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 Form 2 Geography Lessons on Climate

In this lesson we are going to discuss the definition of climate change and the its causes

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Answer Text:
Climate Change
- Establishment of a new
climatic state.
- Continuous changes in
climatic states such as
temperature and precipitation
over time.
Causes of Climate Change
Natural Causes
1. Variations in the Earths
Orbital Characteristics
-Changing of earth’s orbital
characteristics within 1000
years from elliptical
(aphelion) to nearly circular
(perihelion) when the earth is
nearest to the sun and receives
maximum solar energy and
back to elliptical when the
earth is farthest from the sun
and receives least solar
energy.
2. Variation in the
Atmospheric Carbon
Dioxide
-When natural rise in
temperature cause carbon
dioxide held up in Cold Ocean
waters to be released to the
atmosphere after oceans have
been warmed.
3. Volcanic Eruptions
• When large quantities of
volcanic ash and dust thrown
out of the ground block some
of the solar insolation from
reaching the earth’s surface
causing temperatures on the
earth’s surface to drop for a
short period.
• When sulphur dioxide given
off during volcanic eruptions
reacts with water vapour
forming a bright layer within
stratosphere reducing the
amount of solar radiation
reaching the surface by
reflecting some of it back
which also lowers
temperatures on the surface.
4. Variation in Solar Output
- changes in the amount of
solar energy given off by the
sun whereby at times its less
causing drop of temperature
on the earth’s surface and at
others it gives off more
causing rise in temperature on
the surface.
Human Causes
1. Burning of fossil fuels in
industries, transportation,
electricity generation e.t.c
which contributes 65% of
additional co2 in the
atmosphere which is the main
greenhouse gas.
2. Burning of vegetation e.g.
in shifting cultivation and
forest fires which also add co2
in the atmosphere.
3. Clearing large tracts of
forests for agriculture,
settlement etc. which reduces
the main deposal system for
co2 from the atmosphere by
photosynthesis.
4. Industrial developments
which add gases like methane,
nitrous oxide and those
containing chlorine and
chlorofluorocarbons which
damages ozone layer which
filters a greater percentage of
ultra violet radiation given off
by the sun which causes the
average temperatures on the
earth to rise.


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