September 2, 2009 – Original Source: New Scientist, by Fred Pearce
Runaway warming of the Arctic threatens to spread climate havoc across the globe in the coming decades, according to a new study by the environment group WWF. But has the process already begun? Climate scientists meeting at the World Climate Conference in Geneva, Switzerland, where the report was launched today, are in two minds.
Some reckon the WWF report may understate future events. The report’s author, climate adviser Martin Sommerkorn, reckons 90 per cent of the Arctic’s surface permafrost could be lost by 2100. But Jerry Meehl of the US government’s National Center for Atmospheric Research at Boulder, Colorado, told the conference that unless humans curb their greenhouse gas emissions “there will be zero permafrost by 2100”.
Melting permafrost is likely to release huge volumes of methane, accelerating global warming faster than previous predictions, according to many speakers at the conference. Fears of such releases prompted another US government agency, the National Oceanic and Atmospheric Administration (NOAA), this week to start regular research flights over Alaska, sniffing for methane.
What it did last summer
Conversely, the WWF’s headline-grabbing claim that the disappearance of Arctic sea ice during summer 2007 was a tipping point in Arctic warming may be wide of the mark. Vicky Pope, head of climate change advice at Britain’s Met Office, said less ice disappeared in the summer of 2008. And that there had probably been even less melting there this year, though final reports will only come in over the next two weeks.
Met Office scientists reckon they know what really happened in 2007. “High pressure sat over the Arctic, which caused cloudless skies and extra melting,” Pope told New Scientist. “It was basically natural variability, and 2007 was an outlier.”
One theory discussed at the meeting is that the unusual high pressure was connected to the Pacific climate phenomenon called La Niña. But now its opposite, El Niño, is forming – reducing the chances of an Arctic refreeze next year.
“All this shows that we have to be careful not to assume that everything is caused by climate change,” said Pope. But, whatever the short-term swings, the long-term warming will get its way in the end.
Persistent warming has been making Arctic ice thinner. “So when we do get a sunny summer, the effects are much greater than in the past,” said Pope. The world, it seems, is skating on thin ice.