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Original Message
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The trigger for the clathrate gun
Melbourne computer specialist Geoff Hudson explains what clathrates are and the danger they pose to climate change.
Transcript:
Robyn Williams: So, would you like the bad news, the very bad news, or would you settle for atrocious?
It's all about clathrates.
Che?
Well those clathrates, as Geoff Hudson will explain in a minute, are gigantic deposits of methane at the bottom of the ocean. If we could tap them we'd be able to run your barbecue for the next 14-1/2-million years. And your neighbour's as well. Trouble is, they may jump ahead of our well-considered plans, those frozen gas bubbles, and leap to the surface before we can even swerve, and spoil everything, or most things.
Bear in mind that this is only a conjecture. When I last went to the Scripps Institution of Oceanography in California, I was told that an eruption of clathrates is not considered to be imminent.
But it might be, as Geoff Hudson, in Melbourne, makes all too clear.
Geoff Hudson: I want to talk about a remote chance of a dramatically worse global warming than those examined in detail by the IPCC. It is called the Clathrate Gun Hypothesis. It was discussed briefly on ABC TV, on Catalyst last year. The scenario imagined is that methane is released by warming up ices called clathrates, and because methane is a really powerful greenhouse gas, the heating increases, speeding up further release of methane. There have been books written about this possibility. What I want to do today is to suggest a possible trigger for this gun. While the Clathrate Gun Hypothesis is well known, this trigger may be novel, first published here on ABC Radio.
Clathrates are a sort of ice which traps gases. It takes four or six water molecules to form a little cell which can house a molecule of carbon dioxide or methane. Provided the temperature is low, like freezing, or the pressure is high and it is cool, like 1,000 metres down at the bottom of the ocean and cooler than 15-degrees Celsius, the clathrate ice containing the methane, or CO2, will stay frozen and not release the gas inside it.
Now this would all be a minor academic exercise, except for the fact that huge amounts of methane are tapped in clathrates on the sea bed. Your first reaction might be a happy one. After all, methane is 90% or more of the natural gas a lot of us use to heat our homes. The Japanese, who buy liquefied methane from Australia, have even attempted to recover methane from these clathrates. The problem for global warming is that methane is a really bad greenhouse gas, some 70 times worse than Co2. Even though we have 220 times more carbon dioxide than methane in our atmosphere, that methane has one-third the heating effect of the CO2. The IPCC report has carbon dioxide contributing 1.6 Watts per square metre and methane contributing 0.55.
The nastiness ratio, how much worse methane is for global warming compared to carbon dioxide, is often quoted as 20. What you need to know is that that figure of 20 is based on a 100 year average, and methane is removed from the atmosphere in a decade or so, while carbon dioxide stays for much longer. At the rate things are happening, the arctic melting, and droughts in Australia, I do not believe we have the luxury of 100 year averages any more. The nastiness ratio inferred by the ratio from the IPCC data is more than 75, and authoritative sources can be found which give a ratio of 72 when averaged over 20 years. I will use 70 as the global warming strength ratio of methane to carbon dioxide.
At the moment, methane is only at 1.7 parts per million of the atmosphere. Carbon dioxide, by comparison was 280 parts per million before the Industrial Revolution, and is now 380 ppm. We are warned of dire consequences if it reaches 450 p ppm, and even worse consequences if it reaches 550 ppm. Taking methane as 70 times worse than carbon dioxide, an extra 1 ppm of methane is like raising the CO2 level from 380 ppm to 450 ppm.
I claimed that there was a lot of methane trapped in the clathrates under the sea. Bruce Buffett and David Archer, in their article Global inventory of methane clathrate: sensitivity to changes in the deep ocean estimate the methane within the clathrates on the sea floor to weigh 3,000-billion tonnes. It sounds too much to imagine. But what we want to know is: what fraction of the atmosphere would it be? It turns out to be one-thousandth, or 1,000 parts per million. So releasing all that methane would be like raising the carbon dioxide level to 70,000 parts per million, more than 100 times worse than the 540 ppm said to be the point of no return.
You may be saying, 'Can I really believe that figure of 1,000 parts per million?' Here's how I got it. One cubic metre of methane gas weighs just under 700 grams, so 3-trillion tonnes occupies 4-million cubic kilometres at sea level pressure. The height of the atmosphere, if it were all at sea level pressure, would be less than 8,000 metres, lower than the top of Mount Everest. Multiply that 8 kilometres by the area of the earth, 500 million square kilometres, and you get the volume of the atmosphere at sea level pressure, to be 4-billion cubic kilometres. Four million divided by four billion is one in a thousand. Sorry about all those large numbers, but I found it much more believable when I did the sums myself.
