Global temperatures boosted by climate change will still be higher than usual despite the cooling effect of a "moderate to strong" La Nina weather phenomenon, the UN said yesterday. The World Meteorological Organization (WMO) said La Nina "has developed and is expected to last into next year, affecting temperatures, precipitation and storm patterns in many parts of the world."  La Nina is considered the stormy sister of El Nino, which occurs every two to seven years when the prevailing trade winds that circulate surface water in the tropical Pacific start to weaken. El Nino, which has a major influence on weather and climate patterns and associated hazards such as heavy rains, floods and drought, has a warming influence on global temperatures, whilst La Nina tends to have the opposite effect.