By Dan Shapley
With the world's scientists set to make another report on global warming Friday, new scientific results suggest they have underestimated the rate of Arctic sea ice melting. The findings suggest that there could be ice-free Arctic summers 30 years earlier than the scientists, under the auspices of the U.N.'s Intergovernmental Panel on Climate Change, predicted earlier this spring. Melting ice is watched closely not only because it indicates warming temperatures, but because it can accelerate them. Whereas ice and snow reflect 70 percent of sunlight, producing an overall cooling effect, darker open water absorbs more than 90 percent of warmth from the sun. The panel's report due Friday will outline strategies and costs for tackling climate change.