No, wind farms are not causing global warming - Washington Post (blog)

Scientific studies get misrepresented all the time. But now and again the distortions are especially bad. That was the case Monday, when Fox News ran the headline, “New Research Shows Wind Farms Cause Global Warming.” A number of other outlets did the same thing. And it’s ... not true at all.

(George Frey/Bloomberg) The frenzy started after Liming Zhou, a scientist at the University of Albany, published a short study in Nature Climate Change analyzing satellite data for a handful of large wind farms in Texas. What Zhou’s team found was that, between 2003 and 2011, the surface temperature in the immediate vicinity of the wind farms had heated up a fair bit, especially during the night hours, as the wind turbines pulled warmer air from the atmosphere down closer to the ground.

This is mildly interesting â€" if unsurprising. Orange growers in Florida often use giant fans to protect their crops from frost, using the same principle. But it’s not clear that this has any global significance whatsoever. As Zhou himself explained in an accompanying Q&A: “the warming effect reported in this study is local and is small compared to the strong background year-to-year land surface temperature changes. Very likely, the wind turbines do not create a net warming of the air and instead only re-distribute the air’s heat near the surface, which is fundamentally different from the large-scale warming effect caused by increasing atmospheric concentrations of greenhouse gases.”

Read that paragraph again. Wind turbines appear to shift some warm air around in a relatively small slice of Texas â€" a fact that might be of interest to, say, nearby farmers â€" but it’s not the same thing as putting more and more carbon-dioxide into the atmosphere, which traps heat that would otherwise escape out to space and causes the Earth to warm overall. A coal plant helps raise the temperature of the planet by pumping greenhouse gases into the air. A wind turbine... shifts some heat around.

Still, that didn’t stop news outlets and pundits from inflating the study beyond all recognition. The Daily Mail ran the headline, “Wind farms make climate change WORSE.” That is wrong. Zhou himself complained that the media coverage of his study has been “misleading.”

Now, to pull back a bit, there are real questions about what would happen if we massively scaled up wind farms to produce huge amounts of renewable electricity. After all, wind turbines generate power by capturing the kinetic energy of wind and thereby slowing the winds down. On a large enough scale, that might significantly influence the Earth’s temperature and rainfall patterns.

To get a sense for what we know about this broader topic, I called up Mark Jacobson, an environmental engineer at Stanford who has done a lot of modeling work in this area. The first thing to note is that humanity doesn’t currently use anywhere near enough wind power to make a huge difference. Jacobson’s earlier simulations suggested that there’s somewhere around 72 of wind power that could reasonably be harnessed worldwide. But, at the end of 2011, worldwide wind power generation capacity was just 0.2 terawatts. (Humanity, for its part, currently uses about 16 terawatts of energy, all told.)

And it’s not clear what would happen if we erected wind turbines all over the world. One 2004 study (pdf) led by the University of Calgary’s David Keith found that getting just 2 terawatts of electricity from wind could produce “non-negligible climactic change at continental scales” â€" including shifts in rainfall pattern. But, says Jacobson, the effects that Keith’s group found don’t appear to be distinguishable from random fluctuations in the Earth’s climate.

“To me,” says Jacobson, “that’s a meaningless result.” Jacobson himself is working on a more in-depth effort to model the effects of a massive ramp-up in wind that could be published later this year. He says it’s even possible that a huge expansion of wind power on both land and oceans could cool the planet overall, by slowing the rate at which water vapor evaporates from the soil and enters the atmosphere.

But, for these effects to be noticeable, the wind industry would have to be orders of magnitude larger than it is now. For now, there’s no evidence that wind power is having any effect on the global climate, while there’s plenty of evidence that the greenhouse gases we’ve pumped into the air are warming the planet.