ping
In the second half of the 20th century, the world became a darker place.
Defying expectation and explanation, hundreds of instruments around the world recorded a drop in sunshine reaching the surface of Earth, as much as 10 percent from the late 1950s to the early '90s, or 2 to 3 percent per decade. In some areas like Asia, the United States and Europe, the drop was even steeper. Hong Kong saw a 37 percent decrease in its sunlight.
No one is predicting that it may soon be night all day. Still, the dimming trend -- noticed by a handful of scientists two decades ago, but dismissed at the time as unbelievable -- is now attracting wide attention. Research on global dimming and its implications will be presented next week in Montreal at a joint meeting of U.S. and Canadian geological societies.
James E. Hansen, director of NASA's Goddard Institute for Space Studies, said scientists had long known that pollution particles reflected some sunlight, but now they are realizing the magnitude of the effect. "It's occurred over a long time period, so it's not something that perhaps jumps out at you," he said. "But it's a large effect."
"In general, we don't really understand this thing that's going on," said Shabtai Cohen, a scientist in Israel's agriculture ministry who has studied global dimming for a decade.
Since the 1950s, hundreds of radiometers, the instrument to measure sunshine, have been installed worldwide.
At around the same time, Gerald Stanhill of the Israeli Agriculture Ministry noticed similar darkening trends in Israel. "I really didn't believe it," he said. "I thought there was some error in the apparatus."
Stanhill, retired and living in New York City, also found global dimming. In the 1990s, he wrote a series of papers describing the phenomenon.
In 2001, Stanhill and Cohen estimated the worldwide dimming averaged 2.7 percent per decade.
Surf's up, dude.
BTW, I've got the resident meteor/comet/asteroid expert looking at this. He may actually have met this guy at a conference if he's been active in research in the last 20 years.