from drtimball.com: Recently I identified a counterattack trying to defend the failed anthropogenic global warming (AGW) hypothesis. Claims about Arctic ice melt this summer (2012) are another example. Data and analysis are wrong, but they need to scare a disinterested public. I know about arctic sea ice from flying ice and anti-submarine patrols on Canada’s east coat for four years then five years search and rescue in the Arctic. I later worked with members of the Canadian Polar Shelf Project and researchers producing Hudson Bay ice reconstructions. Claims of declining ice conditions use satellite records that produced results after 1980. Mark Serreze, Director of the National Snow and Ice Data Center (NSIDC) publicly attacked “anti-science misinformers” and used this data to claim sea ice is at a record low of 4.1 million sq. km. Anthony Watts shows this was belied by another NSIDC “new and improved” measure of 4.7 million sq. km. Apparently to deflect criticisms of conclusions from a short 32 year record, Kinnard et.al. (2008), and Walsh and Chapman produced reconstruction of past conditions. They say, “In order to extend diagnoses of recent sea-ice variations beyond the past few decades, a century-scale digital dataset of Arctic sea-ice coverage has been compiled. For recent decades, the compilation utilizes satellite-derived hemispheric datasets. Regional datasets based primarily on ship reports and aerial reconnaissance are the primary inputs for the earlier part of the 20th century.” These reconstructions have no value. As the Arctic Climate Impact Assessment (ACIA) said, “The observational database for the Arctic is quite limited, with few long-term stations and a paucity of observations in general.” If you can’t measure accurately with satellites, it’s impossible from the historic record. NSIDC’s different results between models illustrate the problem. Other agencies get different estimates again. NOAA says the ice level is 5.1 million sq..km. while NATICE interactive maps show over 6.1 million sq..km (diagram).