The data centers at the heart of the AI boom are producing so much heat that they’re spiking land temperatures for miles around them by up to 16 degrees Fahrenheit, new research suggests. The effect is so pronounced that the researchers say they’re creating entire “heat islands.”

The findings, detailed in a study that’s yet-to-be-peer-reviewed, add to an already grim picture of the environmental impact of these sprawling facilities, the largest of which consume enough energy to power entire cities. Their commensurate greenhouse gas emissions, however, apparently aren’t the only way data centers are heating up the world around them.

The researchers focused on roughly 8,400 so-called “hyperscalers,” the term used to describe data centers of incredible size that offer cloud computing and AI services. Their construction has surged in the past decade, and the AI boom has pushed their demand and scope to new heights; Meta’s new “Hyperion” data center, for example, cost $27 billion to build and has an expected computing capacity of five gigawatts, an appetite that takes ten gas-powered plants to sate. 

Since temperature can be affected by other environmental factors, the researchers examined data centers in more remote locations. When they mapped their locations against regional temperature data over the past 20 years collected by satellites, a clear pattern emerged. Land surface temperatures, meaning the heat of the ground itself rather than the air or climate, increased by an average of 3.6 degrees Fahrenheit after a data center went online in an area — and in the most extreme cases, the temperature surged by an extraordinary 16 degrees. 

The effects were local, but far reaching. The researchers found that the temperature increases were felt up to 6.2 miles away — though they dropped off with distance — in all affecting more than 340 million people. CNN‘s coverage notes that the trend held globally: Mexico’s burgeoning data center hub in Bajio saw an uptick of around 3.6 degrees over the past 20 years, as did Aragon, Spain, itself a hot new hub for hyperscalers.

Study lead author Andrea Marinoni, an associate professor with the Earth Observation group at the University of Cambridge, told CNN that data centers “could have dramatic impacts on society” in terms of the environment, people’s welfare and the economy.

Other experts were intrigued but cautious about the findings. Ralph Hintemann, a senior researcher at the Borderstep Institute for Innovation and Sustainability, called the figures “interesting” but “very high,” underscoring the need to verify the results. 

The mechanism behind the heating also isn’t immediately clear. “It would be worth doing follow-up research to understand to what extent it’s the heat generated from computation versus the heat generated from the building itself,” Chris Preist at the University of Bristol in the UK told New Scientist, suggesting that sunlight hitting the buildings could be producing the heating effect. This is part of a well-documented phenomenon researchers called the “urban heat island.”

Among other commentators, however, the temperature of response was much more heated. Andy Masley, a writer who frequently “debunks” claims of AI’s environmental impact, called the paper the “single worst writing and research on AI and the environment that I have read” in a lengthy takedown, claiming that the heating effect from sunlight hitting the buildings was powerful enough to look like it was emanating from the ground in satellite data. (Part of his analysis relied on feeding the paper to Claude, however, so make of that what you will.)

Whatever’s going on, it’d be remiss to lose sight of the facilities’ broader environmental impact.

“As far as climate change is concerned, the emissions generated by power generation for data centres remain the more alarming aspect,” Hintemann told CNN.

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