It turns out that digging the channel tunnel was good for more that just a high speed rail link with the rest of Europe: it might help us understand one of the many interconnected strands of our planet's ecosystem and climate.
During the (very slow) excavations on the British side of the tunnel, the engineers dug up a 55 million year-old bog, Cobham Lignite, the BBC reports.
According to research published in Nature, scientists led by Bristol University's Richard Paincost found a link between methane released by the ancient bogs (back in the day) and the dramatic and sustained warming of the Palaeocene-Eocene Thermal Maximum. This period saw an extremely rapid rise in global temperatures. In just a few thousand years, the global average went up at least five degrees.
"This is the first time that we have seen evidence from the geological record of methane cycling in response to a warming event," Dr Pancost told the BBC. "It provides insight into how some ecosystems could respond to rapid warming-induced changes in climate, and, therefore, how they could respond to warming in the future."
The researchers looked to hopanoids to tell them what had happened. These are chemicals made by bacteria, and they survive well over time. At the crucial transition point, the team found that the hopanoids altered: the ratio of the various isotopes of carbon shifted. They attribute this to a change in the amount of methane in the atmosphere.
Climate scientists have long suspected that methane could have played a major role in this long-ago sudden, planet-wide heating. Methane, after all, is an extremely efficient greenhouse gas. It insulates our planet roughly 20 times as well as carbon dioxide.
But methane is relatively short lived, and one sudden bubble of the gas erupting from the sea bed cannot explain the evidence of a sustained change in the atmosphere.
Instead, methane's short life-span suggests the bog itself was releasing the gas over a sustained period, as the warming planet set up a postive feedback loop: warming from methane triggers the release of more methane, which in turn triggers more warming.
The concern, of course, is that as the planet warms today, present day bogs will respond in a similar way. But the Bristol team warns against drawing too many conclusions. The conditions now are not like those 55 million years ago, and their data is from a single site, they say.
Scientific caution aside, Dr Pancost did tell the BBC that as wetlands and bogs get warmer, it implies a switch to anaerobic conditions, which would mean more methane.
"That's what's predicted, and that would be a positive feedback - and we have evidence now that this is what happened," he said. ®