title: Borehole Temperatures and a Baseline for 20th-Century Global Warming Estimates
abstract: Lack of a 19th-century baseline temperature against which 20th-century warming can be referenced constitutes a deficiency in understanding recent climate change. Combination of borehole temperature profiles, which contain a memory of surface temperature changes in previous centuries, with the meteorological archive of surface air temperatures can provide a 19th-century baseline temperature tied to the current observational record. A test case in Utah, where boreholes are interspersed with meteorological stations belonging to the Historical Climatological Network, yields a noise reduction in estimates of 20th-century warming and a baseline temperature that is 0.6&deg; &plusmn; 0.1&deg;C below the 1951 to 1970 mean temperature for the region.
authors.affiliation: Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, USA.
authors.initials: RN
authors.lastname: Harris
authors.initials: DS
authors.lastname: Chapman