Department of bad signs: Arctic sea ice trending below 2007 melt

Dan Shapley in the Daily Green: The annual melting of Arctic sea ice is trending toward another record-low. While it's still too early to say whether the 2009 melt will exceed the record 2007 melt -- the annual low-point isn't reached until September -- the trend line for 2009 for the first time has dipped below 2007, according to the latest data from the National Snow and Ice Data Center.

Another record would be startling, but not surprising. Just 30% of the sea ice in the Arctic at the height of the winter freeze was thicker multi-year ice, leaving 70% susceptible to rapid melting. The amount of ice in the Arctic as of February 2009 -- the height of the annual freeze -- was the lowest on record. Most arctic scientists now say they expect an ice-free Arctic in summer within the next three decades...

…The melting of Arctic sea ice is one of the clearest signals of global warming, and a leading indicator of what is to come. The melting is also an example -- one of many -- of a positive feedback loop that scientists expect will accelerate global warming: As sea ice melts, the darker water that is exposed absorbs more of the sun's energy, which leads to warmer waters and more melting ice…..

Arctic sea ice extent for May 2009, was 13.39 million square kilometers (5.17 million square miles). The magenta line shows the 1979 to 2000 median extent for that month. The black cross indicates the geographic North Pole. Image from the National Snow and Ice Data Center