Supporting information for US trends in GHG emissions

Figure used in the New Yorker Commentary: The Literal Gaslighting That Helps America Avoid Acting on the Climate Crisis

On October 9, 2019 a Commentary was published in the New Yorker by Bill McKibbon using this emmisions figure from Dr. Howarth. You can read the article at this link.

Download this summary as a printable pdf.

US GHG emissions from fossil fuels, 1949 to 2018 US Carbon Emissions Figure
R. Howarth (9/23/19), using emission factors from Howarth manuscript submitted for special journal issue for the 8th International Symposium on Non-CO2 Greenhouse Gases; GWP is 20-yr IPCC value of 86.

Figure shows the sum of carbon dioxide and methane emissions for all fossil fuels and by type of fossil fuel in the United States from 1949 to 2019. Energy data are from the US DOE EIA (, downloaded 23 Sept 2019). Carbon dioxide emission factors are from Hayhoe et al. (2002): 92 g CO2 MJ-1 for coal, 73 g CO2 MJ-1 for petroleum products, and 55 g CO2 MJ-1 for natural gas. The methane emission factor for coal is 0.185 g CH4 MJ-1 (based on Table 2 of IPCC 1996); this value is quite good for 1990. The methane emission factor for petroleum products is 0.093 g CH4 MJ-1 (NETL 2008, as used in Howarth et al. 2011); this value is reasonable for the 20th Century but may underestimate emissions associated with shale oil development over the past decade (Howarth 2019). And the methane emission factor for natural gas is 3.5%, as estimated in Howarth (2019); this value is robust for the past decade and probably well represents emissions in the late 20th Century as well (Howarth 2014). Methane emissions are converted to carbon dioxide equivalents using a 20-year global warming potential of 86 (IPCC 2013), following the guidance in the Climate Leadership and Community Protection Act passed by New York State in July 2019.


  • CLCPA. 2019. Climate Leadership and Community Protection Act, State of New York., Downloaded Sept 4, 2019
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  • Howarth RW. 2014. A bridge to nowhere: Methane emissions and the greenhouse gasfootprint of natural gas. Energy Science & Engineering 2: 47-60, doi:10.1002/ese3.35
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  • IPCC. 1996. CH4 Emissions: Coal Mining and Handling, Good Practice Guidance and Uncertainty Management in National Greenhouse Gas Inventories. Intergovernmental Panel on Climate Change. Link to IPCC Report, Downloaded Sept 4, 2019
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  • NETL. 2008. Petroleum-Based Fuels Life Cycle Greenhouse Gas Analysis - 2005 Baseline Model. National Energy Technology Laboratory, US Department of Energy. Link to article, Downloaded Sept 4,2019