[The Economist] – On november 21st 2016, a line of thunderstorms passed through the Australian state of Victoria. By the end of the following day, it had sent 3,000 people to hospital. Storms typically hurt people by blowing down buildings, flooding streets or setting fires. In this case, though, the casualties were caused by asthma. Late that afternoon a peculiarly powerful downdraft generated by the storm front pushed a layer of cold air thick with pollen, dust and other particles through Melbourne. The city’s ambulance service was swamped within hours. At least ten people died.