6 November 2008
A new NOAA-led scientific assessment on the ozone layer, to be released November 13 as part of the series of Synthesis and Assessment reports coordinated by the U.S. Climate Change Science Program (CCSP), gives a first-time emphasis on the U.S. perspective in the ozone depletion issue, and updates the status of the global ozone layer. The report also offers a glimpse into expectations for recovery of the ozone layer in a changing climate, as well as a first detailed look at U.S. role in emitting – and reducing the emissions of – the chemicals that deplete the ozone layer.
Dr. A.R. Ravishankara, Director of CSD, was the lead for the report. The author team was composed of 16 scientists from NOAA, NASA, NSF, EPA, NRL/DOD, and USDA. NOAA authors were: John Daniel (CSD/ESRL); David Fahey (CSD/ESRL); Steve Montzka (GMD/ESRL); and V. Ramaswamy (GFDL). They developed information for and about the U.S., and drew material from two recent international scientific assessment reports to which the U.S. contributed, to distill a U.S.-specific perspective on this global issue.
The report finds that U.S. production and use of ozone-depleting substances have been significant throughout the history of the ozone depletion issue, contributing about 25 percent of the global amount produced during the period from 1986 to 1994. But by adopting the 1987 international Montreal Protocol agreement to protect the ozone layer, the report finds that the U.S. has also contributed significantly to healing the ozone layer by reducing the production and use of ozone-depleting substances. The U.S. percentage of the global total production has fallen to 10% in recent years.
The numbers reflect a decline of 97-98% in the U.S. production of the ozone-damaging chemicals since the late 1980s. U.S. actions have aided international efforts to achieve a recovery of the ozone layer, which is expected to occur about mid-century for most regions of the globe. Ozone depletion is not worsening, and in some regions the ozone layer is now showing early signs of recovery.
As the CCSP 2.4 report notes, without the Montreal Protocol, the levels of ozone-depleting substances in the "world we avoided" would likely have been 50 percent larger in 2010 than currently predicted.
Background: The ozone layer, which surrounds the globe about 10-15 miles above the surface, protects living things from the Sun's harmful ultraviolet rays. Chlorofluorocarbons (CFCs) used in refrigeration and air conditioning, along with other manmade substances, deplete stratospheric ozone. Above Antarctica, the extreme losses occurring each spring lead to an "ozone hole" above that continent. The ozone layer is expected to recover by mid-to-late this century, largely because of the actions taken by the international community to limit ozone-depleting substances such as CFCs. The 1987 Montreal Protocol and its subsequent amendments established limits and eventual phase-outs for production and consumption of several ozone-depleting substances.
Significance: This report provides a U.S. perspective on the global issue of stratospheric ozone depletion and gives decision-support scientific information on the topic. The work was completed as part of NOAA's Climate Goal-Climate Research and Modeling Program.