FACT CHECK: There is no direct evidence that offshore windfarms cause heavier rainfall on land

Could the presence of offshore windfarms in the North Sea result in heavier rainfall and even flooding in our region? This is a claim that has been doing the rounds on the internet for some time now. However, meteorologists say that the chance that this is the case is very small. Furthermore, all the scientific research carried out to date has found no link between the presence of wind farms off the Flemish Coast and rainfall levels on land. 

In short: A theory that offshore wind farms create a changed microclimate onshore has been doing the rounds on the internet for quite a while. It is claimed that the mixing of cold and warm air layers by the rotor blades of the wind turbines at the offshore wind farms results in heavy rain and even flooding onshore. 

However: There is no scientific evidence that sufficiently supports this claim. Meteorologists consider the possible that it is true to be very small. 

"Intense downpours", "severe climate change" or even "catastrophic tidal waves". All of these could be direct consequences of the installation of offshore wind farms in European waters. This is a theory that has been spread widely on social media. An example of this is the Twitter post featured below. The post has been viewed at least 90,000 times and shared by at least 600 of those that have viewed it. 

However, the photo that the Twitter user attached to his post comes from the Horn 1 wind farm in Denmark and not from a German offshore wind farm as he seems to suggest. Nevertheless, the photo is genuine.


The photograph

The photograph that accompanies the post is of the Danish Horns Rev1 wind farm. It was taken during highly exceptional weather conditions on 12 February 2008.

On that day, a cold, frozen layer of air from the Danish coast met with a warmer layer of air from the North Sea. Due to a light wind gently turning the rotor blades, both layers of air were slowly mixed behind the blades. The warmer layer of air caused the cold layer to condense, creating a mist curtain. Scientists call this phenomenon mixing fog.

Only on a micro scale

However, there is no research to be found that confirms this theory. The oceanographer and meteorologist Stephan de Roode of the Technical University of Delft in The Netherlands writes that "The atmospheric conditions required for clouds to be generated by wind turbines are rare in practice, and the spectacular cloud formation as shown in the photo from Denmark is an exceptional case."

But research by the University of Illinois has shown that the wind turbine blades do indeed mix warm and cold air layers and can thus warm up the temperature locally. That is the reason why, for example, some fruit growers use small wind turbines to protect their crops from frost during the winter months.

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Wind turbines also cause turbulence that mixes up the air layers. Several articles make a comparison with a traffic flow passing by the scene of an accident. The traffic or in this case the wind slows down as it approaches the accident site that in this case is the wind turbine. It then speeds up again when it passes a certain point. After that, it returns to the same speed as before.

In an article in the science magazine EOS the Leipzig University professor of theoretical meteorology Johannes Quaas writes that this has an impact on the micro-climate around the turbines. However, this is an effect that can only be felt up to a few hundred meters from the wind farm and not over a wider area.

More likely to cause dry weather

The VRT’s weatherman Frank Deboosere who is a qualified meteorologist draws the same conclusion. Frank Deboosere says that it is almost impossible that onshore rainfall levels are influence by offshore wind farms. "That is like saying that the beat of a butterfly wing can create a hurricane."

“The effect of offshore wind turbines on the inland weather conditions is negligible. The rainfall theory is mainly spread by people who are firmly against wind energy", Frank Deboosere said.

Scientists from the universities of Utrecht and Wageningen even say that offshore wind farms leave costal areas near to them with less rainfall rather than more. They argue that showers mainly occur in the microclimate around wind farms and that as a result the coastal areas nearby receive less rain as a result.

In other words: offshore wind farms cause rain that is highly localised. But as most wind farms are located around 20 kilometers from the coast those living in coastal areas will not notice much influence on rainfall. In any case the wind farms in the North Sea are not large enough to have a strong impact on the local weather and climate.



Justifiable concerns

Nevertheless, it is not all that clear what the precise impact of larger wind farms is on our climate and the environment. Research suggests that much more study of the consequences of large-scale wind energy projects is needed.

In addition to climatological studies, there are also many questions about the ecological impact of wind farms. The most widely publicised example of this is the number of birds that are killed after being hit by turbine blades each year.

However, this is "a negligible number compared to the number of birds that fly into buildings or are caught by cats," Frank Deboosere says.

Another concern is the impact of the construction of wind turbines on marine life. According to some, the presence of all kinds of corals and mussel species that nestle on the bases of the turbines is beneficial to biodiversity. As these species attract fish and there is a fishing ban around wind farms, their presence can lead to a increase in fish stocks.

But the critics argue that the installation of wind turbines brings with disruption to the habitat of  to some marine life. In particular, the use of supersonic sounds and seismic drilling to put the place the turbine pylons in place is said to confuse certain species that communicate with each other through echo sound.

Earlier this year, environmentalists claimed that the deaths of seven whales off the New Jersey coast were due to the installation of wind farms. However, the American website Politifact writes that scientists could not demonstrate a one-on-one link.


- A theory is doing the rounds on the internet that states that offshore wind farms cause climate change. They are said to, amongst other things, cause heavy rainfall and flooding in onshore areas near to the coast.

- This is said to be a result of the mixing of cold, warm and humid layers of air cause by the movement of wind turbine blades.

- There are studies that show that there is mixing of cold and warm air and also speak of a localised increase in temperatures. But none of the studies mention that this causes heavy rain onshore. Most researchers says that any impact on the weather is highly localised and negligible due to the limited size of the wind farms off our shores.

- Much addition research is needed to determine what are the climatic and ecological effects of offshore wind energy. Whether or not the installation and presence of wind turbines is beneficial to marine life cannot yet be unequivocally determined.

- Based on the facts that are currently available VRT News’ Fact Checking Team has found the assertion that that offshore wind farms cause heavy rainfall and flooding to be not proven and quite untrue.  

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