Across the world, people have felt the impacts of climate change firsthand. The Northern Hemisphere has had another record-breaking summer season of heat and extreme weather events. The Southern Hemisphere now faces a summer of heat waves, flooding, wildfires and droughts. This is driven by decades of climate change, now supercharged by an unprecedented El Niño—the warm phase of the El Niño Southern Oscillation, which is a cyclical warming and cooling of the Pacific Ocean driven by changing trade winds, with global impacts on the climate.