Published on Friday, September 8, 2000 in the San Francisco Chronicle
Ozone Hole Bigger Than Ever, NASA Says
by David Perlman
The familiar and much-feared hole in Earth's protective ozone
layer has widened over Antarctic regions to record levels this year,
extending over more than 11 million square miles, a NASA satellite has
Variations in the size of the ozone hole are expected year to year, but the new measurements show that the seasonal hole has grown dramatically from a year ago, when it was slightly more than 8 million square miles.
Moreover, scientists said, levels of ozone are continuing to decline in the upper atmosphere and are expected to fall even more by early October.
The growth reported yesterday ``reinforces concerns about the frailty of Earth's ozone layer,'' said Michael Kurylo, the space agency's chief of upper atmosphere research.
Scientists believe the protective ozone layer will ultimately recover largely as a result of a 1987 international treaty banning ozone-destroying products. But Kurylo predicted that it will be ``many decades'' before it returns full force.
In a region from 10 to 25 miles high, the ozone layer protects the Earth by absorbing deadly frequencies of ultraviolet radiation from the sun. Loss of the ozone layer has caused health problems ranging from severe sunburns to an increased incidence of skin cancers and eye cataracts in New Zealand and southern Australia.
The radiation is also killing off plankton in the near-surface layers of the southern oceans by breaking up their DNA, scientists report. That, in turn, is affecting fish populations that depend on the microscopic plant and animal life for subsistence.
The latest measurements on the vanishing ozone hole come from the National Aeronautics and Space Administration's TOMS satellite, an instrument-laden spacecraft whose acronym stands for Total Ozone Mapping Spectrometer.
The ozone hole covers an area three times the size of the United States, and beats the previous record size of 10.5 million square miles that the satellite measured two years ago.
A year ago, scientists discovered a similar disruption of the Northern Hemisphere's ozone layer high above the Arctic Circle. Although the so-called northern hole was found to be much smaller, instruments carried by satellites, balloons and two high-altitude aircraft identified regions of the stratosphere where ozone concentrations declined by as much as 60 percent between last November and March.
The disappearance of protective ozone was first detected by satellites 25 years ago, and scientists analyzing the complex chemistry that causes the phenomenon determined that it was primarily due to disruptive gases released by industries on Earth.
The major factor, in turned out, were chlorofluorocarbons, or CFCs, leaking from a wide range of industries. Production of CFCs was banned in the United States in 1986, and in 1987, a treaty known as the Montreal Protocol called for a step- by-step ban worldwide. That treaty has since been signed by more than 140 nations.
The size of this year's Antarctic ozone hole is due to an unusually intense stratospheric air current known as the Antarctic vortex that sweeps around the continent of Antarctica and normally confines the ozone hole. This year, despite its intensity, the path of the vortex was wider than normal and allowed the hole to grow larger.
``Variations in the size of the ozone hole and of ozone depletion from one year to the next are not unexpected,'' said Jack Kaye, NASA's earth sciences research director. ``But at this point we can only wait to see how the ozone hole will evolve in the coming few months and see how the year's hole compares to those of previous years.''
While the TOMS satellite continues in orbit, NASA is planning to launch two more spacecraft, known as QuickTOMS and Aura, to make even more detailed measurements in the upper atmosphere.
©2000 San Francisco Chronicle