Science behind Climate Change

Changes in Aerosol Level

Atmospheric aerosols are very fine particles suspended in air. They are formed by the dispersal of material at the earth's surface (primary aerosols), or by reaction of gases in the atmosphere (secondary aerosols).

They include sulphates and nitrates from the oxidation, respectively of sulphur dioxide and nitric oxide, during the burning of fossil fuels; organic materials from the oxidation of VOCs (Volatile Organic Compounds); soot from fires; and mineral dust from wind-blown processes.

Aerosols affect the climate by

Increasing scattering of sunrays
Interacting with atmospheric gases
Contributing to greenhouse effect
Interacting with clouds and changing the rainfall pattern
Forming smog with water vapour

Aerosols spread out by a volcanic eruption can lead to a net reduction of 5% to 10% in energy received at the earth's surface. An individual eruption may cause a global cooling of up to 0.3 ^oC, with the effects lasting for 1-2 years.

Estimation of the impact aerosols have on long-term global climate change is uncertain, since the geographical distribution of aerosols is highly variable and strongly related to their sources. However, computer modelling exercises have shown that a few aerosols in a particular concentration can have a global cooling effect and this could offset the warming effect of increased greenhouse gas concentrations by as much as 30%.

Aerosols