Clues from the bog

Analysis of sediments from a British bog suggest that methane emissions increased around 55 million years ago due to intense global warming.

Dr Richard Pancost from Bristol University and his colleagues have shown that carbon isotope values of hopanoids – compounds made by bacteria – suddenly decrease in a manner that can only be explained by switching to a diet of methane. This suggests that methane emissions  must have increased at that time.

The team from Bristol University, Royal Holloway and other institutions analysed the geochemical composition of sediments taken from the Cobham Lignite wetland in southeast England, revealed when the Channel Tunnel rail link cut through it.

Fifty-five million years ago, a massive release of carbon into the atmosphere caused significant global warming.  It is likely that this warming and associated climate change caused a change in environmental conditions that brought about increased methane emissions. This in turn, may reflect an increase in methane production and subsequent release from the terrestrial biosphere,' said Dr Pancost.