HR: 0830h
AN: A31D-0075    [PDF]
TI: Atmospheric Carbon Tetrachloride -- A Conundrum?
AU: * Mondeel, D J
EM: debra.j.mondeel@noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: * Mondeel, D J
EM: debra.j.mondeel@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Butler, J H
EM: james.h.butler@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Montzka, S A
EM: stephen.a.montzka@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Hall, B D
EM: bradley.hall@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: King, D B
EM: daniel.king@drexel.edu
AF: Chemistry Department, Drexel University, Philadelphia, PA 19104 United States
AU: Yvon-Lewis, S A
EM: shari.yvon-lewis@noaa.gov
AF: NOAA Atlantic Oceanographic and Meteorological Laboratory, 4301 Rickenbacker Cswy, MIami, FL 33149 United States
AU: Dutton, G S
EM: geoff.dutton@noaa.gov
AF: Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO 80309 United States
AU: Dutton, G S
EM: geoff.dutton@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Thompson, T M
EM: thayne.m.thompson@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AU: Elkins, J W
EM: james.w.elkins@noaa.gov
AF: NOAA Climate Monitoring and Diagnostics Laboratory, 325 Broadway, Boulder, CO 80305 United States
AB: Carbon tetrachloride (CCl$_{4}$) is a significant ozone-depleting gas in the atmosphere that has been decreasing in concentration at just under 1 ppt y$^{-1}$ ($<$ 1% y$^{-1}$) over the past decade. This turnover and decrease in reported mixing ratio can be attributed to lowered production as agreed upon by the parties signing the Montreal Protocol on Substances that Deplete Stratospheric Ozone. The rate of decline, however, is inconsistent with available information regarding the production and atmospheric lifetime of this gas. Other useful information for CCl$_{4}$ is in the interhemispheric difference, which has changed little since the initial turnover in mixing ratio. This is unlike that of the CFCs and methyl chloroform (CH$_{3}$CCl$_{3}$), for which the interhemispheric difference in mixing ratio has become smaller, in some cases rapidly, with the decline in emissions in the mid-1990s. This suggests that emissions of CCl$_{4}$ continue to be significant, particularly in light of the lowered estimates for the atmospheric lifetime of CCl$_{4}$. This seeming paradox raises a number of questions, not just regarding production and emission, but also about the calculated lifetimes of atmospheric trace gases. The lifetime of CCl$_{4}$ from losses solely within the atmosphere currently is calculated at 35(21-43 ) y. Recently reported losses to the ocean have reduced the lifetime estimate to 26(17-36) y and an even more recent estimate of losses to soils reduces the lifetime further to 20(13-32) y. These newly reported losses of CCl$_{4}$ force a re-examination of the magnitudes and distributions of the sources and sinks of this gas. This poster presents some new data and an evaluation of what is known and unknown with regard to the budget of atmospheric CCl4, highlighting uncertainties and the need for additional research to reduce them. Montzka, S. A., et al., Controlled substances and other source gases, Chapter 1, in Scientific Assessment of Ozone Depletion: 2002, Global Ozone Res. and Monitor. Proj., Vol. No. 47, World Meteorol. Organ., Geneva, Switzerland, 2003. Yvon-Lewis, S. A., and J. H. Butler, Effect of oceanic uptake on atmospheric lifetimes of selected trace gases, J. Geophys. Res., 107(D20), 4414, doi:10.1029/2001JD001267, 2002. Happell, J. D., and M. P. Roche, Soils: A global sink of atmospheric carbon tetrachloride, Geophys. Res. Lett., 30(2), 1088, doi:10.1029/2002GL015957, 2003.
UR: http://www.cmdl.noaa.gov
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0322 Constituent sources and sinks
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2003 Fall Meeting