Variations in Thermal Growing, Heating, and Freezing Indices in the Nordic Arctic, 1900–2050

Abstract

Observational series and downscaled scenarios of air temperature are used to describe long-term variations 1900–2050 in different climatic indices that are important for the living conditions in the Nordic Arctic (Northern Fennoscandia, Svalbard, Faeroe Islands, and the Greenland-Iceland-Norwegian Sea regions). In addition to air temperature; indices illustrating vegetation conditions (growing season), energy consumption (heating season), and frost conditions (freezing season) are studied. The analyses are based on smoothed daily temperature series deduced from monthly averages for 27 Nordic climate stations, and are focusing on conditions in the climatological 30-yr reference periods 1901–1930, 1931–1960, and 1961–1990, and the scenario period 2021–2050. Also values for two recent time periods (1976–2000 and 1990–2002) are included. The results show substantial variations in growing, heating and freezing indices in the Nordic Arctic during the 20th century. Compared to the period 1961–1990, the growing season has increased during the recent decades in large parts of the region. Projections up to 2050 indicate that the growing season may increase by 3 to 4 wk at most of the stations in the region. The heating season has been reduced during the latest decades, and the projections indicate a further reduction during the next 50 yr.