Active dunes contain an unread high-resolution archive of past wind strength. Variations in the grain-size spectrum of an active dune through time are compared with historical time series of wind speed. Annually averaged, sediment-derived wind intensity and instrumental records of wind speed show a correlation as high as 0.75. The potential of eolian dunes to gain long-term data series of wind intensity in areas and for time periods lacking an instrumental record is demonstrated by reconstructing 20th century wind-intensity variations in the southern North Sea area. The approach can be used in both recent and fossil dune systems. Potential applications include the validation of climate models, the reconstruction of supraregional wind systems, and the monitoring of future shifts in the climate system.