Record ozone loss over Antarctic
Pastor Dale Morgan
Record ozone loss over Antarctic: European Space Agency*
PARIS, Oct 2 (AFP) Oct 02, 2006
Antarctica in 2006 suffered its highest recorded single-year loss in
ozone, the atmospheric molecule that protects against dangerous
ultraviolet light, the European Space Agency (ESA) said on Monday.
Ozone measurements made by the agency's Envisat satellite showed a loss
of 40 million tonnes in October, exceeding the previous record of 39
million tonnes set in 2000, it said in a press release.
Ozone loss is calculated by measuring the area and depth of the
so-called ozone hole in the stratosphere, about 25 kilometers (15 miles)
above Earth's surface
This year's ozone hole measures 28 million square kilometers (10.81
million square miles), which is nearly as large as in 2000, and the
depth of the ozone hole is 100 Dobson units, a measurement of the
thickness of the layer, which rivals a record set in 1990, ESA said.
Ozone, a molecule of oxygen, filters out dangerous ultraviolet rays from
the Sun that damage vegetation and can cause skin cancer and cataracts.
The layer has been badly damaged by man-made chemicals, especially
chlorine and chlorofluorocarbons (CFCs), according to scientists.
The chemical reaction that thins ozone reaches its peak with colder high
altitude temperatures in the southern hemisphere winter, normally in
late August to October.
"Such significant ozone loss requires very low temperatures in the
stratosphere combined with sunlight," ESA Atmospheric Engineer Claus
Zehner said.
"This year's extreme loss of ozone can be explaimed by the temperatures
above Antarctica reaching the lowest recorded in the area since 1979."
Last Friday, the World Meteorological Organisation (WMO) gave notice
that the seasonal ozone hole in 2006 was heading for a record.
The ozone level globally has lowered by 0.3 percent a year over the past
decade.
CFCs -- mainly aerosol gases and refrigerants -- and other ozone
destroyers were belatedly controlled by an international treaty, the
Montreal Protocol signed on September 16, 1987.
But there is already so much of the pollution stored in the atmosphere
that large ozone holes are expected to persist for the next couple of
decades, the WMO says.
The ozone layer over the Antarctic will only be completely replenished
15 years later than predicted, by 2065, WMO and the UN Environment
Programme (UNEP) said in August.
Ozone in the stratosphere is protective. At ground level, though, ozone,
as a chemical reaction between exhaust fumes and sunlight, is a
pollutant that can be dangerous for people with bad respiratory or heart
problems.