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Earth's Dynamic History of CO2
A Fascinating and Surprising Tale
By:
Anjum Farooqui*
There is an old
saying; “The Whole is greater than the sum of the parts”. We
cannot have complete faith in the ability of any computer models to
predict future behavior of any natural system - especially a system
as complex as that for the whole planet! So we have a lot more to
learn and to study about complexity of ecosystems, climate, and
their computer models before we get too emotional about the
“Greenhouse effect. Any type of system from the micro- atoms to the
macro- galaxies in the Universe are self-organizing and
self-regulating, relating to one another, where we can find clues of
the past events inscribed on the stones as fossils or in other
natural archives. This enlightens us about the future patterns and
predictability of global climatic change. Scientists have enormous
data which enable us to identify and have a better understanding of
the present and possible future global weather by
looking at the planet's weather
through geological time.
There are several scars of cataclysmic events that our planet Earth
has experienced in the past before man arrived. No doubt man has
evolved our planet into the present Eden where only handful of
population is concerned for it and the rest are busy enjoying the
heavenly gifts on this Earth. The several jolts to the Earth in the
past have removed 90% of the species that have ever existed.
It is very hard to say about the precise
reason which was responsible to set the catastrophic events but
surely created a disbalance in the level of the carbon dioxide
content in the air throughout the Earth’s geologic time. Long-term
reconstructions of atmospheric CO2 levels going back in
time show that 500 million years ago atmospheric CO2 was
some 20 times higher than present values. Some 200 million years ago
this level dropped and then rose to 4-5 times of present levels--a
period that saw the rise of giant fern forests--and then continued a
slow decline until recent pre-industrial time. Carbon dioxide
(CO2) forms approximately 0.04% of the Earth’s
atmosphere. It is essential for photosynthesis in plants and other
photoautotrophs, and is also a prominent greenhouse gas.
Global carbon dioxide emissions
Carbon dioxide is released to the atmosphere by a variety of natural
sources, and over 95% of total CO2 emissions would occur
even if humans were not present on Earth. For example, the natural
decay of organic matter in forests and grasslands, such as dead
trees, results in the release of about 220 gigatonnes of carbon
dioxide every year. This carbon dioxide alone is over 8 times the
amount emitted by humans. The increasing measured fraction of CO2
in the atmosphere over the last 100 years implies that the level of
equilibrium between sources and sinks of CO2 is rising.
Biological consequences of earth’s climatic change through
geological periods (macro change) - the age of fishes, age of
amphibians, age of reptiles - resulted in high magnitude changes and
widespread extinctions (with some carry over remnants). These
catastrophic events caused populations of individual species to
shrink or expand inducing changes in the food chain and creating
ripple effect in an ecosystem which is called 'tropic cascading'.
Relationships between the Ocean and Carbon:
Oceans are the 'Carbon Bank' where most of the Earth's carbon
including CO2 is stored. It has been that way for
millions of years with contributions of both organic and inorganic
sources in the oceans, from the atmospheric gas exchanges, and from
fluvial sources through rivers and other erosion methods on land of
terrestrial organic and inorganic materials. Tectonic movement and
undersea volcanic action also release CO2 to the
atmosphere in varying amounts so that there has been periods during
the earth's geological time scale when the ocean released more CO2
into the atmosphere than it removed. The removal and storage of
atmospheric CO2 by the oceans is done by biological means
involving the total oceanic food chain (waste materials and dead
organisms accumulating on the ocean floor) and the structural
recruitment by calcifying organisms (coral reefs and limestone beds
built up by corals, coraline algae, and other plants). Presently the
ocean releases less CO2 back into the atmosphere than it
removes during the 'carbon cycle' because it 'locks' a percentage of
the CO2 into limestone and ocean floor sediments. The CO2
rises to the ocean's surface for atmospheric exchange through
geochemical methods such as tectonic and volcanic activity, up
wellings of deep ocean currents bring dissolved sediments to the
surface and limestone erosion.
Man, Climate & the Carbon dioxide
Man's ancestors appeared at least 2 million years ago. There has
been no perceptible change in man's physiology in 40,000 years - so
why didn't agriculture and civilization begin 40,000 years ago? The
Earth's climate was very erratic (during this 40,000 year period) up
to 10,000 years ago - when the last ice age ended. After that last
ice age (10,000 years ago) the weather went from erratic (normal) to
stable (abnormal) and helped foster the birth of civilization
through predictable climate (regular seasonal cycles of temperature
change and wet/dry periods) best described as the 'steady-state
environment'. This abnormal 'Steady-State' climate has made possible
the progression of agriculture, which resulted in stable human
societies and a greatly accelerated growth in the human population.
Over the past 50 years, man's effect on Earth has been very
detrimental, directly and indirectly - due to the huge growth in
man's population and technology. We have the knowledge to reverse
the negative impact we have made on reefs and oceans. We have the
knowledge to reduce CO2 in the atmosphere by reduction of
emissions and enhancement of biological fixing (capture) methods. It
is just a matter of time and the Earth's 'hot-cold' and 'wet-dry'
macro-climatic cycles will take us out of the present 'steady-state'
environment we have experienced over this short geological period of
the past 10,000 years.
Similarities with our Present World Average global temperatures in
the Early Carboniferous Period were hot- approximately 20° C (68°
F). However, cooling during the Middle Carboniferous reduced average
global temperatures to about 12° C (54° F). Similarly, atmospheric
concentrations of carbon dioxide (CO2) in the Early
Carboniferous Period were approximately 1500 ppm (parts per
million), but by the Middle Carboniferous had declined to about 350
ppm -- comparable to average CO2 concentrations today!
Earth's atmosphere today contains about 380 ppm CO2
(0.038%). Compared to former geologic times, our present atmosphere,
like the Late Carboniferous atmosphere, is CO2
impoverished! In the last 600 million years of Earth's history only
the Carboniferous Period and our present age, the Quaternary Period,
have witnessed CO2 levels less than 400 ppm. There has historically
been much more CO2 in our atmosphere than which exists
today. For example, during the Jurassic Period (200 mya), average CO2
concentrations were about 1800 ppm or about 4.7 times higher than
today. The highest concentrations of CO2 during all of
the Paleozoic Era occurred during the Cambrian Period, nearly 7000
ppm -- about 18 times higher than today.
The Carboniferous Period and the Ordovician Period were the only
geological periods during the Paleozoic Era when global temperatures
were as low as they are today. To the consternation of global
warming proponents, the Late Ordovician Period was also an Ice Age
while at the same time CO2 concentrations then were
nearly 12 times higher than today-- 4400 ppm. According to
greenhouse theory, Earth should have been exceedingly hot. Instead,
global temperatures were no warmer than today. Clearly, other
factors besides atmospheric carbon influence earth temperatures and
global warming.
Scientists are busy developing future technology that may greatly be
important to our adaptation to climatic change rather than its
prevention. These survival technologies to adapt to climatic changes
will help the present day species to sustain on this changing earth
and would put a strong option before mankind to accommodate in Mars
and other planets with the advance technology for sustenance.
*Birbal Sahni Institute of Palaeobotany, 53, University Road,
Lucknow (India), <[email protected]> | 
