factors that influence climate on a global scale slideshare
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Factors which influence Factors which influence climate on a global scaleclimate on a global scale
Higher GeographyHigher Geography
AtmosphereAtmosphere
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Introduction
• The Earth receives heat energy (radiation) from the Sun. But not all of the radiation that arrives at the edge of the atmosphere gets to the Earths surface.
• Also, not all latitudes on the surface receive the same amount of radiation (sunlight).
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The global heat budget
• The global heat budget is an atmospheric system which involves inputs, storage and outputs.
• Generally speaking, incoming solar radiation is balanced by outgoing terrestrial (Earth based) radiation.
• The balance between incoming and outgoing radiation is known as the global heat budget.
Hig
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• The earth receives all of its incoming radiation from the sun (solar energy).
100%
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Atmosphere
17% reflected by clouds
23% absorbed by atmosphere
8% reflected by atmospheric gases and dust
6% reflected by surface
46% absorbed by the surface
100%
Solar Energy (short wave)
The global heat budget
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Earths Albedo
• The earths albedo is the reflectiveness of the surface.
• In our diagram this was responsible for 31% of the radiation loss.
Radiation reflected by clouds (17%) + radiation reflected by atmospheric gases and dust (8%) + radiation reflected by the
surface (6%) = 31% (total albedo).
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Outputs• Balancing the input is an equal output
of heat (terrestrial radiation) from the Earth.
• 6% of this energy is radiated back into space. The remaining 94% is absorbed by water vapour and carbon dioxide in the atmosphere and re-radiated.
Carbon dioxide and water vapour are both examples
of greenhouse gases
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The greenhouse effect
• Eventually all radiation returns to space but the atmosphere’s greenhouse effect slows things down.
• The greenhouse effect acts like a huge blanket, limiting the heat energy lost.
Without the greenhouse effect the global temperature would be 33°C lower.
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Energy Receipt with Energy Receipt with LatitudeLatitude
Factors which influence climate on Factors which influence climate on a global scalea global scale
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Insolation
• Insolation is the suns (solar) radiation which is received by the Earth’s surface.
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Tropical latitudes receive more solar radiation than the
polar latitudes for 3 main reasons.
In Polar regions the radiation has to penetrate a greater depth of atmosphere (absorbs more heat).
The same amount of solar energy is received over a much greater area in Polar regions (less heating).
High energy loss at poles because of ice cap albedo.
Equator (0º)
NorthPole
SouthPole
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Albedo Effect
• The amount of energy actually absorbed by the surface depends on the Albedo effect. This is the proportion of radiation which is reflected by different surfaces.
Water – High reflectionForest – Low reflection
Ice and snow – High reflection
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Albedo of various surfaces
Surface % Reflected
Fresh Snow 80 - 85
Old Snow 50 - 60Sand (Beach or Desert) 20 - 30
Grass 25 - 30
Dry Soil 15 - 25
Forest 5 - 10
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What does this mean?
90ºN
60ºN
30ºN
Equator 0º
30ºS
60ºS
90ºS0 100 200 300
Insolation (Joules)Latitude
35ºN
35ºS
Terrestrial Radiation
Insolation
There is a net gain (surplus) of energy in Tropical areas
because incoming radiation exceeds outgoing radiation.
However in polar areas there is a net loss (deficit) of energy because outgoing radiation is
greater that incoming radiation.
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In theory!
• Theoretically, an imbalance in energy receipt should result in the Tropics becoming hotter and the Poles becoming even colder.
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90ºN
60ºN
30ºN
Equator 0º
30ºS
60ºS
90ºS0 100 200 300
Insolation (Joules)Latitude
35ºN
35ºS
EnergySurplus
EnergyDeficit
EnergyDeficit
However, energy is transferred from areas of
surplus (Tropics) to areas of deficit
(Poles) by atmospheric
circulation and by ocean currents.
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