Ozone Hole Biggest Yet

suchandra · October 23, 2006

Ozone Hole Biggest Yet

Scientists worry about DNA damage to those in southern hemisphere

By Phil Berardelli

ScienceNOW Daily News

20 October 2006

The hole in Earth's ozone layer has grown to its biggest dimensions yet, according to scientists at NASA and the National Oceanic and Atmospheric Administration (NOAA). The gap--observed last month over Antarctica--was nearly three times the size of the continental United States and about 1% larger than the previous record.

Widening gap?

This satellite image, taken 24 September, shows the record-breaking Antarctic ozone hole. The blue and purple colors denote areas with the least ozone, while the greens and yellows indicate higher concentrations of the gas. Credit: NASA

The ozone hole has appeared every Antarctic winter since scientists began taking measurements in 1985. It signals the continued action of ozone-destroying compounds, such as chlorofluorocarbons (CFCs), in the atmosphere, which are magnified by the effect of colder winter temperatures on the fragile gas. Because ozone blocks DNA-damaging rays from the sun, scientists are concerned that a weakening of this protective layer could lead to a higher incidence of cancer and infertility among people living in the southern hemisphere. In 1987, an international agreement known as the Montreal Protocol banned the release of CFCs (once common in refrigerators and air conditioners) into the atmosphere; however, their effect can persist for decades. At the current rate of recovery, scientists estimate it could take another 60 years for the planet's ozone layer to mend completely.

The record-setting ozone hole was observed from 21 September to 30 September by NASA's polar-orbiting Aura satellite, as well as from instrument-laden balloons launched by polar research stations. Scientists calculated the gap at 27.4 million square kilometers, says Paul Newman, an atmospheric scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, which manages Aura. The biggest previous gap was 27.1 million square kilometers, he says, seen in 2003. In addition, the readings showed nearly all of the ozone had been destroyed between eight and 13 miles above Earth's surface. "These numbers mean the ozone is virtually gone in this layer of the atmosphere," says David Hofmann, director of the Global Monitoring Division at NOAA's Earth System Research Laboratory in Boulder, Colorado. "It appears that the 2006 ozone hole will go down as a record-setter." A record-setter perhaps, but not necessarily meaningful, says atmospheric scientist Michael Newchurch at the University of Alabama, Huntsville. He notes that colder-than-normal temperatures over Antarctica this year accounted for the expansion--a trend that's not guaranteed to continue. On the other hand, Newchurch says, atmospheric levels of carbon dioxide are increasing, which could lead to a cooler stratosphere. So "we may not have seen the biggest ozone hole, but soon the effect of declining [CFCs] will overcome the cooling temperatures, and the size of the hole will diminish," he says.