Aerosols and climate

Earth’s climate is changing rapidly these years. This change is overwhelmingly caused by human activities. With fossil fuel combustion, livestock and agriculture, we increase the amount of greenhouse gasses in the atmosphere, especially carbon dioxide, leading to global warming.

Our atmosphere also contains numerous tiny (nanometer to micrometer sized) particles suspended in the air. These aerosol particles have many different sources, both natural, for example volcanoes, deserts, oceans and forests, and manmade, including traffic, industry, cooking, and many more. Aerosol particles are everywhere in the air that we breathe. There is no air, which is particle free. Even in the cleanest, most remote areas of the Arctic, there may still be some 100 particles in every cubic centimeter of air. And in polluted megacities, or in the middle of a forest fire, this number may be millions.

These tiny aerosol particles are globally responsible for much of the health effects and mortality related to air pollution. Aerosols also play key roles in regulating Earth’s climate via their critical influence on both the radiation balance and cloud formation. Every single cloud droplet has been nucleated on the surface of an aerosol particle. Together, aerosols and droplets provide the reaction vessels for condensed-phase chemistry in the atmosphere. Chemical reactions further change the composition of Earth’s atmosphere, after emissions of the original components.

All these processes have profound consequences for the environment and wellbeing of our society. But there are still large gaps in our understanding of aerosols and their effects on the environment and climate. For example, with our current understanding, we can only explain less than a quarter of the organic aerosol mass which is formed in the atmosphere. Of the particles we observe, predicting their cloud forming abilities and climate effects are still highly uncertain after decades of research.

Sources of aerosol particles in the atmosphere, and the effects on formation of clouds and climate.
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Observed rise in global mean temperature since 1950, and future temperature rise predicted by IPCC with different climate models. (Source IPCC
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Known factors leading to climate change since industrialization. Natural factors, including changes in solar cycles, are minor influences. (Source IPCC
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