Environmental Indicators: Ozone Depletion

Technical Supplement

• a copy of the charts from the protection of the ozone layer indicator bulletin;
• the summary data used in preparing the charts;
• names of knowledgeable contacts for additional information;
• references to published data;
• selected information on the purpose of the data collection, geographic coverage, collection period, method and frequency of data collection, and data presentation.

In addition to the format below, the entire Technical Supplement is available in Adobe Acrobat (PDF) format. It is a 139K file called techsupp.pdf.

For additional information, please contact the contacts for each chart or Ms. Susan Auby, Mail Code 2152, Office of Environmental Information, USEPA, 1200 Pennsylvania Avenue, NW, Washington, DC 20460. Phone (202) 260-4901, e-mail: auby.susan@epa.gov.

DATA SOURCE

U.S. production data for chlorofluorocarbons CFC-11 and CFC-12 come from the United States International Trade Commission, Synthetic Organic Chemicals; United States Production and Sales, 1993, Table 3-1, p. 3-21 (Washington, DC: GPO, 1994), and from earlier annual reports in this series. Annual production data are summed and cumulative totals calculated for years 1958 through 1993.

Contact Person for U.S. Production of Ozone-Depleting Chemicals:
Note: The ITC no longer provides production data. For questions regarding production data through 1994, please contact Elizabeth Nesbitt via email: nesbitt@usitc.gov.

World production data for CFC-11 and CFC-12 come from the Alternative Fluorocarbons Environmental Acceptability Study (AFEAS), Production, Sales and Atmospheric Release of Fluorocarbons Through 1993, Data Tables 2 and 3 (Washington, DC: AFEAS, 1995). Annual production data are reported by participating companies to an independent accountant. Production data are summed and reported for years 1958 through 1993 for the purpose of this bulletin. U.S. cumulative totals (ITC) are subtracted from AFEAS world totals to calculate "rest of the world" totals.

Contact Person for World Production of CFCs:
Katie D. Smythe
AFEAS Program Administrator
Alternative Fluorocarbons Environmental Acceptability Study
1200 South Hayes Street
Arlington, VA 22202
Email: info@afeas.org
Telephone: (202) 296-5000, ext. 5264
Web site: http://www.afeas.org

DATA COLLECTED AND PURPOSE

The U.S. International Trade Commission reports annually on domestic production and sales of synthetic organic chemicals and the raw materials from which they are made. The report is prepared under investigation No. 332-135, Synthetic Organic Chemical Reports. This investigation is conducted under the authority of section 332(g) of the Tariff Act of 1930 (19 U.S.C. 1322(g)), for the purpose of collecting data and preparing public reports on synthetic organic chemicals, plastics materials, medicinal chemicals, pesticides, and other chemical products. The data are collected by survey of chemical manufacturers and include the total output of each company's plants, i.e., the quantities produced for consumption within the producing plant, as well as the quantities produced for domestic and foreign sales. Statistics for an individual chemical or group of chemicals are given only when there are three or more producers, no one or two of which may be predominant, and when their publication would not violate the statutory provisions relating to unlawful disclosure of information accepted in confidence by the Commission.

Since 1976, the chemical industry has voluntarily reported the production and sales of fluorocarbons through a survey conducted by an independent accountant (Grant Thornton LLP) on behalf of the Chemical Manufacturers Association until 1991 and AFEAS thereafter. The purpose of the survey is to provide the scientific community with data on atmospheric release of fluorocarbons.

GEOGRAPHICAL COVERAGE

In the AFEAS survey, global production of CFCs reflects production by plants in the following countries: Argentina, Australia, Brazil, Canada, the European Union, Japan, Mexico, South America, the United States, and Venezuela. It has been estimated that the data collected for 1993 represents probably less than 75 percent of worldwide production for dispersive uses. Coverage varies from year to year since 1982, as shown in the following table. For years prior to 1982, 100 percent coverage is assumed.

