NEW DELHI: In a worrying trend, Himalayans have become warmer in last 25 years with significant climatic change seen especially after the year 2000, said a study by DRDO’s Snow & Avalanche Study Establishment (SASE).
The study further says that the impact of global warming is evident over northwest Himalayas in the form of rising maximum and mean temperature at all zones and there has been 0.87 degree Celsius increase in mean temperature in Greater Himalayas.
The study by scientists from Chandigarh-based SASE found that that amount of snowfall has decreased whereas rainfall has increased in the last 25 years in the Himalayan region. It comes at a time when there are concerns over global warming across the world and governments are working to limit the impact of climate change by taking measures to reduce greenhouse gas emissions.
The study discusses the observed long-term (1991–2015) and short-term (1991–2000 and 2001–2015) trends in winter temperature and precipitation over Northwestern Himalaya (NWH) along with its constituents -- Lower Himalaya (LH), Greater Himalaya (GH) and Karakoram Himalaya (KH).
“An overall warming signature was observed over NWH since maximum, minimum and mean temperatures followed rising trends in last 25 years and the increase is statistically significant for maximum and mean temperatures. The rise in mean temperature was observed highest at GH at 0.87 degree C followed by KH at 0.56 degree C,” said the study published in the Current Science journal’s latest issue on February 25.
The study was done by SASE scientist H S Negi, Neha Kanda, M S Shekhar and A Ganju.
However, warming was not consistent over all zones of NWH with minimum temperature at LH showing anomalous cooling by 0.83 degree C during the period. The total precipitation (rainfall and snowfall) was found to increase whereas snowfall was found to decrease with concurrent significant increase in rainfall at all zones of NWH.
The spatiotemporal winter climatic variations over NWH support the impact on recently reported findings on the Himalayan snow cover and glacier variations at different durations.
However, maximum and mean temperature trends during last 15 years (2001–2015) depict cooling at LH and GH which could have resulted from increased aerosol emissions by anthropogenic activities and aerosols, by virtue of their absorbing nature do not allow much of incoming solar radiation reaching the earth surface leading to cooling temperature.
On the contrary, KH and NWH (overall) have experienced warming during last 15 years (2001–2015) which substantiates the impact of climate change in form of global warming. However, the rate of warming over GH is found to be higher than that prevailing over KH which partly explains the observance of higher glacier retreat rates over GH than KH.
Precipitation has increased at all zones of NWH though significant increase is reported at LH only in 25 years. Furthermore, precipitation at all zones except LH follows decreasing trends in last 15 years (2001–2015) which signals significant climatic change especially after year 2000.
“However, such observations must be validated with other sources of information depicting climate change like the extent of glaciated areas and vegetation cover over different regions of NWH,” it suggested.
Comparative analysis of trend and slope observed in snow-fall and rainfall during 25 years
| Region | Rainfall (mm) Trend (+ ) (–) | Snowfall (mm) Trend (+) (–) |
|---|---|---|
| Lower Himalayas | Slope 57.5 | –8.3 |
| Greater Himalayas | Slope 5.2 | –5 |
| Karakoram Himalayas | Slope 4.3 | –1.2 |