Climate Change inferred from Borehole Temperature-Depth Profiles by Rob Harris, Geology-Geophysics UofU AEB 310, 3:20pm Monday, October 21, 1996 Editor's Note: This special lecture is intended for graduate students who may not be familiar with the applied problem, but know a little about climate change and the heat equation. The borehole sites in Utah will be located and discussed via drawings and photographs. Climate Change Inferred from Borehole Temperature Profiles Temperature-depth profiles measured in boreholes contain a history of temperature variations at the Earth's surface. Because rock has a relatively low thermal diffusivity (1 x 10-6 m2/s) , changes in temperature at the Earth's surface propagate slowly downwards into the Earth, perturbing the background temperature field. While the high frequency components of a changing surface ground temperature condition are lost due to diffusion, the Earth retains a robust signal of the long wavelength temperature history at the Earth's surface. This type of analysis provides independent evidence for a changing surface temperature condition that can both complement and extend inferences of climate change based on surface air temperature records. Inverse methods used to determine surface ground temperature histories require a regularized solution to the backwards heat equation. I will discuss a functional space "Bayesian" inverse approach which explicitly incorporates apriori information (parameter values and constraints). I will also summarize results from North America, and discuss our ongoing research linking surface ground temperature histories with surface air temperature time series. Requests for preprints and reprints: rnharris@mines.utah.edu This source can be found at http://www.math.utah.edu/research/ Author Address: Rob Harris University of Utah Dept. of Geology & Geophysics Salt Lake City, UT 84112 (801) 581-3588 rnharris@mines.utah.edu