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  Yahoo News 19 Oct 07
NASA: Ozone hole returns to average size
By Seth Borenstein, AP Science Writer

Yahoo News 3 Oct 07
Hole in Ozone Layer Shrinks 30 Percent
Dave Mosher LiveScience Staff Writer

Yahoo News 3 Oct 07
Ozone hole has shrunk by nearly a third: European Space Agency

The ozone hole over Antarctica shrank by 30 percent this year compared with the record loss recorded in 2006, the European Space Agency (ESA) said on Wednesday.

Measurements made by the agency's Envisat satellite found a peak loss in the ozone layer of 27.7 million tonnes, compared to 40 million tonnes last year, it said in a press release.

Ozone, a molecule of oxygen, forms a thin layer in the stratosphere, filtering out dangerous ultraviolet sunlight that damages vegetation and can cause skin cancer and cataracts.

The protectively layer has been badly damaged by man-made chlorine-based chemicals.

The hole -- in essence, a thinning of the layer -- goes through a cycle each year as the chemical reaction that drives depletion peaks during the deep chill of the southern hemisphere winter, from late August to October.

In 2006, the ozone hole at its biggest measured 28 million square kilometers (10.81 million square miles); in 2007, it was 24.7 million sq. kms. (9.53 million sq. miles), or roughly the size of North America.

Ronald van der A, a senior project scientist at Royal Dutch Meteorological Institute (KNMI), said this year's improvement could not be seen as a confirmation that the ozone layer was in recovery.

"This year's ozone hole was less centred on the South Pole as in other years, which allowed it to mix with warmer air, reducing the growth of the hole, because ozone is depleted at temperatures less than -78 degrees Celsius (- 108 degrees Fahrenheit)," he said.

Over the last decade, the ozone layer has thinned by about 0.3 percent per year on a global scale.

Last September 22, nearly 200 countries agreed to accelerate the elimination of hydrochlorofluorocarbons (HCFCs), a category of ozone-destroying chemicals.

Under the deal reached at a UN-sponsored conference in Montreal, developed countries will phase out the production of HCFCs by 2020 while developing states have until 2030 -- 10 years earlier than previously promised.

The agreement changes the timetable that had been set in 1987 under the Montreal Protocol, which aims to eliminate the use of HCFCs and similar chemicals once commonly found in refrigerators, fire retardants and aerosol sprays.

Yahoo News 3 Oct 07
Hole in Ozone Layer Shrinks 30 Percent
Dave Mosher LiveScience Staff Writer

The gaping hole in Earth's ozone layer has shrunk 30 percent in size compared to last year, according to new measurements made by the European Space Agency's Envisat satellite.

The ozone layer loses about 0.3 percent of its mass annually, yet fluctuates in its thinness through the year. The region of extremely reduced ozone above Antarctica, popularly known as a "hole," generally peaks in size during September and October but regains its composure by the New Year.

Researchers are not certain if this year's smaller ozone hole means the radiation-blocking layer is healing.

"Although the hole is somewhat smaller than usual, we cannot conclude from this that the ozone layer is recovering already, said Ronald van der A, a senior project scientist at the Royal Dutch Meteorological Institute in the Netherlands.

This year, the ozone region over Antarctica dropped 30.5 million tons, compared to the record-setting 2006 loss of 44.1 million tons. Van der A said natural variations in temperature and atmospheric changes are responsible for the decrease in ozone loss, and is not indicative of a long-term healing.

"This year's ozone hole was less centered on the South Pole as in other years, which allowed it to mix with warmer air," van der A said. Because ozone depletes at temperatures colder than -108 degrees Fahrenheit (-78 degrees Celsius), the warm air helped protect the thin layer about 16 miles (25 kilometers) above our heads.

While strides have been made to ban ozone-munching compounds, such as chlorofluorocarbons (CFCs), the ozone layer continues to thin since the problem was widely recognized in 1985. The layer helps absorb harmful ultraviolet radiation from the sun, which increases the health risks of skin cancer and cataracts, as well as poses harm to marine life.

Yahoo News 19 Oct 07
NASA: Ozone hole returns to average size
By Seth Borenstein, AP Science Writer

The Antarctic ozone hole is back to an average size, shrinking about 16 percent from last year's record high, NASA said Friday. But it's still the size of North America.

The ozone hole in mid-September reached a maximum size of 9.7 million square miles, down from its peak of 11.5 million square miles last year, said NASA atmospheric scientist Paul Newman.

Human produced gases, containing chlorine and bromine, damage the Earth's protective ozone layer, forming a hole over the South Pole and into the Southern hemisphere. Because the ozone layer protects life on Earth by blocking ultraviolet rays, countries across the world 20 years ago agreed to ban many compounds such as spray-can propellants.

The ozone hole was first discovered in 1985, is not natural, and at the current rate should be closed up by 2070, Newman said. Nearly 80 percent of the ozone-depleting chemicals in the atmosphere are man-made.

But those compounds stay in the atmosphere 40 to 100 years and the total amount of chlorine compounds in the air is only down 3.1 percent since 2001, Newman said. For the past 15 years or so, the ozone hole has been about the same size, going up slightly and down slightly, mostly based on the weather, he said. It appears from July to October.

Warmer weather and more storms this year are the reason the hole is slightly smaller, Newman said.

"There's no way we could say we're seeing real improvement, but it's smaller because of the weather situation," Newman said.

On the Net: NASA's ozone hole watch: http://ozonewatch.gsfc.nasa.gov/


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