Focus

Context

As the negative impacts of rising global temperatures become increasingly evident, national governments, regional authorities and private stakeholders are increasing efforts to curb the emissions the greenhouse gases (GHG) responsible for global warming.
Measuring the effectiveness of GHG emission reduction policies against agreed-upon international targets require accurate and precise estimates of emissions and their trends. These estimates need to be established and regularly updated using transparent methods, traceable to international standards. DARE-UK will quantify more accurately carbon stocks and the fluxes of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) across the UK based on independent observations in support of inventories that rely only on statistical data. Accurate characterization of the space-time variations of GHG fluxes, separating their anthropogenic and natural components and their drivers, will be based on advanced modelling approaches using atmospheric GHG measurements, tracer transport inversions and various arrays of land observations, in-situ and from space. The improved knowledge of GHG budgets from DARE-UK will be used to improve national inventories, in collaboration with national inventory agency, and to deliver policy-relevant information to track progress of the mitigation efforts to meet the targets of the Paris Agreement on Climate, in line with international cooperation mechanisms promoted by the WMO, the IPCC and the UNFCCC.

Bottom-up vs Top-down UK emissions of methane

Methane estimates from the UK’s National Inventory Report (2018).
Inventory (bottom-up) estimates are shown as black bars.
Top-down (observation based) estimates using two sites (brown) and
those using the UK DECC network (red).

The image above shows how independent estimates of methane emissions have been made in the past using top-down methods, which are observation based, and bottom-up methods, which are based primarily on emission inventory data. By adding extra layers of observational data and sourcing more detailed inventory data DARE-UK will improve the accuracy of these estimates significantly.

Objectives

For the three main GHGs, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), the primary objectives of DARE-UK are to:

  1. Attribute the contribution of individual source and sink sectors to the variability in measured GHG concentrations over the UK and Ireland.
  2. Reconcile any mismatch between fluxes derived from atmospheric measurements and specific sectors of UK’s emissions inventory or biogenic flux estimates.
  3. Determine the overall level of confidence in the UK’s GHG emissions by combining top-down and bottom-up approaches.
  4. Provide the scientific evidence-base and recommendations to the UK government to improve the UK’s reporting of GHGs to the UNFCCC, and to contribute to the Transparency Framework and the Global Stocktake.

To achieve these objectives, scientific and technical advances will be made by:

  1. Developing more comprehensive time- and space-resolved bottom-up flux estimates of the three GHGs from anthropogenic, terrestrial biogenic and aquatic systems with improved uncertainty quantification.
  2. Extending top-down methods to enable the use of new measurements of co-emitted tracers and GHG isotopologues to separate fluxes from different source sectors.
  3. Making use of new high-resolution remotely-sensed data of GHGs and co-emitted tracers for top-down flux estimation over areas of the UK not well-captured by the current surface network.
  4. Improving simulations of atmospheric GHG dispersion, which are vital for linking estimated fluxes with atmospheric observations and developing new methods for evaluating model performance and uncertainty.