The recent warming of Earth's surface is well documented in meteorological records. According to the World Meteorological Organization, the Earth's average surface air temperature (SAT) rose about 0.6°C in the twentieth century [Jones and Moberg,2003].
Any global scale variation in SAT is accompanied by variation of the thermal state of all major climate system components including the continental landmasses. Based on worldwide meteorological and borehole temperature records, this study suggests that the twentieth century global warming has deposited a large amount of thermal energy into the continental landmasses, and has resulted in an intensified heating of rocks underground. The feedback to the global climate system and the long-term environmental consequences of the on-going subsurface warming of the land remain to be recognized.