NASA scientists have discovered that a huge release of methane from gas that had been frozen beneath the ocean floor heated the Earth by up to 13 degrees Fahrenheit 55 million years ago. They used a computer simulation to better understand the role of methane in sudden climate change in the far past. While today?s greenhouse gas studies focus on carbon dioxide, methane is 20 times more potent as a heat-trapping gas in the atmosphere.
In the last 200 years, atmospheric methane has been increasing, along with carbon dioxide. In fact, methane has more than doubled due to decomposing organic materials in wetlands and swamps and emissions from gas pipelines, coal mining, increases in irrigation and livestock flatulence.
However, there is another source of methane, formed from decomposing organic matter in ocean sediments, which is frozen in deposits under the seabed, just as it was over 50 million years ago. ?We understand that other greenhouse gases apart from carbon dioxide are important for climate change today,? says Gavin Schmidt, a researcher at NASA?s Goddard Institute for Space Studies in New York. ?This work should help quantify how important they have been in the past, and help estimate their effects in the future.?
Cold temperatures and high pressure are usually enough to keep methane stable beneath the ocean floor, but that might not always have been the case. A period of global warming, called the Late Paleocene Thermal Maximum (LPTM), occurred around 55 million years ago and lasted about 100,000 years. Scientists believe this was due to a vast release of frozen methane from beneath the sea floor, which led to the earth warming as a result of increased greenhouse gases in the atmosphere.
A movement of continental plates, in the area of the Indian subcontinent, may have initiated a release that led to the methane release, Schmidt says. Today we know that when the Indian subcontinent moved into the Eurasian continent, the Himalayas began forming. This uplift of tectonic plates would have decreased pressure on the ocean floor, and caused the large methane release. Once the atmosphere and oceans began to warm, more methane could have thawed and bubbled out. Scientists speculate that current global warming could eventually lead to a similar scenario in the future if the oceans warm up substantially.
?Ten years of methane is a blip, but hundreds of years of atmospheric methane is enough to warm up the atmosphere, melt the ice in the oceans, and change the whole climate system,? Schmidt says. ?If you want to think about reducing future climate change, you also have to be aware of greenhouse gases other than carbon dioxide, like methane and chlorofluorocarbons. It gives a more rounded view, and in the short term, it may end up being more cost-efficient to reduce methane in the atmosphere than it is to reduce carbon dioxide.?
So we may be able to keep driving gas-guzzling SUVs but have to figure out how to reduce cow flatulence? Stay tuned.
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