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No, wind farms are not causing global warming

at 04:26 PM ET, 04/30/2012

Scientific studies are misrepresented all the time. But now and again the distortions get particularly bad. That was the case Monday, when Fox News ran the headline, “New Research Shows Wind Farms Cause Global Warming.” A number of other media 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. Zhou’s team analyzed satellite data for a handful of large wind farms in west-central Texas. And he found that, between 2003 and 2011, the surface temperature in the immediate vicinity of Texas’ 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.

That’s interesting — if somewhat expected. Orange growers in Florida often use giant fans to protect their crops from frost, using much the same principles. But it’s not at all clear that this has global significance. As Zhou himself explained in an accompanying Q&A (pdf) about his paper: “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 move some warm air around in a relatively small patch of Texas — a fact that might be of note to, say, nearby farmers. But that’s not the same thing as putting more carbon-dioxide into the atmosphere, which traps heat that would otherwise escape out into space and which leads to a net overall increase in the Earth’s temperature. The latter is global warming. The former is not.

Still, that didn’t stop news outlets and pundits from inflating Zhou’s study beyond all recognition. The Daily Mail ran the headline, “Wind farms make climate change WORSE.” That’s 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 might happen if we massively scaled up wind farms to produce huge amounts of renewable electricity. After all, wind turbines generate power by slowing down winds and capturing their kinetic energy. Build enough wind turbines and that might have an effect on the Earth’s temperature and rainfall patterns.

To get a sense for what scientists know about this topic, I called Mark Jacobson, an environmental engineer at Stanford who has done a fair bit of modeling work in this area. The key thing to note is that, for now, humanity doesn’t use anywhere near enough wind power to make a big difference to global wind patterns. Jacobson’s earlier research suggested that there’s somewhere around 72 terawatts of wind power that could feasibly be harnessed worldwide. At the end of 2011, the world’s wind power generation capacity was still just 0.2 terawatts. (Human beings use about 16 terawatts of energy, all told.)

And scientists dispute what would happen if we did start blanketing the globe with wind turbines. One 2004 study 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” — including shifts in rainfall patterns. (That much wind power would not, however, change the overall temperature of the planet.) But, says Jacobson, the effects that Keith’s group modeled 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 very large ramp-up in wind — those results could be published later this year. He says it’s possible that a massive expansion of wind turbines over both land and sea could even cool the planet somewhat, by slowing the rate at which water evaporates from the soil and enters the atmosphere. But his study is still under review.

For any of these effects to be noticeable, however, the wind industry would have to be several orders of magnitude larger than it is now. As far as the present day is concerned, there’s no evidence that wind power is having a major effect on the world’s climate, while there’s plenty of evidence that the greenhouse gases we’re pumping into the air are doing quite a bit to heat the Earth.

 
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