With a good part of Europe baking in the heat, the transatlantic air-conditioning debate has erupted again, at least on X. Some of the American jeering at Europe, where AC is found in only 20 percent of homes is overdone. “Traditional” European weather meant that there has been relatively little need for AC. A warming climate is changing that, but older European houses are often difficult to retrofit for AC. There are understandable historical and aesthetic concerns about what the installation of air-conditioning equipment would, if even practical, mean for the look of Europe’s venerable city centers. Electricity is also ...