Growing understanding of how wind farms can affect local weather and ecosystems a touchy subject for industry 

That is not to imply there is an equivalence between the localised effects wind turbines can have on weather systems and the climate crisis caused by emissions from burning fossil fuels. There is none.

But it raises difficult questions for the wind industry about the unintended consequences that masses of monolithic turbines could have on local climates and ecosystems, just as they are being installed at a frenetic pace to help avert catastrophic global warming.

This turbulence affects the stratification of the atmosphere, said Stefan Emeis, who specialised in wind energy meteorology for three decades at the Karlsruhe Institute of Technology in Germany.

Essentially, it causes a “mixing”, he said, with the heat contained in different atmospheric layers redistributed in the turbines’ wakes.

This is also because turbines produce an “upward motion” at their leading edge, he said. And upward motion is a factor that “promotes the formation of clouds.”

This is because clouds form when rising air cools and the water vapour it contains transforms into droplets. “If it’s really a drastic effect,” Emeis said this will result in precipitation – like rain.

‘Very little’ research into large-scale offshore wind weather impacts

Research into how wind farms impact the local atmosphere dates back over a decade. But there has been “very little” research on how large-scale offshore wind clusters can change local weather conditions, said Naveed Akhtar, a specialist in wind energy and climate modelling.

Akhtar was part of a team at the Helmholtz-Zentrum Hereon research institute in Germany that published one such paper on offshore wind’s potential impact on the weather in Nature in 2022. Most other research has focused on “only on one wind farm, two wind farms,” he said. “I try to look at the bigger picture.”

Using a climate model to simulate the impact of wind farms on local weather dynamics, the team found – echoing the comments from Emeis – that large offshore wind farms “alter the vertical atmospheric structure” in their vicinity by reducing the wind speed and mixing boundary layers.

What is perhaps more interesting – and indeed significant – is that wind turbines were simulated to raise the temperature two metres above sea level by up to 0.25°C, a peak seen in the spring.

The modelled changes in surface climate are “significant in the vicinity\” of offshore wind farms, they said, introducing “pronounced spatial structures in the otherwise largely uniform marine climate.”

The results suggested that it is “important to consider future large-scale clustered offshore wind farms when reconstructing and assessing regional atmospheric dynamics and marine climate.”

This is why considering the bigger picture is so important, said Akhtar. Looking at just one or two wind farms, “you don’t see the cumulative effect.” Akhtar is continuing his research into the issue based on the latest buildout plans, by now “much bigger” than those used in the previous paper, which relied on plans from 2015.

Another research project that has measured the impact large-scale offshore wind deployment can have on local atmospheric conditions is the aforementioned X-Wakes programme.

X-Wakes, which wrapped up a few years ago, was funded by the German Ministry of Economic Affairs and Climate and led by the prestigious Fraunhofer Institute for Wind Energy Systems in Germany.

As well as numerous research institutions, offshore wind heavyweights Vattenfall, Orsted and RWE also partnered on X-Wakes, through which scientists sought to understand not just inter-farm wake losses – an increasingly hot topic in the industry – but the broader effects wind farms have on the atmosphere.

Between 2020 and 2021, the two aircraft that took the measurements flew 49 flights around numerous wind farms in the German Bight, including RWE’s 385MW Nordsee Ost array.

Lampert, the scientific spokesperson for the project, said that the team found not just that turbines were generating wind wakes, as was expected, but that the slower winds were resulting in “weakened waves”.

“In my opinion, this will also trigger other effects like interaction with the ocean,” said Lampert, as well as “changes in microclimates”.

“Of course, if there are wind parks all over the North Sea, then the wind climate will be modified on larger scales,” she said. For now at least, Lampert stressed that any effects turbines do have on the climate remain marginal. “It’s not like we will shut down all the wind.”

Even if wind farms subtly affect the temperature and waves in their vicinity far out to sea, why should we care? One reason is that these changes can have knock-on effects on marine ecosystems.

Another study published in Nature by a team from Helmholtz-Zentrum Hereon found that wakes from North Sea wind farms could “provoke large-scale changes in annual primary production”.

Primary production is the process through which organic matter is produced by microscopic plant-like organisms called phytoplankton that are the base of the marine food web.

Offshore wind clusters could provoke changes in primary production of “up to ±10%,” found the researchers. This is not just nearby wind farms but also over a “wider region”.

The results, they said, provide evidence that offshore wind farms can have a “substantial impact on the structuring of coastal marine ecosystems”.

As a Scottish government scoping report noted late last year, “indirect impacts via ‘bottom up’ trophic cascades,” the process by which changes in one layer of an ecosystem can have far-reaching effects, can be “complex and non-local.”

Modifications in ocean mixing and stratification from offshore wind farms could “change nutrient availability in the uppermost part of the ocean,” it said, starting a “cause-effect chain that translates into changes in primary production, altering the food chain.”

Offshore wind farms ‘could reduce rain onshore’

If offshore wind farms can change the climate in their vicinity, it raises the question: What impact could those closest to the coastline have on the weather onshore?

A 2020 research paper published by researchers from the University of Delaware sought to examine exactly this question, taking measurements from Orsted’s Walney offshore wind cluster – with four phases together boasting over 1GW capacity – in the Irish Sea.

Those researchers found that the Walney cluster, roughly 15km off the British coast, reduced not only the wind speed but also precipitation onshore by a “statistically significant” degree, albeit small in magnitude.

