1. Topic

2. Introduction

A basic requirement of the Framework Directive (96/62/EC) is for the Member States (MS) to report, annually, the zones and agglomerations where the concentrations of any regulated compound is exceeding the Limit Value (LV) plus the Margin of Tolerance (MOT)^*. In those zones the Member States must prepare (an) Action plan(s)^** to show how they will reach the LV by the attainment year.

To be able to develop such action plans, it is necessary to have knowledge of how the driving forces (population, transport needs and industry production and their technologies,…) that cause air pollution emissions will most probably be developing in the future. We refer to this development into the future, as a “scenario”.

To develop an action plan involves developing alternative future scenarios, and introducing these into some modelling tool, which will translate the driving forces/emissions scenarios into projections for how the air quality will develop into the future.

For definition of LV and MOT, see e.g. the topic Terms in the EC Air Quality Directives: What do they mean?.

See also the topic How to develop an Air Quality Action Plan ?.

3. Discussion

Definitions:

· Base year: Development of a scenario always requires that a base year is set, from which the further development is calculated or estimated. The base year is usually the most recent year where the needed status data and information is “complete”. In relation to the Air Quality Directives, the base year is the year for which the last assessment of air quality is made, for reporting to the Commission.

· Baseline scenario: This scenario represents the most probable development in the coming years, considering that the present trends in driving forces will continue, and taking account of plans and actions which are already agreed and in progress.

· Alternative scenarios: These are scenarios which are to be developed as part of the action plan development, where the air quality planner considers various development and abatement options which might be necessary to reach the goal of attainment of the Air Quality Limit Values by the attainment date.

Scenarios may be developed and used with low or high content of details.

Taking account of urban and external trends

The scenarios must contain both the trends in driving forces and emissions which take place inside the urban area the planner is considering, as well as the external trends that affect the air pollution concentrations approaching the urban areas from outside (the “regional” component).

The trends in the regional component must be accessed through data from other programs of assessment of national (contact your national air quality authorities) or European air quality (e.g. the EMEP programme: http://www.emep.int/ ). The trends in the urban component is a combination of abatement actions taking on the national and/or European scale (e.g. vehicle emission regulations, fuel quality regulations, etc., see e.g. http://www.europa.eu.int/comm/environment/air/emissions.htm ) and local abatement actions (e.g. local transport plans, industrial area development, local policies for domestic heating practices, etc.).

Main issues to consider in scenario development

· Driving forces: development in population, energy consumption, transportation needs, industrial production.

· Technologies: how the technologies (of energy use, transportation means, industry processes, etc.) will develop and be implemented in the local area considered. This will have a direct bearing on the emissions from the activities in the area.

· Area development: how the urban area planning will affect the spatial (re)distribution of emissions (and subsequently the air pollution concentration distribution).

· Specific plans for traffic infrastructure, industrial plants development: are specific plans existing regarding roads/tunnels/ring roads construction in the coming years, as well as specific plans for industries (single plant developments/modifications/moving, industrial complexes/parks.

Tools for specifying the scenarios quantitatively

The scenarios shall be specified quantitatively in such a way that they can be introduced into some kind of modelling tool, usually an air pollution dispersion model of some kind, for the urban area considered. This requires that an emission data base for the area is/has been established, which specifies the present spatial distribution of the air polluting activities and resulting emissions, usually on an annual basis, as well the variation of the emissions with time (e.g. hourly variation over the year).

4. Recommendation / Conclusion

· The development of scenarios for future development of air polluting activities and their emissions is a very important part of assessing the future air quality and to show probable compliance with the Air Quality Directives, or as a basis for developing the needed action plans. The scenarios should be quantitatively specified within the activity-and-emissions data base which is necessary to establish for the air quality planning area in question, in order to assess present and future air quality in the context of the EC Air Quality Directives.

· Development of future scenarios is connected to the requirements in the Air Quality Directives to develop Plans and Programmes to make sure that future air quality will be within Limit Values. It is also linked to and a necessary condition for working effectively on the local scale with Environmental Impact Assessment for new infrastructures, industrial plants, etc.

5. Examples / Further Reading

Further Examples:

6. Additional Documents / Web Links

Last Updated

25th January 2005