Physics of the Atmosphere

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Physics of the Atmosphere
Global Warming
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The sun Emits Light that radiates through space
and warms the Earth
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The sun emits most of its light as visible light
Blackbody Curve
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Absorbed radiation heats up the Earth and it
radiates as a blackbody at a lower temperature
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Molecules Combination of atoms most in the
atmosphere contain only a few atoms (e.g. CO2,
O2) Molecules are held together by an attractive
electrical force. If they get too close to each
other, the atoms start to repel. The net result
gives something that behaves like a spring
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Emission and Absorption of Electromagnetic
Radiation by Molecules
Emission
Because of the spring-like forces between atoms
in a molecule, they can vibrate and vibrating
charges emit electromagnetic radiation. For most
molecules this radiation is in the infrared part
of the electromagnetic spectrum
Light
Absorption
If electromagnetic radiation of the right
wavelength passes near the molecule, it can
resonate and the molecule can absorb the
radiation. For many molecules, this is also in
the infrared part of the electromagnetic spectrum
Light
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Composition of the Atmosphere
Major
N2 78.084 O2 20.946 Ar 00.934
99.964
Some Trace Gases (in ppm)
CO2 350 H2O 20-20,000 Ne 12 He 5 NO2
2 CH4 2
Greenhouse gases
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Solar constant increased by about 30 during the
lifetime of Sun
Albedo Snow and clouds have high albedo dark
earth has low albedo
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CO2 Emissions From Fossil Fuel Combustion 1996
Million Tonnes of CO2
Source CO2 Emissions from Fuel Combustion 1971 -
1996, International Energy Agency, page II.4-5,
1998 Edition
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CO2 Emissions Per Person 1996
Million Tonnes of CO2
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Hydroflourocarbons (HFCs), perflourocarbons
(PFCs), and Sulfur hexaflouride (SF6)
Nitrous Oxide
Methane
Carbon Dioxide
Source Inventory of U.S. Greenhouse Gas
Emissions and Sinks 1990 - 1996. U.S. EPA
publication 236-R-98-006
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Global Warming is a complicated problem
There are many complicated affects that work
together
e.g. Increased CO2 causes planet to warm which
causes more water vapor to form. Water vapor is
also a greenhouse gas which will cause more
warming (positive feedback) Increased CO2 causes
planet to warm which causes more water vapor to
form. This causes more clouds which increases
the amount of sunlight reflected away from the
Earth (increases the albedo) which would cause
the planet to cool.
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Actions of the US on Global Warming

• Developing countries are not included
• Cost is too great wait until science is more
  precise
• Warmer temperatures are not necessarily bad
• Too many uncertainties in science
• Climate models have fudge factors
• Global climate models dont agree with each other
• Evidence for connection of solar cycle and
  warming
• Discrepancies between surface and atmospheric
  temperature data