The Earth's current warming is looking similar to what took place 55 million years ago, writes David Bond. And if it works out that way, the news is good: we may avoid a mass extinction. On the other hand, the poles will melt away completely, and it will take hundreds of thousands of years for Earth to get back to 'normal'. It is often said that humans have caused the Earth to warm at an unprecedented rate. However researchers have discovered another period, some 55m years ago, when massive volcanic eruptions pumped so much carbon into the atmosphere that the planet warmed at what geologists would think of as breakneck speed. The good news is that most plants and animals survived the warm spell. The planet has experienced several mass extinctions – and this wasn't one of them. But there's a catch: even after carbon levels returned to their previous levels, the climate took 200,000 years to return to normal.