4. THE GREENHOUSE EFFECT

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• 4. THE GREENHOUSE EFFECT
• If the earth were the diameter of an apple, then
  the earth plus its atmosphere would be the
  diameter of
• A grapefruit
• A basketball
• An apple

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Greenhouse gases constitute a tiny portion of
the atmosphere.

• Nitrogen (N2) 78
• Oxygen (O2) 21
• Carbon dioxide (CO2) .035
• Methane (CH4) 0.00017
• Ozone (O3) 0.000001

What makes the bottom 3 greenhouse gases?
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• Despite being a small component of the
  atmosphere, methane carbon dioxide are potent
  greenhouse gases.
• See handout
• p. 1) Triatomic compounds absorb long wavelength,
  low energy light radiated from earth (through
  rotation vibration).
• p. 2) Light radiation from earth shows troughs at
  wavelengths absorbed by ozone (O3), H2O, and CO2.

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• Sun emits high energy (short wavelength) photons.
• Atmosphere absorbs a lot of it.
• Earth reflects low energy (long wavelength)
  photons.
• When gases in the atmosphere that absorb long
  wavelengths increase, more energy is trapped
  inside the atmosphere ( greenhouse effect).

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• Major Greenhouse Gases
• CO2 Carbon Dioxide
• CH4 Methane
• CFCs Chloroflurocarbons
• O3 Ozone
• N2O Nitrous Oxide

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Estimated climate forcings, 1850 2000 Red /
net warming (jacket) Blue / - net cooling
(parasol)
Punchline CO2 has caused the most warming.
Hansen et al. PNAS 979875
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• Warming of the climate system is unequivocal.
• Most of the observed increase in temperatures
  since the mid-20th century is very likely due to
  anthropogenic greenhouse gas concentrations.
• Atmospheric CO2 (379 ppm) in 2005 exceed by far
  the natural range over the last 650,000 years.
• Also true for methane (1774 ppb)

IPCC 2007
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From your reading the hockey stick
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Future Warming Consequences

• Predicted ? in CO2 forcing, 2000 to 50 1.4 to
  2.4 (IPCC 2001)
• 3.5 - 10º F predicted rise in 21st century
  (IPCC 2001)
• 15-37 of species will be committed to
  extinction by 2050
• (Thomas et al. Nature 427 145).
• If current trends continue, property damage from
  climate change will exceed gross world product by
  2050
• (CGMU insurance, Britain)

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• 5. GREENHOUSE MITIGATION
• SCIENCE -
• There is high agreement and much evidence that
  all stabilisation levels assessed can be achieved
  by deployment of a portfolio of technologies that
  are either currently available or expected to be
  commercialised in coming decades, assuming
  appropriate and effective incentives are in
  place.

(IPCC 2007)
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• Scientists assume that once we knowscientific
  principles we can devise effective policies to
  achieve social goals.

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• In the mid 1990s, the Union of Concerned
  Scientists estimated a near-complete transition
  to renewable energy could occur in the U.S. for
  25 bil. / yr. over 10 years.
• Gelbspan 1995 The Heat is On The Climate
  Crisis, the Coverup, the Prescription p. 98

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• Fossil fuels are
• Centralized
• Capital-intensive
• Produce few jobs
• Renewable energy is
• Decentralized
• Not capital-intensive
• Produces about 10 times more jobs than fossil
  fuels per unit of energy produced

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• The federal government spends more than 20
  billion a year to subsidize the development of
  oil, coal, and natural gas.
• Gelbspan 1995 p. 180

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• Political donations, 1999-2000
• The entire alternative energy industry
  783,000
• Enron
  2.3 million
• Exxon-Mobil
  1.3 million
• 2001 Center for Responsive Politics, A Money In
  Politics Backgrounder on the Energy Industry

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• BUSINESS -
• At a recent meeting in Boston attended by the
• strange bedfellows of investors and
• environmentalists, the leaders of 13 major
  pension
• funds controlling nearly 800 billion in assets
• called on the Securities Exchange Commission
• to require companies to tell shareholders about
• their potential financial exposure from global
• warming and how they plan to respond.

Boston Globe, Tuesday May 4, 2004
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• 6. FEEDBACK LOOPSPositive As planet warms,
  warming accelerates.
• Lost albedo (reflectivity) from glaciers earth
  absorbs more heat

NASA/GODDARD SPACE FLIGHT CENTER SCIENTIFIC
VISUALIZATION STUDIO (DATA) ROB GERSTON, GSFC
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• 2. Fires release CO2
• 3. Habitats become too hot for current vegetation
• Death decay releases CO2
• Termites release CH4

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• Uncertain Feedback
• 4. Water
• A warmer earth will have more atmospheric
  moisture.
• Water is a greenhouse gas.
• Clouds act like a parasol.
• Effect of greenhouse parasol is impossible to
  predict.

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• 5. Permafrost
• Melting permafrost around peatlands leads to
  increased vegetation.
• But it also leads to increased methane emissions.

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7. THE LONGER HISTORY OF CARBON
BR_Nature 453291
Relative to the last 800,000 years, we are headed
off the charts.
What about before that??
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CO2 estimated using isotopic markers from marine
algae note big drop about 30 Mya
Fig. from Stoll, Nature 441579
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Even higher levels 450 Mya!
gt20X more CO2 than now
So, why worry?
Radiation of mammals
x present concen.
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• Greg Retallack, U of O Why did atmospheric
  carbon diminish at end of Devonian? Hypothesis
• Development of large land plants
• Roots caused soil to weather
• Calcium and magnesium weathered from soil went to
  oceans combined with dissolved sodium
  bicarbonate to form insoluble compounds.
• Oceans absorbed more carbon from atmosphere.

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See Ricklefs 3rd ed. Fig. 12-6
- 25,000,000
Most of the carbon from earlier hothouse
atmospheres is bound up in limestone (CaCO3), and
is not in danger of being liberated any time soon.