The signature of ozone depletion on tropical temperature trends, as revealed by their seasonal cycle in model integrations with single forcings

The effect of ozone depletion on temperature trends in the tropical lower stratosphere is explored with an atmospheric general circulation model, and directly contrasted to the effect of increased greenhouse gases and warmer sea surface temperatures. Confirming and extending earlier studies we find that, over the second half of the 20th Century, the model's lower-stratospheric cooling caused by ozone depletion is several times larger than that induced by increasing greenhouse gases. Moreover, our model suggests that the response to different forcings is highly additive. Finally we demonstrate that when ozone depletion alone is prescribed in the model, the seasonal cycle of the resultant cooling trends in the lower stratosphere is quite similar to that recently reported in satellite and radiosonde observations: this constitutes strong, new evidence for the key role of ozone depletion on tropical lower-stratospheric temperature trends.