The scourge
of global warming seems to be spreading. Discussion on global warming
has become the in thing. In a country like India where maximum
illiteracy is there, majority of people find global warming an
engrossing topic to discuss. Each individual has his own perception.
This year the Gangetic Plains of north India underwent a cold spell
around the popular festival of Holi, and lo! It was ascribed to global
warming. If a day becomes warmer global warming is declared the cause
and if it becomes a trifle cool again the horror of global warming is
recalled. But yes global warming is an issue that needs to be tackled
very seriously and sincerely.
Everyday
the media reports are full of the possible hazards and consequences
of the global warming. The present is a key to the past and the past
is the window for future. What were the climates of the past like
has been a daunting the scientists involved with the study of the
climate change.
Our planet was born after the gaseous nebula cooled down. Once it
was formed, it is believed that Carbon dioxide controlled the global
cooling and heating. The earliest record of an ice sheet around the
globe is from 750 million years old rocks of Namibia. Imagine the
impact of a complete cover of ice all around on the living being. It
leads to a complete collapse of life. For millions of years all
biological activity had come to a standstill, till volcanic
eruptions started warming up the environment again.
Thus the earth's climate changed between the 'icehouse state' to
'greenhouse state' says R.K. Kar a palaeobotanist from the Birbal
Sahni Institute of Palaeobotany, Lucknow, in one of his papers.
There were several ice Ages and greenhouse stages. Of these, two
episodes of greenhouse stage left their indelible mark on the flora
of our planet. The first 'greenhouse state started some 500 million
years ago (Ma) and lasted for about 145 Ma. In terms of geologists
this is the Ordovician-Devonian global warming. The next major
greenhouse state of the climate started some 203 Ma and lasted for
138 Ma, known as the Jurassic-Cretaceous global warming.
How did it happen and what were the consequences is an interesting
study. It was Arrhenius (1896) who first introduced the term 'hot
house' theory which later became the greenhouse theory. Greenhouse
effect is a phenomenon by which carbon dioxide, water vapor,
atmospheric methane, nitrous oxide, ozone and aerosol trap more
solar heat within the atmosphere causing a global warming. In
geological past when the earth had become a giant deep freeze, the
global warming came as a relief for the fauna and the flora to
regenerate and rejuvenate. The frozen life was reactivated when the
gases from the sub aerial volcanic activity started to reach the
atmosphere. This increased the atmospheric CO2 content tremendously
and the global warming started.
In other words the greenhouse state is associated with volcanism and
sea level rise. A.E.J. Engel and C.G. Engel (1964) have shown two
peaks of volcanism in the past, says Kar in his paper. The older one
persisted through Late Cambrian (500 Ma) to Late Devonian (355 Ma)
and the other in the Late Jurassic (135 Ma) to Cretaceous (65 Ma)
periods of the earth's history. Researchers have also established
that the CO2 content of the atmosphere was very low during most of
the Ice Ages.
Plant life evolved initially in the sea water. The first land plants
started to appear around 450 Ma. It was during the Devonian period
that is 410 to 355 Ma that plant life evolved and proliferated. It
was during this period plants with naked seeds, Gymnosperms made
their first appearance. The next greenhouse state of the
Jurassic-Cretaceous (250 to 65 Ma) period led to the birth of
Angiosperms, the flowering plants. Even after this greenhouse state,
temperatures kept soaring and one episode known as Paleocene-Eocene
Temperature Maxima (PETM) has been observed by the researchers in
Arctic Ocean during an expedition in 2004. The scientists aboard a
fleet of Icebreakers drilled into the floor of the Arctic Ocean and
collected samples of past life. This was a major feat because no one
had dared this kind of venture earlier.
The findings of the expedition were huge and are still being
published. From the information so far been published by Matthew
Huber, an Assistant Professor of Earth and Atmospheric Science in
Purdue University's College of Science says "sea surface
temperatures at the North Pole had soared to 23 degrees Celsius, or
around 73 degrees Fahrenheit, during the Paleocene-Eocene Thermal
Maximum, or the PETM, about 55 million years ago". Today's mean
annual temperature around North Pole is around 20 degrees Celsius.
The high temperatures of the Arctic were confirmed by the presence
of an alga sensitive to temperatures, called Dinoflagellate, which
is found in high temperature waters only. How such an algae was
surviving in the frozen Arctic Ocean? Obviously what is frozen today
must have been a huge warm water lake some 55 million years ago!
What could have been the source of heat in those pre-historic days
without industries or automobiles to enrich the carbon dioxide
content of the atmosphere? It is known that Clathrates or frozen
Methane Hydrates are present in the ocean bed. Geological events
like an earthquake or a mudslide can disturb the equilibrium and
force release of methane which can break down to carbon dioxide on
reaching the atmosphere. The concentration of carbon dioxide in
today's atmosphere is 380 parts per million, whereas 55 million
years ago it was about 2,000 parts per million.
While the plants evolved and dominated the earth during the
greenhouse phases, many of the marine animals faced extinctions.
Known as periods of crises for marine and land organisms coincided
with periods when the plant life peaked. The sea level changes and
volcanism affected the animals whereas during those turbulent
millennia plants thrived.
Once again we are in the initial phase of a greenhouse state. How
long it would last is anybody's guess! Though, it is more or less
established that if you pump in greenhouse gases in the atmosphere
the result is large scale warming. In a race for development or
rather say our comforts we are trying to pump as much greenhouse
gases as possible in to the atmosphere. Our future generations will
face the worst of the global warming and curse us for leaving a 'hot
legacy' for them.
The worst part is that if the human race survives the greenhouse
state of environment, will we be able to withstand the Ice Age that
normally succeeds a warm phase is a question that will also plague
the future generation.
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The scourge
of global warming seems to be spreading. Discussion on global warming
has become the in thing. In a country like India where maximum
illiteracy is there, majority of people find global warming an
engrossing topic to discuss. Each individual has his own perception.
This year the Gangetic Plains of north India underwent a cold spell
around the popular festival of Holi, and lo! It was ascribed to global
warming. If a day becomes warmer global warming is declared the cause
and if it becomes a trifle cool again the horror of global warming is
recalled. But yes global warming is an issue that needs to be tackled
very seriously and sincerely.