Methane Hydrates

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It is perfectly feasible, therefore, that relatively small areas of land, like the west Siberian permafrost, or the deep sediments around the Gulf of Mexico, have enormous potential both for energy supply and heating the atmosphere to a level that would cause a catastrophic mass extinction of life.

If we take the current controllable methane sources as being about 300 million tonnes (or 6400 million tonnes carbon dioxide equivalent) then the complete release of the western Siberian reservoir would be the equivalent of 233 years of current human methane emissions. It is believed, however, that the total reservoir of methane hydrates within the permafrost and under the sea could be anything between 750 and 3000 billion tonnes of methane, or up to 2000 years worth of human greenhouse gas emissions.

Now, I’m not suggesting for a minute that all of this methane is going to pop into the atmosphere in one great Earthly gasp – there is no chance of this happening – but there is plenty of evidence to suggest that the great permafrosts of the north are no longer staying frozen during the summer months, and may be disappearing entirely. Although methane emissions have temporarily stabilised due to the drying out of wetlands, they will again begin to rise inexorably, and to these emissions will be added the methane that is coming from the hydrates that were previously safely encased in the arctic ice.

No one can put a figure on the expected increase, but this is clearly a greenhouse effect feedback that we could do without. Even if the amount of methane was only doubled, we would see the total global warming potential increase by 20%. If, due to global warming, just the west Siberian permafrost reservoir were to be released, over a period of, say, 50 years, then within 12 years the amount of methane in the atmosphere would rapidly increase to 9000 million tonnes. The impact of this would be catastrophic.

The current (2007) level of methane in the atmosphere is about 1.8 parts per million. This would increase by a factor of 20 to about 36 parts per million, resulting in the amount of human induced global warming increasing by a factor of 3.6. The simple outcome of this would be an increase in global temperatures of at least 3 degrees Celsius, with a dramatic increase in violent storms, desertification, flooding and, of course, the widespread inundation caused by sea level rise. The actual outcome would be far worse – the three degree increase would trigger a further set of feedbacks described by Mark Lynas thus:

“The end of the world is nigh. A three-degree increase in global temperature would throw the carbon cycle into reverse. Instead of absorbing carbon dioxide, vegetation and soils start to release it. So much carbon pours into the atmosphere that it pumps up atmospheric concentrations by 250 parts per million by 2100, boosting global warming by another 1.5C. In other words carbon-cycle feedbacks could tip the planet into runaway global warming much earlier than anyone had expected.”

And all this from just one piece of permafrost, in just one of the two great hydrate complexes on Earth. And we haven’t even considered carbon dioxide.

Defusing The Timebomb

Guess what? This doesn’t have to happen. It really doesn’t.

There is no doubt that humanity, as a whole, has to dramatically cut the amount of carbon dioxide it produces; that is a task that has to remain the top priority for every sector of society – individuals, communities, businesses and governments. Without a dramatic reduction – some estimates put it as 80-90% – in carbon emissions in the next 30 or so years, the planet will be well on the way to the kind of tipping points so graphically described in the previous section.

What struck me when I was researching this article, though, was how quickly the concentration of methane in the atmosphere can fall when its emissions are reduced, compared to the 50-200 years taken by carbon dioxide. Remember how the methane levels remained static at 9000 million tonnes in the west Siberia permafrost example? This stabilisation was because a methane molecule only remains in the atmosphere for an average of 12 years.

According to the IPCC, if we can reduce our emissions of methane by just 50% – which seems perfectly reasonable given the incredibly wasteful lives we currently lead – then within 12 years, atmospheric methane levels will have fallen to 70% of their current level. This is equivalent to a 5.4% reduction in total radiative forcing (the measure of how much extra we are warming the atmosphere) – something that with carbon dioxide would take around a hundred years even if emissions were massively, and rapidly reduced.

So there you have it. A greenhouse gas that could potentially make this planet uninhabitable in a very short time is also a gas that – because we are currently producing it at pointlessly high levels – could easily be reduced with a few simple, if significant, changes, and buy us valuable time in which to fix the problem we have created.

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