Summary/Abstract
July 2023 saw extreme heatwaves in several parts of the Northern Hemisphere, including the Southwest of the United States and Mexico, Southern Europe and China. All-time high heat records were broken on several continents. Hundreds of people died, and the rate of hospitalizations spiked in many countries affected. This article reviews peer-reviewed data from observations and climate modeling to assess how global climate change altered the probability and intensity of these heatwaves. The results show that without human induced climate change the heatwave events would have been extremely rare. In China, the heatwave would have been a 1 in 250 year event, while it would have been almost impossible for maximum temperatures like the ones seen in the United States, Mexico, and Southern Europe to occur in the absence of anthropogenic warming. However, a heatwave like the recent ones would occur every 2-5 years in a world that is 2º C warmer than the preindustrial climate. In the current climate, this scale of heatwave can be expected once every 15 years in the US/Mexico region, once every ten years in Southern Europe, and once in five years for China.