Even ignoring the wildfires and drought this season, the sweltering heat itself is proclaiming this an intense summer. And unusually hot summers are becoming not so unusual, according to a new study in the Proceedings of the National Academy of Sciences.
Researchers averaged the summer and winter temperatures for multiple locations across the globe during the years from 1951 to 1980, establishing a baseline for each season. Then they measured how much the temperature varied from this average over the years. They found an increasing number of anomalies in the past 30 years. We no longer have equal odds of the summer temperatures being unusually hot, or unusually cool. Instead, as the researchers phrase it, we are dealing with loaded dice: we are now much more likely to have a hot summer than an average or cool one. And hot temperatures have become both more frequent and more intense. In the time period from which the researchers drew their average, less than one percent of land on Earth suffered from extreme hotter-than-usual temperatures (more than three standard deviations above the average) at any one time. Now, these temperature hotspots cover 10 percent of the land.