A top-down estimation of subnational CO₂ budget using a global high-resolution inverse model with data from regional surface networks

Abstract

Top-down approaches, such as atmospheric inversions, are a promising tool for evaluating emission estimates based on activity-data. In particular, there is a need to examine carbon budgets at subnational scales (e.g. state/province), since this is where the climate mitigation policies occur. In this study, the subnational scale anthropogenic CO2 emissions are estimated using a high-resolution global CO2 inverse model. The approach is distinctive with the use of continuous atmospheric measurements from regional/urban networks along with background monitoring data for the period 2015–2019 in global inversion. The measurements from several urban areas of the U.S., Europe and Japan, together with recent high-resolution emission inventories and data-driven flux datasets were utilized to estimate the fossil emissions across the urban areas of the world. By jointly optimizing fossil fuel and natural fluxes, the model is able to contribute additional information to the evaluation of province–scale emissions, provided that sufficient regional network observations are available. The fossil CO2 emission estimates over the U.S. states such as Indiana, Massachusetts, Connecticut, New York, Virginia and Maryland were found to have a reasonable agreement with the Environmental Protection Agency (EPA) inventory, and the model corrects the emissions substantially towards the EPA estimates for California and Indiana. The emission estimates over the United Kingdom, France and Germany are comparable with the regional inventory TNO–CAMS. We evaluated model estimates using independent aircraft observations, while comparison with the CarbonTracker model fluxes confirms ability to represent the biospheric fluxes. This study highlights the potential of the newly developed inverse modeling system to utilize the atmospheric data collected from the regional networks and other observation platforms for further enhancing the ability to perform top-down carbon budget assessment at subnational scales and support the monitoring and mitigation of greenhouse gas emissions.

Monitoring and modelling European carbon fluxes using atmospheric observations

“…The high-resolution of these fluxes is advantageous, especially with the observation capacity moving to higher spatially resolved satellites (Sierk et al, 2021). Additionally, a higher spatial resolution allows for better separation between FF and biogenic carbon (Agustí-Panareda et al, 2019;Maksyutov et al, 2021), and allows for the use of higher resolution transport, which is required in more complex terrains such as urban areas (Nayagam et al, 2024).…”

“…The second advancement is a combination of Eulerian and Lagrangian transport within the same framework (Maksyutov et al, 2021;Nayagam et al, 2024). Throughout this thesis, we have used high-resolution Lagrangian transport, generally to assess fine-scale variability in carbon exchange (e.g.…”

“…Recently, Nayagam et al (2024) have taken this one step further, by combining a Eulerian transport model for the larger scales with a Lagrangian transport model for finer (urban) scales. With this, they were able to transport local, anthropogenic emissions of CO 2 on a high-resolution, whilst keeping the capacity to solve for biogenic fluxes on a larger scale.…”

“…With this, they were able to transport local, anthropogenic emissions of CO 2 on a high-resolution, whilst keeping the capacity to solve for biogenic fluxes on a larger scale. This combination allowed Nayagam et al (2024) to assess large-scale biogenic fluxes, and subnational fossil fuel emissions in tandem, and using the best of both transport models.…”