AN INCREASINGLY DIM VIEW OF GLOBAL WARMING.

Byline: David Kronke TV Critic

In case you haven't yet reached your limit on alarmist information, tonight's "Nova" report, "Dimming the Sun," should help you surpass it quite handily.

We've all heard about global warming, which suggests that greenhouse gases have made the planet about a degree warmer than it was a century ago. Now comes global dimming, a phenomenon that ostensibly cools the Earth, but in fact has masked the rate at which global warming has actually been occurring.

Global dimming is the result of pollutants in the air deflecting the sun's rays away from the Earth. One scientist, Gerald Stanhill, wrote about it years ago, but the notion was considered so outlandish that his research was dismissed. In recent years, disparate other studies have confirmed it, and, in a bizarre twist, the terrorist attacks of Sept. 11, 2001, helped push research along.

David Travis of the University of Wisconsin charted America's climate in the days after 9/11, when all planes were grounded.

With jets' condensation trails eliminated from the country's skies, the temperature range days were warmer, nights were cooler was the largest swing in the past 30 years, he discovered.

So while the greenhouse effect has been warming the planet, global dimming has cooled it a bit, which means that global warming is occurring faster than anyone realized. And while particle pollutants have been reduced from our skies, amounts of greenhouse gases escaping into the air proceed apace. Which means the world could be 5 degrees hotter by midcentury or, by one scientist's particularly dire reckoning, by 2100, the temperature could be as much as 18 degrees warmer. And you do not want to know what that would mean.

"Dimming the Sun" explicates a lot of particularly confusing science succinctly and intelligently, and its message is undeniably sobering. But all this creates a bizarre conundrum: Pollution which causes health problems but does block the sun's rays is somehow good?

David Kronke, [phone]

david.kronke(at)dailynews.com

DIMMING THE SUN - Three stars

What: "Nova" report with new information suggesting global warming may be even more dire than previously thought.

Where: KCET.

When: 8 tonight.

In a nutshell: Concise, informative and scary as hell.

CAPTION(S):

photos

Photo:

Nova's ``Dimming the Sun,'' at 8 tonight on KCET, examines a lesser-known phenomenon that ostensibly cools the Earth and has masked the rate at which global warming occurs.