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 km2/year rate of loss of glacierised area in the past 33 years; an increase in absorbed longwave radiation (6 ± 2.41 W/m2); an increase in heat fluxes (2 ± 0.97 W/m2); 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.