1.1 Greenhouse gases such as water vapour,
methane and carbon dioxide stop heat
escaping from the Earth into space. An
increased greenhouse effect can lead to
global warming and climate change.
1.1.1 Human activities are causing
the release of large amounts of
carbon dioxide. These activities
include: deforestation - cutting
down trees for fuel, farms,
buildings and roads increased
use of energy (and so an
increased use of fossil fuels). As
the percentage of carbon
dioxide in the atmosphere has
increased, so in general has the
Earth’s mean temperature.
1.2 Some sources of greenhouse gases are
natural and some are man-made
1.2.1 Natural gases are made by- Decomposing plant
material,Evaporation from oceans, lakes and
rivers and Respiration by plants and animals,
forest fires, volcanoes
220.127.116.11 It is not just human activities that can affect weather patterns and
climate. Ash and gases released by volcanic eruptions also go into
the atmosphere. They reflect radiation from the Sun back into
space, causing cooling. This, and other effects, can make it difficult
for scientists who study the atmosphere and global warming.
1.2.2 Man made sources of gas are made by- Rice
paddy fields, cattle, coal mines,Burning
hydrocarbon fuels and Making cement, burning
1.3 This Diagram shows shows how the Greenhouse Effect Works
1.4 Increased global warming will lead to climate change – changes in the
average weather experienced over 30 years or more. Climate change may
make it impossible to grow certain food crops in some regions. Melting
polar ice, and the thermal expansion of sea water, could cause rising sea
levels and the flooding of low-lying land.
2.1 The atmosphere surrounding the Earth is a mixture of gases. In some
places, human activities have added other gases to the atmosphere, which
are called pollutants.
2.2 The gases in dry air
2.2.1 Nitrogen 78 per cent
2.2.2 Oxygen 21 per cent
2.2.3 Argon 1 per cent
2.3 The atmosphere also contains a small but
important amount of carbon dioxide,
approximately 0.04 per cent, and tiny amounts of
a few other gases.
2.3.1 In addition to these gases, the air also contains
water vapour. The percentage of water vapour
varies from one location to another, and according
to weather conditions
18.104.22.168 The burning of fuels releases a large
amount of carbon dioxide into the
atmosphere. This is thought to cause global
3 The Early Athmosphere
3.1 Scientists believe that the Earth was formed
about 4.5 billion years ago. Its early
atmosphere was probably formed from the
gases given out by volcanoes.
3.1.1 It is believed that there was intense
volcanic activity for the first billion
years of the Earth's existence.
3.2 The early atmosphere was probably
mostly carbon dioxide, with little or
3.2.1 There were smaller proportions of water
vapour, ammonia and methane
22.214.171.124 As the Earth cooled down, most of the water vapour condensed and
formed the oceans.
126.96.36.199 It is thought that the atmospheres of Mars and
Venus today, which contain mostly carbon
dioxide, are similar to the early atmosphere of
3.3 volcanoes release high quantities of carbon dioxide. Iron-based compounds
are present in very old rocks that could only have formed if there was little or
no oxygen at the time.