OSLO : Arctic emissions of a powerful greenhouse gas jumped 30% in recent years in a worrying hint that global warming might unlock vast stores frozen in permafrost, scientists said on Friday.
"It's too early to call it a trend but if it continues this way there will be serious implications," said Paul Palmer, a scientist at Edinburgh University in Scotland who was among authors of the study of methane emissions from wetlands.
The 30.6 percent rise in emissions from the Arctic from 2003-2007, to about 4.2 million tonnes, was the biggest percentage gain for any region of the world's wetlands in the study in the journal Science with colleagues in Scotland and the Netherlands.
Arctic wetlands account for only 2 percent of global emissions from wetlands, most of which are in the tropics. But many experts have pointed to risks that climate change could melt permafrost stores of billions of tonnes of methane, a more potent greenhouse gas than carbon dioxide.
"It's a warning the scientists have been giving for a while now -- what we are seeing are signs of global warming," Palmer told Reuters of the study. Most Arctic wetlands are in Siberia and northern Canada.
Among greenhouse gases from human activities, methane contributes most to global warming after carbon dioxide. The scientists worked out emissions by matching satellite observations to an analysis of surface temperatures.
Temperatures in the Arctic are rising far faster than the global average because of global warming, blamed mainly on emissions from fossil fuels. A retreat of sea ice and snow cover exposes darker water or ground, which soaks up ever more heat.
"It is critical that we understand the extent of overlap between wetlands and regions that are most sensitive to projected future warming," the researchers wrote.
Palmer said several more years of data were needed to decide if the methane rise in the Arctic was the start of a trend or a mere blip. One problem is that current satellites will be going out of service in coming years.
And world methane emissions have been unpredictable -- the study noted that overall concentrations in the atmosphere from 1999-2006 were relatively stable, with renewed growth in 2007. The years of stability were "largely unexplained", they wrote.
Emissions from wetlands make up roughly a third of global methane emissions of 540 million tonnes, Palmer said. Other major sources are fossil fuels, livestock and rice paddies.
