New research uncovers impact of aerosol emissions on climate

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New research has provided further proof that greenhouse gas emissions modify how clouds form. The research, carried out by Giulia Saponaro from the Finnish Meteorological Institute (FMI), looked at the interactions between clouds and aerosols.

It is already known that naturally occurring aerosols – often sulfates, sea salt or ammonium salts – play a critical role for clouds, serving as the tiny ‘seeds’ that catalyze cloud formation.

Aerosols emitted by humans also play a role in cloud formation, producing clouds that paradoxically look brighter even though they are polluted.

Saponaro used data from the Moderate Imaging Spectroradiometer (MODIS), an imaging tool on board NASA’s Earth Observing System (EOS) Terra and Aqua satellites that measures large-scale global dynamics such as changes in Earth’s cloud cover and radiation budget.

Using MODIS as a reference data set, Saponaro evaluated the reliability of three climate models in measuring aerosol-cloud interaction at a local and global level.

At the local and regional level Saponaro found a higher sensitivity of clouds to aerosol changes in cleaner, ambient air and a lower sensitivity in polluted areas.

According to FMI these results “further corroborate the notion that anthropogenic emissions modify clouds.”

On the global scale, Saponaro found that the data from the climate models was corroborated by the MODIS data sets.

Saponaro said, “It was found that ground-based measurements of liquid clouds are in good agreement with MODIS cloud droplet size. Poor correlation was found in the amount of cloud liquid water due to the management of drizzle.”

According to scientists, clouds help to cool Earth by reflecting back solar radiation, ‘brighter’ polluted clouds are even more effective at this. Because of this a better understanding of the relationship between aerosols and cloud formation is important for understanding climate change, they say.

Saponaro said: “The scientific community should work toward the integration of different data sources, while accounting for their respective capabilities and limitations. This way, a robust and exhaustive response to any open questions regarding the effect of aerosol upon clouds can be obtained.”

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