U.S. production reported to ITC is the total quantity of a commodity made available by original manufacturers located within the customs territory of the United States (including the 50 states, the District of Columbia, and Puerto Rico).

Table 1: World coverage of CFC-11 and CFC-12 production data, 1982-1993

Source: World Resources Institute (1982-1989) and AFEAS (1990-1993).

DATA COLLECTION PERIOD

For CFC-12, there is an unbroken time series for world production since 1931 and for U.S. production since 1958. For CFC-11, there is an unbroken time series for world production since 1934 and for U.S. production since 1958. Prior to 1958, total cumulative production of CFC-11 and CFC-12 was less than 750 thousand metric tons. For graphical purposes, only data from 1958 forward are displayed.

METHOD AND FREQUENCY OF DATA COLLECTION

Data contained in the ITC annual report are compiled primarily from the Commission's questionnaires sent to domestic chemical producers (643 companies for the 1993 annual report). Data are collected annually.Data contained in the AFEAS annual report are compiled from questionnaires solicited by the Alternative Fluorocarbons Environmental Acceptability Study and submitted by chemical manufacturers. A listing of all the companies surveyed inclusive of any related subsidiaries and/or joint ventures that may have reported data is contained in each annual report. Sales are divided into use categories, such as refrigeration, foam blowing, aerosols, solvents, and other uses. Some degree of geographical breakdown is also provided. In addition, calculations of atmospheric release of fluorocarbons, based on the survey data, are made. Further detail of data collection and emission estimation procedures and associated uncertainties, and the geographical distribution of emissions has been published (see References below).

DATA PRESENTATION

The data for the indicator (Figure 2) which are listed in Table 2 show the total cumulative production of CFC-11 and CFC-12 for the United States and the rest of the world from 1958 through 1993. See the table above for percent of world coverage in a given year. ITC reports production data in kilograms and AFEAS reports in metric tons. For this bulletin, data were converted to metric tons.

Table 2: Cumulative production of CFC-11 and CFC-12 for the United States and the rest of the world, 1958-1993
(thousand metric tons)

Source: ITC and AFEAS, with world coverage factors applied to AFEAS data.

REFERENCES

Alternative Fluorocarbons Environmental Acceptability Study, Production, Sales and Atmospheric Release of Fluorocarbons through 1993 (Washington, DC: AFEAS, 1995). Note: This report was published annually by the Chemical Manufacturers Association until 1991. Since 1992, it has been published by the Alternative Fluorocarbons Environmental Acceptability Study.

Gamlen, P.H., B.C. Lane, and P.M. Midgely, The Production and Release to the Atmosphere of CCl ₃F and CCl ₂F ₂ (Chlorofluorocarbons CFC-11 and CFC-12). Atmospheric Environment, 20: 1107-1085 (1986).

McCarthy, R.L., F.A. Bower, and J.P. Jenson, The Fluorocarbon-Ozone Theory - I. Production and Release: World Production and Release of CCl ₃F and CCl ₂F ₂ (Fluorocarbons 11 and 12) Through 1975. Atmospheric Environment, 11: 491-497 (1977).

United States International Trade Commission (ITC), Synthetic Organic Chemicals; United States Production and Sales, 1993, Table 3-1, pp. 3-19 and 3-21 (Washington, DC: GPO, 1994), and from earlier annual reports in this series.

DATA SOURCE

Measurements of the atmospheric concentrations of selected ozone-depleting chemicals come from the Atmospheric Lifetime Experiment (ALE)/Global Atmospheric Gases Experiment (GAGE)/Advanced GAGE network.

