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6. Conclusions

We have performed the first simulation of the effects of the Pinatubo eruption by a Stratosphere-Troposphere GCM with interactive chemistry. The simulated partitioning within the chlorine and nitrogen groups, as well as the ozone changes are in reasonable agreement with observations. However, the ozone changes are statistically significant only in the middle and upper stratosphere. The model simulates an ozone loss of up to 15% over the northern middle and high-latitudes. The magnitude of the total-ozone depletion is generally less than the "observed" total ozone anomalies, however, some members of the ensemble are in better agreement with the observed ozone anomalies. The model simulates a pronounced stratospheric warming in the tropics, however, the simulated warming exceeds the "observed" anomalies by 1-2 K. The model matches well the intensification of the polar-night jet in December 1991 and the boreal winter warming of the surface air over the U.S., northern Europe and Russia, as well as the cooling over the Greenland, Alaska and Central Asia.