Climate alarmists have long warned that warming of the Arctic could melt frozen marine and permafrost sediments, releasing methane trapped in peat bogs and ice crystals (clathrate hydrates, see photo above). Methane is a potent greenhouse gas that packs 21 times the global warming punch as CO2 over a 100-year time span and more than 100 times the CO2-warming effect over a 20-year period.

So the fear is that methane emissions from the thawing Arctic will accelerate global warming, which in turn will melt more clathrates and methane-bearing sediments, which will produce still more warming, in a vicious circle of climate destabilization. In a previous post, I offered a skeptical perspective on this doomsday scenario.

This week the journal Nature published a study raising similar concerns about the potential for significant releases of methane from the Antarctic ice sheets. The study’s 14 authors, led by Jemma Wadham of the University of Bristol in the UK, estimate that about 21,000 petagrams (gigatons) of organic carbon (OC) are buried in sedimentary basins under the East and West Antarctic ice sheets – more than 10 times the estimated magnitude of OC stocks in northern permafrost regions. Microbial production of methane from OC (a process known as methanogenesis) is common across many cold subsurface environments, and may have been at work for millions of years beneath the Antarctic Ice Sheets. 

Although “No data exist for rates of methanogenesis in sub-Antarctic marine and terrestrial sediments,” the model used by the Wadham team indicates the potential hydrate reserve could be 70–390 petagrams of carbon (PgC) beneath the East Antarctic Ice Sheet (EAIS) and tens of PgC beneath the West Antarctic Ice Sheet (WAIS). ”This represents a sizeable reservoir of methane hydrate, of a similar order of magnitude to more recent estimates of Arctic permafrost and Arctic ocean hydrate reserves,” the authors state. They contend that subglacial hydrate deposits are likely to be located at shallow depths, “highlighting the strong potential for deglaciation to trigger hydrate destabilization.”

The researchers conclude that “the Antarctic Ice Sheet may be a neglected but important component of the global methane budget, with the potential to act as a positive feedback on climate warming during ice-sheet wastage.”

Well, kudos to Wadham and her colleagues for not injecting apocalyptic rhetoric into a scientific paper. Nonetheless, the paper is attracting media coverage (e.g. here and here) because it raises the possibility of a significant new ‘positive feedback’ that dramatically accelerates global warming.

I wouldn’t lose any sleep about this even if ”deep drilling” later validates the researchers’ estimates of the quantity of hydrates lying beneath the Antarctic Ice Sheets.

Ice core data obtained from the Russian Vostok station in East Antarctica do show a strong correlation over the past 420,000 years between changes in global temperature and atmospheric levels of both CO2 and methane. The data, however, also indicate that two previous interglacial periods were warmer than the Holocene.

Clearly, warming periods release large quantities of methane trapped in frozen marine and terrestrial sediments. Yet in none of the previous interglacials — including the two that were warmer than the present — did warming produce a self-perpetuating, climate de-stabilizing spike in atmospheric methane levels.

The greenhouse effect did not gallop away. Global temperatures largely determined methane levels, not the other way around. Even greater-than-present warmth did not turn Antarctica’s OC deposits into a climate-disrupting methane bomb.

As was widely reported this week,  a new study has just come out concluding that, compared to coal, shale gas fracking is anywhere from just as bad to much worse in terms of greenhouse gas emissions. Despite the holy-grail of peer-revision, there appear to be some very obvious methodological problems and reliance on very poor data (which the researchers have admitted, and wish they had access to better information).

Here is a piece of a review from Matt Ridley, entitled “Black Propaganda.” (Read the whole thing):

So, in other words, shale gas has greater global warming potential than coal only if you rely on lousy data, misunderstood accounting categories, quadrupled assumptions about methane’s relative greenhouse potential — and then only in the short term, when people like Black are always telling us it is the long term we should worry about.

A review from Michael Levi of CFR (again, the whole thing is worth reading):

First, the data for leakage from well completions and pipelines, which is where he’s finding most of his methane leaks, is really bad. Howarth used what he could get – figures for well completion leakage from a few isolated cases reported in industry magazines, and numbers for pipeline leakage from long-distance pipelines in Russia – but what he could get was very thin. There is simply no way to know (without access to much more data) if the numbers he uses are at all representative of reality.

Second, Howarth’s gas-to-coal comparisons are all done on a per energy unit basis. That means that he compares the amount of emissions involved in producing a gigajoule of coal with the amount involved in producing a gigajoule of gas. (Don’t worry if you don’t know what a gigajoule is – it doesn’t really matter.) Here’s the thing: modern gas power generation technology is a lot more efficient than modern coal generation, so a gigajoule of gas produces a lot more electricity than a gigajoule of coal. The per kWh comparison is the correct one, but Howarth doesn’t do it. This is an unforgivable methodological flaw; correcting for it strongly tilts Howarth’s calculations back toward gas, even if you accept everything else he says.

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One last comment: I worry about what this paper says about the peer review process and the way the press treats it. This article was published in a peer-reviewed journal that’s edited by talented academics. It presumably got a couple good reviews, since its time from submission to publication was quite short. These reviewers don’t appear to have been on the ball. Alas, this sort of thing is inevitable in academic publishing. It’s a useful caution, though, against treating peer review as a mark of infallibility, as too many in the climate debate – both media and advocates – have done.

The weak data and unorthodox methodology should make one question its ultimate conclusion, and it doesn’t help that the author is apparently an anti-fracking advocate. The EPA has already called this study an “important piece of information” and it has been reported on without mentioning the critiques in a number of media outlets (and here). Some outlets were better:

Mark D. Whitley, a senior vice president for engineering and technology with Range Resources, a gas drilling company with operations in several regions of the country, said the losses suggested by Mr. Howarth’s study were simply too high.

“These are huge numbers,” he said. “That the industry would let what amounts to trillions of cubic feet of gas get away from us doesn’t make any sense. That’s not the business that we’re in.”

Most business models don’t include plans to allow billions of dollars of your product to escape into the atmosphere.