Let me get back to the main issue. The Clathrate Gun Hypothesis was described in 2004 by James Kennett and others, and it forecast a runaway release of methane. Some methane gets released, that heats the atmosphere and so more methane gets released, and so on. The positive feedback is the same process which operates in explosives, including those in guns. We could get a significant amount of the methane from the clathrates into the atmosphere in a decade or less. Moreover, underneath the methane clathrates is methane gas under pressure, just what you need in a gun. As soon as the thick and impervious clathrate layer above the methane is gone, this gas escapes into the atmosphere as well. Buffett and Archer estimate there is 2,000 billion tonnes of this hot compressed methane gas, more than half the amount frozen in the clathrates.
Of course we don't know when this process will start. It could be triggered by warming in the Tundra, or temperature increases in the oceans.
One possibility is found on the Climate 2012 website. I quote: 'Based on the seismic record, Thomas predicts a methane blowout north of the Unimak Island on January 15th, 2010, at 165-west, 55-north. Unimak Island is west of Alaska and there is a shallow deposit of methane clathrate just north of it. If Kenneth Thomas and his supercomputer are right, the alignment of the planets of the tectonic plates on the 15th will stimulate an earthquake which will dislodge or melt the nearby clathrates. If this blowout is the trigger for the Clathrate Gun, then we don't have to worry about post-Kyoto, and we've all got about 12 months to hoard supplies and weapons. I hope he is wrong, and I suspect that deep down, he does too.
I want to suggest a different trigger. My candidate is the Gulf Stream, the oceanic conveyer which moves warm water from the Gulf of Mexico to the North Atlantic, where it warms Scotland and Scandinavia, and keeps the North Sea from freezing over. The water flow is 80-million tonnes per second, about 100 times the flow of the Amazon and all the other rivers which flow into the Atlantic. The amount of heat moved by the Gulf Stream is similarly colossal. It is 1400-billion kilowatts, roughly 700 times the world electricity production. If you could capture the energy flow for an hour, and convert it all to electricity, you could supply Australia's electricity needs for five years.
Recent broadcasts about the Gulf Stream talk about the changes which will hit Europe if and when the Gulf Stream stops. They will be massive. The latitude of London is 52 degrees. Compare that with the latitude of major towns in North America, like Calgary at 51 degrees and Edmonton at 53 degrees. Be in no doubt, if the Gulf Stream stops, the North Sea will freeze all the way down to Holland.
All that talk distracts your attention from the other end of this heat pipe. If the heat is not moved, the place where it was obtained will get hotter. This means that if the Gulf Stream slows down, the deep sea temperature in the Gulf of Mexico will rise. Suppose the Gulf Stream slowed down by 20%. This slow down would reduce the removal of heat from the Gulf of Mexico and surrounding areas by 280-billion kilowatts, 140 times the world's electricity production. You can count on seeing the effect of that. The sea will evaporate more water and power stronger hurricanes, and the deeper water will warm up.
You might think a 20% slow down is so remotely unlikely you need not worry about it. You would be wrong. Five years ago, Dr Bill Turrell of the Marine Laboratory in Aberdeen is reported as having observed exactly that. Armed with this information the origin of the strength of Hurricane Katrina is obvious. The weaker Gulf Stream had not removed the heat from the water in the Gulf of Mexico and the increased evaporation created the extra strength in Katrina and in the more recent Ike tornado. Unless the Gulf Stream flow picks up, the United States must expect more events like that.
What has this got to do with methane and those unpronounceable clathrates, you ask. Well it turns out there are a lot of clathrates on the sea floor in the Gulf of Mexico. One particular deposit is estimated to store 10 cubic kilometres of methane on its own. Now hurricanes are bad, but what is worse is that the heat is likely to melt these deposits, and if the surface temperatures are already close to 30-degrees Celsius, how long will the water temperature at the sea floor stay close to 15 degrees Celsius? Once the temperature gets too high, the ices melt. That will release hundreds of cubic kilometres of methane presently sitting on the sea floor in the Gulf. The trigger for the Clathrate Gun might be just south of New Orleans.
So what can we do about this impending Armageddon? I recommend two things. Firstly, we want research to find out which clathrates are in danger of releasing methane, and how much, and when. Secondly, the world should encourage Japan to pursue its exploratory attempts to mine the sea floor clathrates. If they could just mine the deposits likely to melt, we might be able to stave off the looming extinction level event. Our government can help with these activities. They need to be encouraged to provide that help.
Robyn Williams: So, that's one of those clear examples of a positive feedback mechanism people refer to when speaking of the urgency, when tackling climate change. There could be a point beyond which you simply can't do anything because the chaos is too huge.
Geoff Hudson in Melbourne is a computer specialist.
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