Analysis of the geothermal gradient near the surface of the Earth is extending knowledge of land surface temperatures hundreds of years into the past before the advent of the instrumental meteorological record. Vertical temperature versus depth profiles of the upper crust (down to 600 m; 2000 ft) contain a recoverable record of surface temperature change over the past few centuries due to particular thermophysical properties of the continental crust, low thermal diffusivity, and a steady-state surface heat flux from the interior. This new method of climate change research provides a direct record of past temperatures, unlike proxy data such as tree rings, paleobotany, stable isotopes, and lake salinity, which rely on analogy or transfer functions. Continued data collection and analysis on all continental areas has the potential to yield a global temperature record that may enable scientists to understand different forcing mechanisms in global climate change.