Page 207 - Chemistry ICSE Class IX
P. 207
Atmospheric Pollution 195
Why is the natural greenhouse effect necessary for life on
the earth
Natural blanket of the greenhouse gases has played an important role in the
evolution of life on the earth. The naturally-occurring blanket of greenhouse
gases absorb some of the solar radiation and help in maintaining temperature
on the earth at a moderate level. Maintaining the earth’s temperature at a
moderate level is essential for the existence of life on the earth.
Without the natural greenhouse effect, the thermal radiation would
escape into the atmosphere and cause cooling of the earth. The earth’s
temperature may fall to –20°C. This will make the earth unlivable and
barren. At such low temperature, evaporation of water will not take place.
As a result, there will be no cloud formation and no rain.
What are the possible adverse effects of the global
warming
The excessive built up of carbon dioxide (CO ) and other greenhouse gases
2
(GHGs) in the atmosphere may have a number of adverse effects on the
earth’s climate. It may lead to major environmental problems. Some major
adverse effects of the global warming are described below.
Rise in sea level
One of the major consequences of the global warming is the rise in sea level.
The sea level rises due to
Expansion of sea water, due to rise in the earth’s temperature
Melting of glaciers, polar ice caps
Rising sea levels may cause oods in coastal and low-lying area in
Maldives, India, Bangladesh, Sri Lanka, Netherlands, etc.
Changes in the pattern of crop cultivation
Global warming may change the rain cycle and adversely affect the world
food production. Wheat growing areas will get shifted from more fertile
regions of Canada and Russia to the less fertile polar region.
Increased CO level in the atmosphere and global warming will cause
2
faster growth of weeds and eruption of plant diseases.
Decrease in biological productivity of oceans
The biological productivity in ocean would decrease due to lower level of
the dissolved oxygen in water at higher temperature.
Loss of ecosystems and biodiversity
Changes in the rainfall pattern disturb ecological balance of several
terrestrial ecosystems. As a result, forests and many species of plants and
animals may die.
Loss of water balance
Rising sea water may pollute fresh water with salty water.
Fresh water resources may be diminished due to shrinking of mountain
glaciers and reduced snow fall.
Rise in the earth’s temperature will make certain parts drier and other
parts wetter due to change in the pattern of rainfall. Thus, global warming
can cause imbalance in the availability of fresh water.
