Assessments of in situ and remotely sensed CO2 observations in a Carbon Cycle Fossil Fuel Data Assimilation System to estimate fossil fuel emissions

<p>The Paris Agreement establishes a transparency framework that builds upon&#160;inventory-based national greenhouse gas emission reports, complemented by independent emission&#160;estimates derived from atmospheric measurements through inverse modelling.&#160;The capability of such a Monitoring and Verification Support (MVS) capacity&#160;to constrain fossil fuel emissions to a sufficient extent has not yet been assessed.&#160;The CO₂ Monitoring Mission, planned as a constellation of satellites measuring&#160;column-integrated atmospheric CO₂ concentration (XCO2),&#160;is expected to become a key component of an MVS capacity.&#160;</p><p>Here we provide an assessment of the potential of a Carbon Cycle Fossil Fuel Data&#160;Assimilation System using synthetic XCO2 and other observations to constrain&#160;fossil fuel CO₂ emissions for an exemplary 1-week period in 2008.&#160;We find that the system can provide useful weekly estimates of&#160;country-scale fossil fuel emissions independent of national inventories. &#160;When extrapolated from the weekly to the annual scale,&#160;uncertainties in emissions are comparable to uncertainties in inventories,&#160;so that estimates from inventories and from the MVS capacity can be used for&#160;mutual verification.&#160;</p><p>We further demonstrate an alternative, synergistic mode of operation,&#160;which delivers a best emission estimate through assimilation of the inventory&#160;information as an additional data stream. &#160;We show the sensitivity of the results to the setup of the CCFFDAS and to&#160;various aspects of the data streams that are assimilated, including&#160;assessments of surface networks.</p>