Sir: The recent heat wave in Karachi, the biggest metropolitan city of Pakistan, claimed numerous lives in just a few days. The temperature rose to unprecedented levels, with intense humidity making the situation worse. Ramadan and lack of water supply added to people’s troubles. Heat waves can elevate the normal body temperature to dangerous levels. Heat waves have a global impact on the planet. This includes melting of glaciers, droughts and floods. These types of natural disasters should be taken seriously. We should prepare ourselves for them. SIDRA NUMAN Karachi Published in Daily Times, May 28th 2018.