Geothermal climate change observatory in south India 1: Borehole temperatures and inferred surface temperature histories

摘要: Abstract Temperature–depth profiles measured in boreholes contain records of changes surface ground temperature over the past few centuries. We have recently set up a geothermal climate change observatory at Choutuppal campus National Geophysical Research Institute (17.29 °N, 78.92 °E) to measure subsurface on annual decadal timescales and quantify how well they track changes. The site is located about 60 km east Hyderabad south India, designated reserved forest land far from potential urban heat islands. In April 2009, two were drilled depths 210 m 21 m respectively after careful selection minimize perturbations temperatures account groundwater flow borehole, large thermal conductivity contrasts rugged topography. Temperature measurements holes are being carried out periodically. Analysis equilibrium temperature–depth profile deep borehole reveals least ongoing events that started during Century: (i) warming 0.5 ± 0.1 °C 92 ± 7 years, (ii) more recent cooling ∼1 °C ∼39 years, probably representing local vegetation caused by presence thicker grass cover throughout year inside since 1967 AD compared short cropping outside it. inferred consistent with estimates three other (170–300 m deep) distributed 10 × 5 km 2 area vicinity (mean: 93 ± 21 years), characteristic Interior Peninsula region India.