“Estimates of cooling degree days are used everywhere,” said Jake Casselman, atmospheric sciences postdoctoral researcher in the UH Mānoa School of Ocean and Earth Science and Technology ( SOEST ). Casselman and Christina Karamperidou, an atmospheric sciences professor in SOEST , combined climate science with refrigeration engineering to develop a new cooling demand metric that explicitly accounts for how cooling system efficiency changes with temperature and humidity. They applied this new cooling demand metric to 50 years of high-resolution weather data (1971–2020) across North America to quantify how climate-driven changes in cooling efficiency have already reshaped cooling demand across regions. “Getting cooling demand right isn’t an academic exercise; it directly affects how we plan, size, and operate future energy infrastructure as the climate changes.” In humid regions, heat and moisture compound each other, so the energy burden is worse than temperature alone would suggest.