Chemistry

Chemistry-Aerosol-Climate Interactions: a challenging scientific issue in global change
Tijian Wang, Nanjing University

While growth in levels of greenhouse gases in the atmosphere is the dominant contributor to climate change, aerosols have made significant contributions to radiative forcing of climate since preindustrial times. Aerosols are small solid or liquid particles in the atmosphere, which can be classified into primary and secondary groups. Primary aerosols, including elemental carbon, organic carbon, sea salt, and mineral dust, are emitted directly from anthropogenic and natural sources, while secondary aerosols, such as sulfate, nitrate, ammonia, and secondary organic carbon, are formed through photochemical, gaseous, aqueous, and heterogeneous chemical reactions in the atmosphere. Aerosols can influence climate directly by scattering and absorbing solar or infrared radiation. They also have impact on climate indirectly by serving as cloud condensation nuclei and ice nuclei and consequently changing albedo and lifetime of clouds.

There exist complex interactions between chemistry, aerosols, and climate. Aerosols are formed through different chemical reactions, and in turn they have impact on photochemical reactions and involve in heterogeneous chemical reactions. Aerosols can modify the global energy balance and lead to climate change, while climate change can affect concentrations of gas-phase species and aerosols by changing oxidation capacity of the atmosphere as well as processes of transport, diffusion, deposition, scavenging, and mixing. The chemistry-aerosol-climate interactions play important roles in air pollution, climate change and water cycle. There are big challenges in understanding the mechanisms of such interactions and in representing them in global and regional climate models.

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Chemistry

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