Planetary Watch: Earth to Exxon: Methane on the Rise Againby Bill Chameides | June 2nd, 2008
posted by Erica Rowell (Editor)
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As the Senate prepares to take up historic climate change legislation this week, Exxon Mobil’s CEO Rex Tillerson has taken a stance against moving toward renewable fuels, stating: “Anybody that tells you that they got this figured out is not being truthful. There are too many complexities around climate science… We have to let scientists continue their investigative work, unencumbered by political influences. This is too important to be cute with it.” In the meantime, a barely noticed, hardly “cute” scientific finding was announced: methane concentrations in the atmosphere are on the rise after several years of no change. Believe me, this is not good news.
So why should we care about this methane news? Methane, the main component of natural gas, is a naturally occurring greenhouse gas 25 times more potent than carbon dioxide, the most abundant global warming pollutant. Over the past century or so atmospheric concentrations of methane have doubled. This increase can largely be attributed to human activities, such as coal mining, increased cultivation of rice paddies, and increasing livestock populations (you may recall news stories about increased methane from cow “burps”).
While most of the excess greenhouse warming over the past century has come from carbon dioxide, increased methane levels have also made a significant contribution — about half that of carbon dioxide. So when methane levels stabilized in the late 1990s, the scientific community breathed a collective sigh of relief. Unfortunately, that was then. In 2007, for the first time since 1998, methane concentrations increased.
What Should We Make of the Uptick?
Is this increase indicative of a new upward trend in methane or just a 1-year blip? There is no way to know — yet. But what has me really worried is that preliminary analyses suggest that the methane increase may be coming from melting permafrost.
Permafrost refers to the huge expanses of land that remain at or below freezing for two or more years. Most of it is found in Canada, Alaska, and Siberia. Over the last decade or so scientists have been troubled by how much and how quickly permafrost has been melting because of global warming. Communities in Alaska, for instance, are seeing their roads buckle and their buildings tilt and fall as the ground softens underneath them. The government is having to relocate indigenous coastal communities where melting permafrost has resulted in widespread erosion.
A Vicious Cycle
It’s bad enough that indigenous communities like Shishmaref are in trouble. But there is also a global impact. Permafrost holds a huge reservoir of carbon. There is arguably more carbon stored in permafrost (perhaps 1,000 billion tons) than all the carbon dioxide in the atmosphere (750 billion tons). There are also large reservoirs of frozen methane (called methane hydrates or clathrates) in the permafrost. Estimates indicate that there could be hundreds of billions of tons of methane in these clathrates. If all that carbon went into the atmosphere as carbon dioxide and methane, you would have a catastrophic increase in the amount of greenhouse warming. Forget about the Greenland ice sheet. Start worrying about the survival of coral reefs and the Amazon rain forest. Worry about America’s vast legacy of forests, And worry about regional conflicts and growing geopolitical instabilities that could potentially dwarf those that are consuming us today.
Could the carbon in the permafrost find its way into the atmosphere? Most likely, yes. As permafrost melts, microbes come to life and begin chewing on that carbon transforming it into carbon dioxide and methane, which then leaks into the atmosphere as greenhouse warmers. Even more methane is released by the melting clathrates. Worse still, there is the possibility of a positive feedback or vicious cycle. Warming temperatures melt permafrost, releasing greenhouse gases, further increasing temperatures and causing more permafrost melting.
A Cautionary Tale: Past Methane Burst
Could that cycle feed on itself and end up releasing huge quantities of greenhouse gases into the atmosphere? Hard to say, but there is evidence that such a scenario has already occurred. In a recent paper in Nature, Martin Kennedy of University of California, Riverside, and his colleagues present data that suggest that “one of the most severe climate change events recorded in Earth history” 635 million years ago was caused by a positive feedback triggered by a destabilization of methane clathrates.
Scientists have not yet reached a consensus concerning the possibility of our seeing a similar rapid release of carbon from the permafrost anytime soon. Is that cause for complacency? I don’t think so. Methane is already seeping out of the permafrost at rates much greater than scientists had initially estimated. In my book that is cause for concern.
Mr. Tillerson and others of similar persuasion are, of course, correct — there is a lot left to debate concerning climate change science and policy. But such is the case with all science — it’s a constant learning process. And it is a rare event indeed when we are given the luxury of deciding with 100% certainty. In fact, we all routinely act in the face of imperfect knowledge and uncertainty. At some point enough of the jigsaw puzzle pieces are in place that you know what the basic picture is even though some pieces are still missing. The vast majority of my colleagues, myself included, believe there are enough climate change puzzle pieces in place that the time for action has arrived.
How certain do you need to be before you get serious about acting to avoid potential catastrophe? Imagine this. You are standing on the edge of a highway and a 50-ton truck is barreling down the road in your direction. Now, it’s possible the truck will whiz right by you, no harm done. But you can’t be sure. So what do you do? I bet you don’t play it “cute” — instead, you step away from the road. And you do it quick because you’re not quite sure how fast that truck is going — if you wait too long it might be too late. After all, you want to be on the safe side, don’t you?
filed under: carbon dioxide emissions, climate change, faculty, global warming, methane, Planetary Watch
and: climate, greenhouse gases