Scientists at the GKSS Research Centre of Geesthacht and the University of Bern have investigated the frequency of warmer than average years between 1880 and 2006.
Scientists at the GKSS Research Centre of Geesthacht and the University of Bern
have investigated the frequency of warmer than average years between 1880 and 2006.
The result: the observed increase of warm years after 1990 is not a statistical accident. The results will now be published in the journal
Geophysical Research Letters.
The average global annual temperature, between 1880 and 2006, was about 15°C. However, in the years after 1990 the frequency of years when this average value was exceeded increased.
The GKSS Research Centre asks: is it an accident that the warmest 13 years were observed after 1990, or does this increased frequency indicate an external influence?
The researchers employed the Monte-Carlo-Simulation“ the coastal researchers and 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 a external driver.
The study was conducted by Dr. Eduardo Zorita and Professor Hans von Storch at the GKSS-Research Centre together with Professor Thomas Stocker of the University of Bern.
The fact that the 13 warmest years since 1880 could have accured by accident after 1990 corresponds to a likelihood of no more than 1:10,000.
These likelihood can be illustrated by using the game of chance "heads or tails": the likelihood is the same as 14 heads in a row.
"In order to understand and statistically analyse the climate system and its interaction between the ocean, land, atmosphere and human activity, the comparison with a game of chance is no longer sufficient.
The natural sequence of warm and cold years no longer functions according to the simple principle of „zero or one“, explains the GKSS scientist Dr. Eduardo Zorita.
An example: After a warm year milder years tend to follow, since the oceans have stored some heat. This natural inertia must also be included in the calculations.
"„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“, says Zorita.
