A study published today claims that if the US generated enough energy from wind to meet its current electricity demand, the surface of the continental US would warm by 0.24掳C. What鈥檚 more, it聽goes on to compare this increase with global warming.
It would take 100 years for the savings in greenhouse gas emissions from all those windfarms to counteract this warming, the researchers estimate. 鈥淟arge-scale US wind power would cause a warming effect that would take roughly a century to offset,鈥� claims the headline on a press release issued alongside the study.
This research is part of an ongoing debate, but other climate scientists say聽this particular claim is misleading.
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For starters, the study assumes that a third of the US is covered in wind turbines, points out wind energy researcher Cristina Archer of the University of Delaware.
Wind turbines everywhere
鈥淭hat means you jump in your car in Ohio and drive all the way to the Rocky Mountains, and all you see at every point is wind turbines,鈥� she says. 鈥淚t鈥檚 a crazy scenario that鈥檚 never going to happen.鈥�
What鈥檚 more, the study relied on a regional climate model called the WRF. This model has a known flaw that exaggerates the air-mixing effect of wind turbines two or threefold, says Archer.
Then there鈥檚 the comparison with global warming. The crucial point here is that wind turbines simply redistribute heat that鈥檚 already in the air.
At night, for instance, the ground cools and so does the layer of air just above it. The turning of turbine blades heats the surface by bringing down warmer air from above 鈥� the overall heat content of the atmosphere does not change and the effect ceases when the turbines stops turning.
By contrast, higher levels of carbon dioxide trap heat and increase the total heat content of the atmosphere and ocean. And the effect lasts for millennia because that鈥檚 how long extra CO2 persists in the atmosphere.
To put this another way, even if this study was right about the magnitude of the effect and every inch of land in the world was covered with wind turbines, it wouldn鈥檛 cause any melting of the polar ice caps.
The impact of wind farms also has to be considered in the context of all the other changes we are making to the world. The urban heat island effect can warm cities by as much as 12掳C compared to surrounding areas 鈥� but has a negligible effect on global temperatures. And buildings affect wind too.
Some of these points are stated in the paper, but they are buried two-thirds of the way through it. They are not made clear in the press release.
Misleading coverage
Asked whether he thought the headline of the press release would lead to misleading coverage, co-author David Keith of Harvard University replied: 鈥淚 expect so. People will seize on all sorts of stuffs and exaggerate it.鈥�
Keith is not questioning the need to move away from fossil fuels. 鈥淭here is no question that wind is better than coal,鈥� he says. But he says he is concerned about the impact of large-scale wind generation.
But researchers should stick to analysing realistic scenarios for the growth of wind, says Archer.
鈥淚t gives such a bad reputation to wind if you start publishing this kind of stuff,鈥� she says. 鈥淧eople don鈥檛 see that it鈥檚 a crazy scenario, all they remember is, oh, there鈥檚 global warming from wind power.鈥� Except there isn鈥檛, of course.
Joule
