Ecologist: Rising global temperatures are likely to double the frequency of the most severe El Nios - the periodic atmospheric disruptions which affect weather across the globe. Tim Radford reports. An El Nio is part of a natural cycle: a huge blister of heat in the equatorial Pacific, usually around Christmas-time. The phenomenon periodically triggers unseasonal floods in the western US, and extreme heat and forest fires in the Indonesian rainforest and the Australian bush. It happens and seems to have...