Winter is setting in across the Northern Hemisphere, and with it, cold and cloudy winter days. Clouds play a vital role in the environment, providing rain but also reflecting sunlight before it reaches the Earth’s surface.

But between 2003 and 2022, clouds over the North Atlantic and Northeast Pacific became less reflective, allowing more sunlight to reach the ocean surface and causing sea surface temperatures to rise.

My colleagues and I recent conducted research that shows global efforts to improve air quality have unintentionally accelerated climate warming by modifying clouds.

While cleaner air has major health benefits, decreasing the amount of particulate pollution has also reduced the cooling effect of clouds, accelerating climate warming.

Our study relied on two decades of satellite data to analyze the impacts of changes in particulate pollution and climate warming on the clouds. The data shows that low-level clouds in the Northern Hemisphere have dimmed rapidly since 2003.

In particular, cloud reflectivity over the North Atlantic and Northeast Pacific has fallen by nearly three per cent per decade. During the same period, sea surface temperatures rose about 0.4 C, intensifying marine heatwaves that

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