* Arctic Meltdown: the polar ice cap may be shrinking much faster than scientist thought.

• Author: Revkin, Andrew C.
• Position: ENVIRONMENT

[ILLUSTRATION OMITTED]

Scientists have known for several years that the Arctic ice cap is shrinking. The sea ice retreats every summer as the weather warms, but this past summer, it shrank 1 million square miles more than the average since 1979, the year satellite measurement began. That's the size of six Californias. By several estimates, the floating ice dwindled more than it has in a century or more.

Now the six-month dark season has returned to the North Pole, and new ice has spread over vast stretches of the Arctic Ocean. But scientists are unnerved by the extent of last summer's melting and its possible implications for both humans and animals, especially polar bears.

Many experts on the Arctic say that global warming is causing the ice to melt and that the warming is at least partly the result of the atmospheric buildup of heat-trapping gases from tailpipes and smokestacks.

Because the gases work like the panes in a greenhouse, they are called greenhouse gases, and their influence on Earth's temperature is known as the greenhouse effect.

All other things being equal, the higher the concentration of such gases in the atmosphere, the warmer the planet gets. Earth's temperature rose about I degree Fahrenheit over the 20th century, but the rate of warming in the last 30 years was three times the average for the last hundred years.

Carbon dioxide in particular poses a challenge because it's a byproduct of burning fossil fuels like coal and oil--the foundation of every modern economy.

"We are in danger of creating a permanent 'carbon summer' in which pollution traps the heat that is normally radiated back out of the atmosphere," former Vice President Al Gore said in his Nobel Peace Prize lecture in December.

'A DIFFERENT PLANET'

Also last month, the U.S. and 186 countries at a United Nations conference on global warming in Indonesia agreed that "deep cuts in global emissions" were necessary and vowed to negotiate a new climate treaty during the next two years.

Melting of the world's polar ice--including the enormous ice sheets covering Antarctica and Greenland--would have an impact way beyond the Arctic: All that water has to go somewhere, and higher sea levels could mean more flooding of coastal areas around the globe.

James E. Hansen, a NASA climate expert, says that if no action is taken to curb greenhouse gases within 10 years, Earth could undergo massive changes in temperatures, sea levels, and polar ice, and "constitute practically a...