Assessment of climate warming in the Western Ghats of India in the past century using geothermal records.

Temperature-depth profiles of boreholes of a region can be analysed to estimate the past variations in climate. Perturbations over the surface ground temperature are imparted deep into the Earth's subsurface. Western Ghats regions of India are considered to be one of the most ecologically rich regions and also play a crucial role in deciding the climatological characteristics of the country. This study quantifies the possible climate warming or cooling in the past century in the Western Ghats using temperature-depth profiles of five boreholes in a depth range of 140–198 m located in Koyna region (17.38° N, 73.74° E) of Maharashtra state, India. The analysis shows that there has been a significant warming of 0.8 ± 0.2 °C over the past 100 years in the region. The inferred warming is comparable with the trends of meteorological records of the area which yields an increasing trend of 0.56 °C in the surface air temperature (SAT). For further validation of results, a combined study of borehole temperature profiles and surface air temperature (SAT) profiles was done which showed that the period was warmer than the earlier long-term temperature records of the region by 0.8 °C. This pre-observational mean (POM) value seems to be consistent with previously studied POMs over India. This study provides a 'true estimate' of climate change and can be used as a robust technique to reconstruct the past climate warming. [ABSTRACT FROM AUTHOR]