A scenario is the description of a possible, consistent future state or development of a system. For assessment of mitigation strategies for pollutant releases the development of emission scenarios is necessary. The first step is the generation of a reference scenario, the so-called baseline. For compiling reference scenarios a projection of stock and/or activities needs to be done (taking into account trends and policy interventions and their influence on economic growth, changes in behaviour, and changes in population, etc.). In a next step the activity projection needs to be combined with current legislation and policies in place and in pipeline (e.g. taking into account the 2008 Energy and climate package of the EU, EURO VI implementation, IPPC revision and autonomous technological changes). Usually, the focussed future years are 2020, 2030 and 2050. Emission scenarios are built based on the emission factor approach. That means that activities and emission factors are separately implemented in the data base and emissions are calculated using them. This has the main advantage that the impacts of legislation and policies can be assessed separately for the activity development and the emission factors, because often policies and legislation can have impact to both or only one of them.

Further literature:

J. Goodwin, M. Hobson and J. Lumbreras, Atmospheric Emission Inventory Guidebook (http://www.eea.europa.eu/publications/emep-eea-emission-inventory-guidebook-2009), Part A: General Guidance Chapters, Chapter 8, Projections, 2009