Reply #2: From bright to dim: what next?

[Liberty Belle]

Global brightening is what will occur the day Bush leaves office.

Seriously, though, the NY Times reported in May that sunlight reaching planet had been brightening, but is now dimming. Here's an article from the archives:



May 28, 2004
After a Period of Brightness, Earth Dims, Researchers Say
By KENNETH CHANG

Tracking the brightness of Earth by looking at its reflection on the Moon, scientists have concluded that sunshine on Earth brightened in the 1990's, then dimmed after 2000.

The findings, being reported today in the journal Science, add a new level of mystery to the recent debate about "global dimming" and its causes. Measurements by ground-based instruments around the world have shown a decrease of up to 10 percent in sunlight from the late 1950's to the early 1990's.

"This would say that it reversed through the 80's and 90's to a global brightening and now it's flattening," said Dr. Philip R. Goode, a professor of physics at the New Jersey Institute of Technology and an author of the Science article. "And the suggestion is that the trend is turning back to the other direction."

The output of the Sun varies only slightly, so scientists theorize that global dimming probably results from air pollution. Some light bounces off soot particles in the air. The pollution also causes more water droplets to condense out of air, leading to thicker, darker clouds, which block light. For that reason, the dimming appears to be more pronounced on cloudy days. . .
The notion remains controversial because it runs counter to expectations of global warming (less sunlight should mean lower temperatures), and some scientists wonder how widespread the dimming effects are. The ground-based measurements do not cover the oceans...

http://home.earthlink.net/~cevent/5-28-04_earth_dims.html