Despite declining emissions, cleaner air, and falling energy prices, natural gas opponents continue to look the gift horse that is the US shale gas revolution in the mouth. The latest canard comes from CO2 Scorecard, the policy wing of environmental consultancy Performeks LLC. Some readers will recall that last year, CO2 Scorecard released a study claiming that rising natural gas generation accounted for only about a quarter of US emissions reductions from 2011 to 2012. Now, in a recent report, which has been cited by the AP and Mother Jones, they claim that rising gas generation accounts for all of the increase in US coal exports. This analytical sleight of hand leads them to claim that fuel switching from high-carbon coal to lower carbon natural gas in the U.S. power sector has resulted in a net increase in global CO2 emissions.
How does CO2 Scorecard reach this remarkable conclusion? First, by looking at year-over-year changes in generation shares between coal and gas and assuming that fuel-switching between coal and gas only occurs in years when coal generation goes down and gas generation goes up. Second, by assuming that gas has displaced zero-carbon nuclear and hydropower in recent years rather than coal. Third, by assuming that all of the increase in US coal exports has been due to coal that has been displaced by gas. And finally by assuming that all US coal exports are additive to total global coal consumption rather than displacing other sources of coal. Only by making all four of these assumptions, none of which can be supported empirically, can CO2 Scorecard make the extraordinary claim that the shift in the US power sector from coal to gas has resulted in increased emissions.
Downplaying Coal-to-Gas Emissions Reductions
Where last year’s CO2 Scorecard analysis focused on one year and looked at economy-wide emissions, the new analysis looks at the period between 2007 and 2012 and focuses solely on the power sector. The most straightforward way to do this would have been to simply look at the aggregate shift in coal and gas emissions between 2007 and 2012 and calculate the amount of coal consumption that gas generation has displaced. Between 2007 and 2012, coal generation declined by about 25 percent while gas consumption increased by almost 40 percent. All told, the increase in gas generation accounts for about three-quarters of the absolute decline in coal generation.
Instead, CO2 Scorecard uses year-over-year changes in the power sector mix to calculate the contribution that coal-to-gas switching has had upon power sector emissions, an analysis that manages to be simultaneously overly complicated and overly simplistic. The year-over-year data adds no more clarity while offering all manner of opportunity for mischief.