Berlin, Jan 11 : Scientists have determined that the observed increase of warm years after 1990 is not a statistical accident as has been claimed by some climate skeptics.

Scientists at the GKSS Research Centre of Geesthacht in Germany and the University of Bern in Switzerland have investigated the frequency of warmer than average years between 1880 and 2006 for the first time.

Between 1880 and 2006 the average global annual temperature was about 15 degrees Celsius. However, in the years after 1990, the frequency of years when this average value was exceeded increased.

The researchers' result indicated that the observed increase of warm years after 1990 is not a statistical accident.

With the help of the so called "Monte-Carlo-Simulation", the coastal researchers Dr. Eduardo Zorita and Professor Hans von Storch at the GKSS-Research Centre, together with Professor Thomas Stocker from the University of Bern, estimated that it is extremely unlikely that the frequency of warm record years after 1990 could be an accident and concluded that it is rather influenced by an external driver.

The fact that the 13 warmest years since 1880 could have accrued by accident after 1990 corresponds to a likelihood of no more than 1:10,000.

This likelihood can be illustrated by using the game of chance "heads or tails". The likelihood is the same as 14 heads in a row.

"Our study is pure statistical nature and can not attribute the increase of warm years to individual factors, but is in full agreement with the results of the IPCC that the increased emission of green house gases is mainly responsible for the most recent global warming", said Zorita. (ANI)