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5 December 2013 11:26 am ,
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An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Ozone Killer Tamed
18 August 2003 (All day)
There's good news for the ozone layer--levels of ozone-destroying bromine have been dropping in the lower atmosphere since 1998, thanks to tighter regulation. The drop is larger than scientists had predicted, meaning that either natural sources of bromine also declined or that industry was responsible for a larger fraction of atmospheric bromine than experts thought.
Bromine destroys ozone 50 times more efficiently than chlorine, the most infamous player in ozone destruction. Luckily, there is far less bromine in the atmosphere. The gas originates from natural sources such as oceans and wetlands, as well as from human activity. Methyl bromide, used in agriculture, and halons, which are used to fight fires, are the principal humanmade sources of the chemical, and their use helped double the amount of bromine in the atmosphere from the mid to the late 20th century. Twenty-three countries began regulating methyl bromide in the late 1980s and since then more than 100 other countries have ratified the legislation, called the Montreal Protocol, and strengthened restrictions on manufacture and use.
To see if these regulations affected bromine concentrations, atmospheric chemist Stephen Montzka of the National Oceanic and Atmospheric Administration in Boulder, Colorado, and colleagues analyzed air samples taken several times each month from 10 land-based sites across the globe between 1995 and 2002. They report in the 15 August issue of Geophysical Research Letters that the total amount of bromine-containing compounds peaked in 1998 and has since declined by 5%. The measures don't reveal exactly how much bromine is in the upper atmosphere, where the ozone layer sits, but they can be used to predict how much of the ozone-destroying chemical will eventually make its way there. The timing of the 1998 peak suggests that curbs on industrial production were responsible, at least in part, for the decline, but the magnitude of the drop has baffled scientists because the best models had predicted a smaller decline.
"It's a great paper because it surprises us," says atmospheric chemist Michael Prather at the University of California, Irvine. "It's encouraging to see environmental [progress] through regulations." Now, he says, scientists must figure out whether natural or industrial changes are responsible for unexpectedly large gains.