Limitation of Annual Impact Focus. Fourthly, and finally, at the european scale, relationships between emission changes and air quality are limited to annual mean values whilst some of the more challenging air quality limit values are based on daily or hourly averages. It is important to note that while such limitations impact the ability of this top down approach to directly assess compliance with air quality limit value at individual measuring stations, the use of european scale IAM to inform the targets of the current Thematic Strategy on Air Pollution indirectly contributes to further progress in reaching compliance. This inability of European scale IAM to directly address the compliance challenge (at least until very recently) has contributed to some of the difficulties in achieving compliance with AQ limit values (e.g. PM10 and NO2) from the implementation of Europe-wide measures in a number of member states. The formal air quality plans designed to address the non- compliance issues have largely been based on bottom up approaches using combinations of local air quality modelling and measurements/measurement campaigns. As we have already begun to see from the pilot questionnaire results, while essentially all responders recognise the need to appropriately account for the wider scale, not all have been able to bring the local (bottom up) and european/national scale together. In this regard, the emergence of regional integrated sssessment tools with their ability to identify cost-optimised local strategies is already opening the door to quantifying the cost- effective split between further european wide measures and regional/local measures. They will inevitably need to find wider application and play an increasing role in this emerging ‘discrete islands of non-compliance’ EU. This points to an increasing role for targeted technical and non-technical measures in order to achieve compliance. As already noted, such measures (low emission zones, special fuels for captive fleets, captive fleet retrofitting etc.) can only be appropriately designed using bottom up tools. To compute emission reduction scenarios and policies, it is necessary to combine emission inventories and technical and non-technical databases. Another weakness highlighted in the APPRAISAL database is the uncertainty and lack of data (activity, emission factor) for quantifying anthropogenic emissions for new technologies, in particular new energy sources and new vehicles. Such data are often provided by different authorities...
