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  • Description: North Atlantic Oscillation (NAO) index. Year is on the x-axis (1900–2005), and the standardised principal-component based winter NAO index on the y-axis. The bars show each winter's mean NAO index (where for instance "winter 1900" means the period from December 1899 up to and including March 1900). The black line is the 5-year running mean of the same index values (smoothed with a Gaussian filter).
  • Source: graph drawn by Hanno using data published on the web by J.W. Hurrell (Climate Analysis Section, National Centre for Atmospheric Research, Boulder, Colorado, USA) as "Climate indices" []
  • Licence: released into the public domain by the originator
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