The
Greenhouse
Effect
Too much of a good
thing?
• Light from the sun is composed of many
frequencies
Different light frequencies carry
different levels of energy
Greenhouse Gases absorb IR frequency radiation
• Radiation energy can increase vibration between
bonded molecules
• Different molecules will absorb and re-emit different
energy levels of light waves as heat
• Greenhouse gasses are gasses that absorb IR
energy radiation
Which gasses are greenhouse gasses?
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Nitrogen
78.1%
Oxygen
20.9%
Argon
0.9%
Neon
0.002%
Helium
0.0005%
Krypton
0.0001%
Hydrogen
0.00005%
Water vapor
0 to 4%
Carbon Dioxide 0.035%
Methane
0.0002%
Ozone
0.000004%
Percentages indicate levels of concentration in Earths atmosphere
What happens when sunlight
reaches the Earth?
Absorbtion and Reflection by the
Earths Surface
• Earth absorbs ultraviolet (UV), visible,
and some infrared (IR) radiation from
the sun. This heats the earth.
• The earth reflects most IR radiation
back towards space and . This process
cools the earth.
Atmospheric gasses can absorb
IR radiation on its way in
Atmospheric gasses can absorb IR
radiation on its way out
Why is absorbtion of IR a problem?
• If an atmospheric gas can absorb
radiation energy it will release that energy
as heat energy back into the atmosphere.
• This results in a warmer overall
atmospheric temperature.
What if there was no
greenhouse effect?
• The earth would be too cold to sustain
life.
• Greenhouse gases are required to keep
the earth’s temperature above freezing.
Water vapor
• Water vapor is the gas most responsible
for the greenhouse effect.
• Human appear to have little influence
over its impact on a global scale.
• It’s levels are regulated by rain/snow.
Carbon Dioxide
• Cycles normally through photosynthesis,
cellular respiration, and volcanic activity.
• Humans affect carbon dioxide levels in three
ways.
– Burning fossil fuels
– Burning vegetation
– Deforestation
• What is the impact of each?
Carbon Dioxide today
Does one cause the other?
• More and more evidence says yes, but
there is not 100% agreement that the
increase in greenhouse gases is
causing climate change.
• Unfortunately, the evidence is getting
stronger that it does.
Effects of Climate Change
• More extreme weather due do more
trapped energy
• Increased sea levels due to loss of ice
caps.
• Changes in amount of farmable land
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