Earth Losing Air-Cleaning Ability

greenspun.com : LUSENET : Grassroots Information Coordination Center (GICC) : One Thread

L.A. Times, Friday, May 4, 2001

EARTH LOSING AIR-CLEANSING ABILITY, STUDY SAYS

Science: Worldwide decline in a molecule that fights pollution is found. But experts call the losses slight and not alarming. By GARY POLAKOVIC, Times Environmental Writer

The Earth's atmosphere is beginning to lose its natural ability to remove air pollutants, a condition that could spread smog and accelerate the accumulation of greenhouse gases, according to a study published today in the journal Science. The study documents for the first time the modest, two-decade-long worldwide decline of a key molecule that cleanses the air. Without enough of the molecules, emissions that contribute to the greenhouse effect, smog and the hole in the ozone layer do not get destroyed as fast as humans release them. "This one molecule is very, very important. It is the critical cleaning chemical for the atmosphere," said Ronald G. Prinn, the Massachusetts Institute of Technology scientist who led a 13-member research team responsible for the study. "If this free-radical [molecule] is decreasing, it could add to global warming." But the losses of the chemical, called a hydroxyl radical, are slight so far and are not currently cause for alarm, experts say. "There's a number of research findings that demonstrate the global atmosphere is changing, but we really do not know the effect it is going to have on us in the long term," said Terry Keating, environmental scientist for the U.S. Environmental Protection Agency. Indeed, some scientists say more research is necessary to understand the complex chemical reactions that occur in the atmosphere. Also, they say it is not clear whether the molecule's decline is a temporary or cyclical event or one that portends a long-term shift. "If this change has happened, it is a slight change. It's significant if it's the beginning of a trend. That would be a warning," said F. Sherwood Rowland, a chemist at UC Irvine who won the Nobel Prize in 1995 for showing how pollutants destroy the Earth's protective ozone shield. The latest findings are further evidence that the planet's fragile atmosphere is undergoing profound change and may have crossed a threshold that threatens its self-cleansing ability. Using measurements taken from Ireland to Tasmania to the Oregon coast, the research team set out to determine changes in concentrations of the ephemeral molecule, an energized oxygen compound so reactive that it attacks and transforms many of the gases it bumps into. In the lower atmosphere, it is a catalyst for ground-hugging ozone, but it also occurs naturally up to seven miles high in the air, where it acts to destroy many man-made pollutants. Yet over the last 22 years, concentrations of the molecule have decreased an average of 10% worldwide, the study found. Because the molecule exists for only one second before changing into something else, scientists arrived at that estimate indirectly. The research team examined changes in concentrations of methyl chloroform at five remote sites starting in 1978. [snip]

Entire article at: http://www.latimes.com/news/state/20010504/t000037688.html

Link

-- Robert McCarthy (celtic64@mindspring.com), May 06, 2001


Moderation questions? read the FAQ