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Ozone destruction slows; refrigerant ban credited

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  • 7/30 SF Chronicle
    Published Wednesday, July 30, 2003, by the San Francisco Chronicle Ozone hole s growth rate slows down Scientists credit refrigerant ban By David Perlman
    Message 1 of 1 , Aug 1 9:51 AM
      Published Wednesday, July 30, 2003, by the San Francisco Chronicle

      Ozone hole's growth rate slows down
      Scientists credit refrigerant ban

      By David Perlman
      Chronicle Science Editor

      Almost 30 years after scientists discovered that common industrial
      gases were destroying Earth's protective ozone layer, satellite
      readings and ground observations show for the first time that the
      dangerous rate of ozone loss is finally slowing.

      Colorless compounds known as chlorinated fluorocarbons (CFCs), such
      as the Freon once used in refrigerators and common spray cans, have
      accumulated in the stratosphere to cause a growing "hole" in the
      ozone layer. That layer normally acts to screen out much of the sun's
      harmful ultraviolet radiation, which can cause skin cancer and damage

      Alarm has grown over the years as satellite observations found that
      an ozone hole was spreading over thousands of square miles in the
      Southern Hemisphere while high-flying NASA missions discovered
      evidence that a similar hole was growing over far northern latitudes.

      Now, atmospheric researchers are reporting "compelling evidence" that
      the rate of ozone depletion in the highest levels of the stratosphere
      is slowing down as a result of an international treaty known as the
      Montreal Protocol that began banning CFCs in 1987 and has been made
      even stronger in subsequent years.

      "This is proof that the treaty is working," said Michael Newchurch,
      an atmospheric chemist at the University of Alabama in Huntsville and
      lead author of the study, in a phone interview Tuesday. "We had a
      monumental problem on a global scale that we have started to solve,
      and we're finally seeing the beginning of the recovery in the upper

      The ozone problem caused by CFCs was first noticed as early as the
      1960s, but was largely ignored until 1974, when Sherwood Rowland of
      UC Irvine and Mario Molina of MIT published the first powerful
      evidence of the impending danger in the journal Nature. Paul Crutzen
      of Germany's Max Planck Institute in Mainz added to the research, and
      the three atmospheric scientists won the Nobel Prize in chemistry in

      It was in 1985, after Australian scientists began fearing an epidemic
      of skin cancer as a result of the fast-spreading ozone hole, that
      international efforts began to limit the spread of CFCs. Despite
      powerful resistance by industry lobbyists, the first treaty banning
      the compounds was signed two years later. It has since been
      strengthened several times.

      The report by Newchurch and his colleagues, to be published in the
      Journal of Geophysical Research, is based on ozone measurements made
      by three NASA satellites and by scientists at ground stations in
      Boulder, Colo.; Arosa, Switzerland, and Tateno, Japan. All are
      maintained by government meteorological agencies.

      Although the scientists measured only the slowing rate of ozone
      depletion in the high stratosphere -- some 22 to 28 miles above the
      Earth -- it is reasonable to assume, he said, that the same process
      is occurring at lower levels of the stratosphere where the bulk of
      the ozone layer exists and its destruction has been most noticeable.

      "We're not gaining ozone, we're just losing it less quickly," he
      said. Between 1997 and 2000, the average growth rate of the ozone
      hole has slowed by approximately 7 percent per decade, according to
      their calculations. It will take at least 40 or 50 years before all
      the ozone depletion stops and recovery begins, Newchurch said.

      Rowland voiced enormous satisfaction at the results of the Newchurch
      team's work in a phone interview Tuesday.

      "It shows clearly that the Montreal Protocol is working as it
      should," he said. "It also shows that when people and industries
      won't voluntarily change the way they operate and are forced to
      change by a treaty, then they'll find that changing is much easier
      than they thought. The industries that produced and used CFCs have
      plenty of very smart people, and they quickly found substitutes for
      the compounds once the treaty required them to."

      To Rowland that lesson also applies to the increasing evidence that
      industrial emissions of greenhouse gases are the major cause of the
      current global warming trend.

      "The Kyoto Protocol could work as powerfully as the Montreal treaty,"
      he said, referring to the agreement to limit greenhouse gas emissions
      that the Bush administration has refused to sign. He praised the
      renewed effort by Sens.

      John McCain, R-Ariz., and Joe Lieberman, D-Conn., to force a vote on
      an effort to control global warming when the Senate takes up an
      energy bill this week.

      Both Rowland and Newchurch warned, however, that this first report of
      success against the ozone hole is only the beginning: The chlorinated
      fluorocarbons last from 45 to 100 years in the atmosphere, they
      noted, so that even if the rate of growth in the ozone holes
      continues slowing, "the CFCs will still be around a for long time
      after we're all gone," Rowland said.

      E-mail David Perlman at dperlman@...
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