Contact Person for Atmospheric Concentrations of Selected Ozone-Depleting Chemicals:
Tom Boden
U.S. Department of Energy
Oak Ridge National Laboratory
Carbon Dioxide Information Analysis Center (CDIAC)
P.O. Box 2008
Oak Ridge, Tennessee 37831-6335
Telephone: (423) 241-4842
Email: bodenta@ornl.gov

For information about CDIAC numeric data packages and select data bases, contact:
Sonja Jones
U.S. Department of Energy
Oak Ridge National Laboratory
Carbon Dioxide Information Analysis Center (CDIAC)
P.O. Box 2008
Oak Ridge, Tennessee 37831-6335
Telephone: (423) 574-3645
Email: cdiac@ornl.gov

DATA COLLECTED AND PURPOSE

In the ALE/GAGE/AGAGE global network program, continuous high frequency gas chromatographic measurements of two biogenic/anthropogenic gases (methane and nitrous oxide) and five anthropogenic gases [chlorofluorocarbons CFCl ₃ (CFC-11), CF ₂Cl ₂ (CFC-12), and CF ₂ClCFCl ₂ (CFC-113); methyl chloroform, CH ₃CCL ₃; and carbon tetrachloride, CCl4] are carried out at four globally-distributed sites: Cape Grim, Tasmania; Point Matatula, American Samoa; Ragged Point, Barbados; and Mace Head, Ireland. Stations also previously existed at Cape Meares, Oregon, and at Adrigole, Ireland. The program, which began in 1978, is designed to accurately determine the atmospheric concentrations and long-term trends of these important trace gases so that their global circulation rates and globally averaged atmospheric lifetimes can be calculated. The Cape Grim, Tasmania station was selected as the source of data for this indicator as it is both representative and has the longest time series for the complete ALE/GAGE schedule of trace gases.

GEOGRAPHICAL COVERAGE

Global. The Cape Grim data are shown.

DATA COLLECTION PERIOD

Data for CFC-11, CFC-12, and nitrous oxide have been collected fairly continuously at each station since July 1978. Beginning in late 1983 at Cape Grim and later at the other sites, the additional measurements were added to the program. By mid-1986, ALE had ended and was succeeded by GAGE at all sites except the Adrigole (Ireland) station, which closed in December 1983 and was replaced by the GAGE station at Mace Head in January 1987.

METHOD AND FREQUENCY OF DATA COLLECTION

Air samples, collected 4 times daily for ALE and 12 times daily for GAGE, are filtered, dried, and analyzed using Hewlett Packard HP5840A (ALE) or HP5880A (GAGE) electron capture gas chromatographs. The recently initiated Advanced GAGE (AGAGE) uses a custom-designed sample module and HP5890 and Carle Instruments gas chromatographic components.

DATA PRESENTATION

The data from Cape Grim used for the indicator (Figure 3), which are listed in Table 3, show monthly mean halocarbon mixing ratios expressed as parts per trillion by volume. The principal investigators calculated monthly mixing ratios by averaging individual measurements (after removing pollution events). Data are available, in principle, from measurements taken four-times daily for ALE from July 1978 through June 1985 and 12 times-daily for GAGE from December 1981 through June 1994. For CFC-11, individual measurements actually represent averages of the separate measurements made on two different chromatographic columns when both values are available. For the graphical presentation of the data, in the bulletin gaps caused by missing monthly values were filled with averages.

Table 3: Atmospheric concentrations of selected ozone-depleting chemicals, 1978-1994
(parts per trillion by volume)

CFC-11 (ALE)

CFC-11 (GAGE)

Table 3: Atmospheric concentrations of selected ozone-depleting chemicals, 1978-1994 (continued)
(parts per trillion by volume)

CFC-12 (ALE)

CFC-12 (GAGE)

Table 3: Atmospheric concentrations of selected ozone-depleting chemicals, 1978-1994 (continued)
(parts per trillion by volume)

CH ₃CCl ₃ (ALE)

CH ₃CCl ₃ (GAGE)

Table 3: Atmospheric concentrations of selected ozone-depleting chemicals, 1978-1994 (continued)
(parts per trillion by volume)

CCl ₄ (ALE)

CCl ₄ (GAGE)

Source: Prinn, et al. (1994) and recent updates to database. See References.

