Arctic Warming Faster say US Scientists

Climate change is continuing to progress in the Arctic, according to the first annual edition of an "Arctic Report Card" issued by a US-led team of scientists.

Although the ozone layer over the Antarctic this year is relatively small, this is due to mild temperatures in the region’s stratosphere this winter and is not a sign of recovery, the United Nations World Meteorological Organization (WMO) said last week.

Since 1998, only the ozone holes of 2002 and 2004 have been smaller than this year’s – both in terms of area and amount of destroyed ozone – and this is not indicative of ozone recuperation, the agency said in a press release. Instead, it is due to mild temperatures in the stratosphere, which still contains sufficient chlorine and bromine to completely destroy ozone in the 14-21 kilometer altitude range.

The amount of gases which diminish ozone in the Antarctic stratosphere peaked around the year 2000. However, despite the decline in the amount by 1 per cent annually, enough chlorine and bromine will be in the stratosphere for another decade or two, which could result in severe ozone holes, WMO said.

The size of the ozone hole will also be determined by the stratosphere’s meteorological conditions during the Antarctic winter. As greenhouse gases accumulate in the atmosphere, temperatures will fall in the stratosphere, increasing the threat of severe ozone holes in the future.

While some elements of the complex Arctic climate system and its associated ecosystems showed a stabilisation in warming, observations collectively indicated that the overall warming of the Arctic as a whole continued in 2007, the scientists said. Some changes are larger and happening faster than previously predicted by supercomputer climate models.

"The bottom line is we are seeing some rapid changes in the Arctic," said Richard Spinrad, assistant administrator for oceanic and atmospheric research at the National Oceanic and Atmospheric Administration which released the report this week. The most dramatic of these has been the reduction in the extent of summer sea ice, which at the end of the melting season in September this year was at a record low – 23 per cent below the previous record, set in 2005. It was 39 per cent below the average over the period 1979 to 2001.

On land, the annual surface temperature over areas north of 60°N was 1.0C above the mean value for the 20th century in 2006, the scientists said. This year, winter and spring temperatures were all above average throughout the whole Arctic, said James Overland, of the Pacific Marine Environmental Laboratory.

"If you go back 100 years, it would be warm in one part of the Arctic and cold in another," he said. "We're not getting that now. This is unusual and looks like the beginning of a signal from global warming."