In a large number of previous studies, the technical wind energy potential was estimated from national to global scale. Usually, it was assumed that the underlying meteorological potential remains constant over time. However, the wind resource greatly varies on different temporal scales including inter-annual and multi-decadal scales. In this study, the long-term variability of national and global technical wind energy potentials was assessed for the period 1971-2010 based on wind speed data from the coupled atmosphere/land-surface/ocean-wave model ERA-20C. Within this period, the annual national and global wind energy generation was reconstructed assuming an average number of 0.01-0.25 wind turbines per km(2) sited on geographically nonrestricted areas. The applied wind turbines have an average rated power of 3.67 MW and a hub height of 100 m. While no significant trend in technical wind energy potential was found in the majority of the countries studied, the Mann-Kendall and Cox-Stuart trend tests revealed significantly increasing trends in 37 countries and significantly decreasing trends in 10 countries. In addition, the results show that the inter-annual variability of the wind energy potential is influenced not only by the wind resource itself, but also by the rate of wind turbine expansion. From the presented results it is clear that the quantification of the long-term variability of the wind energy potential is an important prerequisite for controlling and adapting the expansion of wind energy on national and global scales to future electricity consumption.