Warming hits 'tipping point'

Siberia feels the heat It's a frozen peat bog the size of France and Germany combined, contains billions of tonnes of greenhouse gas and, for the first time since the ice age, it is melting

Ian Sample, science correspondent
Thursday August 11, 2005
The Guardian

A vast expanse of western Sibera is undergoing an unprecedented thaw that could dramatically increase the rate of global warming, climate scientists warn today.
Researchers who have recently returned from the region found that an area of permafrost spanning a million square kilometres - the size of France and Germany combined - has started to melt for the first time since it formed 11,000 years ago at the end of the last ice age.

The area, which covers the entire sub-Arctic region of western Siberia, is the world's largest frozen peat bog and scientists fear that as it thaws, it will release billions of tonnes of methane, a greenhouse gas 20 times more potent than carbon dioxide, into the atmosphere.
It is a scenario climate scientists have feared since first identifying "tipping points" - delicate thresholds where a slight rise in the Earth's temperature can cause a dramatic change in the environment that itself triggers a far greater increase in global temperatures.

The discovery was made by Sergei Kirpotin at Tomsk State University in western Siberia and Judith Marquand at Oxford University and is reported in New Scientist today.

The researchers found that what was until recently a barren expanse of frozen peat is turning into a broken landscape of mud and lakes, some more than a kilometre across.

Dr Kirpotin told the magazine the situation was an "ecological landslide that is probably irreversible and is undoubtedly connected to climatic warming". He added that the thaw had probably begun in the past three or four years.

Climate scientists yesterday reacted with alarm to the finding, and warned that predictions of future global temperatures would have to be revised upwards.

"When you start messing around with these natural systems, you can end up in situations where it's unstoppable. There are no brakes you can apply," said David Viner, a senior scientist at the Climatic Research Unit at the University of East Anglia.

"This is a big deal because you can't put the permafrost back once it's gone. The causal effect is human activity and it will ramp up temperatures even more than our emissions are doing."

In its last major report in 2001, the intergovernmental panel on climate change predicted a rise in global temperatures of 1.4C-5.8C between 1990 and 2100, but the estimate only takes account of global warming driven by known greenhouse gas emissions.

"These positive feedbacks with landmasses weren't known about then. They had no idea how much they would add to global warming," said Dr Viner.

Western Siberia is heating up faster than anywhere else in the world, having experienced a rise of some 3C in the past 40 years. Scientists are particularly concerned about the permafrost, because as it thaws, it reveals bare ground which warms up more quickly than ice and snow, and so accelerates the rate at which the permafrost thaws.