Increasing Himalayan snow cover challenges warming theory
doi:10.1038/nindia.2011.47 Published online 31 March 2011
Decline in snow cover in the Himalayas has been one of the major predicted fallouts of global warming. However, a new study challenges these predictions through records of actual observations over the last decade. The study shows that snow cover has actually increased in some parts of the Himalayas.
The joint team of researchers from Kathmandu-based International Centre for Integrated Mountain Development and the Indian Institute of Science, Bangalore sifted through data between years 2000 and 2010. They found that the area covered by snow has increased in some regions of the Hindu Kush Himalaya in contrast to the decline reported in the previous decade in many parts of the mountain range.
According to the study, the snow cover area in western and eastern region of Hindu Kush Himalaya shows an increasing trend while the central region shows a declining trend in this decade. However, the researchers report a declining trend across the region during springtime.
The change in trend is being attributed to the changing pattern in vertical velocity of the wind. Rise in vertical wind velocity leads to instability in the atmosphere and results in increased snowfall.
The team came to this conclusion when it saw a link between the vertical wind speed data and snow cover. Vertical wind speed trends were studied from the decadal records while snow cover was analysed from satellite imaging data.
"We have used data from a moderate-resolution imaging spectroradiometer since it captures temperature of areas along with cloud and snow cover. The temperature record helps distinguish between cloud and snow cover and eliminates the former," Anil Kulkarni, one of the authors of the paper and a visiting scientist at the Indian Institute of Science, pointed out.
The study has led to doubts about the authenticity of models which predict that increase in greenhouse gases in the atmosphere will lead to rapid melting of Himalayan snow cover. "Models based on historical data have not reached the stage where they can make correct predictions," Kulkarni explained.
Other scientists have also expressed their reservations about the link between global warming and decreasing Himalayan snow cover.
The earth goes through alternate natural warm and cold periods like the medieval warm period between 950–1250 followed by the little ice age. Scientists suggest that the earth may be entering another cold period and the natural cooling in this period is superseding the man-made warming.
"The increasing snow cover may be because the cooling period in the meteorological cycle is superseding the manmade warming. In any case warming due to greenhouse gases in the atmosphere is not effective above the altitude of 3000 meters and the Himalayan glaciers exist at altitudes higher than that," said Ravinder Chaujar, a scientist at the Wadia Institute of Himalayan Geology, Dehradun.
However, the authors have not yet de-linked the influence of climate change. "We have noted a changing pattern in vertical wind velocity but have not explored whether that change is an effect of climate change," said Kulkarni.
Despite acknowledging the wide use of satellite data to measure snow cover, some scientists are still not convinced that it reflects the actual amount of snow cover. "How satellite data accounts for thickness and volume of snow is a question that needs to be explored," said Dwarika Prasad Dobhal, another scientist at the Wadia Institute of Himalayan Geology.
- Gurung, D. R. et al. Changes in seasonal snow cover in Hindu Kush-Himalayan region. The Cryosphere Discuss doi: 10.5194/tcd-5-755-2011 (2011)