AGW Observer

Observations of anthropogenic global warming

Papers on temperature reconstructions from boreholes

Posted by Ari Jokimäki on February 24, 2010

This is a list of papers on temperature reconstructions from boreholes. Emphasis is on global analysis so there’s not much papers on single locations. The list is not complete, and will most likely be updated in the future in order to make it more thorough and more representative.

A late Quaternary climate reconstruction based on borehole heat flux data, borehole temperature data, and the instrumental record – Huang et al. (2008) “We present a suite of new 20,000 year reconstructions that integrate three types of geothermal information: a global database of terrestrial heat flux measurements, another database of temperature versus depth observations, and the 20th century instrumental record of temperature, all referenced to the 1961–1990 mean of the instrumental record. These reconstructions show the warming from the last glacial maximum, the occurrence of a mid-Holocene warm episode, a Medieval Warm Period (MWP), a Little Ice Age (LIA), and the rapid warming of the 20th century. The reconstructions show the temperatures of the mid-Holocene warm episode some 1–2 K above the reference level, the maximum of the MWP at or slightly below the reference level, the minimum of the LIA about 1 K below the reference level, and end-of-20th century temperatures about 0.5 K above the reference level.” [Full text]

Borehole climate reconstructions: Spatial structure and hemispheric averages – Pollack & Smerdon (2004) “We demonstrate the consistency of GST warming estimates by showing that over a wide range of grid element area and occupancy weighting schemes, the five-century GST change falls in the range of 0.89–1.05 K. We examine the subhemispheric spatial correlation of GST and SAT trends at various spatial scales. In the 5-degree grid employed for optimal detection, we find that the majority of grid element means are determined from three or fewer boreholes, a number that is insufficient to suppress site-specific noise via ensemble averaging. Significant spatial correlation between SAT and GST emerges in a 5-degree grid if low-occupancy grid elements are excluded, and also in a 30-degree grid in which grid element means are better determined through higher occupancy. Reconstructions assembled after excluding low-occupancy grid elements show a five-century GST change in the range of 1.02–1.06 K.” [Full text]

Optimal surface temperature reconstructions using terrestrial borehole data – Mann et al. (2003) “We derive an optimal Northern Hemisphere mean surface temperature reconstruction from terrestrial borehole temperature profiles spanning the past five centuries. The pattern of borehole ground surface temperature (GST) reconstructions displays prominent discrepancies with instrumental surface air temperature (SAT) estimates during the 20th century, suggesting the presence of a considerable amount of noise and/or bias in any underlying spatial SAT signal. The vast majority of variance in the borehole dataset is efficiently retained by its two leading eigenvectors. A sizable share of the variance in the first eigenvector appears to be associated with non-SAT related bias in the borehole data. A weak but detectable SAT signal appears to be described by a combination of the first two eigenvectors. Exploiting this eigendecomposition, application of optimal signal estimation methods yields a hemispheric borehole SAT reconstruction that is largely consistent with instrumental data available in past centuries, and is indistinguishable in its major features from several published long-term temperature estimates based on both climate proxy data and model simulations.” [Full text]

Climate from Borehole Data: Energy Fluxes and Temperatures since 1500 – Beltrami (2002) “Here I apply singular value decomposition (SVD) Here I apply singular value decomposition (SVD) inversion methods to 826 temperature-depth profiles distributed world wide, in order to reconstruct ground surface temperature histories (GSTH) and surface heat flux histories (SHFH) from the temperature and heat flux anomalies detected in the shallow subsurface. Inversions yielded a mean ground surface temperature and surface heat flux histories flux histories for the Earth’s continents for the last 500 years. Results indicate that the global average ground temperature and ground heat flux have increased an average of 0.45 ° K and 18.0 $mWm^{2}$ respectively over the last 200 years, and 0.9 ° K in the last five centuries.” [Full text]

Earth’s Long-Term Memory – Beltrami (2002) “Two methods-multiproxy and geothermal-are commonly used to reconstruct Northern Hemisphere climate of the last 500 to 1000 years. Both show warming in the 20th century, but in earlier centuries the temperature curves diverge strongly. In his Perspective, Beltrami investigates the reasons for these discrepancies. He explains the difficulties that arise in trying to compare the two types of records and calls for integrated analyses in which all models are interpreted jointly.”

Mid-latitude (30°–60° N) climatic warming inferred by combining borehole temperatures with surface air temperatures – Harris & Chapman (2001) “We construct a mid-latitude (30°–60° N) reduced temperature-depth profile from a global borehole temperature database compiled for climate reconstruction. This reduced temperature profile is interpreted in terms of past surface ground temperature change and indicates warming on the order of 1°C over the past 100 to 200 years. The combination of an initial temperature (the primary free parameter) with the last 140 years of gridded surface air temperature (SAT) data yields a synthetic temperature profile that is an excellent fit to observations, accounting for 99% of the observed variance and a RMS misfit of only 12 mK. The good correlation suggests that this reduced temperature profile shares much information with the mean SAT record over large areas and long time-scales. Our analysis indicates 0.7°±0.1°C of ground warming between pre-industrial time and the 1961–1990 mean SAT.”

