Global temperatures 'to decrease' By Roger Harrabin BBC News environment analyst La Nina caused some of the coldest temperatures in memory in China and global temperatures this year will be lower than in 2007 due to the cooling effect of the La Nina current in the Pacific, UN meteorologists have said. The World Meteorological Organisation's secretary-general, Michel Jarraud, told the BBC it was likely that La Nina would continue into the summer. This would mean global temperatures have not risen since 1998, prompting some to question climate change theory. But experts have also forecast a record high temperature within five years. 'Variability' La Nina and El Nino are two great natural Pacific currents whose effects are so huge they resonate round the world. El Nino warms the planet when it happens, La Nina cools it. This year, the Pacific is in the grip of a powerful La Nina. It has contributed to torrential rains in Australia and to some of the coldest temperatures in memory in snow-bound parts of China. LA NINA KEY FACTS La Nina translates from the Spanish as "The Child Girl" Refers to the extensive cooling of the central and eastern Pacific Increased sea temperatures on the western side of the Pacific means the atmosphere has more energy and frequency of heavy rain and thunderstorms is increased Typically lasts for up to 12 months and generally less damaging event than the stronger El Nino Mr Jarraud told the BBC that the effect was likely to continue into the summer, depressing temperatures globally by a fraction of a degree. This would mean that temperatures have not risen globally since 1998 when El Nino warmed the world. A minority of scientists question whether this means global warming has peaked and the earth has proved more resilient to greenhouse gases than predicted.