Official Nasa Communication 95-115

Brian Dunbar Headquarters, Washington, DC 1995 (Phone: 202/358-1547)

July 20,

RELEASE: 95-115 NASA-FUNDED RESEARCH SEES FALL OF OZONE-DEPLETING CHEMICAL NASA-sponsored university research has indicated that levels of an ozone-depleting chemical are falling, the first decrease ever measured of a substance restricted by the Montreal Protocol, an international treaty limiting the production of ozone-depleting chemicals. The research, led by Dr. Ronald Prinn of the Massachusetts Institute of Technology, Cambridge, MA, showed that concentrations of methyl chloroform have decreased at approximately two percent a year since mid-1990. Until that point, levels had increased approximately four percent a year since 1978. Concentrations of methyl chloroform are measured from four ground stations around the globe. NASA funded this research through its Upper Atmosphere Research Program, part of its Mission to Planet Earth (MTPE). Results of the study were published in the journal Science last week. "This is a very important measurement," said Dr. Robert Harriss, head of the Science Division of NASA's Office of Mission to Planet Earth. "We've already seen slowing increases in chlorofluorocarbons and other ozone-depleting chemicals. Now, for the first time, we've actually measured

a decrease in one of these chemicals. "What we're seeing are the effects of the Montreal Protocol and its amendments. Continued monitoring of ozone and the chemicals involved in ozone depletion will be crucial over the next several decades to ensure that the treaties continue to work, so that ozone levels ultimately recover," Harriss said. Scientists believe that under the Montreal Protocol, ozone levels will begin to return to their pre1980s concentrations early in the next century. The Antarctic "ozone hole" is not expected to subside until at least the middle of the 21st century. -more-

-2Monitoring ozone depletion is one of the ongoing programs of MTPE, which studies the Earth as a single global environment. MTPE scientists study how the Earth changes and how human activities contribute to those changes. -endNASA press releases and other information are available automatically by sending an Internet electronic mail message to [email protected]. In the body of the message (not the subject line) users should type the words "subscribe pressrelease" (no quotes). The system will reply with a confirmation via E-mail of each subscription. A second automatic message will include additional information on the service. Questions should be directed to (202) 358-4043.