HATS Publications - Press Releases

Here are current press releases published by NOAA. You can find more by jumping to the NOAA public affairs office page.

UNITED STATES DEPARTMENT OF
COMMERCE NEWS
Washington, D.C. 20230

NATIONAL OCEANIC and ATMOSPHERIC ADMINISTRATION

EMBARGOED UNTIL:
Thursday 5/30/96 at 5 P.M. EDT

Contact: Barbara McGehan 303-497-6286
Stephen Montzka 303-497-6657
James Butler 303-497-6898

STUDY INDICATES OZONE-DESTROYING CHEMICALS DECLINING

It looks like a brighter future for Earth's stratospheric ozone layer. According to a new study by Commerce Department scientists in Boulder, Colo., the total amount of ozone-destroying chemicals in the troposphere (lower atmosphere) has declined for the first time since humans began producing these substances. This decline is expected to affect the stratosphere, where the ozone layer is found, in a few years.

In findings published in the current issue of Science, Stephen A. Montzka and colleagues from the Climate Monitoring and Diagnostics Laboratory in Boulder, part of Commerce's National Oceanic and Atmospheric Administration, conclude that chlorine and equivalent chlorine (chlorine plus bromine) decreased in the troposphere in 1995. The scientists believe this decline has occurred because many nations have limited the production of materials that cause ozone depletion in the stratosphere. This is good news for the ozone layer, which has been under attack from ozone-depleting chemicals produced by humans for many years.

Limits to ozone-damaging compounds were first set forth in the Montreal Protocol, an international agreement that was originally signed by the United States and 22 other nations in 1987, and subsequently revised and amended.

While the study results do not suggest that ozone depletion is no longer a concern, they do show for the first time that the outlook for stratospheric ozone has improved. The ozone layer was expected to recover in coming decades as a result of restrictions placed on CFCs and other chemicals by the Montreal Protocol, but, before this study, many uncertainties remained regarding the timing for initial recovery.

Unlike other recent measurement studies, this one considers all of the important ozone-depleting substances generated by human activity, and how the total amount of chlorine and bromine (relevant to stratospheric ozone depletion) has changed in recent time. Conclusions drawn by the scientists are based upon their measurements of chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), halons, and chlorinated solvents from tropospheric air samples collected at remote locations across the globe over the past four to five years. Only by considering all of these ozone-depleting substances together does it become possible to draw conclusions regarding amounts of ozone in the future stratosphere.

"Both chlorine and bromine are known ozone-depleting agents that had been increasing steadily in the atmosphere over the 30 years before 1990 because of the use of CFCs, chlorinated solvents, HCFCs, and halons in refrigerators, air conditioners, foams, cleaners and fire extinguishers," says Montzka.

According to the researchers, chlorine in the lower atmosphere was decreasing at about 1 percent per year in mid-1995, and had dropped approximately 1.5 percent from the observed maximum. "Our data show that the mean global abundance of chlorine in the lower atmosphere peaked in 1994," Montzka continued. "Small yearly increases are still observed for bromine, which destroys ozone more efficiently than chlorine. However, these increases are small enough to be offset by the observed decrease in chlorine, even when the greater ozone-depleting efficiency of bromine is considered."

Montzka and his colleagues believe that ozone-depleting gases in the stratosphere will peak within one to three years, and thereafter begin declining. Changes in the stratosphere lag behind those observed in the troposphere because it takes several years for air in the lower atmosphere to reach the stratosphere. Stratospheric ozone forms an invisible shield around the Earth, protecting it from the biologically damaging ultraviolet rays of the sun.

The scientists warn, however, that this bit of good news is not irreversible. "Decreases in ozone-depleting gases are a direct result of international limits on the production and consumption of ozone-depleting chemicals. Without widespread adherence to restrictions outlined in the revised Montreal Protocol, additional emissions of chlorinated and brominated compounds could slow or reverse the trends we have observed, and delay recovery of stratospheric ozone," asserted Montzka.

The air samples analyzed were from NOAA sites in Point Barrow, Alaska; Mauna Loa, Hawaii; Cape Matatula, American Samoa; and the South Pole. Other stations in the network include the Canadian Atmospheric Environmental Services station at Alert, Canada; the University of Colorado station at Niwot Ridge, Colo., and the Australian Baseline Air Pollution station at Cape Grim, Tasmania.

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Note to Editors: For more information, you can access NOAA's Climate Monitoring and Diagnostics Lab - Halocarbons and other Atmospheric Trace Species Division home page at:
http://www.cmdl.noaa.gov/hats/
A color figure can be accessed at:
http://www.cmdl.noaa.gov/hats/totalcl/totalcl.html

Following are some experts in the area of ozone research if you would like additional comments on the paper:

Dr. Richard Stolarski
NASA/Goddard 301-286-9111

Prof. Steven Wofsy
Harvard University 617-495-4566

Dr. Michael Kurylo
NASA Headquarters 202-358-0237

NOAA 95-86 12/14/95
Contact:
Barbara McGehan
(303) 497-6286
Dr. Stephen Montzka
(303) 497-6657

NOAA SCIENTISTS SAY REDUCED LEVELS OF TROPOSPHERIC CHLORINE ARE RESULT OF MONTREAL PROTOCOL LIMITS

A decrease in levels of chlorine in the lower atmosphere is a result of limits on the production of these ozone-depleting substances set by the Montreal Protocol, according to scientists at the Commerce Department's National Oceanic and Atmospheric Administration. The decrease in tropospheric chlorine arising from human activity that the scientists have observed bodes well for the ozone layer in the upper atmosphere, which protects Earth from harmful ultraviolet rays.

