Methane gas released by peat bogs in the northern-most third of the globe probably helped fuel the last major round of global warming, which drew the ice age to a close between 11,000 and 12,000 years ago, UCLA and Russian Academy of Sciences scientists have concluded.
But the new information in no way lets human sources of greenhouse gases off the hook for the present round of global warming, warn the team of researchers whose findings appear in the Oct. 13 issue of Science.
"If anything, our findings show just how sensitive the planet's environment is to change and just how complex the results of these changes may be," said Glen M. MacDonald, the lead author of the study and a UCLA climate change scholar.
As the incipient bogs were strong producers of methane, the findings help solve a long-standing mystery about the source of a massive infusion of atmospheric methane that helped raise the Earth's surface temperature following the ice age.
"Scientists have long known that the northern bogs produce methane, but until now they were generally dismissed as the source of this change at the close of the last ice age because they were thought to have formed too slowly and too late to be a factor," said Laurence C. Smith, a UCLA professor of geography and study coauthor. "The initial development of the huge complex of northern bogs that now cover 1.54 million square miles occurred earlier than previously thought."
With funding from the National Science Foundation, MacDonald, Smith and four other researchers cored 84 peat bogs in Siberia. By radiocarbon dating the samples, they were able to reconstruct the timing of initial bog development. The researchers then assembled previously gathered radiocarbon dates for an additional 1,432 peat bogs throughout Northern Europe, Asia and North America, including Greenland.
They then compared the formation dates for these 1,516 bogs with high-resolution ice core records of t
Contact: Meg Sullivan
University of California - Los Angeles