Earth’s global warming fever spiked to deadly new highs across the Northern Hemisphere this summer, and we’re feeling the results—extreme heat is now blamed for hundreds of deaths, droughts threaten food supplies, wildfires have raced through neighborhoods in the western United States, Greece and as far north as the Arctic Circle. At sea, record and near-record warm oceans have sent soggy masses of air surging landward, fueling extreme rainfall and flooding in Japan and the eastern U.S. In Europe, the Baltic Sea is so warm that potentially toxic blue-green algae is spreading across its surface.