Top-down methane emissions estimates for the San Francisco Bay Area from 1990 to 2012

Journal Article · Wed Apr 01 00:00:00 EDT 2015 · Atmospheric Environment (1994)

DOI:https://doi.org/10.1016/j.atmosenv.2015.01.065· OSTI ID:2325268

Fairley, David ; Fischer, Marc L.

Methane is a potent greenhouse gas (GHG) that is now included in both California State and San Francisco Bay Area (SFBA) bottom-up emission inventories as part of California's effort to reduce anthropogenic GHG emissions. Here we provide a top-down estimate of methane (CH₄) emissions from the SFBA by combining atmospheric measurements with the comparatively better estimated emission inventory for carbon monoxide (CO). Local enhancements of CH₄ and CO are estimated using measurements from 14 air quality sites in the SFBA combined together with global background measurements. Mean annual CH₄ emissions are estimated from the product of Bay Area Air Quality Management District (BAAQMD) emission inventory CO and the slope of ambient local CH₄ to CO. The resulting top-down estimates of CH₄ emissions are found to decrease slightly from 1990 to 2012, with a mean value of 240 ± 60 GgCH₄ yr⁻¹ (at 95% confidence) in the most recent (2009–2012) period, and correspond to reasonably a constant factor of 1.5–2.0 (at 95% confidence) times larger than the BAAQMD CH₄ emission inventory. However, we note that uncertainty in these emission estimates is dominated by the variation in CH₄:CO enhancement ratios across the observing sites and we expect the estimates could represent a lower-limit on CH₄ emissions because BAAQMD monitoring sites focus on urban air quality and may be biased toward CO rather than CH₄ sources.

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 2325268
• Alternate ID(s): OSTI ID: 1208641
• Journal Information: Atmospheric Environment (1994), Journal Name: Atmospheric Environment (1994) Vol. 107 Journal Issue: C; ISSN 1352-2310
• Publisher: Elsevier
• Country of Publication: United Kingdom
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
methane emissions
emissions inventory
greenhouse gas
inventory verification
top-down estimates