Climate researchers discover that clouds have a surprising effect on surface warming

Researchers at McGill University have found that changes in clouds are slightly mitigating global warming. While temperatures continue to rise due to greenhouse gases, the amount of heat trapped near the surface has slightly decreased due to less low-lying cloud cover over land.

“We started this study to observationally test the increasing greenhouse effect of the Earth’s atmosphere,” said Yi Huang of McGill University’s School of Atmospheric and Ocean Sciences, who designed the recent study published in Nature. said the associate professor. Surprisingly, we also found a countervailing effect due to cloud changes. ”

“Without these cloud changes, the Earth’s surface would warm even faster,” said Lei Liu, a graduate student in McGill University’s School of Atmospheric and Ocean Sciences and lead author of the study. “This study provides an observational truth about how clouds influence warming, which can be used to improve climate models and guide environmental policy,” Liu said. .

To discover this surprising effect, the research team used measurements from a key radiation instrument, the Atmospheric Emission Radiation Interferometer (AERI), as well as satellite data, climate models, and a study co-designed by Yi Huang and Lei. The researchers used a technique called “optimal spectral fingerprinting.” Liu aims to separate the effects of clouds from other atmospheric processes.

The researchers focused on longwave radiation, the thermal energy that Earth emits into the atmosphere. Clouds typically trap some of this heat and send it back to the ground. But as the climate warms, some regions will have fewer low-lying clouds, which means less heat is returned to the surface.

McGill’s Atmosphere and Ocean Division, which operates three AERI instruments in Montreal, will continue to use the important data to understand regional climate dynamics and enhance climate modeling, researchers said. Ta.

“Our study highlights the value of accurate long-term climate observations,” said co-author John Gyakum, a professor in the Department of Atmospheric and Oceanic Sciences. “This is essential to understanding the Earth’s response to global warming and making informed decisions for future generations.”

The researchers cautioned that their findings do not cast doubt on global warming.

“It’s like a thermostat that automatically makes small adjustments,” the researchers explained. “But even with this adjustment, the room is still heating.”