GLOBAL WARMING

Global warming is the increase in the average temperature of the Earth's near-surface air and the oceans since the mid-twentieth centrury and its projected continuation. Global surface temperature increased 0.74 +- 0.18 C (1.33+- 32 F) during the last century.

Warming is expected to change the distribution and type of clouds. Seen from below, clouds emit infrared radiation back to the surface, and so exert a warming effect;  seen from above, clouds reflect sunlight and emit infrared radiation to space, and so exert a cooling effect. Whether the net effect is warming or cooling depends on details such as the type and altitude of the cloud, details that are difficult to represent in climate models.