A new study has measured the potential environmental impacts of running a nation on wind power.

Wind turbines cause warming by redistributing heat in the atmosphere, according to computer models developed at Harvard University.

Although it would be preferable to coal-fired power generation in the long-term, a switch to large-scale wind power in the US could cause warming of 0.24°C locally because of this effect, according to the study.

Furthermore, they say that temperature rise could take around a century to be cancelled out by the reduction in greenhouse gas emissions afforded by ditching fossil fuels.

“Wind beats coal by any environmental measure, but that doesn't mean that its impacts are negligible,” says senior author David Keith, an engineering and public policy professor at Harvard University.

“We must quickly transition away from fossil fuels to stop carbon emissions. In doing so, we must make choices between various low-carbon technologies, all of which have some social and environmental impacts.”

To compare the impacts of wind and solar, the researchers established a baseline for the 2012-2014 US climate using a standard weather forecasting model.

They then added in the effect on the atmosphere of covering one third of the continental US with enough wind turbines to meet present-day US electricity demand. This is a relevant scenario if wind power plays a major role in decarbonizing the energy system in the latter half of this century.

They found this scenario would warm the surface temperature of the continental US by 0.24 degrees Celsius.

Their analysis focused on the comparison of climate impacts and benefits. They found that it would take about a century to offset that effect with wind-related reductions in greenhouse gas concentrations. This timescale was roughly independent of the specific choice of total wind power generation in their scenarios.

“The direct climate impacts of wind power are instant, while the benefits accumulate slowly,” says Professor Keith.

“If your perspective is the next 10 years, wind power actually has--in some respects--more climate impact than coal or gas. If your perspective is the next thousand years, then wind power is enormously cleaner than coal or gas.”

A series of studies have now observed local warming caused by US wind farms. The researchers on the latest study compared their simulated warming to observations and found rough consistency between the observations and model.

They also compared wind power's impacts with previous projections of solar power's influence on the climate.

They found that, for the same energy generation rate, solar power's impacts would be about 10 times smaller than wind, but there are downsides and benefits to both sources of energy.

“In terms of temperature difference per unit of energy generation, solar power has about 10 times less impact than wind,” said first author Lee Miller.

“But there are other considerations. For example, solar farms are dense, whereas the land between wind turbines can be co-utilised for agriculture.”

The density of wind turbines and the time of day during which they operate can also influence the climatic impacts.

Additionally, the simulations do not consider any impacts on global-scale meteorology, so it remains somewhat uncertain how such a deployment of wind power may affect the climate in other countries.

“The work should not be seen as a fundamental critique of wind power. Some of wind's climate impacts may be beneficial. So rather, the work should be seen as a first step in getting more serious about assessing these impacts,” said Professor Keith.

“Our hope is that our study, combined with the recent direct observations, marks a turning point where wind power's climatic impacts begin to receive serious consideration in strategic decisions about decarbonising the energy system.”