Fix the brakes first
Q: With the recent discovery that methane is bubbling out of the Arctic faster than expected, how worried should we be about abrupt changes in climate such as this one? Are there precautions we should be taking that both the political and scientific communities have been overlooking?
As concentrations of carbon dioxide (CO2) and other greenhouse gases continue to increase and warm the Earth there are numerous feedbacks that occur that can either moderate or accelerate the amount of warming. For example, increased cloud cover may reflect more of the sun's energy back into space, while reduction in Arctic sea ice may have the opposite effect, causing the darker ocean to absorb more heat. As temperatures warm, the release of CO2 from degrading organic matter in soils (mainly the remains of plants) and of methane (CH4) stored in frozen tundra soils or in ocean sediments further increase the concentrations of these greenhouse gases in the atmosphere, causing warming to accelerate. The geological record indicates that this is one of the ways by which climate change may be abrupt rather than gradual.
Scientists have long pointed out that global warming could accelerate if even modest warming of ocean waters caused the melting of a kind of ice called methane hydrates that is common in ocean sediment deposits lying under the cold waters of polar seas and elsewhere on the slopes around the continents. There are huge quantities of these methane hydrates stored in sediments, so much so that the National Research Council has just published a report assessing their potential for supplying natural gas resources long into the future. Furthermore, a molecule of methane has a greenhouse heat trapping effect thirty times greater than a molecule of CO2 and the concentration of methane in the atmosphere has already more than doubled since the industrial revolution. Consequently, alarm has been expressed because of the recent findings from the continental shelf north of Siberia suggesting that methane released from the melting of subsea permafrost under the Arctic Ocean may be much larger and faster than anticipated.
Is now the time to get frightened? In an answer that should surprise those who criticize climate scientists as alarmists, but actually reveals how science works, David Archer, an expert on the global carbon cycle, answers this question with an unqualified "no". We don't know whether the observed release of methane has increased over the last centuries and, unlike CO2, methane only lasts in the atmosphere for a decade. Archer points out that CO2 is plenty to be frightened of and remains the big story. In a brilliantly timed parable he explains: "Imagine you are in a Toyota on the highway at 60 miles per hour approaching stopped traffic, and you find that the brake pedal is broken. This is CO2. Then you figure out that the accelerator has also jammed, so that by the time you hit the truck in front of you, you will be going 90 miles per hour instead of 60. This is methane. Is now the time to get worried? No, you should already have been worried by the broken brake pedal". Moral of the parable: fix the brakes.
Posted by: stanassc | March 13, 2010 11:57 AM
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