Akhtar said that research he and colleagues are currently conducting indicates that if North Sea countries – especially Denmark, Germany and the Netherlands – hit their ambitious offshore wind targets, this will have a “significant impact” on coastal precipitation.

This is because more rainfall will occur over the wind farms, he said, so there will be less moisture to transport to the coast.

Lampert cautions that there is “not an easy answer” regarding the relationship between cloud formation and wind farms. “You cannot say” that having wind farms nearby will consistently change the amount of rain on the coast in one particular way, she said, “it’s too simple.”

It also depends on the atmospheric conditions, she said. If conditions are unstable, there could be no effect at all.

Offshore wind weather impacts ‘will not be shared equally’

The fallout from climate change is not shared equally, or fairly. Rich northern hemisphere nations are primarily responsible for a climate crisis that has some of the most catastrophic effects in poor African countries like Chad and Somalia.

The same will be true – albeit on a fraction of the scale – for the atmospheric impacts of a huge offshore wind buildout in the North Sea, said Martin Fengler, the CEO of Swiss weather modelling firm Meteomatics.

Take Germany. Sitting as it does downstream of the North Sea’s natural wind flows, Fengler said the country will be more exposed than others to impacts wind farms have on the local climate.

Fengler, who founded Meteomatics in 2012, said that if North Sea nations hit their target of deploying 300GW of offshore wind by 2050, this will have a “significant impact” on weather conditions, onshore and off.

“Looking into the temperature increase onshore, I strongly believe that we will see in the northern parts of Germany an increase of at least half a degree, maybe even more, just because of that.

“It shouldn’t be a surprise,” he said. “It’s more surprising that politicians might be surprised by it. But you’re harvesting energy, so it shouldn’t be, technically speaking, a surprise that this is going to [have an] impact.

“Harvesting energy at this scale might create an increase in temperatures in coastal regions,” he said, possibly causing “drier conditions” as a result.

“Change does not necessarily mean that it’s to a disadvantage,” said Fengler, joking that, “if you ever spent your vacation on a German beach, then you might want to have it one degree higher.

“It’s not so much a problem for the UK,” he adds. “No chance to get any better weather.”

Touchy subject: ‘You can lose friends talking about it’

Try telling someone in your local bar or pub that wind turbines are changing the weather and you may find them shifting uncomfortably and casting their eyes for the nearest exit.

It’s precisely because it’s something you might expect to hear from a card-carrying conspiracy theorist – perhaps before a follow-up salvo on how 5G masts cause Covid-19 – that researchers and scientists are nervous discussing the issue.

“Don’t get me wrong, I’m a huge fan of renewable energy,” stressed Fengler after discussing the topic. “I drive an electric vehicle… I’m not a [climate change] denier.”

Fengler said he is “super cautious” talking about this issue. There are strong and deeply set opinions on this, he said. Say the wrong thing and “you don’t get funding, you don’t have any friends any longer.”

It’s also a dangerous topic for a CEO of a business that relies on clients from the renewables sector, he said. Saying something too “polarising” on the issue “cuts the market in half, or even worse.”

Akhtar said that, after one of his recent papers was published, people who are “really against wind farms” tried to “misinterpret our research”.

There was “a lot of discussion on Twitter” (now X) from people who used the paper to attack wind farms, said Akhtar. “That was not our aim.”

“We don’t want to discredit the wind industry. We want to encourage it,” he said. But Akhtar and his colleagues also want to investigate how wind farms will affect the climate so that they can try and “reduce the risk” that large-scale deployment could bring.

Emeis highlighted a cautionary tale from over a decade ago when a study found that a wind farm in Texas was warming the ground near it at nighttime.

“Taking this as a single piece of information” and not putting it in the proper context, “you could say wind farms are warming up the area” and even contributing to global warming. “Wind farms are warming the earth, researchers say,” read a Fox News headline at the time.

In fact, the turbines were merely redistributing the air, with their blades pulling some warm air down to ground level and pushing some cold air up. “People who have an agenda, they sometimes misuse science,” said Emeis.

So, however well intentioned, research and discussion regarding the topic pose a headache for the wind industry.

Christoph Zipf, communications manager for WindEurope, said the association acknowledges that wind farms have a “localised effect” on weather conditions but stressed they do not “significantly alter” large-scale weather patterns.

There is he said an obvious danger that research into the topic gets “blown out of proportion”.

Even more dangerous in today’s political environment is that mis- and disinformation about wind energy is now moving out of those online blogs and fora and into “mainstream policymaking.”

Right-wing politicians globally are now aping Donald Trump’s rhetoric on wind, with those otherwise unknown for their environmental activism suddenly claiming concern for every whale life turbines supposedly threaten.

Some arguments from climate sceptic parties now go “beyond opposition and reform,” said Zipf, veering into “mis- and disinformation.”

So how should the industry approach the issue of wind farms’ weather impacts? Are these effects mere atmospheric curiosities that can be largely disregarded, or a major ticking time bomb waiting to go off?

Xiaoli Guo Larsén, a professor in the department of wind and energy systems at the Technical University of Denmark, stresses that while wind farms can change local atmospheric conditions, it is on a “marginal” scale compared to weather’s natural variability.

For Fengler, “the message is, we manipulate locally, at least, the climate. And, of course, it will take decades until we learn the results.”

One thing is certain: given the increasingly toxic and polarised debate around wind farms, trying to have a nuanced discussion about how they can change the weather will be a formidable task for the sector in decades to come.”