Ground Surface Temperature History in Poland in the 16th–20th Centuries Derived from the Inversion of Geothermal Profiles

Ground Surface Temperature (GST) history in Poland was derived from the inversion of temperature-depth profiles in over 20 wells. Temperature histories for the period 1500 A.D. through 1977 A.D. agree well with the instrumental record of the surface-air temperature available for the last two centuries. A statistical correlation of the reconstructed histories (from the well temperature data) with the instrumental record (air temperature) from the homogeneous Warsaw series is high (>0.8). Functional space inversion (FSI) of the temperature data with depth shows that beginning in the early 19th century, temperatures warmed by 0.9 ± 0.1 C following a long period of colder climate before. The last number could be a minimal as higher warming was calculated using a simple model based on surface temperature for the observational period (homogenized Warsaw surface temperature series, LORENC, 2000) and POM (pre-observational mean; HARRIS and CHAPMAN, 1998) of )1.53oC below the 1951–1980 mean temperature level.