12. The amount of aerosols in the air has direct effect on the amount of solar radiation hitting the Earth's surface. Aerosols may have significant local or regional impact on temperature. Water vapour is a greenhouse gas, but at the same time the upper white surface of clouds reflects solar radiation back into space. Albedo - reflections of solar radiation from surfaces on the Earth - creates difficulties in exact calculations. If e.g. the polar icecap melts, the albedo will be significantly reduced. Open water absorbs heat, while white ice and snow reflect it.