Atmospheric Chemistry and Physics Discussions www.atmos-chem-phys-discuss.net 1680-7367 1680-7375 7 2 2007 10.5194/acpd-7-3963-2007 http://www.atmos-chem-phys-discuss.net/7/3963/2007/ http://www.atmos-chem-phys-discuss.net/7/3963/2007/acpd-7-3963-2007.html http://www.atmos-chem-phys-discuss.net/7/3963/2007/acpd-7-3963-2007.pdf 3963 4000 2007-03-22 A new formulation of equivalent effective stratospheric chlorine (EESC) P. A. Newman paul.a.newman@nasa.gov J. S. Daniel D. W. Waugh E. R. Nash Atmospheric Chemistry and Dynamics Branch, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA NOAA Earth System Research Laboratory/Chemical Sciences Division, Boulder, Colorado, USA Johns Hopkins University, Baltimore, Maryland, USA Science Systems and Applications, Inc., Lanham, Maryland, USA Equivalent effective stratospheric chlorine (EESC) is a convenient parameter to quantify the effects of halogens (chlorine and bromine) on ozone depletion in the stratosphere. We show and discuss a new formulation of EESC that now includes the effects of age-of-air dependent fractional release values and an age-of-air spectrum. This new formulation provides quantitative estimates of EESC that can be directly related to inorganic chlorine and bromine throughout the stratosphere. Using this EESC formulation, we estimate that human-produced ozone depleting substances will recover to 1980 levels in 2041 in the midlatitudes, and 2067 over Antarctica. These recovery dates are based upon the assumption that the international agreements for regulating ozone-depleting substances are adhered to. In addition to recovery dates, we also estimate the uncertainties in the estimated time of recovery. The midlatitude recovery of 2041 has a 95% confidence uncertainty from 2028 to 2049, while the 2067 Antarctic recovery has a 95% confidence uncertainty from 2056 to 2078. 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