Emissions 'not caused by warming sea,'
By Lewis Page, 25th July 2013 The Register
Three academics have written an opinion piece in hefty boffinry mag Nature, saying that humanity must reduce carbon emissions hugely or methane belching from the Arctic seabed will do $60 trillion of economic damage. But the latest research suggests that Arctic methane emissions are nothing to do with rising temperatures.
Gail Whiteman (professor of "sustainability, management and climate change"), Chris Hope (an economist) and Peter Wadhams (an oceanologist) present their arguments in the Comment section of Nature, here (pdf). They start off by suggesting that disappearing ice and warmer seas in the Arctic (caused by human carbon emissions, they say) are already causing methane emissions, and that further warming - with associated ice loss - will see these emissions increase hugely.
As methane is a vastly more powerful greenhouse gas than carbon dioxide, the trio contend that this will mean still more warming and so on in a runaway feedback loop of doom. Using a modified version of the famous 2006 Stern climate economics theory (which was later dubbed "wrong, but for the right reasons") Hope suggests that the result might be economic damage to the tune of $60tn this century - equivalent to one year's gross domestic product for the entire human race.
There are several problems with this, but the first one is the most basic. Whiteman, Hope and Wadhams base their suggestion that current Arctic methane emissions are caused by recent, human-driven warming - and so might be expected to accelerate hugely, perhaps - on published calculations from 2010 and last year. This theorising began when airborne surveys discovered that methane was being emitted from the Arctic at various locations along the Siberian continental shelf in recent times.
Nobody at that time knew how long this had been going on, or what its cause might be. However it was known that a good deal of methane lay stored along the shelf in the form of hydrates, which are only stable at very low temperatures and high pressures. It seemed reasonable to suppose that warming seas in recent times were causing hydrates to break down into gas, which was then bubbling up into the atmosphere: but this was just a guess.
It turns out to be a guess which was wrong, however. Last year a German research vessel set out for the Arctic to find out more about the mysterious seabed methane emissions. Underwater robots were sent down at promising locations, automatic equipment left on earlier expeditions was recovered, and ground truth was established. Because of the lengthy scientific publishing cycle there aren't yet any published papers, but the results were so clear - and so important - that the scientists aboard the ship were happy to reveal them publicly.
A statement from Helmholtz-Zentrum für Ozeanforschung (Centre for Ocean Research, aka GEOMAR), the organisation whose ship was used, revealed the "surprising result" that methane emissions from the Arctic seabed are "no new thing". It went on:
Above all the fear that the gas emanation is a consequence of the current rising sea temperature does not seem to apply.
“The observed gas emanations are probably not caused by human influence," comments Professor Doktor Christian Berndt, the expedition leader. "At numerous emergences we found deposits that might already be hundreds of years old ... On any account, the methane sources must be older."
So there you have it. Humans did not cause the Arctic methane emissions, which have been happening for hundreds of years. There's no real reason to believe that they will suddenly accelerate as Wadhams, Hope and Whiteman suggest they might.
[remainder at The Register]
See also: Climatologist Dr. Judith Curry calls Arctic time bomb claims ‘impossible’: ‘Each of these assumptions is highly implausible, based upon my understanding; the combination of these two assumptions into a single scenario seems impossible to me’
See also: NYT: Arctic Methane Credibility Bomb Warmist Gavin Schmidt: 'implausible'
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