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New research confirms global surface winds are slowing, blames land use changes

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Are surface winds around the world really slowing down? That’s the suggestion of a new study in Nature Geoscience. The authors built on previous studies indicating such a trend by analyzing surface wind data from 822 wind stations in Europe, Asia and North America. The study concludes that the widespread "atmospheric stilling" has more to do with what’s happening on the ground than it does changes in general atmospheric circulation—specifically, increased "surface roughness" due to land-use changes may be responsible for the slow-down.

Recent research indicates surface winds are slowing in China, The Netherlands, the United States and the Czech Republic. But this data have been confined to localities, says lead author Robert Vautard of the Laboratoire des Sciences du Climat et de l’Environnement in France, due to reasons stemming from the inherent difficulty of collecting surface wind data. Many of the weather stations have large breaks in their data, and in other cases, stations have changed locations or switched instruments, compromising data quality. This has led research groups to limit analysis to data they could vouch for locally. "In the past, people have been very careful, but they have not used a global data set because didn’t trust the data of other countries," says Vautard.

His group examined the data of more than 5,000 stations that used anemometers to measure wind speed, eliminating stations with large gaps and changes in location and instruments. They subtracted 85 percent of the stations, leaving data from 822, collected during the period between 1979 and 2008. They found that surface wind speed decreased over the 30-year period at 73 percent of the stations, and that surface wind speeds have decreased by -0.09, -0.6, -0.12, -0.07 meters per second per decade in Europe, Central Asia, Eastern Asia and North America, respectively. 

Why is this happening? "That’s where the thing gets more complicated," says Vautard, "There may be several causes." 

First, wind data is difficult to collect, and the trend could be an artifact of anemometer degradation or changes in observation methods. But the authors conclude the trend was too pronounced to be due solely to the way the data were collected. "It is difficult to believe that all the anemometers have the same problem all over the world," says Vautard, adding, "In previous papers, there are some discussions of the quality of these measurements, but nobody came to the conclusion that these phenomena could come from the observations themselves." 

Next, the authors explored whether or not the slow-down was due to changes in general atmospheric circulation—in particular, changes in the speed of upper winds. Specifically, they note, if these changes are to blame for surface wind slowing, a similar slowing trend should be seen in the "reanalysis" of 3-D wind models from the National Centers for Environmental Prediction/National Center of Atmospheric Research and European Center for Medium-range Weather Forecast. "The reanalysis do have some trends in some areas, but not everywhere, not with the same pattern, and are not fully correlated" to the observed surface wind changes. Thus, the authors concluded that changes in general circulation account for only 10-50 percent of the changes at the surface.

Finally, the researchers analyzed changes in land use that may have led to increased "surface roughness," which can slow winds. Indeed, says Vautard, surface roughness has been increasing due in part to abandonment of cropland, which is being replaced with trees and shrubs, and to previously deforested land in North America and Europe becoming reforested. The growth of cities could also be contributing. The authors estimated that these factors were responsible 20-65 percent of the surface wind slowdown.

Do slower winds mean we should temper our optimism for the global wind power industry? We don’t know enough yet, says Vautard. Wind energy is not collected at the surface, and requires a specific range of wind speed (between five and 25 meters per second). "We have to really look at whether and in which regions the decline is really in this range of wind, and we have to take into account that wind power is taken at 80 meters," he says, "We need a model to understand that."

Image credit: Flickr/ Sheep purple





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  1. 1. jtdwyer 2:22 pm 10/19/2010

    The article states:
    "Finally, the researchers analyzed changes in land use that may have led to increased "surface roughness," which can slow winds. Indeed, says Vautard, surface roughness has been increasing due in part to abandonment of cropland, which is being replaced with trees and shrubs, and to previously deforested land in North America and Europe becoming reforested. The growth of cities could also be contributing. The authors estimated that these factors were responsible 20-65 percent of the surface wind slowdown."

    Indeed! The researchers attribute 20-65% of a diminishment of global wind speeds between 1979 and 2008 to abandoned cropland in North America and Europe being overrun with trees and shrubs, increasing surface roughness, and maybe the growth of cities? What an extraordinary conclusion!

    I hope their analysis is exceedingly robust, since their data seems to be considered highly questionable. I suggest the variation in wind speed could much more easily be explained by anemometer degradation over the past 30 years, likely from bearing wear and lubricant contamination, which was apparently not investigated. This simple explanation should have at least been eliminated before considering that it could not have affected the presumptuous results.

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  2. 2. drafter 2:44 pm 10/20/2010

    this contradicts what global warming alarmist say, according to them the wind should be getting worse.

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  3. 3. Astrodont 4:34 pm 10/20/2010

    It’s refreshing to have a climate study that doesn’t dismiss the difficulty of plugging in variables… and then doesn’t claim some dire insight into man’s folly unless we change our evil ways.

    The climate is a complex interaction of dozens of variable…some known and some not known.

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  4. 4. jtdwyer 3:30 am 10/21/2010

    If the current per capita human energy consumption rate was the same as it was during the Renaissance, for example, I suspect 9 billion people would still require a lot of power and produce a significant environmental and climatic impact.

    I wonder how much methane 9 billion elephants would produce, and what the resulting climatic impact would be…

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  5. 5. jtdwyer 3:36 am 10/21/2010

    Sorry, drafter, the preceding comment was completely misdirected.

    My response to you ("…the wind should be getting worse"):

    Well, that would seem to be generally consistent with an increase in atmospheric thermal energy, anyway…

    Sorry again for the confusion.

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