What Arctic sea-ice levels can tell us about global warming.

But the North Pole is so far away, you say. Why should I care that the ice up there is melting? Well, besides the fact that our friends the polar bears live on those ice floes, the loss of sea ice means that the ocean gets warmer. Highly reflective sea ice bounces most solar radiation back into space, while darker ocean water absorbs it. Not only do higher water temperatures cause even more sea ice to melt (a classic example of a positive feedback loop), but it may also speed the melting of the Arctic permafrost, releasing tons of methane and carbon dioxide along the way. Scientists are still trying to figure out what the impacts of melting polar ice will be on the middle latitudes, but they may range from reduced rainfall in the American West to increased winter precipitation in Europe.

The most immediate and visible effect, though, might be a political one. As summer ice rapidly declines in the Arctic, valuable shipping routes are beginning to open up, as is the seabed itself, with its tantalizing promise of vast untapped resources—perhaps as much as 90 billion barrels of oil and 1.7 trillion cubic feet of natural gas reserves. Russia has already begun rattling its sabers in an attempt to claim the territory, and other nations, such as Canada and the United States, are quickly following suit. The environmental impact of drilling in the Arctic? Well, that's a topic for another column.

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