Periodic Reporting for period 2 - PARIS (Process Attribution of Regional Emissions)
Reporting period: 2024-07-01 to 2025-12-31
Anthropogenic greenhouse gas (GHG) emissions are driving climate change, and national GHG inventories are crucial for identifying emissions and assessing reduction measures. PARIS operates in a setting where European countries must report greenhouse gas and air-pollutant emissions accurately and transparently under international frameworks such as UNFCCC and CLRTAP. These national reports are mainly built from statistics about activities like fuel use, transport, and agriculture. While this approach is well established, some emission sources are difficult to estimate precisely. The project addresses this practical challenge by developing a harmonised method that uses atmospheric measurements — observations of gases and particles in the air — together with inverse models to produce independent emission estimates. PARIS links improved measurement techniques with modelling tools and inventory practice. It produces national-scale estimates for major greenhouse gases as well as black carbon. New analytical methods help clarify where emissions are likely coming from and how they vary over time and space, especially for gases with complex patterns. The main outcome of PARIS are draft annexes to the National Inventory Documents (NIDs) which can be used to further enhance the identification and estimation of greenhouse gas emissions.
The expected impact is a clearer and more consistent framework for comparing different ways of estimating emissions. By enabling side-by-side evaluation, the project helps identify agreement, differences, and remaining uncertainties. This supports gradual improvement of reporting methods and strengthens confidence in emissions data. Because the tools and workflows are harmonised across countries, the approach can be reused and expanded, helping build a transparent and scalable system for long-term emissions verification.
The expected impact is a clearer and more consistent framework for comparing different ways of estimating emissions. By enabling side-by-side evaluation, the project helps identify agreement, differences, and remaining uncertainties. This supports gradual improvement of reporting methods and strengthens confidence in emissions data. Because the tools and workflows are harmonised across countries, the approach can be reused and expanded, helping build a transparent and scalable system for long-term emissions verification.
PARIS transitioned from building infrastructure to delivering an operational, harmonised atmospheric verification framework. A core achievement has been the consolidation of multi-model inverse systems and observational datasets into interoperable workflows that directly support national greenhouse gas inventories. Engagement with inventory compilers matured into a structured annual cycle, enabled by harmonised inversion outputs and analytical tools hosted on European research infrastructures. Expanded collaboration with sister initiatives — AVENGERS and EYE-CLIMA — strengthened cross-project harmonisation of datasets, modelling protocols, and quality control, resulting in consistent European-scale analyses. Several countries are already evaluating integration of top-down emission estimates into official reporting, demonstrating a shift from exploratory science toward operational verification.
Technically, the project delivered major advances in atmospheric measurement networks and modelling capability across multiple gases and aerosol species. The European F-gas network moved into sustained operation, feeding new high-quality datasets into inversion frameworks and enabling independent detection of previously unresolved point sources. Methane activities progressed to large-scale multi-year inversions supported by isotope measurements and complementary modelling systems, improving source attribution. Harmonised nitrous oxide datasets and aligned inversions revealed seasonal variability not captured in bottom-up inventories, supported by targeted process-model development. Novel approaches for fossil fuel CO2 detectability using atmospheric potential oxygen, as well as scalable aerosol and black carbon inversion systems, expanded verification capability beyond proof-of-concept. Together, these advances establish a technically robust, cross-gas framework capable of supporting transparent, reproducible emission assessment at national and regional scales.
Technically, the project delivered major advances in atmospheric measurement networks and modelling capability across multiple gases and aerosol species. The European F-gas network moved into sustained operation, feeding new high-quality datasets into inversion frameworks and enabling independent detection of previously unresolved point sources. Methane activities progressed to large-scale multi-year inversions supported by isotope measurements and complementary modelling systems, improving source attribution. Harmonised nitrous oxide datasets and aligned inversions revealed seasonal variability not captured in bottom-up inventories, supported by targeted process-model development. Novel approaches for fossil fuel CO2 detectability using atmospheric potential oxygen, as well as scalable aerosol and black carbon inversion systems, expanded verification capability beyond proof-of-concept. Together, these advances establish a technically robust, cross-gas framework capable of supporting transparent, reproducible emission assessment at national and regional scales.
The project’s results demonstrate that harmonised top-down atmospheric verification can meaningfully complement conventional inventory methodologies. Operational measurement networks, interoperable inversion systems, and shared analytical tools now enable routine comparison of independent emission estimates across gases and countries. Early adoption discussions with inventory agencies show strong potential for institutional uptake, particularly where discrepancies highlight opportunities for methodological refinement. Scientifically, the ability to detect sectoral or point-source anomalies strengthens confidence in emissions accounting and provides actionable evidence for targeted mitigation strategies.
To ensure long-term impact, continued investment is needed to maintain and expand observational infrastructure, support cross-model harmonisation, and integrate top-down methods into routine inventory workflows. International coordination, open data frameworks, and alignment with evolving reporting standards will be essential to scale adoption. A supportive regulatory and standardisation environment — including recognition of atmospheric verification within reporting guidance — would accelerate mainstream uptake and ensure sustained scientific and operational value.
To ensure long-term impact, continued investment is needed to maintain and expand observational infrastructure, support cross-model harmonisation, and integrate top-down methods into routine inventory workflows. International coordination, open data frameworks, and alignment with evolving reporting standards will be essential to scale adoption. A supportive regulatory and standardisation environment — including recognition of atmospheric verification within reporting guidance — would accelerate mainstream uptake and ensure sustained scientific and operational value.