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— Greg Harman
SAN ANTONIO, Texas—On Tuesday, the official high in San Antonio was 98 degree Fahrenheit. But, as folks who follow Deceleration know, that doesn’t mean squat for those in the urban core, where all this concrete and asphalt and unceasing highway traffic amplify the heat of summer. When the temps reported by the meteorologists click into the danger zone, we have to protect ourselves. Because we know that temperatures where we live can be 10 degrees hotter—or more—than the official numbers.
While 98F was logged in the shade at San Antonio International Airport, my street briefly hit 107.
At Deceleration we think a lot about the heat. For good reasons.
When our neighbor Albert Garcia died in 2023, we measured his old camp site at 114 during the day when the official temp was 105. And when our friend Jessica Witzel died during an extreme heat event in the summer of 2024, the temperature at the site of her death was 106F. But just one day before, I recorded downtown temps of 119—just a few miles away from where she died—and a heat index of a dizzying 129.
Heat at Albert Garcia's former campsite in 2023 (left) and temperature recorded the following year one day before Jessica Witzel's death in the Five Points area of San Antonio.
Extreme heat driven by the combustion of fossil fuels and destruction of global forests strains our power grid. It drives up our energy bills. And it claims lives.
While temps in Texas have been rising steadily in recent decades, cities like San Antonio are investing in policies in try to dampen the heat’s impacts. Tree planting campaigns, “cool” pavement programs, preservation of greenspace, encouraging rideshares.
But how would you respond if massive industrial facilities that excel in pushing out superheated air moved into the neighborhood? What if they were suddenly popping up across your community, threatening to undermine all of your best heat work?
It turns out hyperscale data centers aren’t merely gluttons for water and power; they are also frequently generators of massive heat islands, raising area temps on average around 4 degrees Fahrenheit.
And sometimes much more.
We wanted to see what that looked like in San Antonio, Texas.
Deceleration Video
The official temp was 98°F but in the shadow of a clutch of large data centers in San Antonio the temps cranked up to 112°F. This investigation explores the urban heat island effect and reveals how massive data centers are contributing to an escalating heat emergency. Follow Deceleration on YouTube.
Survey!
SA Climate Ready 2035 Survey: 'A Priority Plan for a Climate Ready San Antonio'
The extreme heat and storms associated with global warming are already unraveling human and ecological societies across broader swaths of the planet. U.S. cities are far from immune.
“What we're seeing in some parts of the city is: it's very unlivable, in a way, during certain months of the year,” said Jennifer Brady, senior data analyst and research manager at Climate Central. She heads the nonprofit’s data-driven investigations into climate trends and impacts.
“It's going to become really unmanageable to be outside at the very least,” Brady said. “Like, how can people live in cities and go outside their homes? And then you see places like Phoenix where they're thinking about, you know, 3 or 4 months a year, how does a city function in this heat?
"On top of this, we must now consider the heat being pushed out around the clock by data centers. Facilities that are actively, in Brady's words, “creating more spaces where that [ie. livability] might be a challenge and a question.”
The most significant paper we found on data center-generated heat was produced by an international team of researchers from a collection of universities and research institutions. The group reviewed decades of heat data for their study and considered data centers across the planet. To weed out other potential influences, they isolated large scale (or hyperscale, to use industry parlance) data center operations in rural areas.
Their finding? Heat increases ranging from just half a degree Fahrenheit to 16.4F. The average across all hyperscale data centers studied was 3.73F. And it was heat that could still be measured up to seven (or more) kilometers away.
Amount of heat released (left) and geographical spread of that heat in kilometers (right), from recent study into hyperscale data centers operating in rural areas around the world. From: 'The data heat island effect: quantifying the impact of AI data centers in a warming world.'
In greater San Antonio, Texas, with no action by local elected leaders to slow them down, we now have about 56 data centers either in operation or nearing operation, according to a database created by the Texas Tribune. Discussions to date have been mostly limited to questions of water and power. This newsletter is the first foray in Texas, to our knowledge, on the subject of their impact on urban heat.
Some may recall our June 7 newsletter about a public hearing held over the planned expansion of Vantage Data Centers near Sea World, where the exasperation of residents with TX-2 expansion plans was on full display.
Greg Harman
Days later, I popped our drone up to get a birds-eye view of that project, and was struck by the immense size of these facilities—later learning more about the planned power plants here and at the company's Texas Research Park location. This is an expansion now seemingly about to be challenged in court. Recently three environmental organizations filed their 30-day notice of intent to sue.
We next stumbled next into a community forum with far too many open seats in the room considering the tens of thousands of interested views some of our social media clips garnered.
Here we encountered a goodly amount of talk about “doing data centers right,” but no promises to pause them until the City or County can work out adequate safeguards. In the meantime, City-owned CPS Energy reps described being overwhelmed by the volume of power requests: 27GW of inquires and requests in a city that today runs on about 3GW of power. After a year spent winnowing the wheat from the data center chaff, the utility has only drawn that 27GW figure down to about 17GW while roughly 3GW are actively moving toward contract phase.
Greg Harman
All of this with the utility’s board of directors climbing on board for more gas-fired power in a new generation plan that blows up our climate commitments.
Greg Harman
But there has been no public discussion yet about what data centers mean for an increasingly heat-vulnerable city located in a state now 3.5 degrees hotter on average than a few decades ago, where rising nighttime temperatures are making open windows less and less of a protection. No one has asked what happens if these data centers push out what researchers are finding to be an “average” amount of heat for this industry.
That figure is 4 degrees Fahrenheit according to the survey of hyperscale data centers we found posted to ArXiv (pronounced "archive"), an open-source, pre-print archive where STEM researchers upload papers they've submitted for publication, seeking additional feedback beyond the peer review process.
Meanwhile, a peer-reviewed study of Phoenix, Arizona published to the Journal of Engineering for Sustainable Buildings and Cities places that average heat impact at 1.5F. This is heat that doesn’t stop at the fence line, but radiates out for miles.
Here’s a crude attempt to illustrate that potential heat influence using an industry-run online data center map—which suggests it's not a trivial question.
Our own exploration, as you'll see in the video above, suggests a definite influence.
Before we started, we checked the wind direction and packed our water bottle. We were headed back to that Sea World Vantage location, where there are also several Microsoft data centers across the street. Quite a cluster. But we stopped to check the heat at a few sites upwind first.
Here are our findings:
