New data enable targeted policy to lessen GHG emissions

Methane (CH4) emissions from oil and natural gas (O&NG) systems are an important contributor to greenhouse gas emissions. In the United States, recent synthesis studies of field measurements of CH4 emissions at different spatial scales are ~1.5–2× greater compared to official greenhouse gas inventory (GHGI) estimates, with the production-segment as the dominant contributor to this divergence. Based on an updated synthesis of measurements from component-level field studies, we develop a new inventory-based model for CH4 emissions, for the production-segment only, that agrees within error with recent syntheses of site-level field studies and allows for isolation of equipment-level contributions. We find that unintentional emissions from liquid storage tanks and other equipment leaks are the largest contributors to divergence with the GHGI. If our proposed method were adopted in the United States and other jurisdictions, inventory estimates could better guide CH4 mitigation policy priorities.

Introduction The recent Intergovernmental Panel on Climate Change (IPCC) special report on global warming of 1.5°C highlighted the importance of reducing short-lived greenhouse gases like methane (Intergovernmental Panel on Climate Change, 2018). Methane, a major component of natural gas, has a global warming potential that is 36 times that of carbon dioxide over a 100-year period (Myhre, et al., 2013), and even higher over shorter time periods (Etminan, Myhre, Highwood, & Shine, 2016). Furthermore, methane emissions contribute to sea-level rise over much longer timescales than their atmospheric lifetimes (Zickfeld, Solomon, & Gilford, 2017). These consequences are troubling given that official methane emissions inventory in the US and Canada have been found to be systematically underestimated (Alvarez, et al.,

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