Silly Thinking

Pretend we're on Krypton and George Monbiot is Marlon Brando:




The events which brought the Permian period (between 286 and 251 million years ago) to an end could not be clearly determined until the mapping of the key geological sequences had been completed. Until recently, palaeontologists had assumed that the changes which took place then were gradual and piecemeal. But three years ago a precise date for the end of the period was established, which enabled geologists to draw direct comparisons between the rocks laid down at that time in different parts of the world.

Having done so, they made a shattering discovery. In China, South Africa, Australia, Greenland, Russia and Spitsbergen, the rocks record an almost identical sequence of events, taking place not gradually, but almost instantaneously.

[snip]

Some scientists have argued that the mass extinction was caused by a meteorite. But the evidence they put forward has been undermined by further studies. There is a more persuasive case for a different explanation. For many years, geologists have been aware that at some point during or after the Permian there was a series of gigantic volcanic eruptions in Siberia. The lava was dated properly for the first time in the early 1990s. We now know that the principal explosions took place 251 million years ago, precisely at the point at which life was almost extinguished.

The volcanoes produced two gases: sulphur dioxide and carbon dioxide. The sulphur and other effusions caused acid rain, but would have bled from the atmosphere quite quickly. The carbon dioxide, on the other hand, would have persisted. By enhancing the greenhouse effect, it appears to have warmed the world sufficiently to have destabilised the super concentrated frozen gas called methane hydrate, locked in sediments around the polar seas. The release of methane into the atmosphere explains the sudden shift in carbon isotopes.

Methane is an even more powerful greenhouse gas than carbon dioxide. The result of its release was runaway global warming: a rise in temperature led to changes which raised the temperature further, and so on. The warming appears, alongside the acid rain, to have killed the plants. Starvation then killed the animals.

Global warming also seems to explain the geological changes. If the temperature of the surface waters near the poles increases, the circulation of marine currents slows down, which means that the ocean floor is deprived of oxygen. As the plants on land died, their roots would cease to hold together the soil and loose rock, with the result that erosion rates would have greatly increased. So how much warming took place? A sharp change in the ratio of the isotopes of oxygen permits us to reply with some precision: six degrees centigrade. Benton does not make the obvious point, but another author, the climate change specialist Mark Lynas, does.2 Six degrees is the upper estimate produced by the UN's scientific body, the Intergovernmental Panel on Climate Change, for global warming by 2100.3

A conference of some of the world's leading atmospheric scientists in Berlin last month concluded that the IPCC's model may have underestimated the problem: the upper limit, they now suggest, should range between 7 and 10 degrees.4 Neither model takes into account the possibility of a partial melting of the methane hydrate still present in vast quantities around the fringes of the polar seas.

Suddenly, the events of a quarter of a billion years ago begin to look very topical indeed. One of the possible endings of the human story has already been told. Our principal political effort must now be to ensure that it does not become set in stone.