Droughts, hurricanes and floods are generated worldwide by the periodic warming and cooling of the tropical Pacific Ocean's surface waters. El Nino's impacts are now widely known, but the equally serious consequences of its counterpart, La Nina, are only now being highlighted. Although both phenomena have generally been associated with death and destruction, there are benefits in understanding more about their occurrence, their strength and their impacts worldwide, so that their worst effects can be forecast and mitigated. This new edition of Currents of Change explains in simple terms what El Nino and La Nina are and how they can be forecast. Examining for the first time the major El Nino of 1997-1998, this book explores what we can learn from past events, what we can do to ameliorate the worst excesses of these phenomena and how climate change might affect them in future decades.