ИСТИНА

Since the beginning of the 20th century, the rise of global surface temperature according to instrumental observations was not monotonous and was characterized by two global warming periods – warming of the mid-20th century and modern warming, separated by a period of global temperatures decline. Different reanalysis datasets – global gridded data on atmospheric characteristics obtained with the atmospheric models with assimilation of various empirical data - are increasingly used for the analysis of the climate change. Due to significantly lower quantity and quality of observational data in the first half of the 20th century, as well as the use of various models and assimilation data, the ability of reanalysis to reproduce changes in climatic characteristics for the 20th Century requires quantitative assessment. Here we analyze evolution of the surface air temperature (SAT), sea level pressure and geopotential height in the Northern Hemisphere (with a focus on the northern Extratropics) according to three reanalyses covering the entire 20th century: NOAA-CIRES 20th Century Reanalysis and ECMWF ERA20C and CERA20C and compare them to GISS/NASA GISTEMP and HadSLP2 Hadley Center gridded datasets based on station observations. Spatial trend structures, area averages and indices of leading atmosphere circulation modes are inter-compared focusing on the Early Twentieth Century Warming period. It is revealed that reanalyses data differ significantly between each other and observations within the entire 20th century, most strongly in the first half of the 20th century, at high latitudes. An overall assessment points to European reanalyses as to relatively more realistic product, with relatively best results shown by CERA20C. In particular, the temperature and pressure evolution in NOAA-CIRES 20th Century Reanalysis represents significant discrepancies in climatic characteristics throughout the 20th century.