Temperature and crime
Using U.S. government data on average yearly temperatures and the number of violent crimes between 1950 and 2008, the researchers estimate that if the annual average temperature in the U.S. increases by 8°F (4.4°C), the yearly murder and assault rate will increase by 34 per 100,000 people -- or 100,000 more per year in a population of 305 million. . . .
Now this part is clearly wrong. Higher temperatures will increase the area of the world that can grow food and increase the growing season.
In addition to the "heat hypothesis," they report that rising global temperatures also increases known risk factors for the development of aggression in violence-prone individuals -- such as increasing poverty, growing up amid scarce resources, malnutrition and food insecurity. They contend that one of the most catastrophic effects of climate change will be food availability, producing more violence-prone individuals in the process. . . .