Greenhouse gases may not be the only reason the Arctic is thawing so rapidly.
A report released Wednesday at an international meeting in Norway says scientists have discovered a new factor behind the surprisingly rapid meltdown -- so-called "black carbon," otherwise known as soot.
"It's something that has been growing up over the last two years," said Lars-Otto Reiersen, who worked with the researchers who wrote the report. "We started to look into it two years ago."
The report was written for the Arctic Council made up of Canada and seven other nations that ring the North Pole. High-level officials from all eight countries, including Foreign Affairs Minister Lawrence Cannon, have been in Tromso, Norway, this week for meetings.
Scientists have been puzzled for years about why Arctic sea ice is melting faster than climate models predict. Reiersen said black carbon might be part of the answer.
"This could maybe one of the factors that could be intervening in the melt, why all the models that focus on CO2 are too conservative, that the reality goes faster than the models," he said on the phone from Oslo, Norway.
Most of the black carbon in the Arctic comes from the mid-latitudes of the Northern Hemisphere and is released from diesel engines and burning wood.
Burning agricultural fields to clear them, still done in Europe, is also a contributor. So is the flaring of natural gas from oil wells -- something widely practised in Russia.
Research in the report shows that tiny particles of soot can reach the Arctic through air currents in just a few days. Some of those particles hang around in the atmosphere, absorbing sunlight and warming the air. The rest fall to the ground, where their darker colour speeds the melting of snow and ice.
The report suggests that black carbon may be responsible for more than 20 per cent of all Arctic warming, with the effect most pronounced in the late winter and spring.
Problem could be 'easily handled'
The good news is that black carbon could be relatively easy to clean up. That would buy the international community time to deal with the much more complex issue of carbon dioxide emissions.
"There are easy to put in place some actions that can be in operation within a few years while you are getting the CO2 negotiations in place," said Reiersen.
New-generation diesels emit far fewer particulates, he said. As well, activities such as gas flaring and agricultural burning could be relatively easy to control.
"These are some sources of contaminant that can be easily handled."
An existing international treaty regulating the emissions that produce ozone and acid rain could be modified to cover black carbon as well, Reiersen suggested.
"You don't need to negotiate a new treaty. You can use the one you have and just expand it."
Finally, black carbon is considered a short-lived contaminant, so choking off its sources would produce relatively quick results.
The report says that reducing black carbon emissions by one tonne would have the same effect over a 20-year period as a 2,000-tonne reduction in CO2 emissions.
In a statement at the close of the Arctic Council meeting, the various governments agreed to establish a task force on short-lived "climate forcers" such as black carbon to identify ways to cut the amount released.
