Annual and seasonal climatic variations over the northern hemisphere and Europe during the last century

Provides a method which allows the detection of an abrupt climatic change and which localizes approximately the date of its beginning. The identification of such a change is made by means of a non-parametric test, the Mann-Kendall rank statistic. The efficiency of this test has been compared to the efficiency of other usual techniques used for detecting a change and the reliability of the localization of the change has been analysed using a Monte-Carlo technique. The data used are the long-term series of average northern hemisphere temperature, the instrumental records of temperature and precipitation for western european countries and the long-term european reconstructed series. Most of the temperature series exhibit a general long-term warming which supports the reality of the early 20th century northern hemisphere warming, as noted by many authors. However, this study shows that an abrupt change towards a warming occurred generally around 1900+/-25 years and that we are still experiencing this longterm warm climate.