Climate is the state of the atmosphere over long time periods, usually over years, decades, centuries or greater. It represents the prevailing weather conditions such as the average temperature, humidity, wind speed and direction, cloudiness and precipitation (e.g. rain). Climate is warm at the equator and cold at the poles. The climate averaged over all the regions of the Earth makes up the Earth’s global climate.
Climate has cooled and warmed throughout the Earth’s history for various reasons, notably variations in the Sun activity and in Earth’s rotation with respect to the Sun. However, the very rapid warming occurring today is the result of the increasing levels of greenhouse gases in the atmosphere.
The figure shows an example of atmospheric temperature at the Earth’s surface in January. Temperatures are averaged over the 1959-1997 period. Red areas correspond to a warm climate and blue areas to a cold climate.