Friday, December 29, 2006

[glacier adrift] do you understand what's happening

Sunlight and warming …

"The data also reveal that from 2000 to now the clouds have changed so that the Earth may continue warming, even with declining sunlight," said study leader Philip R. Goode of the New Jersey Institute of Technology.

"These large and peculiar variabilities of the clouds, coupled with a resulting increasing albedo, presents a fundamental, unmet challenge for all scientists who wish to understand and predict the Earth's climate."

Earth's albedo is measured by noting how much reflected sunlight in turn bounces off the Moon, something scientists call earthshine. The observations were made at the Big Bear Solar Observatory in California.

On any given day, about half of Earth is covered by clouds, which reflect more sunlight than land and water. Clouds keep Earth cool by reflecting sunlight, but they can also serve as blankets to trap warmth. High thin clouds are better blankets, while low thick clouds make better coolers.

Separately, satellite data recently showed that while the difference between high and low clouds had long been steady at 7-8 percent, in the past five years, for some unknown reason, the difference has jumped to 13 percent. High, warming clouds have increased while low clouds have decreased.

Earth's albedo appears to have experienced a similar reversal during a period running from the 1960s to the mid-1980s.

How do the findings play into arguments about global warming and the apparent contribution by industrial emissions? That's entirely unclear. "No doubt greenhouse gases are increasing," Goode said in a telephone interview. "No doubt that will cause a warming. The question is, 'Are there other things going on?'"

What is clear is that scientists don't understand clouds very well, as a trio of studies last year also showed. "Clouds are even more uncertain than we thought," Goode said.

So, after all that, where does it leave us, the ordinary mortals? On the Ayles Ice Shelf, drifting out to sea it seems.

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