Last century changes in ocean wind wave height from global visual wave data

Centennial time series of visually observed wave height were derived from the International Comprehensive Ocean‐Atmosphere Data Set along the major ship routes in the World Ocean and homogenized. They demonstrate positive trends in significant wave height over the North Pacific with a maximum of 8–10 cm/decade in the northeast Pacific. In the North Atlantic and other basins significant upward changes (up to 14 cm/decade) are observed only for the last 50 years and not for centennial records. Long‐term changes in wind wave height are closely associated with the North Atlantic Oscillation in the Atlantic and with North Pacific Oscillation and El‐Niño–Southern Oscillation in the Pacific.