Can wind farms change the weather?

China simply cannot win. It is attacked for being a large-scale polluter. It builds the Yangtze dam complex which provides immense amounts of clean power. And is condemned because of results that come from damming the Yangtze. So it tries wind power. Stick up a windmill that is attached to a generator and you produce electricity. (It is perhaps worth noting that in Sussex where the writer has a house, there was a massive campaign against windmills. Blight on the landscape. Damn ugly things. Should not be allowed. Probably frighten the pheasants. And that was in the early seventeenth century. Nothing much has changed.)

Large-scale wind farms, consisting of hundreds to thousands of wind turbines spread over large areas for generating electricity, are likely to play an increasingly important role in providing a climate-friendly source of energy. Good. Understood.

Unlike power plants that burn oil, coal or natural gas, wind power requires no fuel, emits no pollution and produces no carbon dioxide nor any other greenhouse gas. Also true and commendable.

The efficiency, effectiveness and economic value of wind power clearly depends critically on the weather, along with factors such as terrain, vegetation and building structures, which affect the speed, direction and variability of the wind striking the blades of wind turbines.

Also understood. But now the question is being asked: can wind farms affect the weather? If so, would it not be appropriate for the Greens to mount a protest and lash themselves to the bottom of windmills?

Researchers are investigating the potential for large wind farms in one region to alter weather patterns in another region downwind. Specifically, the turning of the windmill propellers creates considerable turbulence, which mixes air up and down. The resulting bumpiness of the air could significantly influence winds at low levels of the atmosphere.

University of Maryland atmospheric scientist Daniel Kirk-Davidoff in a recent Christian Science Monitor story said, "If you have a couple of wind farms over a 10-kilometer patch in the Midwest, that’s not going to make some kind of global impact on the weather." But if the whole Midwest "is somewhat roughened over a large area, then you could imagine having a large-scale impact on the atmosphere."

Kirk-Davidoff and his UMD colleague, Daniel Barrie, used a global general circulation model of the atmosphere (similar to the models used to predict climate change) to calculate the effects of blanketing the Midwest with a grid of interconnected wind farms with thousands of wind turbines. On average, the study found that wind speeds were lowered by 5.5-6.7 miles per hour immediately downwind.

The magnitude and degree of the impact of such wind farms would presumably be less than in the model simulation. But ensemble forecasting has shown that even apparently innocuous changes in the low-level wind field can result in large uncertainties in the timing, strength and motion of major storms over a period of just a few days. As in: if a butterfly flaps its wings in San Francisco does this create a rain storm in London?

The Washington Post ran the story and pointed out that based on computer modeling, researchers at Duke and Princeton universities found that wind mill-generated turbulence raised pre-dawn surface temperatures by about four degrees and resulted in drier soil conditions. (Whether this is connected to global warming or enhances the effect is not explained.)

We should now all await with eager anticipation of the deletrious effects on the world of solar panels reflecting all those nasty rays backwards. And house insulation which has managed to banish chillblains in so many parts of the world. Which were, until a few years ago, an important part of life.

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