GLOBAL WARMING

Is Planet Earth Under Threat?
GLOBAL WARMING has been described as the greatest threat facing humanity. What worries researchers, says the journal Science, “is the prospect that we’ve started a slow-moving but relentless avalanche of change.” Skeptics question this assertion. True, many agree that the earth is warming, but they are uncertain of both the causes and the consequences. Human activities may be a factor, they say, but not necessarily the primary one. Why the disagreement?

For one thing, the physical processes that underlie global climate systems are complex and not fully understood. In addition, interest groups tend to put their own spin on the scientific data, such as that used to show why temperatures are rising.

Temperature Rise—Is It Real?
According to a recent report of the UN-sponsored Intergovernmental Panel on Climate Change (IPCC), global warming is “unequivocal,” or a fact; and “very likely,” mankind is largely to blame. Some who differ with this conclusion, especially in regard to the human factor, concede that cities may be heating up because they are growing in size. Moreover, concrete and steel readily absorb the sun’s heat and tend to cool down slowly at night. But urban readings, skeptics say, do not reflect the trend in rural areas and can distort global statistics.

On the other hand, Clifford, a village elder who lives on an island off the coast of Alaska, says he has seen changes with his own eyes. The people of his village travel across sea ice to the mainland to hunt caribou and moose. Rising temperatures, though, are making the traditional lifestyle impossible. “The currents have changed, ice conditions have changed, and the freeze-up of the Chukchi Sea has . . . changed,” says Clifford. The sea used to freeze up at the end of October, he explains, but now it does not freeze until late December.

In 2007, warming was also evident in the Northwest Passage, which was fully open for the first time in recorded history. “What we’ve seen this year fits the profile of lengthening melt seasons,” said a senior scientist for the National Snow and Ice Data Center in the United States.