Assessment of the future development of the ozone layer

ECHAM3/CHEM is used to estimate the future development of the ozone layer. The general circulation model ECHAM3 and the chemistry module CHEM are coupled in a CTM-like mode, i.e. no feedback of simulated chemical species on radiation is considered. Currently CHEM does not include bromine chemistry. Two time-slice experiments representing 1991 and 2015 conditions are carried out. Chemical species are transported by winds calculated with different CO2 mixing ratios as a proxy for other greenhouse-gases. For 2015, the adopted increase of CO2 and the corresponding modification of the sea-surface temperature lead to a warming of the troposphere and a cooling of the stratosphere. The assessment for 2015 indicates that the ozone layer will not homogeneously recover, despite the employed decrease of chlorine in the model. Whereas in low and mid-latitudes an ascent of stratospheric O-3 is obvious, no significant increase of O-3 is found in the polar regions during spring time.