The rise of the truly cruel summer

In Japan it starts with the pulsating song of cicadas; in Alaska, with salmon swimming upstream. However it begins, summer in the northern hemisphere—where more than 85% of the world’s population live—soon involves dangerous levels of heat. This year is no exception—indeed, it carries the trend further. In Saudi Arabia more than 1,300 pilgrims died during the hajj, the pilgrimage to Mecca, as temperatures exceeded 50°C. India’s capital, Delhi, endured 40 days above 40°C between May and June. And in Mexico scores of howler monkeys have been falling dead from the trees with heatstroke.