One of the frequently discussed topics of today is the nature and causes of global warming observed in the last 100-150 years and the prediction of its future development. The answers to these questions are mainly sought using climatic and meteorological models based on the current (imperfect) state-of-the-art about processes in the
atmosphere, hydrosphere and lithosphere. In addition to data from observations proxy data on the climate history over longer periods of time are also used for model calibration. One of the paleoclimatic methods producing proxy data is the reconstruction of the ground surface temperature history from temperature-depth profiles measured in deep boreholes. The lecture will focus on the principles and results of this method.