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The recent projections made by the IPCC regarding the future climatic
changes makes everyone believe that the 20th century warming
caused has been caused only due to anthropogenic activities. The rise in
atmospheric CO2, 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 20th
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.
By
observing the geological past with the eye of a geologist and closely
understanding the present behavior and recessional pattern of Himalayan
glaciers, it is more logical to assign the current rise of 0.6° C
temperature since mid-nineteenth century, to Global temperature cycle,
rather than accuse the mankind. |