Clouds play key role in moderating Earth's surface warming

Clouds play key role in moderating Earth's surface warming
by Clarence Oxford
Los Angeles CA (SPX) Jan 16, 2025

McGill University researchers have revealed that changes in cloud cover are helping to slightly counteract global warming. While greenhouse gases continue to drive temperatures upward, a reduction in low-cloud cover over land has contributed to a small decrease in the amount of heat retained near the Earth's surface.

"We started this research to observationally verify the increase of greenhouse effect of the Earth atmosphere," said Yi Huang, Associate Professor in McGill's Department of Atmospheric and Oceanic Sciences, who conceived a study published in Nature. "We indeed verified that, although to our surprise we also found an offsetting effect due to changes in clouds."

According to Lei Liu, a graduate student in McGill's Department of Atmospheric and Oceanic Sciences and the study's lead author, "Without these cloud changes, the surface would warm even faster. This work offers observational truth about how clouds affect warming, which can be used to improve climate models and guide environmental policies."

The team employed measurements from the Atmospheric Emitted Radiance Interferometer (AERI), satellite data, climate models, and a specialized technique called "optimal spectral fingerprinting" co-developed by Yi Huang and Lei Liu. This method allowed them to separate the impact of clouds from other atmospheric influences.

Their focus was on longwave radiation-the heat energy Earth emits back into the atmosphere. Typically, clouds trap some of this heat and redirect it toward the surface. However, as the climate warms, fewer low clouds form in some regions, resulting in less heat being sent back to the ground.

McGill's Atmospheric and Oceanic Department, which operates three AERI instruments in Montreal, plans to continue using their critical data to refine understanding of regional climate dynamics and enhance climate modeling, the researchers noted.

"Our research emphasizes the value of precise, long-term climate observations," said John Gyakum, co-author and Professor in the Department of Atmospheric and Oceanic Sciences. "This is essential for understanding Earth's response to global warming and making informed decisions for future generations."

The researchers stressed that this finding does not diminish the seriousness of global warming. "It's like having a thermostat that adjusts itself a little," they explained. "But even with this adjustment, the room is still heating up."

Research Report:Clouds reduce downwelling longwave radiation in a warming climate