First report on reconciliation of bottom-up and top-down methods at sub-national scales (M9), STICHTING VU : deliverable D5.2

Summary

European greenhouse gas (GHG) emission reduction policies require accurate and robust estimates of anthropogenic emissions. Internationally recognized methods are needed to produce, and regularly update, these emission estimates, following TACCC (transparency, accuracy, comparability, consistency, completeness) UNFCCC requirements. New research is required to more accurately quantify carbon stocks and fluxes of carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). The development and improvement of methodologies for a GHG verification system will address its applicability in Europe, and, whenever needed, the upscaling from Europe to other GHG emitting countries and regions, through international cooperation mechanisms promoted by the WMO, the IPCC and the UNFCCC in the context of the Paris Agreement on Climate.
The EU funded project VERIFY aims to develop a framework for the synthesis of different data streams to produce harmonized European country-scale GHG budgets, with uncertainties and to provide scientific and observation-based evidence on the estimates. By reconciliation of data from different sources (e.g. bottom-up, top-down, regional emission estimates and national emission inventory reports) we aim to reduce overall uncertainty and identify and categorize key differences that are related to specific methods.
This first report is intended as a ‘proof of concept’, and our preliminary analysis is based on total EU28 and sector totals from UNFCCC and EDGAR with a focus on a) Agriculture (UNFCCC, CAPRI, EDGAR, FAO, GAINS) and b) LULUCF biogenic fluxes - carbon stocks and sinks (UNFCCC, EFISCEN, CBM and TRENDY.v6). We analyzed as well inverse C fluxes from four inversions of the global carbon project (GCP) and N2O fluxes from the InGOS project. Together with CH4 fluxes from GCP we also mention the CH4 fluxes from natural wetlands. For the sector totals, we find a relatively good match between UNFCCC and the other sources with differences pertaining mostly to sectoral aggregation and/or expert judgment emission factors (EFs). We find large differences in the LULUCF carbon stocks and fluxes when comparing modelled results to UNFCCC reports. Differences in method (Tier 1 or Tier 2) and model set-up, might be the underlying cause of these discrepancies.