Greenhouse effect

Greenhouse gases, including water vapour, carbon dioxide and methane, absorb some of the long-wave radiation emitted by the Earth's surface. They then emit energy in all directions, including back towards the surface. This warms the surface and lower atmosphere: the natural greenhouse effect.

The natural greenhouse effect keeps Earth warm enough to support life. Most incoming solar energy is short-wave radiation, which passes through the atmosphere and warms the surface. The warmed surface then emits long-wave radiation.

This is the natural greenhouse effect. It is essential for life: without it, the Earth's average temperature would be about −18°C. Greenhouse gases are therefore not simply unwanted pollutants; the problem is the additional warming caused by increasing their concentrations.