The two main features of the earth's energy balance are that:
Input into the global heat budget comes in the form of short-wave solar energy. This is called insolation [insolation: solar radiation received in the Earth's atmosphere or at its surface.] . Only 51% of this insolation reaches and is absorbed by the earth's surface. The rest is absorbed by water vapour, dust and clouds, or is reflected by the earth's surface and scattered by particles in the air (the albedo [albedo: the albedo of an object is the extent to which it diffusely reflects light from the sun.] effect). The atmosphere is largely heated from below, by long-wave terrestrial radiation from the earth's surface.
You can see that there is a surplus of energy between 35N and 35S. In this region, incoming insolation exceeds outgoing radiation. There's an energy deficit between 35N and the north pole, and between 35S and the south pole. Here the outgoing radiation exceeds incoming insolation.
Insolation rises sharply from 50 joules at the poles to 275 joules at the equator. Terrestrial radiation varies less, from 120 joules at the poles to 200 joules at the equator.
Energy is transferred from the low-latitude energy surplus areas to the high-latitude energy deficit areas by atmospheric circulation. If there was no atmospheric circulation, the low latitudes would get hotter and hotter and the high latitudes colder and colder.
The diagram tells us that tropical areas get more insolation than polar regions.
See how the technology of satellite radar has enabled vast weather systems to be detected, mapped, monitored and forecasted.
How can the movement of sea water affect climate? Watch this clip from Learning Zone Scotland for an in-depth explanation of El Niño and La Niña.
Evidence of global warming
Environmentalist James Lovelock on global warming
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