The world will experience global cooling this year, according a leading climate scientist.

The head of the World Meteorological Organisation said La Nina - the weather phenomenon which is cooling the Pacific - is likely to trigger a small drop in average global temperatures compared with last year.

The prediction - which follows a bitterly cold winter in China and the Arctic - is prompting some sceptics to question the theory of climate change.

Iceberg Photo
The news that the earth appears to be cooling would seem to contradict most experts who say that global warming is melting ice at the Poles.

However, the World Meteorological Organisation insists that this year's cooling has nothing to do with global climate change.

In fact, this year's temperatures could still be way above the average - and it is possible that 2008 will exceed the record year of 1998 because of global warming induced by greenhouse gases.

La Nina is Spanish for "The Girl" and describes a cooling of the central and eastern Pacific.

It typically lasts for 12 months. In recent months it caused one of the coldest winters in memory in China, and brought torrential rains to Australia.

While La Nina can affect weather around the world, it is usually less of an influence than El Nino (The Boy). In an El Nino year, the Pacific warms up.

Michel Jarraud, the World Meteorological Organisation's secretary general, said La Nina was expected to continue into the summer, depressing global temperatures by a fraction of a degree.

But he said temperatures in 2008 would still be well above average for the last 100 years.

The Met Office predicts that 2008 will be around 0.4C warmer than the average for 1961-1990.

It said temperatures are influenced by a range of variables - including changes in the sun's output, pollution and weather cycles such as La Nina.

But most scientists argue that the long-term temperature rises since 1880 can only be explained by carbon dioxide from human activity.