The limitations of the AOT40 concept currently used in pan-European assessments of the risk of ozone damage to vegetation have now clearly been recognised.

Over the subsequent two years, several research groups have made progress in the development of such methods, whether applied to chamber studies, field sites, national-scale modelling or European-scale modelling.

One such model has now been linked to the EMEP photo-oxidant model, hence providing the potential to assess the effects of different policy strategies on ozone flux to vegetation. A more accurate description of total deposition to vegetation could also provide better predictions of loss processes within such atmospheric transport models.

While a conceptual approach to assessing ozone flux and deposition at these different scales has now been identified, and there has been success in demonstrating that such models can simulate ozone flux to individual leaves and to plant canopies, many uncertainties remain. In particular, it is uncertain whether a Level II approach to ozone risk assessment based on the flux concept could be included with confidence in the revision of the Göteborg Protocol planned for 2005.