The vast Arctic B次元官网网址渃ompostB次元官网网址� is thawing, dumping billions of tonnes of carbon dioxide into the atmosphere, which has been unaccounted for in global climate models,

University of Victoria graduate students Andrew MacDougall and Chris Avis, along with noted climate scientist Andrew Weaver, made this claim in a study published this week by Nature Geoscience Letters.

The team used UVicB次元官网网址檚 coupled global climate model, a system originally derived from weather forecasting, to conclude that melting permafrost B次元官网网址� frozen soil, sediment or rock B次元官网网址� could release between 68 and 508 billion additional tonnes of carbon into the atmosphere over the next 90 years, raising global temperatures by an average of 0.4 to 0.8C on top of what has been previously estimated.

B次元官网网址淚tB次元官网网址檚 basically frozen compost,B次元官网网址� MacDougall said. B次元官网网址淚tB次元官网网址檚 grasses and manure and bits of animals that have gotten frozen into the permafrost over thousands of years, so you have this frozen material that canB次元官网网址檛 decay, then you melt the permafrost suddenly.

B次元官网网址淛ust as if you unfroze compost in your garden, it would start to rot, but it does so very slowly over the course of a hundred years.B次元官网网址�

About 18.8 million square kilometres of northern tundra holds about 1,700 billion tonnes of organic carbon, or about four times more than all the carbon emitted by human activity in modern times, and twice as much than is currently in the atmosphere.

Given that global temperatures have already risen by about 0.8C since the Industrial Revolution, limiting global warming to less than 2C B次元官网网址� the goal identified in the 2009 Copenhagen Accord B次元官网网址� doesnB次元官网网址檛 leave much room for future emissions, MacDougall said.

B次元官网网址淲hat weB次元官网网址檝e been trying to do more lately is trying to find emissions pathways that allow you to stay below two degrees. This makes that a lot harder. B次元官网网址� Not impossible, but difficult.B次元官网网址�

To stay below the 2C threshold, humans will have to make B次元官网网址渧ery large and immediate reductions in emissions,B次元官网网址� he noted.

B次元官网网址淏usiness as usualB次元官网网址� scenarios, MacDougall said, usually account for a three-to-four degree rise in temperatures by 2100. The new model would drive temperatures up an additional 10 per cent and more after the 21st century.

nnorth@saanichnews.com