antarctic ozone hole - oh dear

[Crepuscular Ray]

Oct. 19, 2006

Erica Hupp/Dwayne Brown

Headquarters, Washington

202-358-1237/1726

Anatta

NOAA, Earth System Research Laboratory, Boulder, Colo.

303-497-6288

RELEASE: 06-338

NASA AND NOAA ANNOUNCE ANTARCTIC OZONE HOLE IS A RECORD BREAKER

NASA and National Oceanic and Atmospheric Administration (NOAA)

scientists report this year's ozone hole in the polar region of the

Southern Hemisphere has broken records for area and depth.

The ozone layer acts to protect life on Earth by blocking harmful

ultraviolet rays from the sun. The "ozone hole" is a severe depletion

of the ozone layer high above Antarctica. It is primarily caused by

human-produced compounds that release chlorine and bromine gases in

the stratosphere.

"From September 21 to 30, the average area of the ozone hole was the

largest ever observed, at 10.6 million square miles," said Paul

Newman, atmospheric scientist at NASA's Goddard Space Flight Center,

Greenbelt, Md. If the stratospheric weather conditions had been

normal, the ozone hole would be expected to reach a size of about 8.9

to 9.3 million square miles, about the surface area of North America.

The Ozone Monitoring Instrument on NASA's Aura satellite measures the

total amount of ozone from the ground to the upper atmosphere over

the entire Antarctic continent. This instrument observed a low value

of 85 Dobson Units (DU) on Oct. 8, in a region over the East

Antarctic ice sheet. Dobson Units are a measure of ozone amounts

above a fixed point in the atmosphere. The Ozone Monitoring

Instrument was developed by the Netherlands' Agency for Aerospace

Programs, Delft, The Netherlands, and the Finnish Meteorological

Institute, Helsinki, Finland.

Scientists from NOAA's Earth System Research Laboratory in Boulder,

Colo., use balloon-borne instruments to measure ozone directly over

the South Pole. By Oct. 9, the total column ozone had plunged to 93

DU from approximately 300 DU in mid-July. More importantly, nearly

all of the ozone in the layer between eight and 13 miles above the

Earth's surface had been destroyed. In this critical layer, the

instrument measured a record low of only 1.2 DU., having rapidly

plunged from an average non-hole reading of 125 DU in July and

August.

"These numbers mean the ozone is virtually gone in this layer of the

atmosphere," said David Hofmann, director of the Global Monitoring

Division at the NOAA Earth System Research Laboratory. "The depleted

layer has an unusual vertical extent this year, so it appears that

the 2006 ozone hole will go down as a record-setter."

Observations by Aura's Microwave Limb Sounder show extremely high

levels of ozone destroying chlorine chemicals in the lower

stratosphere (approximately 12.4 miles high). These high chlorine

values covered the entire Antarctic region in mid to late September.

The high chlorine levels were accompanied by extremely low values of

ozone.

The temperature of the Antarctic stratosphere causes the severity of

the ozone hole to vary from year to year. Colder than average

temperatures result in larger and deeper ozone holes, while warmer

temperatures lead to smaller ones. The NOAA National Centers for

Environmental Prediction (NCEP) provided analyses of satellite and

balloon stratospheric temperature observations. The temperature

readings from NOAA satellites and balloons during late-September 2006

showed the lower stratosphere at the rim of Antarctica was

approximately nine degrees Fahrenheit colder than average, increasing

the size of this year's ozone hole by 1.2 to 1.5 million square

miles.

The Antarctic stratosphere warms by the return of sunlight at the end

of the polar winter and by large-scale weather systems

(planetary-scale waves) that form in the troposphere and move upward

into the stratosphere. During the 2006 Antarctic winter and spring,

these planetary-scale wave systems were relatively weak, causing the

stratosphere to be colder than average.

As a result of the Montreal Protocol and its amendments, the

concentrations of ozone-depleting substances in the lower atmosphere

(troposphere) peaked around 1995 and are decreasing in both the

troposphere and stratosphere. It is estimated these gases reached

peak levels in the Antarctica stratosphere in 2001. However, these

ozone-depleting substances typically have very long lifetimes in the

atmosphere (more than 40 years).

As a result of this slow decline, the ozone hole is estimated to

annually very slowly decrease in area by about 0.1 to 0.2 percent for

the next five to 10 years. This slow decrease is masked by large

year-to-year variations caused by Antarctic stratosphere weather

fluctuations.

The recently completed 2006 World Meteorological Organization/United

Nations Environment Programme Scientific Assessment of Ozone

Depletion concluded the ozone hole recovery would be masked by annual

variability for the near future and the ozone hole would fully

recover in approximately 2065.

"We now have the largest ozone hole on record," said Craig Long of

NCEP. As the sun rises higher in the sky during October and November,

this unusually large and persistent area may allow much more

ultraviolet light than usual to reach Earth's surface in the southern

latitudes.

[MAF]

i feel quite sad after reading that. when are the goverments of the world sit up and listen?

[Bottesford]

Think they already have- CFC's banned globally (I think). Problem is, there's lots of old fridges, etc still with CFC's in them and with the slow destruction of ozone killing compounds it'll take ages to heal.

Good job the hole isn't over the arctic. We'd have a lot more skin cancer cases.