Ozone Radiative Feedback and Climate Sensitivity

Occurence of an ozone radiative feedback has been demonstrated in CO2-driven global warming simulations with coupled chemistry climate models. In some models, this ozone feedback is associated with changes of other feedbacks like the stratospheric water vapour feedback or the cloud feedback. While the direct ozone radiative feedback is negative in all models simulations available so far, the coupling to other feedbacks shows considerable inter-model variability. Hence, in some models the climate sensitivity is substantially reduced by the presence of interactive chemistry, while in others the climate sensitivity is left almost unchanged. If the forcing is provided by perturbations other than CO2 increase, the picture may become even more complex. We sshow that in a simulation driven by enhanced ozone precursor emissions at the Earth's surface, the climate sensitivity is enhanced in spite of a negative ozone radiative feedback. This counter-intuitive effect can again be explained by changes in other feedbacks in response to interactive model ozone.