IT HAS been the seventh warmest year on record, part of the hottest decade on record, but 2007, or at least its first 11 months, was also a time of climactic extremes.
It included record-low ice levels in the Arctic and a Western Australian summer five degrees hotter than average, yet also Australia's coldest June in recorded history.
According to a preliminary World Meteorological Organisation report released in Bali overnight, overall rising temperatures contrasted with an Australian June 1.5 degrees below average and an unusually cold South American winter that brought winds, blizzards and snowfall in unlikely places.
Other remarkable climatic events included the development of La Nina - a drop in sea surface temperature in the central and eastern equatorial Pacific by more than half a degree - and devastating floods, drought and storms across the globe.
Sea levels continued to rise substantially faster than the 20th century average of 1.7 millimetres a year - the current level is about 20 centimetres higher than the 1870 estimate, rising at about three millimetres a year since 1993. And the global average surface temperature has risen by 0.74 degrees since 1900, increasing at a much faster rate in the second half of the century.
The report, including data to the end of November, comes a month after the UN's Intergovernmental Panel on Climate Change described the evidence for man-made global warming as "unequivocal". It projected global temperatures increasing 1.1 to 6.4 degrees and sea levels rising by 18 to 59 centimetres this century, coinciding with worsening glacial melting, extreme weather conditions, water stress, hunger and disease.
The analysis is principally based on data collected by the UK Meteorological Office and the University of East Anglia. A second set of data in the report, by the US Department of Commerce, suggests 2007 may be the fifth warmest year globally.
Scientists yesterday said the record pace of ice melt in the Arctic Circle - allowing ships to sail for the first time through the Canadian Northwest Passage - was the latest sign that climate change was accelerating.
"In 2007, we had off-the-charts warming," University of Washington oceanographer Michael Steele said.
Donald Perovich of the US Army Cold Regions Research and Engineering Laboratory in New Hampshire, said an ice sheet about the size of the US covered the North Pole in the summer of 1980, but this northern summer the ice would not have covered the states west of the Mississippi River. As temperatures in the Pacific and Atlantic oceans have risen, warmer water has moved into the Arctic Ocean, helping melt the polar icecap, which this year floated in water about 3.5 degrees warmer than the historical average.
As more of the Arctic Ocean has been exposed, it has absorbed the extra sunrays, further hastening the rise in temperature.
Mr Perovich said: "It's a classic positive feedback. And these feedbacks are important from a climate perspective, because they can take small changes and amplify them."
Julianna Fessenden of the Los Alamos National Laboratory said it would be another 10 years before the first geosequestration plant allowing carbon dioxide from coal-fired power plants to be stored under ground, comes online.
With REUTERS
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