EarthTrends (http://earthtrends.wri.org) Searchable Database Results Provided by the World Resources Institute (http://www.wri.org) "Climate and Atmosphere -- Global Gas Concentrations: Carbon tetrachloride" "Units: Parts per trillion" ,,2006,2005,2004,2003,2002,2001,2000,1999,1998,1997,1996,1995,1994,1993,1992,1991,1990,1989,1988,1987,1986,1985,1984,1983,1982,1981,1980,1979,1978, World "World {1}","",90.05,90.89,91.76,92.33,93.20,94.21,95.12,96.10,97.07,98.16,98.96,99.91,100.91,101.40,102.15,101.92,102.34,101.08,100.63,99.84,98.23,96.80,95.09,93.65,92.78,90.34,89.82,87.94,88.33, Footnotes "1 -- World" "In 1978, annual average only includes the months of July through December." "In 2004, annual average only includes the months of January through September." Source "Carbon Dioxide Information Analysis Center (CDIAC), Environmental Sciences Division, Oak Ridge National Laboratory. 2007. ALE / GAGE / AGAGE Network " "Data on Concentrations of Greenhouse and Ozone-depleting Gases. Available online at http://cdiac.ornl.gov/ftp/ale_gage_Agage/ " "" "Data originally reported in: Simmonds, P.G., Cunnold, D.M., Weiss, R.F., Prinn, R.G., Fraser, P.J., McCulloch ,A., Alyea, F.N., and O'Doherty, S. 1998. Global trends and emission estimates of CCl4 from in situ background observations from July 1978 to June 1996. Journal of Geophysical Research, 103 (D13), 16017-16027. " Technical Notes "Definition:" "Carbon tetrachloride (CCl4) is an intermediate product resulting from the production of CFC-11 and CFC-12. It is also used in other chemical and pharmaceutical applications and for grain fumigation. Compared with other gases, carbon tetrachloride makes a small contribution to the greenhouse effect and to stratospheric ozone depletion. The concentration of carbon tetrachloride is the annual average dry air mole fraction. Concentrations are measured in parts per trillion. " "" "Years Covered and Frequency of Update: " "The ALE/GAGE/AGAGE program has been collecting data continuously since 1978. As of July 2007, data are available on-line through September 2006. CDIAC reports the most recent available data approximately every six months. " "" "Methodology: " "Carbon tetrachloride data are from the monitoring station at Cape Grim, Tasmania (45 degrees " "41 minutes South latitude, 144 degrees 41 minutes East longitude) under the ALE/GAGE/AGAGE program. The program is divided into three parts based on three different types of instrumentation using different calibration gases. The data reported here from 1978-81 are from the Atmospheric Lifetime Experiment Program (ALE); 1982-93 data are from the Global Atmospheric Gases Experiment (GAGE); 1994-2006 data are from the Advanced GAGE. Cape Grim generally receives unpolluted air from the Southeast and is the station with the longest, most complete dataset. WRI's calculations have only used values that are considered to be ""unpolluted"", and have not incorporated data values that are considered to be influenced by pollution events. " "" "Air samples were collected 4 times daily for ALE, 12 times daily for GAGE, and 36 times daily for AGAGE at the Cape Grim site. The annual values shown here are averages calculated by WRI of monthly values calculated by CDIAC. Missing monthly values were ignored and yearly averages were calculated from the remaining data. " "" "During late 1999 and the first part of 2000, the ALE/GAGE/AGAGE program adopted new primary standards for its entire data base. CFC-11, CFC-12, CH3CCl3 (methyl chloroform), CCl4 (provisional), N2O, and CFC-113 values were based upon the ""SIO-1998"" scale maintained at the Scripps Institution of Oceanography (R. Weiss, et. al.). In 2006 all these data were recalibrated to the SIO-2005 scale. " "" "Details on these primary standards and their application to the data base can be found in Prinn et al. (2000), A history of chemically and radiatively important gases in air deduced from ALE/GAGE/AGAGE. Journal of Geophysical Research 115: 17751-92. " "" "For a complete explanation of the methodology used, please visit http://cdiac.ornl.gov/ftp/ale_gage_Agage/ " "" "" "" "Data Reliability: " "Data from the ALE/GAGE/AGAGE system reflect very precise measurements. Data are revised to correct for drift in instrument calibration, hardware changes, and perturbations to ""background"" conditions. Early in the data series, some measurements are missing for up to 3 consecutive months; for these series, annual mean figures were derived using interpolated data. " "" "The carbon tetrachloride measurements presented here reflect global trends. However, it is important to note that carbon tetrachloride concentrations differ significantly among monitoring sites at any given time. For example, the mean monthly concentrations of CCL4 in Adrigole, Ireland were as much as 10% larger than the averages in Cape Grim. For a more complete record of the monthly data showing the number of measurements taken and the standard deviation of each set of measurements, please consult the following web pages: " "ALE data: http://cdiac.ornl.gov/ftp/ale_gage_Agage/ALE/monthly/tamon.sum " "GAGE data: http://cdiac.ornl.gov/ftp/ale_gage_Agage/GAGE/monthly/tgmon.sum " "AGAGE Data: http://cdiac.ornl.gov/ftp/ale_gage_Agage/AGAGE/gc-md/monthly/tAmon.sum "