The sensitivity of polar ozone depletion to proposed Geo-engineering schemes and volcanic eruptions

The eruption of Mt Pinatubo in June 1991 had a significant impact on the Arctic ozone loss. The large burden of sulfate aerosols in the lower stratosphere after the volcanic eruption resulted in enhanced ozone destruction in winter 1991/92 and 1992/93, at altitudes below 400 K, compared to other Arctic winters. The large ozone loss values in these winters were shown to be outliers in the relationship between chemical ozone loss and the potential volume of PSC existence for the Arctic. Here, we will present that the empirical relationship between chemical ozone loss and the potential of activated chlorine is compact for all winters between 1991 and 2005. The potential of activated chlorine is a measure that includes the impact of sulfate aerosols and temperature conditions in the lower stratosphere, based on the newly derived chlorine activation temperature (Drdla et al, submitted manuscript, 2007). This compact relationship further allows estimating how geo-engineering schemes and future volcanic eruptions would influence polar ozone. The impact of a proposed geo-engineering scheme to compensate a warming caused by the removal of anthropogenic aerosols in the troposphere would have a minor impact. A large injection of sulfur to compensate CO2 doubling, or a large volcanic eruption would result in a drastic increase of polar ozone depletion, especially in the Northern Hemisphere.