Global warming might…

Global warming might be an effect of a cleaner atmosphere. No, really.

Reversing a decades-long trend toward “global dimming,” Earth’s surface has become brighter since 1990, scientists are reporting today.

The brightening means that more sunlight – and thus more heat – is reaching the ground. That could partly explain the record-high global temperatures reported in the late 1990’s, and it could accelerate the planet’s warming trend.

“We see the dimming is no longer there,” said Dr. Martin Wild, a climatologist at the Swiss Federal Institute of Technology in Zurich and the lead author of one of three papers analyzing sunlight that appear in today’s issue of the journal Science. “If anything, there is a brightening.”

Some scientists have reported that from 1960 to 1990, the amount of sunshine reaching the ground decreased at a rate of 2 percent to 3 percent per decade.

In some places, the brightening of the 1990’s has more than offset the dimming, Dr. Wild said. In other places, like Hong Kong, which lost more than a third of its sunlight, the dimming has leveled off, but skies remain darker than in the past. In a few places, like India, the dimming trend continues, he said.

The new papers also call attention to a major gap in the understanding of climate. Scientists do not exactly know what caused the dimming and the brightening, or how they affect the rest of the climate system.

There’s that phrase again: “Scientists do not exactly know….” But many certainly want to impose policies based on it. Scott Ott of the satire site ScrappleFace hits the nail on the head yet again.

“However,” the U.N. report states, “the new evidence that more sunlight pouring through a cleaner stratosphere may have spurred the temperature increases shouldn’t cause people to lose faith in global warming. In others words, don’t let contradictory evidence stand in the way of your conclusions. We urge the nations of the world to approve the Kyoto protocols on global warming while there’s still time.”

Right on, Scott.

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