future, along with increasing climate sensitivity.
A cloudy understanding of low clouds
Scientists know low clouds reflect sunlight back into space and that this can result in a cooling effect. However, there is still uncertainty about how these clouds are affected by a warming planet. Most climate models expect low clouds over tropical oceans to decline as the planet warms and further amplify that warming, but how much they might decline and the degree to which they will affect warming vary among models.
Thus far, satellite cloud records have been fragmented because instruments, calibrations and cloud definitions have changed over time. This has prevented a reliable direct estimate of how low clouds have changed during the modern warming period, making it difficult to model cloud effects in future projections.
Some studies have inferred low-cloud feedback from the relationship between clouds and cloud-controlling factors (CCFs), then combined that with CMIP phase 6 (CMIP6) model projections. These generally result in positive low-cloud cover (LCC) feedback values with varying magnitudes, meaning they have a warming effect (while negative LCC feedback values mean a cooling effect).
The authors of the new study say present-day low-cloud feedback is not often discussed, but prior studies showed that inferred tropical low-cloud feedback could be three to four times smaller when CCF changes are taken from the historical record instead of CMIP6 projections. They say this casts doubt on the plausibility of future cloud feedback estimates based on idealized warming scenarios.
Satellite data provide some historical clarity
The team combined observations from 13 satellites with atmospheric reanalysis data in an attempt to reconstruct past cloud conditions from 1979 to 2025. To do this, they developed an anomaly-based framework that minimizes platform- and algorithm-dependent biases and provides more consistent comparisons across satellites.
Their results showed that tropical low-cloud cover increased by about 0.18% per decade from 1979 to 2025. This rise mainly consisted of stratocumulus clouds, which are especially effective at reflecting sunlight. They also estimated that the rise in cloud cover produced a negative low-cloud feedback of about −0.79 watts per square meter per degree Celsius, a cooling influence that contributed to slowed warming in the past few decades.
"This overall LCC increase has occurred alongside a ∼1 K rise in global mean surface temperature, linking cloud changes to the observed warming trend. The CCF decomposition indicates that the positive LCC trend is primarily driven by increases in estimated inversion strength (EIS) and surface wind speed contributions (0.14 ± 0.04%/decade and 0.07 ± 0.02%/decade, respectively), while the SST contribution (−0.08 ± 0.02%/decade) acts in the opposite direction and partly offsets the increase," the study authors write.
Combining historical data with climate models
Although historical warming shows an association with a negative low-cloud feedback that provides a welcome cooling effect, the team found that when models matched this historical data, the news was still not good. When the team compared the observed historical record with simulations from CMIP6 climate models, they found that the models that best matched observed cloud patterns and trends projected the strongest positive future low-cloud feedback and higher climate sensitivity.
In other idealized climate-model experiments that did not match historical observations, the average response showed low-cloud losses and extra warming. This appears to be because historical observations indicate more reflective clouds, particularly in the East Pacific, while idealized warming patterns favored less reflective clouds.
Most models predicted more heating in the eastern Pacific, similar to western Pacific regions, but observed patterns instead show that a mix of hot and cool air has allowed for the formation of low-cloud cover. However, scientists predict that further heating and changes in atmospheric circulation will eventually reverse this protective effect.
While this study contributes cloud feedback estimates that could improve projections of future temperature rise, there is still room for improvement in these models. The authors write, "Improving the representation of SST trends in coupled climate models—and better constraining their forced versus internal components—will therefore be critical for narrowing uncertainties in cloud feedbacks and climate sensitivity."
Written for you by our author Krystal Kasal, edited by Lisa Lock, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly).
More information: Gregory V. Cesana et al, A Reconciled Satellite Record Reveals a Negative Low Cloud Feedback Over the Past 47 Years, Geophysical Research Letters (2026). DOI: 10.1029/2026gl124158
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This story was originally published on Phys.org.
