General Aerosol Forcing Information

What we need to know to understand aerosol climate forcing and why we need to know it

The contribution of aerosol particles is one of the most uncertain components of radiative forcing. Atmospheric aerosol particles impact the energy balance by scattering and absorbing solar radiation. Aerosol scattering can redirect incoming solar radiation back to space and thus has a cooling effect. Aerosol absorption can change the temperature profile in the atmosphere which can then influence processes like cloud formation. Aerosol absorption and scattering are driven by multiple factors including aerosol size distribution, aerosol composition, and aerosol amount. These factors can change in the atmosphere, for example, particles can take up water which changes both their size and composition. Other atmospheric processes such as new particle formation, deposition and scavanging can also play a role in determining aerosol properties at any location in the atmosphere. External factors such as sun angle and underlying surface properties also determine the aerosol radiative forcing. Aerosol particles also indirectly impact radiative forcing by acting as cloud condensation nuclei.

What do we need to know?	Why?
Aerosol Amount	Correlated with forcing
Aerosol 'Darkness'	Determines the atmospheric cooling/warming potential of particles
Aerosol Size	Related to anthropogenic aerosol contribution Amount of incoming radiation scattered back to space
Aerosol Type	Source identification/contribution
Location	Aerosol forcing depends on the underlying surface and whether they are above or below clouds.