The study identifies a nonlinear relationship between temperature, humidity, and cooling capacity, meaning incremental warming produces disproportionate reductions in economization availability
Decision Focus
A study by Karamperidou, Casselman, Cleveland, and colleagues, published in Scientific Reports in June 2026, provides the most quantitatively grounded assessment to date of how climate change is eroding the usable operating window for air free cooling in data centers. The research draws on climate modeling, thermal system analysis, and empirical data from operational facilities across multiple geographies. The operational signal for energy leaders is specific: facilities in the tropics and southeastern United States are already losing viable economization hours, and the share of sites constrained for more than a quarter of the year is reportedly rising. As mechanical cooling moves from backup to baseline in more markets, energy spend rises, sustainability targets tighten, and the assumptions embedded in long-horizon facility designs come into question.
90-Second Brief
This week, research published in June 2026 models the impact of rising temperatures and humidity on air free cooling viability in data centers globally. The study finds that over the past 45 years, hours characterized by conditions limiting direct air cooling have increased significantly, particularly in the tropics and southeastern United States. A growing share of data center sites worldwide now faces constraints for at least one quarter of the year, with projections through mid-century indicating continued deterioration under sustained warming. The study identifies a nonlinear relationship between temperature, humidity, and cooling capacity, meaning incremental warming produces disproportionate reductions in economization availability.
What Is Really Happening?
Air-side economization — pulling ambient outdoor air to cool server infrastructure — is widely deployed because it reduces dependence on energy-intensive chillers and minimizes water consumption. It sits at the intersection of operational cost control and sustainability strategy. The 2026 study argues that this efficiency lever is climate-sensitive in a way that has been systematically underestimated.
The mechanism the researchers describe is not merely linear warming. Their models identify a compounding effect: as temperature and humidity rise together, the thermodynamic headroom for effective heat exchange collapses faster than either variable alone would suggest. High humidity also introduces moisture-related hardware risks — condensation on circuit boards, accelerated corrosion of metal components — that constrain how broadly operators can open air-side systems even during otherwise favorable hours.
The geographic concentration of risk is notable. The tropics and southeastern United States emerge as current hotspots, regions that also host substantial and growing data center capacity. The study frames the 45-year trend as already measurable and already affecting operating windows — not a distant future scenario.
Why It Matters for Global Heads of Data Center Energy
The energy cost implication is direct. Air free cooling, when viable, materially lowers PUE and mechanical cooling energy consumption. When it is not viable, chillers and compressors carry the load. A shrinking economization window translates to rising base energy draw per MW of IT load — an effect that compounds across a multi-site portfolio and lands directly on the energy budget line.
For operators who have locked in long-term PPA structures or renewable energy commitments calibrated to a facility’s historical cooling energy profile, a shift in the mechanical-to-economization ratio introduces basis risk between contracted clean power and actual consumption. Sustainability commitments built on projected PUE improvements may need re-evaluation if the assumed economization hours are no longer climatically realistic.
Site selection is equally affected. Facilities sited partly for their climate suitability for air-side economization may now carry higher stranded-efficiency risk than initial energy models captured. For portfolios with assets across the southeastern United States, Southeast Asia, or tropical colocation markets, a systematic review of cooling regime assumptions is no longer a precautionary exercise — it is a portfolio hygiene issue.
The study also raises a physical resilience dimension. Concurrent stresses — grid instability during peak heat events, water scarcity constraining alternative cooling methods — can converge precisely when mechanical cooling demand is highest. The authors raise this as a systemic vulnerability worth integrating into risk assessments, not as a certainty.
Forward View
The study’s mid-century projections indicate that climate-driven constraints on air free cooling will continue to expand under sustained warming and increasing humidity. While specific thresholds are not confirmed here, the direction is consistent across the modeled climate futures the researchers examined.
Two operational fronts are worth watching. First, hybrid cooling architectures — systems designed to switch dynamically between air-side and mechanical modes based on real-time atmospheric parameters — are framed in the research as the adaptive response the industry needs to develop. The study presents this not as a niche design choice but as a structural requirement for facilities built to operate across a 15–20 year horizon in vulnerable geographies. Second, the authors point to liquid cooling technologies and lower-impact refrigerant alternatives as complementary paths where air-side economization proves insufficient. Neither is characterized as fully mature or cost-equivalent today.
For new facilities, the research provides a practical tool: a predictive framework for assessing air free cooling viability under projected climate scenarios, designed to inform site selection, design specifications, and operational protocols.
What Is Still Uncertain
Several material questions remain open. The study does not publish a site-by-site risk ranking, so operators cannot directly apply its findings to a specific facility without additional climate modeling at the local or regional scale. The degree to which humidity-driven constraints are already affecting measured PUE in currently operational facilities is not confirmed in the source — the study presents projections and trend analysis, not audited operational outcomes.
The economic crossover point — at what level of economization loss hybrid systems become financially justified versus continued mechanical cooling — is not quantified in the available findings. Timeline and cost curves for liquid cooling and low-impact refrigerant alternatives remain a function of supply chain maturity and vendor development paths that the study does not address.
One Question for Your Team
For which sites in your portfolio were the original PUE assumptions and energy cost models based on air-side economization availability that climate projections now suggest is materially at risk — and has that exposure been priced into long-term energy contracts?
Sources
- Bioengineer — Challenges of Air Free Cooling in Hot, Humid Data Centers (Link)
