Thursday, January 08, 2009

We may be cold, but Earth's still warming

By Peter E. Black

The seemingly contradictory widespread frigid cold weather across the United States around Dec. 21 and global warming are quite understandable if we recall some basics.
Those basics begin with the law of conservation of energy: We cannot create or destroy energy. It is not that more heat energy arrives at Earth; it is that all the heat energy arriving here is not leaving. The greenhouse effect traps some of the long wave energy re-radiated from Earth's warm surfaces to space, not the incoming short wave energy that Earth receives from the sun. The greenhouse effect is caused primarily by water vapor, carbon dioxide and methane. If it weren't for the greenhouse effect, we'd freeze.
If Earth cannot re-radiate all the long wave energy from its surface, the amount of energy in the atmosphere warms. Simultaneously, the area of tropical rain forests, tundra, coral reefs and floating vegetation diminishes by human activities. Normally, those plant-rich areas take up large quantities of carbon dioxide. As that occurs, the increased atmospheric carbon dioxide dissolves in water, making carbonic acid, which makes it difficult for life to survive in the oceans.
As Earth's surfaces, atmosphere and oceans warm, the major mechanism for moving warm equatorial air poleward -- hurricanes or typhoons -- increase in number, intensity and duration. The warm air displaces the cold air at the poles, which moves toward the equator. Being denser and heavier, the cool air slips beneath the warm moist air. The resultant lifting of the unstable warm, moist air and mixing with the cold, dry air from the poles is what causes the more violent weather.

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