Background The EU needed a better information base for the Thematic Strategy on Air Pollution and the negotiations of post-Kyoto climate agreements. Reaching political acceptance of further environmental measures required: identification of the most cost-effective measures; demonstration of their full range of environmental benefits taking into account simultaneous impacts on multiple endpoints; and exploration of the macro-economic feedback of further environmental expenditures. Some air pollutants and some greenhouse gases have interactive effects. Thus, an extension of the multi-pollutant/multi-effect approach (SO2, NOx, VOC, NH3, PM, as used by the EU’s CAFE programme), towards GHGs was considered to be an important step. Objectives The EC4MACS project aimed to build and maintain a network of well-established modelling tools for a comprehensive integrated assessment of the policy effectiveness of emission control strategies for air pollutants and GHGs. This included the following goals: 1. Provide scientific and economic analyses (air pollution and GHGs) for the revision of the Thematic Strategy on Air Pollution and the European Climate Change Programme. 2. Enhance the analytical capacity of the current models for policy application in 2010/2011. 3. Update the model databases with the most recent statistical data and projections on energy, transport, agriculture, emissions for all European countries and economic sectors. 4. Improve techniques for assessing benefits of pollution control strategies and explore synergies and trade-offs with GHG reductions. 5. Achieve acceptance of modelling tools and data from stakeholders (states, industry and others) 6. Make the assessment tool available to the public via the Internet. Results The EC4MACS project was a success story and fulfilled its technical objective to harmonise and join several European simulation systems in order to form a powerful machine to calculate scenarios covering: Emissions in different sectors like transport, energy generation and consumption and agriculture; Their atmospheric dispersion; Their impact on ecosystems and human health; The costs of these impacts and costs of measures; and Thus delivering environmental scenarios combined with macro-economic results. Such EC4MACS results have remarkably enhanced not only the quantitative base for the development of policies in the fields of air pollution and climate, but also the way in which options, scenarios, measures and costs/benefits are being negotiated. The results make it easier for experts and politicians to agree with the data because all data is provided by the national experts. What’s more, the methods for calculation are absolutely transparent and widely discussed before agreement. This has a positive impact on the selection and implementation of more (cost) efficient measures. Hence, the reputation of the system is very high and the countries are eager to deliver high quality data - which in turn again improves the validity of the results. Thus negotiations and decision-making concerning thresholds and measures at EU level can now take place in a well-informed context. In the currently running review of all European-wide air legislation and measures, the EC4MACS input will most probably result in stricter thresholds (from 25% to 75%) and obligatory measures worth €3 billion more than they would be without EC4MACS (mainly for agriculture and private heating). The reason for this is because EC4MACS proved those measures to be cost-effective. The extension of the model’s projections to 2050 was not possible because these are probably not meaningful with the same set of models/tools and uncertainty would increase to astronomic levels. EC4MACS terms of reference do not include scenarios beyond 2030. For models on a worldwide scale such projections may be possible. For national projections however, other types of energy and agricultural models would be necessary, which currently were not available. For projections to 2050, current legislation and technical assumptions are meaningless. In this case the issue is rather the reverse question "Where do we want to be in 2050 and how could we get there?" Working on the basis of the 2030 scenarios the project has made major contributions to legislative processes. This represents a huge step forward in EU air legislation. The project's quantitative analyses were used as inputs for a wide range of policy initiatives, such as the: Revision of the Emission Ceilings Directive; Review and revision of the entire EU air legislation and the Thematic Strategy on Air Pollution; Commission proposals on the control of emissions from maritime activities; Climate and Energy Package; Commission Communication on Carbon Capture and Storage; EU Roadmap for moving to a low-carbon economy in 2050; Options to move beyond 20% GHG emission reductions, and Communication on EU climate policy initiatives for the post-Kyoto phase under UNFCCC.Major organisational activities involved the cooperation of the beneficiary and the eight project partners in six countries. Another main sub-task was to set up a network of national integrated assessment modellers (NIAM). This provides a close link between data acquisition in the countries and helps to achieve high quality data. Data, projections and emission inventories for 27 Member States were updated. On the technical side the design of the integrated assessment, the ‘orchestration of the models’ and the detail work of developing practical interfaces between the formerly separated sectorial models was carried out successfully. The speed of analyses was increased as well as the quality of the results. The consortium will continue the maintenance and further development of the individual modelling tools as part of their own research programmes, with internal resources devoted to these tasks. In particular, the beneficiary IIASA will maintain the central EC4MACS databases and options for interactive access online at least up to 2020. For this purposes, core funds provided by IIASA will be used and will allow further policy analyses with the EC4MACS toolbox upon request. Further information on the project can be found in the project's layman report and After-LIFE Communication Plan (see "Read more" section).