Crime and aggressive behaviour are often noted to increase during heatwaves. This could be a physical reaction to changes in, for example, heart rate and hormone levels, or it could be a psychological reaction caused by discomfort and stress; scientists are still trying to work it out. In 2014, however, a study in the
Journal Of Environmental Economics And Management went one step further, predicting that climate change in the US will cause 22,000 more murders, 180,000 more rapes and 1.2 million more aggravated assaults between 2010 and 2099. Researchers have even tied wars and the collapse of societies such as the Mayans to climatic changes.