Prospects of scientific monitoring ,verification and reporting to support national and subnational GHG inventories

Scientific monitoring, verification and reporting (MRV) is necessary to independently examine the quality of national greenhouse gas (GHG) inventories as assessment methods are inherently uncertain including systematic effects from biased input information and lack of knowledge. The atmospheric research community develops observation systems to monitor the large-scale net GHG exchange with remote sensing and tall tower based concentration field measurements and atmospheric transport model inversion techniques. Because the spatial and temporal scales of these approaches are too coarse for small nations and even more so for local government districts, we used an alternative direct method to estimate the GHG budget of an agricultural landscape in Denmark, the tall tower eddy covariance method. In the presentation, we will use this case study to illustrate the strengths and limitations of net GHG flux measurements to test against GHG inventories.

We compared our one year’s data set of continuous GHG (CO₂, N₂O and CH₄) flux measurements  with the estimates from IPCC based emission methods that were refined for the Danish agricultural landscape. We calculated GHG emissions and their uncertainties using the IPCC methods and propagated those to annual estimates. Likewise, we estimated the uncertainty for annual budgets from turbulent flux measurements including a number of factors that are deemed most important for the quality of net flux estimates.

While the emission estimates for the non-CO₂ GHG were at least similar, the IPCC inventory characterized the area as a net GHG source, whereas the measured fluxes determined a large GHG sink, owing to an overwhelming CO₂ uptake.

In our presentation, we will resolve this apparent contradiction and conclude on the strengths and limitation of MRV from scientific net GHG exchange approaches.

Acknowledgement:

We acknowledge funding by the Free Danish Research Council (DFF, grant number 1127-00308B) and the contribution of MSc. Victoria Abelenda and MSc. Isabel Lopez in their MSc. Project “Comprehensive Assessment of Greenhouse Gas Emissions  (N2O, CO2, CH4) in Agricultural Practices: A Case Study from a Rural Area in Denmark”, Inst. of Resouce and Environmental Engineering, Technical University of Denmark (DTU) Kgs. Lyngby, Denmark (2024).