Biologically damaging radiation amplified by ozone depletions

Abstract

Many recent studies^1–3 indicate that releases of chlorofluoro-carbons (CFCs)—mainly chlorofluoromethanes (CFMs)—into the atmosphere deplete the stratospheric ozone layer. Potentially dangerous consequences of these ozone depletions, such as increases in skin cancer, are expected due to a subsequent increase in biologically damaging solar UV radiation reaching the ground. The biological effectiveness of this radiation amplification can be quantified by a radiation amplification factor (RAF) for which a value of 2 has been previously assumed: RAF = 2 means, for example, that a 1% ozone depletion will result in a 2% increase in damaging UV dose at ground level. Using accurate radiative transfer calculations together with a detailed modern data base, we calculate here the RAFs for erythemally and DNA-weighted UV–B dose assuming ozone depletions as resulting from a two-dimensional model, as well as a global ozone depletion of 10%. The amplification factor as a function of latitude and season is found to be between 1.9 and 2.2 for erythema and between 2.5 and 2.8 for DNA. This is a smaller range variation than previously claimed.