Record CO2 emissions as ice sheets shrink

Posted: 14 March 2006

Confirmation that the planet is warming, and indications that the climate is changing faster than previously thought, are now becoming almost daily events. Today comes news of record CO2 levels, and fresh evidence that the enormous ice sheets covering both Greenland and Antarctica are showing a net loss of ice to the seas.

The first report from the US National Oceanic and Atmospheric Administration (NOAA) says that scientists have recorded a significant rise in the concentration of carbon dioxide in the atmosphere, pushing it to a new record level.

Snowmelt on the Greenland ice sheet. The dark red area represents the extent of snowmelt in 2005. Photo: NOAA and CIRES
Snowmelt on the Greenland ice sheet. The dark red area represents the extent of snowmelt in 2005. Photo: NOAA and CIRES
Satellites are used to map the extent and duration of snowmelt on the Greenland ice sheet. The dark red area represents the extent of snowmelt in 2005, three years beyond Dr. Zwally's survey. It is the most extensive in the 27 year history of data collection.© NOAA and CIRES)
According to BBC science correspondent David Shukman the latest data shows CO2 levels now stand at 381 parts per million (ppm) - 100ppm above the pre-industrial average.

The research indicates that 2005 saw one of the largest increases on record - a rise of 2.6ppm.

Following analysis of air taken from all over the world, the chief carbon dioxide analyst for NOAA says the latest data confirms a worrying trend that recent years have, on average, recorded double the rate of increase from just 30 years ago.

"We don't see any sign of a decrease; in fact, we're seeing the opposite, the rate of increase is accelerating," Dr Pieter Tans told the BBC. Climate scientists fear certain thresholds of greenhouse gases may be "tipping points" that trigger sudden changes.

The UK government's chief scientific adviser, Professor Sir David King, said the new data highlighted the importance of taking urgent action to limit carbon emissions.

"Today we're over 380 ppm," he said. "That's higher than we've been for over a million years, possibly 30 million years. Mankind is changing the climate."

Net loss of ice

The second piece of evidence also comes from the United States where the most comprehensive survey ever undertaken by NASA scientists shows a net loss of ice from the combined polar ice sheets of both Greenland and Antarctica between 1992 and 2002, and a corresponding rise in sea level.

Antarctica lost more ice to the sea than it gained from snowfall, resulting in sea level rise.Photo: NASA/SVS
Antarctica lost more ice to the sea than it gained from snowfall, resulting in sea level rise.Photo: NASA/SVS
Antarctica lost more ice to the sea than it gained from snowfall, resulting in sea level rise.© NASA/SVS
According to the Environment News Service (ENS) the survey shows that 20 billion tons of water melted into the oceans in each of those 10 years. It was accompanied by extensive thinning of the West Antartica ice shelves, an increase in snowfall in the Greeland interior, and a thinning of the ice at its edges.

If thse trends continue, the polar ice sheets could change dramatically, said the survey lead author, Dr H.Jay Zwally, of NASA's Godard Space Flight Center in Maryland. "The Greenland ice sheet could be facing irreversible decline by the end of the century," he said.

If that happens, says Dr Peter Clark and other climate researchers at the Oregon State University, sea levels would be raised by about 20-25 feet. One predication is that sea levels could rise by a foot or two by 2100 and by up to 25 feet within 500 years.

Sources: BBC News and ENS. The NASA survey report by Dr Zwally appears in the March 8 issue of the Journal of Glaciology.

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