This summer shattered temperature records across the globe, with Western Europe experiencing five grueling heat waves that dried up rivers, turned vegetation into wildfire fuel, and overwhelmed emergency services. Early estimates indicate at least 35,000 excess deaths from just the first four heat waves in about half of Europe, though the World Health Organization considers this a mere preview of worse to come. Two key factors—El Niño, currently in its strongest cycle in a millennium, and human-caused climate change—are expected to push global temperatures even higher in coming years.