HR: 10:40h
AN: A52A-01 INVITED     [Abstracts]
TI: The contribution of NOAA/CMDL ground-based measurements to understanding long-term stratospheric changes
AU: * Montzka, S A
EM: Stephen.A.Montzka@noaa.gov
AF: Climate Monitoring and Diagnostics Laboratory, NOAA, 325 Broadway, Boulder, CO 80305 United States
AU: Butler, J H
EM: James.H.Butler@noaa.gov
AF: Climate Monitoring and Diagnostics Laboratory, NOAA, 325 Broadway, Boulder, CO 80305 United States
AU: Dutton, G
EM: Geoff.Dutton@noaa.gov
AF: CIRES, University of Colorado, Boulder, CO 80309 United States
AU: Thompson, T M
EM: Thayne.M.Thompson
AF: Climate Monitoring and Diagnostics Laboratory, NOAA, 325 Broadway, Boulder, CO 80305 United States
AU: Hall, B
EM: Bradley.Hall@noaa.gov
AF: Climate Monitoring and Diagnostics Laboratory, NOAA, 325 Broadway, Boulder, CO 80305 United States
AU: Mondeel, D J
EM: Debra.J.Mondeel@noaa.gov
AF: CIRES, University of Colorado, Boulder, CO 80309 United States
AU: Elkins, J W
EM: James.W.Elkins@noaa.gov
AF: Climate Monitoring and Diagnostics Laboratory, NOAA, 325 Broadway, Boulder, CO 80305 United States
AB: Atmospheric histories of halocarbons and other gases provide a basis for understanding long-term changes in stratospheric ozone. Furthermore, long-term measurement records enable more accurate projections of future halocarbon mixing ratios and stratospheric ozone recovery. At NOAA's Climate Monitoring and Diagnostics Laboratory, we have measured halocarbons in ambient air during the past 25 years and have inferred changes for earlier years through studies of air trapped in firn (consolidated snow). Firn air measurements reveal that most long-lived, ozone-depleting halocarbons are entirely anthropogenic, though methyl halides clearly have substantial natural sources. The results over the past two decades have provided a picture of the atmospheric response to efforts by humans to eliminate ozone-depleting gases from the atmosphere. They show the abundance of both chlorine and bromine declining in the lower atmosphere in recent years, after decades of continued increases. The observed declines to date stem primarily from rapid decreases in short-lived gases; atmospheric levels of chlorine and bromine in long-lived gases remain near their peak. While the declines are good news for stratospheric ozone, the direct radiative influence of long-lived halocarbons continues to increase
DE: 0300 ATMOSPHERIC COMPOSITION AND STRUCTURE
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0365 Troposphere--composition and chemistry
SC: Atmospheric Sciences [A]
MN: 2005 Joint Assembly