The effect of two decades of ozone change on stratospheric temperature as indicated by a general circulation model

The effect on stratospheric temperatures of ozone change since 1979 is investigated using a general circulation model employing observations of the vertical profile of ozone change. The stratopause region is generally cooler in 1997 than in 1979 by about 2 K. Results from a ‘Seasonally Evolving Fixed Dynamical Heating’ simulation indicate that this cooling is mostly radiative in origin. In Antarctica the model indicates statistically significant cooling of the lower stratosphere between 1979 and 1997, peaking at 13 K in November; this agrees quite well with observations. In the Arctic no significant cooling is seen in winter or early spring, in contrast with observations, indicating that ozone loss is not the main cause of the observed temperature change here. The peak Antarctic cooling is accompanied by a warming of the upper stratosphere; dynamics are responsible for this warming and for making the lower stratospheric cooling less severe than it would otherwise be.