In the course of the annual air temperature in Wrocław (TWr variable) a rapid change of the thermal regime was found between 1987 and 1989. A similar temperature change has occurred in Central Europe. TWr increased by more than 1 deg a strong, statistically significant positive trend emerged. The analysis of processes showed that strong warming in the cold season of the year (December–March) occurred as a result of an increase in the NAO intensity and warming in the warm season as a result of increased sunshine duration. Multiple regression analysis has showed that the winter NAO Hurrell’s index explains 15% of TWr variance, and the sunshine duration of the ‘long day’ (April–August) period 49%, whereas radiative forcing 5.9%. This indicates that the factors incidental to the internal variability of the climate system explain 64% of the TWr variability and the effect of increased CO 2 concentration only ~6%. The reason for this rapid change of the thermal regime was a radical change in macro-circulation conditions in the Atlantic-European circular sector, which took place between 1988 and 1989. It has similarly changed the structure of the Central European weathers. The heat, which is the cause of warming in Wrocław, comes from an increase in solar energy inflow (April–August) and also is transported to Europe from the North Atlantic surface by atmospheric circulation (NAO). These results indicate that the role of CO 2 in shaping the contemporary temperature increase is overestimated, whereas internal variability of the climate system is underestimated.