As wind energy capacity continues to grow, those who oppose it—for instance, people who don't want turbines built near their property—have seized upon all sorts of reasons to argue against construction of new turbines.
One of these reasons is the idea that in harnessing wind energy, turbines disturb air currents to a degree that they actually alter the climate of the surrounding area. Most of these arguments cite a 2012 study that observed 1.3°F in warming over the course of a decade in westerm Texas and attributed it to the construction of several large wind farms.
But the researchers of that study noted that the warming they observed occurred only at night, and was simply the effect of warmer air—which generally settles higher than ground level during nighttime—getting chopped up by whirling turbines, with some of it coming down to ground level. As a result, this mechanism would not drive long-term climate change in the same way as the greenhouse effect—it would simply make the area immediately surround the turbines a bit warmer than otherwise, and air at higher altitudes a bit cooler.
A new study, published today in Nature Communications, considers the climatic effect of mass wind turbine construction on a much broader region: Europe. Using climate modeling software, a group of French researchers led by Robert Vautard calculated the impact of doubling current wind energy capacity across Europe, the amount necessary to hit the EU's goal of reducing greenhouse gas emissions by 20 percent by 2020.
They found that the construction of all these turbines would only alter climate during the winter, and wouldn't cause temperatures to rise by more than 0.54°F (0.3°C)—firmly within the range of natural year-to-year variability, and far less than the long-term effect of greenhouse gas emissions in driving global climate change.
The researchers came to the finding by using existing atmospheric models and adding in the simulated effect of turbines, which causes increased turbulence between air layers and increased drag on wind currents. For existing turbines, they incorporated manufacturer data on height and rotor size, using it to calculate effects on passing wind currents. They placed hypothetical future turbines in areas with the fastest wind speeds (mostly in Northern Germany, Denmark, Spain and Italy, along with offshore farms on the coasts of the English Channel, the North Sea and the Baltic Sea). With the turbines in place, they simulated Europe's climate over the course of 33 years, and compared it a scenario where the continent had no turbines at all.
The model predicted that, even with the projected increase in European wind turbines by 2020, the effects on daily temperature and rainfall would be minimal. The turbines would produce a slight current of air flow moving clockwise over Europe, but its influence on weather would be undetectable for most of the year.
Only in December, January and February were the turbines projected to trigger fluctuations in weather that the researchers could detect, but these were still considered negligible: temperature might increase or decrease, but not by more than 0.54°F, and precipitation might increase somewhere between zero and five percent in total.
Compare this to normal fluctuations: On an annual basis, European temperatures naturally vary by 10 percent on average, and precipitation varies by 20 percent. Superimposed on this, the effect of the turbines barely registers a blip.
Of course, with any predictive model, there is uncertainty. But in building the model, the scientists calibrated it with actual weather data (temperature, wind speed, precipitation, air pressure and other measures) collected every three hours in thousands of weather stations across Europe for all of 2012, making slight adjustments until the model closely replicated the behavior of air currents as they actually flowed across Europe during that period. This calibration increases the chance that the model reflects real world conditions.
The researchers do allow that water-atmosphere interactions are more complex (and less well-understood) than land-atmosphere interactions, so the findings may apply better to onshore wind farms than those located offshore. Another possible limitation is that rotating turbines could alter atmospheric currents at an even larger scale, which wouldn't be detected by the model, as it only simulated climate conditions over Europe.
Nevertheless, the new study is one of the largest-scale pieces of research into the climatic effects of wind turbines yet, and its findings are pretty damning for the claim that they dramatically alter climate. There are other plausible environmental reasons why you might be anti-wind power (they do kill birds, although significantly fewer than fossil fuel power plants do through pollution and climate change), but if you're looking for a more substantive argument against turbines other than the fact that they ruin your view, you'll probably have to look elsewhere.