With the American Geophysical Union holding its annual fall meeting in San Francisco this week and the release of a new report from the U.S. Geological Survey, some interesting new developments in climate science have been made public in the last few days. Here are some of the climate change highlights:
Increase in Methane Release in Siberia
“Five years ago, I was not sure it’s very serious, but now I’m sure something is going on and we should warn people,” says Igor Semiletov from the University of Alaska in Fairbanks, chief scientist of the International Siberian Shelf Study, an oceanographic expedition that surveyed the entire Siberian coastline this summer. The study found methane bubbling up from the seafloor over hundreds of square kilometres in the Laptev and East Siberian Seas, according to Semiletov.
Water measurements indicate that methane concentrations were up to 200 times higher than the background levels, he says. In earlier, less extensive studies in the 1990s, Semiletov did not find such significant releases of methane. “Based on the newly obtained data, we suggest an increase of methane releases from the East Siberian Arctic Shelf,” he says.
Methane is a potent greenhouse gas, and scientists estimate that the Arctic permafrost — both on land and underwater — could hold trillions of tons of methane stored mostly in the form of frozen gas hydrates, says Semiletov. The submerged permafrost is on the threshold of melting, and air temperatures in the East Siberian Arctic Shelf have increased by as much as five degrees Celsius over the last decade, he says. “We didn’t know that this huge carbon pool is extremely vulnerable.”
Greenland Glaciers Melting Faster Than Projected
Across the Arctic from Siberia, Greenland was also keeping researchers busy this summer, as satellite measurements revealed record melting along the far northern margin of its ice cap. In most summers, temperatures rise enough to permit melting in that region on only 10–15 days on average. But in 2008, the melt period totalled 35 days. “It’s a place where you do not expect to see this extreme melting because it’s a northern area,” says Marco Tedesco of the City College of New York, who analyzed microwave data collected by a defence meteorological satellite.
Record melting also happened last summer along the edge of southwestern Greenland, Tedesco reported. The changes in 2008 mark a continuation of rapid climate change in Greenland over the past few years. Estimates based on satellite measurements of the entire ice cap suggest that the island is now losing hundreds of billions of tons of ice each year. In another example of extreme changes, a 29-square-kilometre patch broke off the end of the Petermann glacier in northern Greenland during the summer of 2008.
Permanet Drought in the American Southwest
“We simulate the future changes with our climate models, but those models have not always incorporated some of our latest data and observations,” said Peter Clark, a professor of geosciences at Oregon State University and a lead author on the report. “We now have data on glaciers moving faster, ice shelves collapsing and other climate trends emerging that allow us to improve the accuracy of some of our future projections.”
Some of the changes that now appear both more immediate and more certain, the report concludes, are rapid changes at the edges of the Greenland and West Antarctic ice sheets, loss of sea ice that exceeds projections by earlier models, and hydroclimatic changes over North America and the global subtropics that will likely intensify and persist due to future greenhouse warming.
“Our report finds that drying is likely to extend poleward into the American West, increasing the likelihood of severe and persistent drought there in the future,” Clark said. “If the models are accurate, it appears this has already begun. The possibility that the Southwest may be entering a permanent drought state is not yet widely appreciated.”
Sea Level Rise Could Be Higher Than Expected This Century
In related news the U.S. Geological Survey has published a stating that scientists have underestimated the potential level of sea level rise this century.
The risk presented by rising sea levels is likely to be far worse than official UN projections, according to a major new study from the US Geological Survey on the threats presented by “abrupt” climate change.
The report claims that while predictions on sea level changes arising from climate change are predictions are “highly uncertain due to shortcomings in existing climate models” the latest evidence suggests rises will “substantially exceed” UN estimates and could reach one and a half metres by the end of the century.
Such a rise would prove disastrous for vast areas of low lying land and coastal cities resulting in hundreds of millions of people be affected by flooding.
The UN’s Intergovernmental Panel on Climate Change’s most recent 2007 study predicted that sea levels would rise by between 28cm and 42cm by 2100.
However, the new US report, commissioned by the US Climate Change Science Program, claims that the latest observable evidence shows that glaciers in Greenland and the West Antarctic are sliding into the ocean significantly faster than was predicted by the models cited by the UN report. It claims that the potential for the melting of glaciers to accelerate further means that rapid increases in sea levels of over 150cm by the end of the century could result.
And to the annoyance of Climaticide denialists 2008 has turned out to be the 10th warmest year on record, continuing the trend of the last decade.
2008 10th Warmest Year in Recorded History
THE year 2008 is set to be the 10th warmest on record for the globe, with a temperature 0.31°C above average.
And Australia is on track for its 15th warmest year on record, with a temperature 0.37°C above average, according to the World Meteorological Organisation.
Senior Climatologist with the Bureau of Meteorology, Andrew Watkins, said 2008 was a La Nina year, in which the Pacific Ocean cools and temperatures tend to be lower across Australia.
“In spite of that La Nina event we still came out with the 15th warmest on record year for Australia,” he said.
Dr Watkins pointed out the preliminary global figure means 2008 was “warmer than all but two years in the previous century, so we are still seeing considerable warming here post-2000.”
He said many mid-latitude areas of the globe, including Australia, experienced drought in 2008. “We had drought in California and British Columbia in western North America. There was drought through Uruguay, Paraguay and Argentina in South America.