Clues to climate change?
2007-09-20 15:03
London - An ancient British bog that
pumped out high amounts of greenhouse gases during a period of
global warming 55 million years ago may offer clues about future
climate change, researchers said on Wednesday.
An analysis of sediments from the bog suggests that global
warming caused methane emissions to rise in the wetlands, which
in turn sent temperatures there even higher, the researchers
said.
Scientists are interested in this period because the Earth
warmed fairly quickly as increased amounts of carbon dioxide
entered the atmosphere at a pace similar to what is happening
today, said Richard Pancost, a geochemist at Bristol University,
who led the study.
Greenhouse gases such as methane and carbon dioxide are
widely blamed for global warming. Scientists say average
temperatures will rise by two to six degrees Celsius by the end of the century, causing droughts, floods and violent storms.
"It is in the same ballpark of what we have done over the
past 100 years and what we might do over the next 100 years," Pancost said.
The team analysed sediments taken from a wetland in
southeast England that was unearthed during construction of a
rail link between London and Paris.
This section of exposed rock offered a clear sediment record
of changes in vegetation and indicated how global warming
affected the area tens of millions of years ago, Pancost said.
The researchers looked at molecular fossils that came from
bacteria and found that as temperatures rose, the organisms
switched to a diet of methane - probably because there was more
of it around, Pancost said.
"Methane is a very powerful greenhouse gas," he said. "So if the processes at (the bog) were widespread, then the increase in methane emissions could have caused further warming, amplifying the climate change at this time."
The bog became part of a vicious cycle - warmer
temperatures caused higher emissions of methane, which drove
temperatures even higher, he said.
"The main event made it warmer and wetter," Pancost said. "What we are talking about is a response to the system."
The researchers, who published their findings in the journal
Nature, cautioned that the data was only from a single site but
said it nevertheless shows how some ecosystems might respond to
rapid climate change in the future.
This means that warming could occur both because of more
carbon pumped into the atmosphere through the burning of coal
and oil and from the biological response of the individual
ecosystems, the team said.
"If wetlands exhibit similar response, they will produce
more methane and amplify the effect of global warming," he
Pancost said. "That is what we suggest happened 55 million years ago."