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Wind power is a rapidly growing alternative energy source to achieve the goal of the Paris Agreement under the United Nations Framework Convention on Climate Change, to keep warming well below 2 •C by the end of the 21 st century. Widely reported reductions in global average surface wind speed since the 1980s, known as terrestrial stilling, however, have gone unexplained and have been considered a threat to global wind power production. Our new analysis of wind data from in-situ stations worldwide now shows that terrestrial stilling reversed around 2010 and global wind speeds over land have recovered most of the losses since the 1980s. Concomitant increased surface roughness from forest growth and urbanization cannot explain prior stilling. Instead we show decadal-scale variations of nearsurface wind are very / quite likely caused by the natural, internal decadal ocean/atmosphere oscillations of the Earth's climate system. The wind strengthening has increased the amount of wind energy entering turbines by 17 ±2% for 2010-2017, likely increasing U.S. wind power capacity by 2.5%. The increase in global terrestrial wind bodes well for the immediate future of wind energy production in these regions as an alternative to fossil fuel consumption. Projecting future wind speeds using ocean/atmosphere oscillations show wind turbines could be optimized for expected wind speeds, including small and large speeds, during the productive life spans of the turbines. Reports of a 8% global decline in land surface wind speed (~1980 to 2010) have raised concerns about output from future wind power 1-5. Wind power varies with the cube of wind speed (u) 6. The decline in wind speed is evident in the northern mid-latitude countries where the majority of wind turbines are installed including China, the U.S. and Europe 1. If the observed 1980-2010 decline in wind speed continued until the end of the century, global u would reduce by 21%, halving the amount of power available in the wind. Understanding the drivers of this long-term decline in wind speed is critical not merely to maximize wind energy production 9-11 but also to address other globally significant environmental problems related to stilling, including reduced aerosol dispersal, reduced evapotranspiration rates, and adverse effects on animal behavior and ecosystem functioning 1,3,4,12. The potential causes for the global terrestrial stilling are complex and remain contested (e.g.,

The demise of swidden cultivation in Southeast Asia may have devastating environmental consequences.

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