It is the volcanic gases emitted that concern scientists. The SO 2 particles react with water vapour in the air to form aerosols. Click here to see the full image These aerosols are responsible for the radiative forcing of the atmosphere. Whether aerosols are warming or cooling depends on the size of the particles. If the particle is 2mm in diameter, it has a warming effect.
Tropospheric aerosols found in the atmosphere due to pollution have a warming effect.
The ones produced during volcanic eruptions reflect back incoming solar radiation, preventing it from reaching the earth s surface, therefore volcanic aerosols have a cooling effect. Mount Pinatubo Mount Pinatubo erupted in the Philippines in 1991. The eruption cloud was 18km wide and 30km high. It had a very big atmospheric effect. Although the aerosols were emitted from a very small point i.e. the vent of the volcano, they are quickly distributed globally.