Climate Reconstruction from Subsurface Temperatures – Pollack & Huang (2000) A review article. “Temperature changes at the Earth’s surface propagate downward into the subsurface and impart a thermal signature to the rocks. This signature can be measured in boreholes and then analyzed to reconstruct the surface temperature history over the past several centuries. The ability to resolve surface temperature history from subsurface temperatures diminishes with time. Microclimatic effects associated with the topography and vegetation patterns at the site of a borehole, along with local anthropogenic perturbations associated with land use change, can obscure the regional climate change signal. Regional and global ensembles of boreholes reveal the broader patterns of temperature changes at the Earth’s surface. The average surface temperature of the continents has increased by about 1.0 K over the past 5 centuries; half of this increase has occurred in the twentieth century alone.” [Full text]

Temperature trends over the past five centuries reconstructed from borehole temperatures – Huang et al. (2000) “Here we use present-day temperatures in 616 boreholes from all continents except Antarctica to reconstruct century-long trends in temperatures over the past 500 years at global, hemispheric and continental scales. The results confirm the unusual warming of the twentieth century revealed by the instrumental record, but suggest that the cumulative change over the past five centuries amounts to about 1 K, exceeding recent estimates from conventional climate proxies.” [Full text]

Climate Change Record in Subsurface Temperatures: A Global Perspective – Pollack et al. (1998) “Analyses of underground temperature measurements from 358 boreholes in eastern North America, central Europe, southern Africa, and Australia indicate that, in the 20th century, the average surface temperature of Earth has increased by about 0.5°C and that the 20th century has been the warmest of the past five centuries. The subsurface temperatures also indicate that Earth’s mean surface temperature has increased by about 1.0°C over the past five centuries. The geothermal data offer an independent confirmation of the unusual character of 20th-century climate that has emerged from recent multiproxy studies.” [Full text]

Late Quaternary temperature changes seen in world-wide continental heat flow measurements – Huang et al. (1997) “Analysis of more than six thousand continental heat flow measurements as a function of depth has yielded a reconstruction of a global average ground surface temperature history over the last 20,000 years. The early to mid-Holocene appears as a relatively long warm interval some 0.2–0.6 K above present-day temperatures, the culmination of the warming that followed the end of the last glaciation. Temperatures were also warmer than present 500–1,000 years ago, but then cooled to a minimum some 0.2–0.7 K below present about 200 years ago. Although temperature variations in this type of reconstruction are highly smoothed, the results clearly resemble the broad outlines of late Quaternary climate changes suggested by proxies.” [Full text]

Geothermal Evidence from Permafrost in the Alaskan Arctic – Lachenbruch & Marshall (1986) “Temperature profiles measured in permafrost in northernmost Alaska usually have anomalous curvature in the upper 100 meters or so. When analyzed by heat-conduction theory, the profiles indicate a variable but widespread secular warming of the permafrost surface, generally in the range of 2 to 4 Celsius degrees during the last few decades to a century. Although details of the climatic change cannot be resolved with existing data, there is little doubt of its general magnitude and timing; alternative explanations are limited by the fact that heat transfer in cold permafrost is exclusively by conduction. Since models of greenhouse warming predict climatic change will be greatest in the Arctic and might already be in progress, it is prudent to attempt to understand the rapidly changing thermal regime in this region.”

Underground temperature and inferred climatic temperature of the past millenium – Cermak (1971) “Any change at the surface is propagated downwards, and it is shown that the detailed record of temperature with depth can be used to trace the past climatic history. The theory of climatic correction of heat flow is used, and the data is obtained from two boreholes in northeastern Ontario. After analysis the measured underground temperature clearly confirmed the notably warm climate that lasted a few hundred years around A.D. 1000–1200 and the following cold period after 1500. … The results presented indicate for the Kapuskasing area a surface temperature during the Little Climatic Optimum at least 1.5°C higher than the reference value; the mean temperature during the Little Ice Age was about 1°C below this reference value. A remarkable increase since about 1850 reaches value in excess of 3°C.”

Analysis of Heat Flow Data—I Detailed Observations in a Single Borehole – Beck & Judge (1969) “Heat flow data from a 600-m deep diamond drilled borehole has been used to estimate how short a section of borehole will give a valid heat flow value, to test for recent and ancient climatic changes, underground water-flows and the variation of terrestrial heat flow with depth. Temperatures were repeatedly measured at 3-m intervals; measurements of thermal conductivity, density and porosity were made on specimens sampled at approximately 4-m intervals along the length of the hole. The mean heat flow for the whole borehole before applying any corrections is 0.76 h.f.u. while after correcting for the Wisconsin glaciation the mean value is 1.17 h.f.u., but in both cases some 30 to 100-m sections of the borehole differ by ±20 per cent from the mean values. The differences cannot be entirely explained as being due to structure, topography, climatic changes or underground water-flows.”

Postglacial Time Calculations from Recent Geothermal Measurements in the Calumet Copper Mines – Hotchkiss & Ingersoll (1934) “The retreat of the glacial sheet a number of thousand years ago and the subsequent long-period surface temperature variations must almost certainly have left their impress on the geothermal curve. An attempt has been made to find such an effect and to interpret it in terms of past surface temperatures by subjecting to mathematical analysis a series of geothermal measurements recently made in the Calumet and Hecla conglomerate mine. The results indicate that the glacial epoch ended for this region 20,000-30,000 years ago, and that it was followed by a period with ground temperatures distinctly warmer than the present, succeeded in turn by one cooler, and lasting until comparatively recent times.”

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