REFERENCES

Cunnold, D.M., P.J. Fraser, R.F. Weiss, R.G. Prinn, P.G. Simmonds, F.N. Alyea, and A.J. Crawford. Global trends and annual releases of CCl ₃F and CCl ₂F ₂ estimated from ALE/GAGE and other measurements for July 1978 to June 1991. J. Geophys. Res. 99(D1):1107-1126 (January 1994).

Prinn, R.G., P.G. Simmonds, R.A. Rasmussen, R.D. Rosen, F.N. Alyea, C.A. Cardelino, A.J. Crawford, D.M. Cunnold, P.J. Fraser, and J.E. Lovelock. The Atmospheric Lifetime Experiment. 1. Introduction, instrumentation and overview. J. Geophys. Res. 88 (C13):8353-8367 (January 1983).

Prinn, R.G., D.M. Cunnold, R.A. Rasmussen, P.G. Simmonds, F.N. Alyea, A.J. Crawford, P.J. Fraser, and R.D. Rosen. Atmospheric emissions and trends of nitrous oxide deduced from 10 years of ALE-GAGE data. J. Geophys. Res. 95(D11):18369-18385 (October 1990).

Prinn, R.G., D.M. Cunnold, P.G. Simmonds, F.N. Alyea, R. Boldi, A.J. Crawford, P.J. Fraser, D. Gutzler, D. Hartley, R. Rosen, and R.A. Rasmussen. Global average concentration and trend for hydroxyl radicals deduced from ALE/GAGE trichloroethane (methyl chloroform) data for 1978-1990. J. Geophys. Res. 97(D2):2445-2461 (February 1992).

Prinn, R.G., R.F. Weiss, F.N. Alyea, D.M. Cunnold, P.J. Fraser, P.G. Simmonds, A.J. Crawford, R.A. Rasmussen, and R.D. Rosen. 1994. "Atmospheric CFC-11 (CCL3F), CFC-12 (CCL2F2), and N2O from the ALE-GAGE network," pp. 396-420 . In T.A. Boden, D.P. Kaiser, R.J. Sepanski, and F.W. Stoss (eds.), Trends '93: A Compendium of Data on Global Change. ORNL/CDIAC-65. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, Oak Ridge, TN, U.S.A.

Prinn, R.G., R.F. Weiss, B.R. Miller, J. Huang, F.N. Alyea, D.M. Cunnold, P.B. Fraser, D.E. Hartley, and P.G. Simmonds. Atmospheric trends and lifetime of Trichloroethane and global hydroxyl radical concentrations. Accepted for publication in Science (May, 1995).

Simmonds, P., D. Cunnold, F. Alyea, C. Cardelino, A. Crawford, P. Fraser, R. Prinn, R. Rasmussen, and R. Rosen. Carbon tetrachloride lifetime and emissions determined from global daily measurements during 1978-1985. J. Atmos. Chem. 7: 35-58 (1988).

Ozone Depletion Over Antarctica, Mean October Values at Halley Station, Graph 1

DATA SOURCE

British Antarctic Survey (BAS)
High Cross, Madingley Road
CAMBRIDGE, CB3 0ET
United Kingdom
Contact Person for Ozone Concentrations Over Antarctica:
Jon Shanklin
email: j.shanklin@bas.ac.uk

DATA COLLECTED AND PURPOSE

Data are collected using the Dobson ozone spectrophotometer. Some experimental zenith observations at low solar elevation are included in data beginning in April 1993.

GEOGRAPHICAL COVERAGE

The Dobson ozone spectrophotometer is at the Halley Research Station, located at 75°35’ South and 26°34’ West on the Brunts Ice Shelf in Coats Land, Antarctica.

DATA COLLECTION PERIOD

The data collection period is from 1956 through 2002.

METHODOLOGY AND FREQUENCY OF DATA COLLECTION

Data are collected with a Dobson ozone spectrophotometer at the Halley Station in Antarctica. 1987/88 data include ozonesonde flight results. Data are approximately corrected to Bass-Paur ozone absorption coefficients.

DATA PRESENTATION

Data are expressed in Dobson units for the time period 1956 through 2002.

