Has Global Warming passed the "Tipping Point"?

News articles in today's British papers, The Guardian (Warming hits 'tipping point') and The Telegraph (Melting bog may lead to 'ecological landslide'), discuss the findings of research teams that have returned from Siberia. An area of the permafrost, larger than the size of Germany and France combined, is melting for the first time since its formation during the last ice age.

What effect will this have?

From The Telegraph:

A melting permafrost peat bog stretching across an area the size of France and Germany could unleash billions of tons of greenhouse gas into the atmosphere

and from The Guardian:

It would effectively double atmospheric levels of the gas, leading to a 10% to 25% increase in global warming

Methane is a greenhouse gas, which is estimated to be twenty times more harmful than carbon dioxide. The additional release of this gas makes all the current attempts to predict future temperatures greatly underestimated.

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.

The thawing of the permafrost is a one of "these positive feedback with landmasses". When the permafrost melts it exposes more ground. The ground absorbs more heat from the sun than the frozen ice and snow. The additional heat absorbed increases the rate of the thawing permafrost.

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 Guardian article ends with a reference to New Asia-Pacific Partnership on Clean Development and Climate and the failure of the G8 summit to deal with climate change:

Last month, some of the world's worst air polluters, including the US and Australia, announced a partnership to cut greenhouse gas emissions through the use of new technologies.

The deal came after Tony Blair struggled at the G8 summit to get the US president, George Bush, to commit to any concerted action on climate change and has been heavily criticised for setting no targets for reductions in greenhouse gas emissions.