Guardian: When I lived in Nigeria, it was always said that there was more fighting in the weeks before the rains broke. Equally, in Pakistan and India, there is lots of anecdotal evidence to suggest there is more crime when it is extremely hot. It is the same in China and the US, where riots invariably take place in the summer, and there is a well-known increase in murders between the months of July and September. Warmer than usual weather appears to mean more people on the streets, more conflict between...