Table 4: Ozone Depletion Over Antarctica, Mean October Values, 1956-2002

REFERENCES

Natural Environment Research Council, British Antarctic Survey. 2002. “Halley Research Station.” http://www.antarctica.ac.uk/Living_and_Working/Stations/Halley/index.php. Accessed 5/30/03.

Natural Environment Research Council, British Antarctic Survey. 2003. “British Antarctic Survey Ozone Halley, Rothera, and Vernadsky/Faraday.” http://www.antarctica.ac.uk/met/jds/ozone/. Accessed 5/30/03.

Shanklin, J.D. British Antarctic Survey, Madingley Road, Cambridge, England. CB3 0ET. “Provisional monthly mean ozone values for Faraday/Vernadsky and Halley between 1956 and 2002.” http://www.antarctica.ac.uk/met/jds/ozone/data/zoz5699.dat. Accessed 5/30/03.

DATA SOURCE

Information extracted from industry reports was used as input to a model that generates estimates of chlorine loading to the stratosphere. Industry reports are on file at the U.S. Environmental Protection Agency.

DATA COLLECTED AND PURPOSE

Data on chlorine loading were not collected, but were generated by a model, based on reported information.

GEOGRAPHICAL COVERAGE

Global.

DATA COLLECTION PERIOD

Model-generated estimates based on reported data are from 1985 through 1991. Later estimates are model-generated forecasts are based on assumptions to 2030.

METHODOLOGY AND FREQUENCY OF DATA COLLECTION

Data were not collected, but generated by the Atmospheric Stabilization Framework (ASF), a model developed during a 1988 workshop sponsored by NASA and EPA. The ASF is documented at NASA. The ASF is not a physical simulation. Rather, it is a parameterized model based on more complicated simulations and calibrated to meet historical measurements of ozone depletion in 1985 and 1989.

DATA PRESENTATION

The data for the indicator (Figure 5), which are listed in Table 5, show adjusted atmospheric chlorine loading in parts per billion (ppb) for the time period 1985 to 2030. One scenario assumes no controls to limit chlorine loading and the other scenario assumes the phaseout of production and consumption of ozone-depleting chemicals in accordance with the Montreal Protocol on Substances that Deplete the Ozone Layer (which entered into force in 1989).

Table 5: Adjusted atmospheric chlorine loading, 1985-2030
(parts per billion)

REFERENCES

National Aeronautics and Space Administration (NASA), Goddard Space Flight Center (GSFC). An Assessment Model for Atmospheric Composition. NASA Conference Publication 3203 (94N17827) (Greenbelt, MD: NASA/GSFC, 1988).

TERMINOLOGY

A chlorofluorocarbon is one of a group of organic chemicals containing carbon, fluorine and chlorine. CFCs have been used as coolants in refrigerators and air conditioners and as foaming agents, solvents, and aerosol propellants. Chlorofluorocarbons discussed in this technical supplement include CFC-11 (Trichlorofluoromethane), CFC-12 (Dichlorodifluoromethane), CFC-113 (Trichlorotrifluoroethane), and HCFC-22 (Chlorodifluoromethane).

Carbon tetrachloride is an industrial solvent. It is largely used in the manufacture of chlorofluorocarbons and similar chemicals.

A Dobson unit is a unit of measure used to estimate the thickness of the ozone layer. One hundred (100) Dobson units represent a quantity equivalent to a 1 mm thick layer of ozone at sea level.

Hydrochlorofluorocarbons contain hydrogen, in addition to carbon, chlorine and fluorine. HCFCs have many of the same uses as CFCs and are increasingly used as interim substitutes for CFCs. HCFCs retain many of the desirable properties of CFCs but because they exist for a shorter time in the atmosphere, ozone depletion and global warming concerns are significantly reduced.

Irradiance refers to solar light that is reflected in the atmosphere.

Methyl chloroform (1,1,1-Trichloroethane or CH ₃CCl ₃) is an industrial solvent for essential uses.

Radiance refers to solar light.

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