Fingerprint of ozone depletion in the spatial and temporal pattern of recent lower-stratospheric cooling

OBSERVATIONS of air temperatures in the lower stratosphere from 1979 to 1990 reveal a cooling trend that varies both spatially and seasonally(1). The possible causes of this cooling include changes in concentrations of ozone or of other greenhouse gases(2,3), and entirely natural variability, but the relative contributions of such causes are poorly constrained. Here we incorporate the observed decreases in stratospheric ozone concentrations(4) over the same period into a general circulation model of the atmosphere, to investigate the role of the ozone losses in affecting patterns of temperature change. We find that the simulated latitudinal pattern of lower-stratospheric cooling for a given month through the decade corresponds well with the pattern of the observed decadal temperature changes, This result confirms the expectation, from simpler model studies(2,3,5), that the observed ozone depletion exerts a spatially and seasonally varying fingerprint in the decadal cooling of the lower stratosphere, with the influence of increases in concentrations of other greenhouse gases being relatively small. As anthropogenic halocarbon chemicals are important causes of stratospheric ozone depletion(2,3), our study suggests a human influence on the patterns of temperature change in the lower stratosphere over this 11-year period.