"Because ozone depletion is related to the amount of chlorine in the stratosphere, decreases in chlorine levels in the troposphere [which is below the stratosphere] suggest that the threat to the ozone layer from chlorofluorocarbons, methyl chloroform, and carbon tetrachloride will also begin to decrease as lower atmospheric air circulates into the stratosphere -- as long as the Montreal Protocol production limits prescribed for these compounds are not exceeded in future years," said Stephen A. Montzka, team leader of NOAA's Climate Monitoring and Diagnostics Laboratory (CMDL) in Boulder, Colo.

The Montreal Protocol is a 1987 international agreement to limit the global production of chlorofluorocarbons and other ozone-depleting substances. "Measurements of air collected from remote sites located across the globe suggest that the tropospheric abundance of chlorine arising from use of refrigerants, solvents, and foam-blowing agents is now decreasing," Montzka said.

CMDL scientists maintain that this decline in tropospheric chlorine has resulted from adherence to the Montreal Protocol on Substances that Deplete the Ozone Layer and subsequent amendments, and is not offset by increases in chlorine arising from use of alternative compounds such as hydrochlorofluorocarbons (HCFCs). The compounds considered in this study account for the majority of chlorine present in the stratosphere due to human activity.

Full recovery of the ozone layer to natural levels will take many years because of the long atmospheric residence times (up to 100 years) for chlorofluorocarbons. The timing for recovery of the ozone layer also will depend on how atmospheric temperatures and levels of aerosols and bromine change in the future.

Both chlorofluorocarbons and their alternatives contribute to greenhouse warming of the atmosphere. Although yearly increases in atmospheric heating attributable to these industrial compounds have slowed as a result of the Montreal Protocol, the total contribution to atmospheric heating from these gases continues to rise.

NOAA scientists have based their conclusions on analyses of air samples collected over the past four years at seven remote, land-based sites located in both hemispheres of the globe. The sites include: American Samoa; Mauna Loa in Hawaii; Point Barrow, Alaska; Tasmania; Niwot Ridge, Colo.; Alert, Canada; and Antarctica.

NOAA 95-10 2/17/95
Contact:
Barbara McGehan
(303) 497-6286
Dr. James Butler
(303) 497-6898

NOAA SCIENTISTS DISCOVER OZONE-DEPLETING CHEMICAL IS CONSUMED BY OCEAN

The ocean, up to now believed to be a main source of an ozone- depleting chemical, methyl bromide, also consumes the compound, effectively removing a significant amount from the atmosphere, according to a new study conducted by scientists at the National Oceanic and Atmospheric Administration.

The investigators, working with NOAA's Climate Monitoring and Diagnostics Laboratory in Boulder, Colo., have found that the ocean is largely undersaturated in methyl bromide, thus representing a significant mechanism for its removal from the atmosphere.

Up to this time, the ocean was believed to be a main source of atmospheric methyl bromide, contributing about 30% of the methyl bromide in the atmosphere. Other major sources of this gas include biomass burning and fumigation of soils, produce and buildings.

Methyl bromide is a strong ozone-depleting chemical that may ultimately contribute as much as 10% to global stratospheric ozone destruction. Unlike the chlorofluorocarbons (CFC's) and halons, which are entirely man-made, methyl bromide has both natural and anthropogenic sources.

According to the study by J. Lobert and co-authors, published in the Feb. 17 issue of Science, surface waters in the open oceanic regions of the east Pacific had much less methyl bromide than anticipated, indicating that the amount of methyl bromide being destroyed in the ocean exceeds the amount being produced. This destruction is driven mainly by reaction of methyl bromide with water and salt dissolved in seawater.

Project scientist and co-author, James Butler, said, "The results suggest that 30-40% of the methyl bromide in the atmosphere is destroyed in the ocean and that, consequently, its lifetime in the atmosphere is 30-40% shorter than previously believed."

Measurements were taken during January and February 1994 along a cruise track from Seattle, Wash., to Punta Arenas, Chile, as part of a scientific expedition aboard the NOAA Ship Discoverer. These analyses of methyl bromide in both the atmosphere and surface water show that it was highly undersaturated in the central part of the open ocean, which represents 80-90% of the global oceanic coverage. At the same time, coastal waters and other upwelling regions were supersaturated in methyl bromide, but represent a much smaller global coverage.

This is the most comprehensive data set on oceanic methyl bromide published to date. Although the study was limited to the eastern Pacific Ocean, the authors noted that more recent, preliminary results from another expedition last fall in the Atlantic Ocean are consistent with these findings.

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30-May-1996