Across North America, Europe and Asia, hundreds of millions of people suffered from blistering heatwaves. The US special envoy for climate change called it a “threat to all of humanity.” Heatwaves swept across three continents on Tuesday, breaking records in cities across the Northern Hemisphere less than two weeks after the Earth experienced what scientists said were likely the hottest days in modern history. Firefighters in Greece struggled to put out wildfires as parched conditions increased the risk of more fires across Europe. Beijing experienced another day of 95-degree heat, and people in Hangzhou, another Chinese city, compared the sweltering conditions to a sauna. From the Middle East to the American Southwest, delivery drivers, airport workers and construction crews toiled under scorching skies. Those who could stay inside did so. (Alan Yuhas)