Lost: enough ice to cover California, according to the National Snow and Ice Data Centre (NSIDC) 18 February 2009 and Bloomberg.com 20 Feb 2009. The extent of ice covering the Arctic Ocean in January and February 2009 was underestimated by about 500,000 square kilometres (193,000 square miles), an area about the size of California, due to a problem with one of the satellite sensors used to monitor the ice. The problem was 'sensor drift' and NSIDC scientists were alerted to it when "puzzled readers" asked NSIDC about reports that showed ice covered areas as open ocean. NSIDC has since recalculated the sea ice extent using data from another satellite and is conducting a quality control check. The centre also said "There is a balance between being as accurate as possible at any given moment and being as consistent as possible through long time-periods. Our main scientific focus is on the long-term changes in Arctic sea ice."

Editorial Comment: The experience of NSIDC's "puzzled readers" shows there is nothing like the direct observations of people who are there to get an accurate record of what is really happening. Nevertheless, NSIDC are right about the importance of keeping the big picture in mind, and their records are a good illustration of the big picture of sea ice. As more and more catastrophic predictions about the world drowning from melting sea ice, NSIDC's records show that sea ice undergoes regular cycles of melting and freezing and after thirty years of records the sea ice is back to being the same as it was in 1979, when the records begin. (Ref. polar, climate, mapping)

Evidence News 8 April 2009