Global warming - just hot air?

LectureWe know from weather station records that Earth's surface temperature has increased on average by 0.6 degrees C in the last 100 years. The 1990s have been the warmest decade on record. Over the same period, global sea level has increased by 10-20 cm. We know also that planet Earth has an atmosphere that creates a natural greenhouse effect, keeping our surface warmer than it would otherwise be. Human activities are substantially increasing the atmospheric concentrations of greenhouse gases, principally carbon dioxide and methane, to levels far above those that have existed for the past 200,000 years

Stop-go temperature logging for precision applications

Journal ArticleWe describe a new field procedure for stop-go temperature logging of boreholes that attains millikelvin precision. Temperature is recorded continuously throughout the entire log, but the logging probe is held stationary for a fixed time at discrete depth intervals. Equilibrium temperatures at the discrete depths are based on extrapolations of time series using the heat-diffusion theory for an infinitely long cylinder

Mid-Latitude (30°-60° N) climatic warming inferred by combining borehole temperatures with surface air temperatures

Journal ArticleWe 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

Gravity signals at the Geysers geothermal system

Journal ArticleThree high-precision gravity and GPS surveys have been conducted over The Geysers geothermal reservoir and surrounding area. These surveys, in September 2000, April 2001, and September 2001, provide an initial baseline for future imaging studies of spatial mass changes from the Santa Rosa Effluent Pipeline currently under construction. Analysis of the three surveys provides a measure of the seasonal and annual gravity and deformation signals currently occurring at The Geysers. GPS results show an average subsidence of 3±2 cm over the production field from September 2000 to April 2001, although some stations have significant deviations from this average

Inversion of bottom-hole temperature data: the Pineview field, Utah-Wyoming thrust belt

Journal ArticleThe present day temperature field in a sedimentary basin is a constraint on the maturation of hydrocarbons; this temperature field may be estimated by inverting corrected bottom-hole temperature (BHT) data. Thirty-two BHTs from the Pineview oil field are corrected for drilling disturbances by a Horner plot and inverted for the geothermal gradient in nine formations

Borehole temperatures and climate change: ground temperature change in south India over the past two centuries

Journal ArticleVariations in surface g round temperature (SGT) at the Earth's surface diffuse downward in a predictable way causing systematic perturbations to the subsurface temperature field. The pioneering study of Lachenbruch and Marsh all [1986] in Alaska demonstrated that present-day borehole temperature-depth profiles have the potential to reveal a surface ground temperature history over past several decades to a few centuries. Through the process of heat diffusion the Earth acts as a low-pass filter and a recorder of past surface temperature variations. Borehole temperature-depth profiles thus serve not only to complement the meteorologic record of climate change, but also provide important constraints on temperature trends prior to the occurrence of a global instrumental meteorological record (i.e., ^ 1 8 6 0 A.D.) and in areas where there is a paucity o f instrumentally recorded data.

Climate change in India inferred from geothermal observations

Journal ArticleTemporal variations in surface ground temperature impart a signal to the subsurface thermal regime that is captured in borehole temperature-depth profiles. Seventy temperature-depth profiles in India, located between 12o and 28oN, are analyzed to infer past changes in ground temperature

Monitoring aquifer recharge using repeated high-precision gravity measurements: a pilot study in South Weber, Utah

Journal ArticleRepeated high-precision gravity surveys were conducted over two infiltration cycles on an alluvial-fan aquifer system at the mouth of Weber Canyon in northern Utah as part of the Weber River Basin Aquifer Storage and Recovery Pilot Project (WRBASR). Gravity measurements collected before, during, and after infiltration events indicate that a perched groundwater mound formed during infiltration events and decayed smoothly following infiltration. Data also suggest the groundwater mound migrated gradually south-southwest from the surface infiltration site

Techniques, analysis, and noise in a Salt Lake Valley 4D gravity experiment

Journal ArticleRepeated high-precision gravity measurements using an automated gravimeter and analysis of time series of 1-Hz samples allowed gravity measurements to be made with an accuracy of 5 μGal or better. Nonlinear instrument drift was removed using a new empirical staircase function built from multiple station loops. The new technique was developed between March 1999 and September 2000 in a pilot study conducted in the southern Salt Lake Valley along an east-west profile of eight stations from the Wasatch Mountains to the Jordan River