Reviewed by Lexie CornerMar 12 2025
A study in Environmental Research Letters reveals that cloud cover over oceans is reflecting less sunlight, which is contributing to climate change alongside rising greenhouse gas levels. The study identifies this dimming effect in areas like the coasts of California and Namibia, as well as near Antarctica, where the melting of sea ice is increasing ocean heat absorption.
Cloudy regions now reflect less sunlight than before, which accelerates climate change by allowing more heat to be trapped by rising greenhouse gas levels.
Think of Earth as a mirror reflecting sunlight to space. Over time, that mirror is getting dirtier, particularly over our oceans, where clouds are changing. This means more solar energy is being absorbed rather than reflected, adding to the heating caused by greenhouse gas emissions. An important puzzle to solve is that the clouds melting away as temperatures rise like a mirror steaming up?
Richard Allan, Professor and Study Lead Author, University of Reading
Richard adds, “Or is declining air pollution that artificially brightened the mirror like a cleaning spray now wearing off? We need to find out which explanation is causing clouds to become less shiny to understand how much global warming will occur and how fast. The remarkable global dimming helps explain why we saw such unprecedented warming in 2023.”
Air Pollution Impacts
The ocean surface warmed faster than expected from increased energy absorption alone during 2022–2023. The researchers concluded that either more heat was being released from deeper ocean layers, or the heat was concentrating in a shallower layer of the ocean. The second hypothesis aligns with the development of El Niño conditions in 2023, when warm water from the deep Pacific rose to the surface.
The study also found that, likely due to successful efforts to reduce air pollution, eastern China is reflecting less sunlight than expected. This is significant because while reducing air pollution improves public health, cleaner air allows more sunlight and clouds to reach the Earth's surface, contributing to global warming by increasing heat-trapping greenhouse gases.
Journal Reference:
Allan, P. R., & Merchant, C. J. (2025) Reconciling Earth's growing energy imbalance with ocean warming. Environmental Research Letters. doi.org/10.1088/1748-9326/adb448