7 September 2006

Pleistocene Era Methane Adds To Greenhouse Misery

by Kate Melville

A Florida State University (FSU) scientist says that as the permafrost in Northern Siberia melts because of climate change, methane frozen there since the Pleistocene era will be released into the atmosphere, further fueling the greenhouse effect.

FSU's Jeff Chanton explained that methane's contribution to the greenhouse effect is more than 20 times that of carbon dioxide. Even worse, the methane now melting after 40,000 years will encourage a feedback mechanism, warming the climate and releasing even more of the methane. The study, published in Nature, paints a gloomy picture of permafrost decomposition accelerating further because of this feedback mechanism. "This is not good for the quality of human life on Earth," Chanton lamented.

Measuring the methane bubbling from two Siberian lakes revealed the world's northern wetlands as a much larger potential source of atmospheric methane than previously believed. Worryingly, Chanton's findings have increased these estimates by up to 63 percent.

Chanton said that understanding the contribution of North Siberia thaw lakes to global atmospheric methane is critical, because the concentration of that potent greenhouse is highest at that latitude. Additionally, methane levels have risen sharply in recent decades and exhibit a significant seasonal jump at those high northern latitudes.

Chanton believes the thawing permafrost along the margins of the thaw lakes are the primary source of methane released in the region. "My fellow researchers and I estimate that an expansion of these thaw lakes between 1974 and 2000, a period of regional warming, increased methane emissions by 58 percent there," said Chanton. "Because the methane now emitted in our study region dates to the Pleistocene age, it's clear that the process, described by scientists as 'positive feedback to global warming,' has led to the release of old carbon stocks once stored in the permafrost."

Source: Florida State University