A new formulation of equivalent effective stratospheric chlorine (EESC)

[摘要] Equivalent effective stratospheric chlorine (EESC) is a convenientparameter to quantify the effects of halogens (chlorine and bromine) onozone depletion in the stratosphere.We show, discuss, and analyze anew formulation ofEESC that now includes the effects of age-of-airdependent fractional release values and an age-of-air spectrum.ThisEESC can be more appropriately applied tovarious parts of thestratosphere because of this dependence on mean age-of-air. This newformulation provides quantitative estimates of EESC that can be directlyrelated to inorganic chlorine and bromine throughout the stratosphere.In this paper, we first provide a detaileddescription of the EESCcalculation.We then use this EESCformulation to estimate thathuman-produced ozone depleting substances will recover to 1980 levels in2041 in the midlatitudes, and 2067 over Antarctica.These recoverydates are based upon the assumption that the international agreementsfor regulating ozone-depleting substances are adhered to.In additionto recovery dates, we also estimate the uncertainties and possibleproblems in the estimated times ofrecovery.The midlatitude recoveryof 2041 has a 95% confidence uncertainty from 2028 to 2049, while the2067 Antarctic recovery has a 95% confidence uncertainty from 2056 to2078.The principal uncertainties are from the estimated meanage-of-air and fractional release values, and the assumption that thesequantities are time independent.Using other model estimates of agedecrease due to climate change, we estimate that midlatitude recoverymay be significantly accelerated.

[学科分类] 大气科学