Constraining sector-specific CO<sub>2</sub> and CH<sub>4</sub> emissions in the US

Abstract

Abstract. This review paper explores recent efforts to estimate state-and national-scale carbon dioxide (CO 2 ) and methane (CH 4 ) emissions from individual anthropogenic source sectors in the US. Nearly all state and national climate change regulations in the US target specific source sectors, and detailed monitoring of individual sectors presents a greater challenge than monitoring total emissions. We particularly focus on opportunities to synthesize disparate types of information on emissions, including emission inventory data and atmospheric greenhouse gas data.We find that inventory estimates of sector-specific CO 2 emissions are sufficiently accurate for policy evaluation at the national scale but that uncertainties increase at state and local levels. CH 4 emission inventories are highly uncertain for all source sectors at all spatial scales, in part because of the complex, spatially variable relationships between economic activity and CH 4 emissions. In contrast to inventory estimates, top-down estimates use measurements of atmospheric mixing ratios to infer emissions at the surface; thus far, these efforts have had some success identifying urban CO 2 emissions and have successfully identified sector-specific CH 4 emissions in several opportunistic cases. We also describe a number of forward-looking opportunities that would aid efforts to estimate sector-specific emissions: fully combine existing top-down datasets, expand intensive aircraft measurement campaigns and measurements of secondary tracers, and improve the economic and demographic data (e.g., activity data) that drive emission inventories. These steps would better synthesize inventory and topdown data to support sector-specific emission reduction policies.

Inversion Estimates of Lognormally Distributed Methane Emission Rates From the Haynesville‐Bossier Oil and Gas Production Region Using Airborne Measurements

“…This wide range in CH 4 leak rates in turn leads to uncertainty in the net climate impacts of replacing coal with natural gas as a fuel source (Alvarez et al, 2012(Alvarez et al, , 2018. Quantifying CH 4 emission rates from the O/NG production sector is therefore an active area of scientific inquiry (Miller & Michalak, 2017).…”

Authors response to comments from reviewer No. 2

“…Near-surface-sensitive satellite observations of atmospheric methane have been used in recent years to obtain quantitative information on methane emissions (e.g. Alexe et al, 2015;Bergamaschi et al, 2007Bergamaschi et al, , 2009Bergamaschi et al, , 2013Bloom et al, 2010;Turner et al, 2015Turner et al, , 2016Fraser et al, 2013;Monteil et al, 2013;Cressot et al, 2014;Wecht et al, 2014a, b;Kort et al, 2014;Jacob et al, 2016;Houweling et al, 2017). Nevertheless, there are still many important aspects which need further investigation.…”

Potential of European <sup>14</sup>CO<sub>2</sub> observation network to estimate the fossil fuel CO<sub>2</sub> emissions via atmospheric inversions

“…Away from the emitting source, the atmospheric signals of FFCO 2 emissions mixes with those of natural fluxes, so that FFCO 2 emissions can hardly be monitored by atmospheric CO 2 measurements only (Shiga et al, 2014). Because of this, monitoring FFCO 2 emissions at national scales, using continental networks of stations located outside the vicinity of the largest sources, is only possible when measuring an additional tracer specially sensitive to the signal of FFCO 2 emissions (Miller and Michalak, 2017;Basu et al, 2016). Radiocarbon in CO 2 is arguably the best tracer (Levin et al, 2003;Turnbull et al, 2006).…”