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As the Arctic sea ice melts, be wary of 'Methane Emergency' claims

• 14 Aug 2012, 14:30
• Christian Hunt

The Arctic summer sea ice minimum is around a month away, and it seems possible that there will be a new record low in sea ice extent, along with all the media attention that will entail. 

Arctic sea ice is clearly in long-term decline, and scientists have been telling us to pay attention to what's happening in the region. But one group - the Arctic Methane Emergency Group (AMEG) - argues that sea ice loss could lead to even more dramatic consequences.

AMEG, small campaign organisation, suggests continuing sea ice loss will lead to the rapid release of the greenhouse gas methane into the atmosphere, destabilising the climate. It says:

"The Arctic summer sea ice is in a rapid, extremely dangerous meltdown process... [leading] to an accelerated rate of Arctic carbon feedback emissions of methane from warming wetland peat bogs and thawing permafrost."

AMEG received some attention earlier in the year when it argued that governments must immediately use geoengineering techniques in the Arctic area to prevent this outcome. The group also made the same case to the UK government's Environmental Audit Committee.

Methane in the Arctic

So with sea ice shrinking, is an Arctic methane bomb the next big story?

The Arctic is warming up faster than the global average, and recent years have seen continuing drops in the amount of Arctic sea ice - (click here to see this animated graph):

Source: Open Mind

The loss of sea ice means that more heat is absorbed by the region, as a smaller ice cap reflects less of the sun's energy back into space.

Methane is a potent greenhouse gas - much more powerful than carbon dioxide - and large amounts of it are stored in the Arctic, trapped in frozen ground. There's also a lot of methane buried in sediments under the Arctic ocean.

As the Arctic warms, methane currently stored there could be released into the atmosphere as the permafrost melts, the ocean warms, and underwater sediments are disturbed.  

Methane plumes

AMEG is worried that the Arctic will start to release methane very soon, and very quickly. The organisation points to plumes of methane rising from the Arctic ocean floor as evidence "suggesting an escalation of methane emissions could be happening already, even without further warming of the Arctic."

Newspapers predictably love this story as it combines a new angle on the Arctic and climate change with the threat of imminent apocalypse. The scientific literature is much more equivocal, however.

One recent paper suggests methane plumes may be a result of the planet's continuing and very slow response to its emergence from an ice age, not due to manmade climate change. Another recent review of the scientific literature on the subject concluded:

"Our current estimates of gas hydrate storage in the Arctic region are ... extremely poor. It is still unknown whether future ocean warming could lead to significant methane release..."

The scientific literature does not appear to suggest that massive releases of Arctic methane are imminent.

Methane emergency?

This hasn't restrained AMEG. Its website hosts this warning:

"We declare there now exists an extremely high international security risk from abrupt and runaway global warming being triggered by the end-summer collapse of Arctic sea ice towards a fraction of the current record and release of huge quantities of methane gas from the seabed. Such global warming would lead at first to worldwide crop failures but ultimately and inexorably to the collapse of civilization as we know it. This colossal threat demands an immediate emergency scale response to cool the Arctic and save the sea ice."

Perhaps unsurprisingly, given such statements, climate scientists have challenged this argument. Professor Julia Slingo of the Met Office told the UK's  Environmental Audit Committee:

"Our estimate ... is that that we're not looking at catastrophic releases of methane. I think there is a lack of clarity in thinking about how that heating at the upper level of the ocean can get down, and how rapidly it can get down into the layers of the ocean."

Professor Tim Lenton, an expert in climate tipping points based at Exeter University, told the same meeting that methane release from the Arctic is likely to affect the climate, but over a longer time period. He said:

"My personal view ... [is that] methane in the long run and methane loss from these frozen reservoirs will be a long-term significant amplifier. It might even double long-term warming, and by long-term I mean thousands and tens of thousands of years from, say, 3 to 6°C, but ... It plays out slowly, partly because you have to propagate a warming signal not just at the bottom of the shelf or the bottom of the ocean, but through sediments, and that is not inherently a fast process."

Professor Corinne Le Quéré, Director of the Tyndall Centre, told the Ecologist that the presence of methane plumes in the Arctic needs to be interpreted with care, as there aren't long term records to compare against:

"We don't know whether these spikes are natural or not. In the Arctic there are storms, changes in ice coverage and fluctuations in weather systems so before you can make this kind of extrapolation you have to look in terms of time and space, and consider other sources of methane production also."

Methane emissions still important

None of this is to say that Arctic methane might not end up having an influence on the planet's climate. The scientific website Realclimate suggests that methane emissions from the Arctic could be a significant long-term contributor to further warming. Scientists have been arguing for a long time that the warming of the Arctic is worth paying attention to.

But enough scientists have challenged the idea that imminent catastrophic release of Arctic methane could provide a short term 'bomb' effect and destabilise our climate to suggest that the scientific community isn't buying the argument.