Future CO2 emissions from currently operating coal- and gas-fired plants. Future emissions from currently operating coal and gas plants will depend upon the average lifetimes and utilization of those plants. If existing plants operate over historically average lifetimes, then pledged reductions in U.S. power-related emissions (its Nationally Determined Contribution (NDC), denoted by red dashed lines) can be met at the current average capacity factor (60%) in 2025, but must decrease by a third to 40% or below to meet the NDC target in 2050. Similarly, if existing plants operate at average capacity factors, plants must retire by 35 years or sooner to meet the NDC for 2050. Credit: Shearer et al., 2020, Figure 4a
Source: AGU Advances

From 2000 to 2018, CO2 emissions from the U.S. power sector decreased by 24%. This is primarily attributed to increased use of natural gas for electricity, as gas-fired plants emit roughly half the CO2 per megawatt-hour of coal burning plants. In a novel analysis, Shearer et al. [2020] examine the long-term implications of the natural gas boom from the perspective of “committed emissions”­—the cumulative future CO2 emissions from fossil fuel energy infrastructure assuming average lifetimes and utilization rates. They find that the relative decrease in committed emissions is much smaller than the decrease in annual emissions, due to the rapid increase in newer gas-fired power plants. Methane leakage would further reduce this offset. If operated as historically, currently operating coal and gas plants are incompatible with U.S. pledges under the Paris climate agreement, requiring a substantial reduction in the capacity and/or lifetime of these plants—even if no new fossil capacity is added.

Citation: Shearer, C., Tong, D., Fofrich, R., & Davis, S. J. [2020]. Committed emissions of the U.S. natural gas boom. AGU Advances, 1, 2020AV000162. https://doi.org/10.1029/2020AV000162

—Don Wuebbles, Editor, AGU Advances

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