Adapted from World Meteorological Organization and the United Nations Environment Program, 1995. Greenhouse gases include carbon dioxide, methane, nitrous oxide, ozone and halocarbons. Aerosols include dust particles and very small chemical droplets. Human activities over the last 150 years have significantly altered the composition of the atmosphere and thus enhanced its ability to retain heat.
Greenhouse gases act radiatively to warm the atmosphere.
Their effect is long-lived. In opposition, the presence of aerosols combined with the depletion of the stratospheric ozone layer, have a cooling effect. Greenhouse gases remain in the atmosphere for many years and are globally distributed.