Did the North Atlantic's 'birth' warm the world?

The volcanic eruptions that created Iceland might also have triggered one of the most catastrophic episodes of global warming ever seen on Earth, a new study suggests.

Michael Storey at Roskilde University in Denmark and colleagues have found evidence that a huge volcanic eruption, 55 million years ago, unleashed so much greenhouse gas into the atmosphere that world temperatures rose by as much as 8°C – with the Arctic ocean reaching a toasty 25°C.

"It was already a warm Earth, and it got a lot warmer," says Storey. The climatic turmoil that ensued was disastrous for most life, he says, killing off many deep-sea species.

Ancient ocean sediments that record this episode, called the Palaeocene-Eocene Temperature Maximum (PETM), also contain an unusually small amount of the heavier isotope of carbon, carbon-13. The sediments point to a sudden influx of available carbon dioxide or methane – which would explain the sudden warming – from some source with reduced carbon-13 levels.

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