 Snow storms in China that have killed more than 60 people are not directly linked to climate change, say scientists, but simply an extreme event caused by very cold winter temperatures and a La Nina weather pattern. La Nina has brought moist air over southern China at a time of very cold winter temperatures, resulting in heavy snow falls, said Chinese weather experts. "This is mainly related to abnormal atmospheric circulation and the La Nina event," Dong Wenjie of the National Climate Centre told the official People's Daily. "The National Climate Centre predicts that this La Nina event will continue at least up to summer 2008 at a medium to strong level," Dong said. "With climate warming, extreme weather events are clearly increasing in frequency and intensity." The worst snows in 50 years in southern China have hit as tens of millions of people attempt to return home to celebrate the Lunar New Year with families. Australian climate scientist Penny Whetton, one of the authors of the U.N.'s Intergovernmental Panel on Climate Change (IPCC) fourth assessment report, said the Chinese explanation for the storms was valid, adding the bad weather was not linked to climate change. "Those conditions are things that occur naturally and so every few years, few decades, everything just comes together right to produce an extreme event," said Whetton, who wrote the IPCC chapter "Regional Climate Projections". The panel's four reports were released last year in phases. "My guess is this is a natural event without any particular reason to link it to climate change. The climate change models are not predicting increases in snow events like this," Whetton told Reuters on Thursday. She said China could expect a less stable climate because of global warming, with various regions experiencing drier, wetter, hotter conditions, as well as more intense tropical storms. "Cold extremes are generally not predicted to become more intense and frequent because we have a warming climate," she said. WORLD'S CLIMATE UNBALANCED But as China warms, its cold northern regions might experience more intense snow storms as moisture levels in the atmosphere rise, creating similar conditions to those that have caused the snow storms now in southern China. "Snow will hang around for less but you will probably get more heavy snow events in winter," said David Jones, head of climate analysis at Australia's National Climate Centre. "We are seeing that in places like northern Canada, where there's been almost a doubling of rain and snow in the last few decades, and that's exactly what you expect cold polar desert regions to become, a lot wetter in a warmer world." Jones also said China's snow storms could not be directly linked to climate change, unlike floods, heat waves and fires that are a result of rising world temperatures and rainfall. "Winter is a time of year in the northern hemisphere where you often get these extreme events. We have always had them and we will always have them," he said. One of the world's largest scientific bodies, the American Geophysical Union, says the world's climate is now out of balance and the rate of climate change is no longer natural. In its first revised climate change report since 2003, the union said last week that the world's climate system was "now changing at rates and in patterns that are not natural". The AGU has a membership of 50,000 researchers, teachers and students in 137 countries. "Not only are we moving into a hotter world but a different world," said Jones. "You get more and more surprises as the world changes, because you are moving into a world where the atmosphere and climate just doesn't behave like it used to."