Methane is number two among the man-made climate warmers worldwide. Its concentration in the atmosphere has increased threefold since the industrial revolution. But with more warming, the worst could still be to come.
 | Seeping gas burns in the Cataract River bed west of Sydney, Australia. The methane gas leaks through cracks in the bedrock, which has been blamed on mining in a coal deposit 400 meters below (Photo: Reuters) |
Contribution to Human-Induced Climate Change: 23 percent
Global Warming Potential (100 years): 25 times stronger than CO2
Methane, the second most important greenhouse gas after carbon dioxide and the primary component of natural gas, is virtually omnipresent. The odorless, colorless gas leaks from the Earth’s mantle through volcanoes, vents from the stomachs of millions of livestock, rises from wetlands, marshes, and coal mines, and bubbles up from all things decaying.
The bad news first: Methane’s warming effect over a period of 100 years is 25 times stronger than that of CO2. Fortunately, methane appears in lower concentrations and disappears faster from the atmosphere than CO2. After about seven years, half of all methane emissions have transformed into water and carbon dioxide, a greenhouse gas in its own right.
Since 1750 methane levels have increased by about 150 percent, according to the UN Intergovernmental Panel on Climate Change. This has been responsible for about a fifth of the enhanced greenhouse effect over the past 200 years.
For the last decade, however, methane emissions had somehow stabilized and even decreased slightly, while carbon dioxide levels increased rapidly. Scientists finally figured out that this was due to the fact that many wetlands were being drained for agricultural use, the increased capture of methane from landfills, and reduced emissions from the production of natural gas. But methane emissions have started to rise again due to increased consumption of fossil fuels in Asia. And an even bigger time bomb is ticking.
 | Greenhouse Gas Gallery (click on the image to start)Discover ten of the most important sources of man-made greenhouses gases (Photo: Reuters) |
A lot of methane is trapped in permafrost soils and under the world’s oceans. Scientists fear that these deposits could be freed by further global warming. This would cause more warming and, in a vicious cycle, the release of even more methane thereby triggering runaway climate change.
Permafrost soil in Siberia has started to melt for the first time since it formed 11,000 years ago at the end of the last ice age. It now threatens to release billions of tons of methane. According to Larry Smith, a hydrologist at the University of California, the west Siberian peat bog alone could hold some 70 billion tons of methane, a quarter of all of the methane stored in the ground around the world.
More methane could come from melting methane deposits in ocean seabeds if water temperatures rise sufficiently. Scientists speculate that large, sudden releases of methane have in the past resulted in periods of rapid global warming and mass extinction events.
Once such a destructive feedback loop is triggered, humanity has little chance of halting runaway climate change. Preventing further methane release is thus one of the most important reasons to fight global warming, and methane’s short life span makes it a critical target for immediate action.
One of the most convenient strategies to reduce methane emissions is burning the excess gas that rises from landfills, natural gas production sites, or other natural sources. However, this releases CO2 into the atmosphere, also a greenhouse gas but with a lower global warming potential.
Even better is using the methane to power gas turbines or fuel cars. A number of farmers now use their animals’ manure to produce methane for heating or electricity, while landfills and gas producers switch from simply flaring the gas to actually using it as a source of energy.
Nitrous Oxide - Nothing to Laugh About
Carbon Dioxide - Endless Warming
editor: Thilo Kunzemann
publishing date: November 27, 2008
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