NOAA 2005-R528
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Analysis of several different satellite records and surface monitoring instruments indicates that the ozone layer is no longer declining, according to a study by scientists from the National Oceanic and Atmospheric Administration and four U.S. universities. The analysis also shows that in some parts of the world, the ozone layer has increased a small amount in the past few years, although ozone is still well below normal levels.

The results will be published Aug. 31 in the Journal of Geophysical Research and follow 18 years after an international agreement, the Montreal Protocol, was established to limit the production of chemicals determined to be harmful to the atmosphere.

“These early signs point to a successful example of international cooperation to address an environmental threat,” said retired Navy Vice Admiral Conrad C. Lautenbacher, Jr., Ph.D., under secretary of commerce for oceans and atmosphere and NOAA administrator. “NOAA is proud to have played a major role with the international community to meet these environmental challenges. NOAA’s science was crucial to reaching this turning point and we hope to see future improvements in ozone levels.”

“For the past few years, studies have focused on ozone in the topmost layer of the atmosphere where there is naturally very little ozone. However, this study addresses the total ozone column which has significant impact on how much ultraviolet radiation is coming through the atmosphere,” said Betsy Weatherhead of the Cooperative Institute for Research in Environmental Sciences (CIRES), a joint institute of the University of Colorado at Boulder and NOAA.

“Our work focuses on the thickness of the ozone layer and is therefore relevant to the amount of harmful ultraviolet (UV) radiation reaching the surface of the Earth,” said Weatherhead, a co-author on the paper.

Scientists say that ozone in some areas is still quite low compared to historical times and that the return of ozone to normal levels will be slow – likely taking several decades. The chemicals responsible for the ozone depletion can take years to filter up to the stratosphere, where most of the ozone is located, said Weatherhead.

Some of these chemicals remain in the stratosphere for many decades, meaning that chemicals produced years ago will continue to be harmful for decades to come, say scientists.

Other factors can affect the recovery process, such as changes in temperature, clouds, volcanic particles, water vapor and methane. Internationally, scientists continue to work to understand the recent changes and the likely future concentrations of ozone.

Lead author of the study, Greg Reinsel of the University of Wisconsin-Madison, was one of the first researchers to quantify the decline in ozone more than 20 years ago. He died unexpectedly after completing this study, the first to show the leveling off of the total ozone layer, Weatherhead said.

Other co-authors are Alvin Miller, Lawrence Flynn, and Ron Nagatani from NOAA, George Tiao, of the University of Chicago; and Don Wuebbles of the University of Illinois.

The National Oceanic and Atmospheric Administration, an agency of the U.S. Commerce Department, is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of our nation’s coastal and marine resources. Through the emerging Global Earth Observation System of Systems (GEOSS), NOAA is working with its federal partners and nearly 60 countries to develop a global monitoring network that is as integrated as the planet it observes.

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