Tuesday, May 12, 2009

Global Sea-ice, Deceptive Reporting, and Truthful Lies

"The latest Arctic sea ice data from NASA and the National Snow and Ice Data Center show that the decade-long trend of shrinking sea ice cover is continuing." That statement, from the JPL, is dated April 2009. The actual data for northern hemisphere sea ice, measured as the deviation from its 1978-2000 mean, are shown below. The source is "The Cryosphere Today," a web site of the Polar Research Group, Department of Atmosphere Sciences, University of Illinois at Urbana-Champaign, not a site devoted to critics of global warming. If your browser doesn't show the complete graph, click on the image to get to the webbed original. Looking at the graph, the pattern is pretty clear. For about ten years, from 1997 to late 2007, the area of sea ice was decreasing. That trend then reversed, and the area has now been increasing for more than a year. The claim quoted from the JPL is a flat lie. Reading further in the article, one finds: "that this winter had the fifth lowest maximum ice extent on record. The six lowest maximum events since satellite monitoring began in 1979 have all occurred in the past six years (2004-2009)." That's a nice example of how to lie while telling the truth. The trend has reversed—whether temporarily or permanently we don't know. But since the area had been trending down for a decade and has only recently started to trend up, the current figure is still low relative to the past. Except for the recent past, which is all that is relevant in judging whether the current trend is continuing.