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Conclusions

The evaluation of the change between the "present" and "near past" simulations has revealed that the stratopause region and the antarctic lower stratosphere are most sensitive regions. The results are here summarized:

The temperature changes at the stratopause are associated with ozone destruction (homogenous chemistry), decrease of 10-20% in the 10-1 hPa range, as well as changes in the greenhouse gases concentrations. The sensitivity of the stratopause region is consistent with the estimate of temperature trends, increasing with elevation (WMO, 1998).
The temperature changes in the antarctic lower stratosphere are due to ozone destruction by heterogeneous chemistry. Thus, the polar vortex lasts to December.
Temperature changes of about 2 K occur close to the equatorial tropopause and are associated with an increase in tropical upwelling.
Cooling of the arctic stratosphere, affected by dynamical variability. It is suggestive of a change in the seasonal stability of the polar vortex, more active although colder in the early winter of the "present" simulations. In qualitative agreement with Labitzke and Naujokat (2000). The specified 1960 and 1990 conditions of the two simulations impede the comparison with the temperature trends of Randel and Wu (1999).