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September 02nd 2008 print

Keith Windschuttle

Chicken Little Logic

In the ancient fable, Chicken Little thought one acorn dropping on her head meant the entire sky was falling. Today’s Chicken Littles show similar insight.

In the ancient fable, Chicken Little thought one acorn dropping on her head meant the entire sky was falling. Today’s Chicken Littles show similar insight.

If there is a one centimetre sea rise through ice-sheet melting in the decade 2005 to 2015, and if that rate doubles in every subsequent decade, by 2095 the sea level will have risen by more than five metres … In a major and inspiring speech, Al Gore, the Winston Churchill of our age, issued a call for his country to move from a fossil-fuel to a renewable-energy economy within a decade.

— Robert Manne, ‘The Nation Reviewed’, The Monthly, August 2008

If Greenland’s ice sheet melts, the world sea level will rise 20 feet [6.1 metres]. Maps of the world will have to be redrawn. Rising seas will inundate Florida, the Netherlands and the cities of San Francisco, Beijing, Shanghai, Calcutta and Manhattan. This will create 100 million environmental refugees.

— Al Gore, An Inconvenient Truth, May 2006

The sea level rises predicted by Gore and Manne depend upon the great ice sheets of Antarctica and Greenland suddenly disappearing, a scenario deriving more from Hollywood than science. Even the doomsters on the UN IPCC scientific panel observe comparatively tiny sea level rises.

Global mean sea level has been rising. From 1961 to 2003 the average rate of sea level rise was 1.8 mm plus or minus 0.5 mm per year. For the twentieth century the average rate was 1.7 mm plus or minus 0.5 mm per year … For the period 1993 to 2003, for which the observing system was much better, the contributions from thermal expansion (1.6 mm plus or minus 0.5 mm per year) and loss of mass from glaciers, ice caps and the Greenland and Antarctic ice sheets together give 2.8 mm plus or minus 0.7 mm per year.

— UN Intergovernmental Panel on Climate Change, Fourth Report, 2007, Chapter Five, ‘Oceanic Climate Change and Sea Level’, p 387

Hence, if the IPCC’s worst-case observations remain the same, by 2095 world sea level will have risen by between 18.3 cm and 30.4 cm. At this rate, it will take between 1741 years and 2902 years for the sea to rise 20 feet.