FORUM

[Views expressed in this Forum may be considered as the views of the concerned scientist and not necessarily of the Earth Science India or the Organizations they belong - H.E.]

World Environment Day Special

Himalayan Glaciers and Global warming

 Rameshwar Bali

Associate Professor

Centre of Advanced Study in Geology

University of Lucknow, Lucknow

The Himalayan region has one of the most spectacular valley glaciers of the World. The glacial inventory carried out by the Geological Survey of India, reveals the existence of over 9,000 valley glaciers in India and at least about 2,000 glaciers in Nepal and Bhutan. Their size ranges from small (e.g. 5 km long Pindari Glacier in Kumaun Himalaya) to very large (e.g. the 70 km long Siachin glacier in the Kashmir and the 30 km long Gangotri Glacier in the Garhwal Himalayan region).

The recent projections made by the IPCC regarding the future climatic changes makes everyone believe that the 20^th century warming caused has been caused only due to anthropogenic activities. The rise in atmospheric CO_2, along with other green house gases produced by anthropogenic activities has been unprecedentedly high and is unique during the last millennium. The computer modeling based on these measurements makes one feel that with the current trend, the earth is very soon going to “Burn down”.

However, if one views the climatic fluctuations with an eye of a geologist or a palaeoclimatologist, one does not get amused, but finds them to be relatively very small changes that are comparable to the many that have been taking place at regular intervals on this earth. Based on the geological records, it has been observed, that the climate on the Planet earth Is and Has been variable ever since its birth. There have been periods of intense Glaciation (cooling) and Interglaciations (warming) in the geological past. The earth has experienced more extreme and hostile climatic fluctuations in geologic past as compared to the one it is experiencing presently.

Three major periods of glaciation are recorded at around 600-700 million years, 280 million years and during the last 2 million years. Similarly, there have been periods of warmer climate at around 400 million years and between 240- 20 million years. Presently, the temperature is almost 6° C less than what was 100 million years before. The CO₂ level too has come down appreciably. There have been appreciable temperature fluctuations as well as sea level changes. The earth has been experiencing regular warmer and cooler periods over the past 4000 years. Palaeoclimatologists, after examining several climatic proxies argue and postulate that during the “Little Ice Age” (1300-1850 AD), the planet experienced one of the coldest periods in the last 1200 years.

Work carried out by several workers has shown that in Garhwal Himalaya, Gangotri glacier which was earlier receding at a rate of around 26 m/yr between 1935- 1971, has shown a gradual decline in the rate of recession. It has come down to around 17 m/yr between 1974 – 2004 and lastly showed a recession of about 12 m/yr during 2004-2005. The Dokriani Glacier too has maintained an overall constant rate of recession (around 16-18 m/yr) between the year 1962 and 1995. Similarly, monitoring of the Pindari glacier in Kumaun Himalaya suggested that the rate of recession has come down to almost 6.5 m/ yr between 1966- 2007 as compared to around 26 m/year between 1845-1906. Milam glacier in the Goriganga valley, Pithoragarh district has shown a rate of recession of around 16.5 m/yr since last 150 years. The snout of Donagiri glacier has shown signs of moderate recession along with intermittent advances. Parbati Glacier in Beas basin, which had earlier retreated at higher rate possibly due to the valley floor topography, has also shown an appreciable reduction in the rate of retreat by the end of the 20^th century. Similarly, the Satopanth glacier which had earlier been receding at the rate of 22.86 m/a has of late shown a recession rate of 6.5 m/a during 2005-2006

The palaeoclimatological data of recent historical past derived out of several proxies suggests that the appreciable temperature deviation during the Medieval warm period and the Little Ice age were undoubtedly natural occurrences. That was a time when there were no emissions of CO₂ and other green house gases and least interference of the humans with the natural system.

Of late, the environmentalists have been alarmed by the rise in global temperatures since mid-nineteenth century. A geologist on the other hand has a broader perspective and knows for sure that our planet has been much warmer in the past. The U.N.’s graph for temperature change for the past 1000 years does not include the globally recorded Medivial warm  Period as well as the Little Ice Age. This view seems to have been blindly followed and carried forward in context to the melting of Himalayan glaciers too. An undue sensation has been made in the media and the people in general have been made to believe of the bleak future. However, the field monitoring of glacial snout in the Central Himalayan region is not in correspondence with the above views. It is very much evident from the above that the glaciers in the Indian subcontinent, although are showing a recessional trend in general, however, the rate of recession is steadily coming down in most of the cases. They are receding at a much slower pace in comparison to what they were about a few decades back. The much talked about Gangotri glacier, which has been accused of being on the verge of extinction, still needs around 2,500 years to perish at the current recessional rate.  The glacial fed rivers are thus not going to die an immediate death. The scientists who are involved in the glaciological and hydrological studies, however, point out that even at the foot hills, the contribution of glacial melt water is only around 10-15 %, the rest being the rain and ground water. The glacial melt and the snowmelt contribute maximum during the summer time. Thus, even if a time comes that there are no glaciers around, the rivers will still flow. The situation thus is in no circumstances alarming. Lately, the Hockey Stick Curve has been critically reviewed and it is gradually been acknowledged that this curve has been deduced using poor mathematical and statistical calculations. Thus, the entire concept of anthropogenically induced Global warming of IPCC, on the basis of which melting of Himalayan glaciers and future calamities for the Indian subcontinent have been forecasted, is debatable.