Heat waves and cyclones; droughts ravaging farmland; rising seas swamping beach havens; forests drying up and species dying out; the Barrier Reef and Kakadu, icons of nature, doomed. This is Australias future if nothing is done to tackle global warming, scientists warn - though exactly what will happen, and how soon, remain uncertain.The biggest single source of global greenhouse gas emissions is the burning of coal to produce electricity and Australia is the worlds biggest coal exporter. The best way for Australia to help, the Howard Government believes, is to invest in the search for technologies that will drastically reduce the emissions that come from burning coal.