Assessment of regional climatic changes in the Eastern Himalayan region: a study using multi-satellite remote sensing data sets.

In this study, an attempt has been made to capture the sensitivity of a mountainous region to elevation-dependent warming and the response of a glacier-laden surface to increasing greenhouse gases (GHGs) and aerosol concentration. Some of the changes Sikkim has undergone due to urban sprawl are as follows: an increase of ~0.7 ± 0.46 °C temperature in the past 40 years at an altitude of 5.5 km; a 2.21 km(2)/year rate of loss of glacierised area in the past 33 years; an increase in absorbed longwave radiation (6 ± 2.41 W/m(2)); an increase in heat fluxes (2 ± 0.97 W/m(2)); a decrease in albedo during the last 30 years; an increase in the concentrations of carbon dioxide (4.42%), methane (0.61%), ozone (0.67%) and black carbon column optical depth (7.19%); a decrease in carbon monoxide (2.61%) and an increase in aerosol optical depth (19.16%) during the last decade; a decrease in precipitation, water yield, discharge and groundwater; and an increase in evapotranspiration during 1971-2005. Detection of three climate signals (1976, 1997 and 2005) in the entire analysis is the quantification of the fact that the climate of Sikkim is moving away from its inter-annual variability. An increase in temperature (0.23 °C/decade) at higher altitude (~5.5 km), suppression of precipitation, decreasing water availability and rapid loss of glacierised area are the evidences of the fact that air pollution is playing a significant role in bringing about regional climatic changes in Sikkim. In this study, change detection method has been used for the first time for the estimation of change in a glacierised area of the region.