Abstract
Abstract. Individual countries report national emissions of methane, a potent greenhouse gas, in accordance with the United Nations Framework Convention on Climate Change (UNFCCC). We present a global inventory of methane emissions from oil, gas, and coal exploitation that spatially allocates the national emissions reported to the UNFCCC (Scarpelli et al., 2019). Our inventory is at 0.1∘×0.1∘ resolution and resolves the subsectors of oil and gas exploitation, from upstream to downstream, and the different emission processes (leakage, venting, flaring). Global emissions for 2016 are 41.5 Tg a−1 for oil, 24.4 Tg a−1 for gas, and 31.3 Tg a−1 for coal. An array of databases is used to spatially allocate national emissions to infrastructure, including wells, pipelines, oil refineries, gas processing plants, gas compressor stations, gas storage facilities, and coal mines. Gridded error estimates are provided in normal and lognormal forms based on emission factor uncertainties from the IPCC. Our inventory shows large differences with the EDGAR v4.3.2 global gridded inventory both at the national scale and in finer-scale spatial allocation. It shows good agreement with the gridded version of the United Kingdom's National Atmospheric Emissions Inventory (NAEI). There are significant errors on the 0.1∘×0.1∘ grid associated with the location and magnitude of large point sources, but these are smoothed out when averaging the inventory over a coarser grid. Use of our inventory as prior estimate in inverse analyses of atmospheric methane observations allows investigation of individual subsector contributions and can serve policy needs by evaluating the national emissions totals reported to the UNFCCC. Gridded data sets can be accessed at https://doi.org/10.7910/DVN/HH4EUM (Scarpelli et al., 2019).
Highlights
Methane is the second most important anthropogenic greenhouse gas after CO2, with an emission-based radiative forcing of 1.0 W m−2 since pre-industrial times, as compared to 1.7 W m−2 for CO2 (Myhre et al, 2013)
We present a global inventory of methane emissions from oil, gas, and coal exploitation that spatially allocates the national emissions reported to the United Nations Framework Convention on Climate Change (UNFCCC) (Scarpelli et al, 2019)
For the few countries that do not report to the UNFCCC, we use the coal emissions data embedded in EDGAR v4.3.2 Fuel Exploitation with additional information from EDGAR to separate coal from oil and gas; these countries account for less than 1 % of global coal emissions
Summary
Methane is the second most important anthropogenic greenhouse gas after CO2, with an emission-based radiative forcing of 1.0 W m−2 since pre-industrial times, as compared to 1.7 W m−2 for CO2 (Myhre et al, 2013). Individual countries must estimate and report their anthropogenic methane emissions by source to the United Nations in accordance with the United Nations Framework Convention on Climate Change (UNFCCC, 1992) These estimates rely on emission factors (amount emitted per unit of activity) that can vary considerably between countries in particular for oil and gas (Larsen et al, 2015). Top-down inverse analyses of atmospheric methane observations can provide a check on the national emission inventories (Jacob et al, 2016), but they require prior information on the spatial distribution of emissions within the country. This information is not available from the UNFCCC reports. We present results for 2016, which is the most recent year available from the UNFCCC, but our method is readily adaptable to other years
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