UPDATE (12/3/2013; 8:17am ET): A must-read post on the blog RealClimate highlights another important fact about methane: the atmospheric concentration is still not rising quickly, even assuming the emissions data from Miller et al. are accurate. From the post:
American Methane Emissions Higher Than Previously Thought
Miller et al (2013) combine measurements of methane concentrations in various locations through time with model reconstructions of wind fields, and “invert” the information to estimate how much methane was released to the air as it blew over the land. This is a well-established methodology, pushed to constrain US anthropogenic emissions by including measurements from aircraft and communications towers in addition to the ever-invaluable NOAA flask sample network, and incorporating socioeconomic and industrial data. The US appears to be emitting 50-70% more methane than the EPA thought we were, based on “bottom up” accounting (adding up all the known sources).
Is this bad news for global warming?
Not really, because the one real hard fact that we know about atmospheric methane is that it’s concentration isn’t rising very quickly. Methane is a short-lived gas in the atmosphere, so to make it rise, the emission flux has to continually increase. This is in contrast to CO2, which accumulates in the atmosphere / ocean system, meaning that steady (non-rising) emissions still lead to a rising atmospheric concentration. There is enough uncertainty in the methane budget that tweaks of a few percent here and there don’t upset the apple cart. Since the methane concentration wasn’t rising all that much, its sources, uncertain as they are, have been mostly balanced by sinks, also uncertain. If anything, the paper is good news for people concerned about global warming, because it gives us something to fix. (emphasis added)
This is critical to keep in mind, especially since several “experts” have suggested Miller et al. means the “climate impact” of U.S. oil and natural gas development is now much higher than previously thought. (One blogger even tried to spike the proverbial football after the study was released, suggesting it “proves” natural gas is a “gangplank” to irreversible global warming.) But according to RealClimate, for that claim to be accurate, it would require methane concentrations — not just emissions — to have grown precipitously. They have not. More from RealClimate:
Because methane is mostly well-mixed in the atmosphere, emissions from the Arctic or from the US must be seen within the context of the global sources of methane to the atmosphere. Estimates of methane emissions from the Arctic have risen, from land (Walter et al 2006) as well now as from the continental shelf off Siberia. Call it 20-30 Tg CH4 per year from both sources. The US is apparently emitting more than we thought we were, maybe 30 Tg CH4 per year. But these fluxes are relatively small compared to the global emission rate of about 600 Tg CH4 per year. The Arctic and US anthropogenic are each about 5% of the total. Changes in the atmospheric concentration scale more-or-less with changes in the chronic emission flux, so unless these sources suddenly increase by an order of magnitude or more, they won’t dominate the atmospheric concentration of methane, or its climate impact. (emphasis added)
Just some more helpful context to keep in mind.
—Original post, Nov. 25, 2013—
A new study published by the Proceedings of the National Academy of Sciences suggests that EPA’s greenhouse gas inventory may be underestimating total methane emissions in the United States, possibly by as much as 50 percent. According to the authors, emissions from oil and gas production could be twice as high as EPA data suggest, if not higher. But it’s worth noting a few key facts about the study, including some additional context that should prevent all of us from leaping to any particular conclusion based on this limited research.
KEY FACT 1: Looks at old operating environment.
As Andy Revkin of the New York Times pointed out: “It’s important to note that the new study is a snapshot of conditions in 2007 and 2008, before concerns increased about the need for tighter standards for gas and oil drilling operations.” In the oil and gas industry, ignoring a half decade of research and innovation is almost comical, even more so because the researchers suggest that snapshot is somehow indicative of the current operating environment!
Don’t just take our word for it, either. Researchers from MIT found just last year that industry use of “green completions” (i.e. reduced emissions technologies) was far more common than previously thought. Research from the University of Texas earlier this year actually took direct measurements from well pads, and those data essentially confirmed EPA’s estimates — based on wide adoption of methane reducing technologies. Last but not least, there’s plenty of evidence to suggest that, if anything, EPA’s inventory actually overstates methane emissions, owing to the agency’s inflation of flowback periods and demonstrably false assumptions regarding flaring.
EPA revised its emissions estimates downward earlier this year based on more comprehensive data that had been collected since its previous inventory. That data, and EPA’s subsequent change, were the result of activities that have occurred after 2008, making that data much more relevant to today’s operating environment.
KEY FACT 2: What’s the actual source?
The researchers used aircraft and observation towers to collect emissions data, analyzed it, and then plugged those findings into a model to estimate what the source(s) could have been. Contrast this, for example, to the data collected in the UT/EDF study earlier this year, which were the result of direct measurements. In other words, Miller, et. al., does not tell us definitively where the methane is coming from, only a guess (albeit an educated one) based upon mathematical modeling.
Miller, et. al., used the presence of propane to link certain methane readings to oil and gas production, although this is more of an exercise in correlation than causation. “Cows don’t produce propane; oil and gas does,” said study co-author Marc Fischer. But propane doesn’t only get emitted when folks are drilling or completing wells, either. The California Air Resources Board, for example, has its own webpage describing how propane emissions from product transfers is an ozone concern. A study published in Science a few years ago found a variety of natural seepages “inject propane into the atmosphere.”
Does that mean the oil and gas industry was not responsible for any methane that has a propane fingerprint? Of course not. But as David Allen, the author of the UT/EDF study, told NBC News, “a logical follow-up question [to Miller, et. al.] is which sources within these sectors are responsible for the emissions.”
KEY FACT 3: More data mean better understanding.
The lead author of the study, Scot Miller, told NBC News that getting a handle on methane emissions “really requires a collaborative effort,” and that his study is one of many “different pieces of a much bigger puzzle.” That’s absolutely right, and as more research is done on this subject, we’ll all be better informed. Additional research allows us to make better policy decisions, and — this is worth stressing — the constant innovation occurring within the industry is a result of credible scientific research, including the $81 billion invested in emissions reductions technologies over the past 12 years by the oil and gas industry.
One study cannot tell us everything we need to know, and this latest research is no different.