Climate changes of the last two millennia inferred from borehole temperatures: results from the Czech Republic — Part II

Borehole temperature logs are indicators of the temperature variations associated with the past climate change. Temperature-depth records from 98 holes drilled on the territory of the Czech Republic were inverted to assess the ground surface temperature history. For most boreholes the climatic episodes over the two past millennia were identified, including warmer period around 400 A.D., followed by colder times between 700–1000 A.D., the Little Climatic Optimum with its culmination around 1250 ± 50 A.D., and the Little Ice Age with a temperature minimum at 1650 ± 30 A.D. Since the beginning of the 19th century a general warming has dominated the climate pattem interrupted by several short-term oscillations. The characteristic times of the minimum (min) and maximum (max) alternating extremes are: max 1730 ± 20, min 1780 ± 10, max 1820 ± 10, min 1880 ± 10, max 1935 ± 7, min 1943 ± 5, max 1976 ± 3 A.D. The results are in good agreement with the long-term meteorological observations and proxy climatic records. As to the recent general warming trend (last about 30 yr), there exists a certain geographical pattern of regions where the rate of warming was particularly intense or where it was relatively weaker possibly indicating a certain impact of human activities. The highest amount of warming of 2.6–2.8 K were obtained for the industrial regions of the Praha, northern Bohemia and Ostrava coal basins, while the lowest warming of 0.07–0.6 K corresponds to the southwestern and southern slopes of the Bohemian Massif, areas are generally forested