Archive · 9 Dec 2025
Cleaner Air Reduces Cloud Cooling Effect
Clouds help keep the Earth cool by reflecting sunlight.
But over the past 20 years, clouds in some parts of the ocean have become less reflective, letting more sunlight through and making the ocean warmer.
This is because there are fewer tiny particles in the air, called aerosols, which come from pollution.
These particles help make clouds bright and long-lasting.
Cleaner air is good for our health, but it means there are fewer aerosols to make clouds reflective.
This makes the Earth warmer faster, like taking off a cooling shield.
Scientists say we need to keep watching the clouds and improve our climate models to understand how this will affect our planet in the future.
Clouds over the North Atlantic and Northeast Pacific became less reflective between 2003 and 2022, allowing more sunlight to reach the ocean surface and causing sea surface temperatures to rise.
Reduction in particulate pollution, particularly aerosols, led to fewer but larger cloud droplets, making clouds less reflective and shorter-lived, reducing their cooling effect.
China's sulfur dioxide emissions dropped by about 16 million metric tonnes per decade since 2003, contributing to the decline in aerosol concentrations.
Declining aerosols accounted for 69% of the cloud reflectivity loss, while warming explained 31%, adding about 0.15 watts per square metre per decade to Earth’s global energy imbalance.
Satellite monitoring is essential for understanding the link between cleaner air, dimmer clouds, and regional warming, with many climate models underestimating the magnitude of these changes.
- Who
- Researchers led by Knut von Salzen
- What
- Clouds over the North Atlantic and Northeast Pacific became less reflective, accelerating climate warming due to cleaner air
- When
- Between 2003 and 2022
- Where
- North Atlantic and Northeast Pacific
- Why
- Reduction in particulate pollution led to fewer aerosols, making clouds less reflective and shorter-lived, reducing their cooling effect
- Time Period
- 2003-2022
- Cloud Reflectivity Decrease
- 3% per decade
- Sea Surface Temperature Rise
- 0.4°C
- Aerosol Emission Reduction (China)
- 16 million metric tonnes per decade
- Cloud Droplet Concentration Decline
- 5-10%
- Energy Imbalance Increase
- 0.15 W/m² per decade
- CO₂ Energy Imbalance Increase
- 0.31 W/m² per decade