Over the past
century, the earth’s surface has increased in temperature by 0.60
C. Scientists believe it is likely for a further rise of earth’s
temperatures by another 1.4 to 5.80 C by the end of 21st
century. This predicted increase of temperatures is generally known as
‘Global Warming’. Global
warming is caused by an increase in the concentration of the greenhouse
gases due to human activities. These greenhouse gases are carbon
dioxide, methane, nitrous oxide and chlorofluorocarbons. The enhanced
greenhouse gases are results of the following human activities :
- Carbon
dioxide : deforestation, burning of fossil fuels eg. coal, oil and
natural gas for cars, electricity generation, heating of homes etc
- Methane
: rice cultivation, livestock (ruminant) raising, coal mining,
drilling for oil and natural gas, garbage in landfills
- Nitrous
oxide : use of nitrogen based fertilisers, dispose of human and
animal waste in sewage treatment plants, automobile exhaust
- Chlorofluorocarbons
: use of aerosols, refrigerators, air conditioners
Global warming cause
the oceans to warm and expand, inducing a rise in the sea levels (see
Figure 1). As a result vast low lying areas (coastal areas) of
Bangladesh may be submerged with the rise of sea levels. This sea level
rise could further cause an intrusion of saline water into inland
causing a destruction of agriculture land, freshwater resources and
deterioration in water quality.
Bangladesh may
experience an increase in rainfall due to global warming (a warmer air
causes more water to evaporate). This could increase the frequency and
intensity in rains that may lead to some worse floods. In addition,
Global warming would help to melt down icy mountains tops of the
Himalayas, from where melted water would flow down through Bangladesh to
the sea causing more floods. Furthermore, warmer water and increased
humidity may encourage an increase in the frequency and intensity of
cyclones (a rise in sea surface temperature helps in formation of
increasing cyclones).
Global warming may
affect the types of crops being grown in Bangladesh, though it appears
that some crops may be benefited in higher temperatures and increased
carbon dioxide concentrations (an essential nutrient for photosynthesis)
but other crops may be affected. Some plants and animals may not be able
to cope with the predicted changed of temperatures that may cause the
loss of biodiversity. There is a possibility for an increase of malaria
and dengue fever due to more rains and moisture content predicted, which
may help to breed mosquitos and other pests
Figure
1 : Graph showing history of sea level and extrapolating
possible increases in sea level over the next century. The blue line
represents the history of sea level. The yellow line is a high
estimate of sea level extrapolated. The red line is a central
estimate, and the green line is a low projection (source :
www.envirolink.org/orgs/edf/sitemap.html)
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The
above information was based on various sources including the following: (a) Intergovernmental Panel on Climate Change (IPCC); (b)
National Oceanic and Atmospheric Administration, USA; (c) United Nations
Environment programme (UNEP); (d) United States Environment Protection
Agency (USEPA). The information was compiled by Dr Golam Kibria in June
2005 for http://www.sydneybashi-bangla.com/
. Views expressed in this article are those of the author and are not to
be taken to be the views of any others including third parties. The
author disclaims any liability for any error, loss or other consequences
which may arise from relying on any information in this article.
Dr Golam Kibria, Ph.D is a Senior Environmental Scientist with a
Rural Water Authority and based in Victoria, Australia.
