Ground Surface Warming in Peninsular India:Evidence from Geothermal Records

Analyses of borehole temperature profiles provide useful information about regional climate change over a few centuries. Data from 146 borehole sites in the crystalline terrain of peninsular India were used to reconstruct surface ground temperature history. Depths of the boreholes ranged from 150 to 1522 m. The temperature profiles were characteristic of heat flow by conduction, being largely unaffected by perturbations due to groundwater flow. The profiles show temperature anomalies in the top few hundred metres that is consistent with changing surface temperature over the past two-three centuries. Analysis of individual profiles for a ramp change in temperature reveals predominant surface ground warming in peninsular India with a mean magnitude of 1.0 ± 0.2°C for 129 ± 18 years at 95% confidence level corresponding to onset ca 1860 a d for the change.