by Zeeshan Hasan
Many people have a
false perception of an ongoing 'debate' regarding the dangers of
global warming and climate change. In particular, elected
politicians
intent on avoiding unpopular carbon taxes and higher fuel prices
continue to assert that the relevant scientific issues are
doubtful.
Unfortunately, until now the non-scientist public has been
deceived
by a large number of books and newspaper articles by misinformed
'skeptics' of climate science who themselves have no understanding
of
the science involved. Fortunately, a glimpse into the real world
of
climate science is available through Global Warming: Understanding The Forecast by
David
Archer, an ocean chemistry professor at the University of Chicago.
Archer's book is
an introductory climate science text which aims to make the basics
of
climate science comprehensible to any one with a high school
background in science.
The basic science
of
how carbon dioxide emissions raise global temperatures is outlined
by
Archer. On the one hand, the earth is constantly being heated by
sunlight. On the other hand, the Earth is also cooled by loss of
heat
into space as infrared radiation. These two continuous mechanisms
of
heat gain and heat loss by the Earth result in a thermal
equilibrium
at the average global temperatures which we experience.
Heat gain from the
sun is relatively constant, varying only slowly over time;
however,
heat loss into space has been reduced significantly by humans over
the last century. Atmospheric 'greenhouse gases' such as carbon
dioxide have the property of absorbing the infrared radiation
which
carries heat from the earth into space, and thus reduce the
cooling
of the earth. This effect of carbon dioxide is called the
Greenhouse
effect; it was discovered over a century ago and is undisputed.
Since
the Industrial Revolution, humans have been continuously burning
fossil fuels such as coal, oil and gas, and thus adding huge
amounts
of carbon dioxide to the atmosphere. This has resulted in an
increase
of the carbon dioxide concentration in the atmosphere from 320
parts
per million in 1960 to about 400 parts per million today, or about
20%. This additional carbon dioxide functions like a blanket or
greenhouse around the planet, slowing down loss of heat into
space.
If the same amount of solar heat comes into the Earth, while
simultaneously heat loss from the Earth to space is reduced by
additional carbon dioxide, then the Earth has to get warmer. At a
higher temperature the Earth's heat loss by radiation into space
increases, because hotter objects lose more heat through infrared
radiation than cooler ones; and the planet once more reaches a
stable
temperature.
A good analogy to
the above is a pot of food simmering on an oven above a low flame;
putting the lid on the pot does not change heat gain from the
oven,
but reduces heat loss through evaporation from the open pot and
thus
makes the food cook at a higher temperature. Our carbon dioxide
emissions are effectively putting a lid on the earth, making heat
from the sun 'cook' the planet at a higher temperature.
The question is
whether a hotter stable temperature of the globe would be one
capable
of sustaining human life as we know it. Climate scientists have
evidence from ancient ocean sediments that increasing the level of
greenhouses gases in the
atmosphere can cause temperatures to rise. Such an event took
place
55 million years ago, when thousands of billions of tons of
greenhouses gases were released into the atmosphere (probably
because
of a peak in volcanic activity). This event is known as the
Permian
Eocene Thermal Maximum (PETM). During the PETM, global average
temperature rose by about 5 degrees C and 90% of life on the
planet
perished. Such an increase in global average temperature today
would
have terrible consequences, rendering much of tropical and
sub-tropical Asia, Africa, central America and southern Europe too
hot and dry for agriculture. The consequences would be famine on a
scale never seen before, and billions of deaths.
Dangerous global
heating events like the PETM may seem distant and irrelevant. But
as
a comparison, burning all world's known reserves of coal would
release about 5000 billion tons of carbon dioxide, comparable to
the
surge in greenhouse gases which caused the PETM. Our current
course
is to exploit not only existing coal reserves but also oil and
gas.
So it is entirely within our power to destroy our planet.
(Printed in Bangladesh on Nov. 30, 2014 by the Dhaka Tribune.)
