The prevailing winds in the "free" atmosphere about 1,000 meters above the ground are maintained by a temperature gradient that decreases toward the poles.
"For example, Wichita, Kansas is cooler, in general, than Austin, Texas," Ren says. "The stronger the temperature contrast, the stronger the wind." But as the climate changes and global temperatures rise, the temperature contrast between the lower latitudes and the poles decreases slightly, because polar regions tend to warm up faster. And as that temperature contrast becomes weaker, so too do the winds.
Wind turbines are powered by winds at lower altitudes — about 100 meters above the ground — where, Ren says, "frictional effects from local topography and landscapes further influence wind speed and direction. In my study, I assume that these effects are constant — like a constant filter — so wind speed changes in the free atmosphere are representative of that in the frictional layer."
Ren calculates that a 2-4 degree Celsius increase in temperatures in Earth’s mid to high-latitudes would result in a 4-12 percent decrease in wind speeds in certain high northern latitudes. This means, he says, that with "everything else being the same, we need to invest in more wind turbines to gain the same amount of energy. Wind energy will still be plentiful and wind farm still profitable, but we need to tap the energy source earlier" — before there is less to tap.
Journal of Renewable and Sustainable Energy (JRSE) is an interdisciplinary, peer-reviewed journal published by the American Institute of Physics (AIP) that covers all areas of renewable and sustainable energy-related fields that apply to the physical science and engineering communities. As an electronic-only, Web-based journal with rapid publication time, JRSE is responsive to the many new developments expected in this field. The interdisciplinary approach of the publication ensures that the editors draw from researchers worldwide in a diverse range of fields. See: http://jrse.aip.org/
The article, "Effects of global warming on wind energy availability" by Diandong Ren appears in the Journal of Renewable and Sustainable Energy. See: http://link.aip.org/link/jrsebh/v2/i5/p052301/s1