We assess the large-scale, top-down constraints on regional fossil fuel emissions provided by observations of atmospheric total column CO2 , XCO2 . Using an atmospheric general circulation model (GCM) with underlying fossil emissions, we determine the influence of regional fossil fuel emissions on global XCO2 fields. We quantify the regional contrasts between source and upwind regions and probe the sensitivity of atmospheric XCO2 to changes in fossil fuel emissions. Regional fossil fuel XCO2 contrasts can exceed 0.7 ppm based on 2007 emission estimates, but have large seasonal variations due to biospheric fluxes. Contamination by clouds reduces the discernible fossil signatures. use change and biomass burning (Le Qúeré et al., 2009). Given the risk of global climate change due to increasing atmospheric CO2 (Meehl et al., 2007), the international community has pursued treaties, such as the Kyoto Protocol, to limit the emissions of CO2 to the atmosphere. Currently, the international communityInstrumentation
relies on self-reporting of greenhouse gas emissions but lacks the abilityand
to verify these reports against independent data (NRC, 2010). A methodology to use observations of atmospheric CO2 to verify national level emissions would therefore be highly desirable to support an international agreement.
Monitoring fossil fuel emissions from atmospheric CO2 Nevertheless, our simulations show that atmospheric fossil observations represents a challenge different from attempts XCO2 can be tied to its source region and that changes in the regional XCO2 contrasts scale linearly with emissions. We test the GCM results against XCO2 data from the GOSAT
Open Access andet al., 2007). In satellite. Regional XCO2 contrasts in GOSAT data generally scale with the predictions from the GCM, but the comparison is limited by the moderate precision of and relatively few observations from the satellite. We discuss how this approach may be useful as a policy tool to verify national fossil emissions, as it provides an independent, observational constraint.