Human-Made Aerosols Cool Clouds at Unprecedented Rate, Scientists Warn

A new study published in Nature reveals that human-made aerosols are cooling clouds—and the atmosphere—more than previously thought, effectively masking the true extent of global warming. The international research, led by the University of Eastern Finland and the Finnish Meteorological Institute, demonstrates that cloud formation in the lower atmosphere is highly sensitive to aerosol pollution, significantly altering their reflective properties and cooling effect.

Long-Term Data Reveals Stronger Climate Impact

The study focuses on long-term data collected at ACTRIS (Aerosol, Clouds and Trace Gases Research Infrastructure) monitoring stations in Svalbard and Finland. These observations suggest that cloud properties respond more strongly to changes in aerosol levels than believed in the past. Because cloud characteristics vary widely over time, long-term, high-quality measurements are essential to accurately assess how aerosols influence cloud behavior.

How Do Aerosols Cool the Climate?

According to scientists, emission of anthropogenic fine particles can cool the climate by modifying cloud properties and counteract greenhouse gas-induced climate warming. Based on the results of this research, this cooling effect is at the upper end of previous estimates based on satellite data,” said Professor Annele Virtanen from the University of Eastern Finland to EuroNews.

Climate Models Fall Short

The study also evaluated climate models’ ability to simulate aerosol-cloud interactions. Comparisons with real-world data exposed gaps in how key processes are represented, with significant discrepancies between models. “These insights will help refine climate models, improving predictions for future warming under different emission scenarios,” explains Research Professor Sami Romakkaniemi of the Finnish Meteorological Institute.

The Science Behind the Cooling Effect

The research focused on how cloud droplet numbers respond to aerosol concentrations—a critical factor in determining how much solar radiation clouds reflect. Using 3–10 years of in situ data from high-latitude regions, scientists found that low-level stratiform clouds are more susceptible to aerosols than satellite data implied. Their calculations estimated an aerosol-induced radiative forcing of −1.16 W m⁻², aligning with the higher end of past projections.

A Double-Edged Sword

While aerosols contribute to air pollution and health risks, this study confirms they also play an unexpected role in offsetting global warming. “Without aerosols, Earth’s climate would already be hotter,” the researchers note. However, relying on aerosol cooling is not a solution—reducing greenhouse gas emissions remains imperative to curb long-term climate change.

References: https://www.nature.com/articles/s41561-025-01662-y 

https://www.euronews.com/green/2025/04/07/scientists-say-human-caused-pollution-may-be-masking-the-true-extent-of-climate-warming 

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