Global Warming and the Ozone Hole

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Global Warming and the Ozone Hole
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The Greenhouse Effect

• A normal climatic warming effect caused by
  permitting incoming solar radiation but
  inhibiting outgoing terrestrial radiation.
• Three gases are the primary cause
• Carbon Dioxide (CO2)
• Methane (CH4)
• Water Vapor (H2O)
• The effect is possible because outgoing earth
  radiation is of much longer wavelengths than
  incoming insolation and it gets caught or trapped
  in the atmosphere.

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The Greenhouse Effect

• Keeps Earths average temperature 35ºC warmer
  (15ºC now, -20 ºC otherwise)
• Human role? A heated
  debate

Venus 480ºC thick carbon
dioxide
Mars -62 ºC little carbon dioxide
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The Carbon Cycle
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Global Surface Temperature Increase 1865-2000
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Note that very recent rate of increase greatly
exceeds anything in last 1000 years.
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b
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Note correlations in the data.
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Critics note that historic temperatures were
higher.
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Critics note that historic temperatures were
higher.
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650,000 years of climate and CO2
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Changes in Solar Radiation
Milankovitch Cycles explain much (60) of the
changes

• 21,000 year cycle perihelion shifts throughout
  the year
• 41,000 year cycle /- 1.5 change in Earth's
  tilt
• 100,000 year cycle Orbital eccentricity of the
  elliptical orbit of the Earth

The most recent ice age lasted 100, 000 years. We
are currently in an interglacial period
(Holocene).
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Climate models suggest that the changes are just
beginning now and will accelerate.
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The Global Warming Hypothesis

• Human-induced rise in CO2 levels is likely to
  lead to increased greenhouse forcing and
  unnatural warming of atmosphere.
• Some probable effects
• Increased storminess and more droughts
• Rising sea level (.36 to 2.5 feet) in 100 years
  (IPCC, 2007)
• Loss of farmable land (some areas hotter, others
  cooler)
• Extinction of thousands of species
• Loss of nearly all coral reef
• Increased range of tropical diseases
• Flooding of low-lying coastal regions

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Warming of the climate system is unequivocal, as
is now evident from observations of increases in
global average air and ocean temperatures,
widespread melting of snow and ice, and rising
global mean sea level.
IPCC Report, 2007
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So is sea level rise happening? How much?
Sea level rise is not well understood. In their
2001 report, the Intergovernmental Panel on
Climate Change stated that global warming should
cause sea levels to rise 0.11 to 0.77 meters
(0.36 to 2.5 feet) by 2100. When added to storm
surges and high tides, these small changes may
have large effects.
Source UN IPCC, 2001
Source UN IPCC, 2001
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Global Warming?

• Climate change will lead to more chaotic and
  unpredictable weather"Climate change will bring
  warm, wet weather, which will encourage plants to
  grow, followed by long periods of drought, during
  which they will burn." - Meinrat Andreae, Max
  Planck Institute for Chemistry, August 2001.

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So is Global Warming Happening?

• Scientific consensus now exists (link to
  Wikipedia)
• "In the light of new evidence and taking into
  account the remaining uncertainties, most of the
  observed warming over the last 50 years is likely
  to have been due to the increase in greenhouse
  gas concentrations 1." (IPCC, 2001)
• We must act to ensure continued economic growth
  for our citizens and for citizens throughout the
  world. - George W Bush, June 2001, Explaining
  his opposition to the 1997 Kyoto Protocol, a
  document that calls for only 5 reduction of
  greenhouse gases. IPCC says a 60 reduction
  needed to stabilize levels.

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Predicted temperature changes Hadley Centre model
Source UKMO Hadley Center http//www.met-office.
gov.uk/research/hadleycentre/
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Predicted precipitation changes Hadley Center
model
Source UKMO Hadley Center http//www.met-office.
gov.uk/research/hadleycentre/
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Ecosystem change

• Very difficult to model!
• Response depends on CO2 fertilization,
  temperature, Precipitation, evapotranspiration,
  competition...

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The Ozone Hole
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The Vertical Thermal Structure of the Atmosphere
IONOSPHERE
OZONOSPHERE
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• Ozone forms naturally in stratosphere
• UV radiation (sun) --gt mutations
• plankton reduced (food chain base), crops decline
• weaker immune systems, skin cancer
• Stratospheric ozone (O3) absorbs UV rays

light
?
O2 ? 2 O then O O2 ? O3
UV rays
?
O3 ? O2 O
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The Importance of Stratospheric Ozone

• CFCs
• link to ozone hole established in 1970s
• Chloroflourocarbons (refrigerants, aerosols)
• one Cl can decompose more than 100,000 O3

Cl2 light ---gt 2 Cl Cl O3 ---gt ClO O2 ClO
O Cl O2
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NASA Ozone Watch Images Data Animations
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The Importance of Stratospheric Ozone

• What has been done?
• Montreal Protocol, 1987 U.N. agreement on ban
• up to 10 years for rising CFC gases to reach
  stratosphere once in the stratosphere, CFCs can
  last up to 50-100 years
• Nasas Ozone Hole Site

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Key Points

• Ozone Hole caused by CFCs
• Ozone protects life from UV rays
• destroys ozone in stratosphere
• has little effect on temperature
• Montreal Protocol, 1987 outlawed production of
  CFCs
• Global Warming caused by carbon dioxide and
  methane
• Carbon dioxide traps heat radiated towards space
  by the earth
• leads to warming at surface of earth
• Will effect temperature, sea level, storm
  intensity, and ecosystems
• No global agreement to solve problem