Bridging inventory reporting and atmospheric inversion estimates of anthropogenic greenhouse gas emissions in Europe: The PARIS project

National greenhouse gas emission reporting in Europe is facilitated by national agencies based on activity data and emission factors, and in some cases, more sophisticated process modeling approaches, for many different activities and emission sectors. These “bottom-up” emission estimates are essential for providing guidance for emission mitigation measures relevant for international treaties and negotiation, for monitoring national progress towards targets, and for separating emissions processes and sector level breakdowns of sources and sinks.

Emissions of gases to the atmosphere result in atmospheric concentrations that are locally enhanced compared to background levels. These enhancements can be measured with precise instrumentation and used to quantify the emissions. When these measurements are evaluated with inverse atmospheric transport models, they can deliver independent “top-down” emission estimates, i.e., emission estimates that are consistent with the measured concentration enhancements. Due to the complexity of atmospheric transport, such estimates are difficult, but they have now reached a level where they can provide independent information on emissions and can support the bottom-up approach.

Switzerland and the UK are two countries that already provide top-down emission estimates as annexes to their annual national emission reports to the UNFCCC. Within the PARIS project we have extended the top-down approach for national scale emission estimates to 6 further countries (Germany, the Netherlands, Italy, Norway, Hungary, Ireland), and produced consistent drafts for annexes to the National Inventory reports for all 8 countries.    

A weakness of top-down approaches is that they can not always distinguish between emissions from different source sectors, which makes comparison to the National Inventories difficult. As a second focus of PARIS, we aim at developing measurable signatures to facilitate a more detailed attribution of the derived emissions to specific source sectors. These signatures include measurements of isotopic composition for CH₄ and N₂O, atmospheric O₂ for CO₂, other co-emitted species, as well as detailed composition measurements for organic and black carbon aerosols.

This presentation will include some interesting aspects from the draft annexes to the National Inventory Reports, innovative new measurements for source sector attribution and new tools for evaluation and comparison of emission estimates.