The potential radiative impact of ozone changes on stratosphere-troposphere exchange (STE) is investigated by a series of climate model simulations.The impact of an arbitrary 15% O3 change on temperature, stratospheric water vapor and cross-tropopause mass flux are compared to the corresponding effects from a doubling of atmospheric CO2.Our analysis shows that a 15% global O3 decrease can cause a maxi mum cooling of 2.4 K in the stratosphere and ~7.2 % increase in the tropical upwelling.