BONN - Scientists issued a dire warning Tuesday to UN climate negotiators in Bonn of a vicious global warming cycle that will be unlocked with the thawing of carbon-bearing permafrost.
There may be 1,500 billion tonnes of carbon locked away in permafrost - perennially frozen ground covering about a quarter of exposed land in the Northern Hemisphere - said Susan Natali, a researcher with the Woods Hole Research Center in Massachusetts.
The carbon will be released incrementally as global temperatures rise on the back of soaring emissions from mankind's voracious burning of fossil fuels, making permafrost a vast and underestimated source of future greenhouse gas emissions, said Natali.
"By 2100 we expect 130 to 160 gigatonnes of carbon released into the atmosphere," Natali told journalists in Bonn. "That is on par with our current rate of US emissions as a result of fossil fuel and cement production."
Country negotiators in Bonn are seeking to streamline a draft global climate pact, which is scheduled to be adopted at a UN conference in Paris in December.
Delegates however say the talks have been bogged down in procedural wrangling since they opened last Monday.
The amount of carbon stored in permafrost, where it has accumulated over tens of thousands of years, is estimated to be about twice as much as that in the atmosphere, she said.
Natali co-authored a scientific paper on the greenhouse gas threat posed by thawing permafrost, which was published in the journal Nature in April.
But the data came too late to be included in the latest warming projections of the Intergovernmental Panel on Climate Change - the UN's top science panel for climate.
The team projected permafrost loss of between 30 and 70 per cent by 2100, depending on the world's emissions trajectory.
The lower estimate is based on a pathway of strict cuts that achieves the UN goal of limiting overall global warming to two degrees Celsius (3.6 degrees Fahrenheit) over pre-Industrial Revolution levels, and the highest on unrestrained emissions.
The global pact being crafted by UN negotiators will be supported by a roster of national pledges for emissions curbs, which observers say are not yet nearly ambitious enough to achieve the two degrees goal.
"The actions that we take now in terms of our fossil fuel emissions are going to have a significant impact on how much permafrost is lost and in turn how much carbon is released from permafrost," Natali said on the sidelines of the Bonn talks.
"While there is some uncertainty, we know that permafrost carbon losses will be substantial, they will be irreversible," she added.