- What is new in the study is that a comprehensive approach has been taken on weather data from all over Europe, and the results indicate that mainly the warm temperature extremes have increased, says Erik Kjellström, professor of climatology at SMHI.

During the summer heat waves several European heat records were broken. In southern France, for example, where the mercury in several places crossed the 46-degree line. But on individual days, no conclusions can be drawn. By contrast, 70 years of data from nearly 1,000 weather stations across Europe show a clear pattern.

Among other things, the number of extremely hot days has more than tripled since 1950. They have also become an average of 2.3 degrees warmer. This is evident from the study by Swiss researchers published at the American Geophysical Union, AGU.

The models miss

The study also shows that the number of extremely cold days halved during the same period. In addition, these have become on average 3 degrees milder.

The authors have also compared actual measurement results with the data simulations that researchers usually use to study and predict climate change. The conclusion is that these climate models are not very accurate.

- It shows that today's models underestimate the warming of the extremely hot days of summer, but overestimate the warming of the extremely cold days of winter, says Erik Kjellström.

- There is a continuing need to understand why this is so and to develop our models so that they better represent the climate.