Like it or not, data centers are now intrinsic to our modern lives, supporting not just the AI boom but healthcare, banking, government services, and other essential sectors. Reliable data center operation depends on effective cooling, which is already a major challenge as many methods require huge inputs of water or energy. To make matters worse, new research suggests that one of our cheapest, most efficient cooling strategies could stop working in a warmer world. The findings, published Monday in the journal Scientific Reports, show that rising temperatures and humidity levels threaten the viability of direct air free cooling, an energy-efficient, waterless technique that pulls outside air in to cool data center servers. Over the past 45 years, weather conditions that limit direct air cooling have become significantly more common, particularly across the tropics and the southeastern United States, according to the study. As the global temperature continues to rise, this problem is only going to get worse. “We found that periods of time when temperature and humidity exceed recommended operating thresholds for direct air free cooling are becoming more frequent and lasting longer in many regions,” lead author Christina Karamperidou, a professor of atmospheric sciences professor at the University of Hawaii at Mānoa, said in a statement. “This will reduce the availability of air free cooling for a growing number of data centers globally.”