1. Atmosphere and Climate
Module 8
Atmosphere and Climate
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2. Learning Objectives Explain what is meant by the term “global warming”
Know the major greenhouse gases and their main sources
Describe the objectives of the Kyoto Agreement
Describe examples of climate change impacts
Explain the link between CFCs and ozone depletion
Describe the objectives of the Montreal Protocol
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3. Atmosphere
The layers of air masses surrounding the Earth are collectively referred to as the atmosphere.
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4. How is atmosphere important?
The atmosphere controls climate - which keeps us comfortable and safe
Ozone depletion and increasing GHGs are a current concern
We use it to dispose of wastes
within the past century, the composition of the atmosphere has been changed on the scale of human time
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5. Atmospheric Layers Troposphere Where weather is.
Where most of the pollutants are.
Thickness - 15 km at the equator, and about 8 km over the poles.
It is well mixed by air motions which disperse pollutants
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6. Atmospheric Layers Stratosphere
Extends from about km. The ozone layer.
This “good” ozone protects us from solar UV radiation
Very thin air with virtually no weather or turbulence.
Compared to Troposphere, the volume of water vapor is 1000 x less, and volume of ozone is 1000 x greater.
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7. Ozone: the Good and the Bad
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8. Climate Control and Atmospheric Composition
Earth’s surface absorbs incoming solar radiation, and converts it into heat.
Some of this heat escapes into space
Some is absorbed by greenhouse gases in the atmosphere, warming the air
 Heat is radiated back to Earth, warming it by about 33oC
This trapping of heat is called the Greenhouse Effect
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9. Greenhouse Effect
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10. Trace Gases Most of Earth’s atmosphere is climatically neutral
the important gases are present in trace amounts only
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11. Anthropogenic Climate Change
The Greenhouse Effect that warms the surface of the Earth occurs because of a few minor constituents of the atmosphere (GHGs) that absorb IR radiation very efficiently.
As a result of human activities, the concentrations of GHGs is increasing.
This will lead to a warmer Earth, the amount depending on other climate effects.
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12. Main Greenhouse Gases
Carbon Dioxide - fossil fuel burning (80% of emissions), deforestation (20%).
Methane - breakdown of organic material by anaerobic bacteria.
Nitrous Oxide - biomass burning, breakdown of nitrogen-rich products.
Chlorofluorocarbons - refrigerants.
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13. What is Global Warming
The term Global Warming is widely used to describe a potentially dramatic rise in the average global temperature as a result of the continuing and accelerating buildup of greenhouse gases in the atmosphere.
It is different to the problem of ozone depletion in the Stratosphere, although this also arises from atmospheric pollution
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14. Atmospheric carbon dioxide (CO2):1750 to present
Atmospheric Carbon Dioxide (CO2) Concentrations (1750 to present)
Preindustrial atmospheric CO2 concentrations were approximately 275 parts per million. Today concentrations are approximately 367 ppmv, an increase of over 30 percent.
Data Source: C.D. Keeling and T.P. Whorf, Atmospheric CO2 Concentrations (ppmv) derived from in situ air samples collected at Mauna Loa Observatory, Hawaii, Scripps Institute of Oceanography, August A. Neftel et al, Historical CO2 Record from the Siple Station Ice Core, Physics Institute, University of Bern, Switzerland, September See
Data Source: C.D. Keeling and T.P. Whorf, Atmospheric CO2 Concentrations (ppmv) derived from in situ air samples collected at Mauna Loa Observatory, Hawaii, Scripps Institute of Oceanography, August A. Neftel et al, Historical CO2 Record from the Siple Station Ice Core, Physics Institute, University of Bern, Switzerland, September See
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15. The Historical Data
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16. Cumulative Radiative Forcing of GHG Emissions
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17. Temperature Change, 1400-2000 (Northern Hemisphere)
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18. Global climate change …..
We frequently view climate change in terms of a global average - but nobody lives in a global average climate.
Location (geography) is important.
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19. … is spatial Climate change is not uniform over the Earth.
Magnitude varies with location
And with season ….
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20. Canada: Temperature Changes
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21. Possible Effects of A Warmer World
Higher temperatures (wider extremes?)
Changes in precipitation - wetter and drier
Rising sea level (e.g. Fig in text) and melting of ice bodies
Changes in food production and ecosystems
Longer growing seasons
Range of tolerance
See Figure in text
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22. 45:211: Environmental Geography

23. Ecozones
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24. Rising Seas: The Future
One of the most striking consequences of global warming will be the associated rise in global mean sea level.
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25. Change in Arctic Ocean: Summer Ice Cover
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26. Permafrost in Canada
Present
2xCO2
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27. Good or Bad?
Whether global warming is “good” or “bad” is a matter of perspective (and self-interest)
There will be “winners” and “losers”
This is not a scientific issue but social and economic
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28. Slowing Global Warming
Reduce emissions - the quickest, cheapest, most effective way to reduce emissions is to use energy more efficiently.
Slow population growth - if we cut per capita greenhouse gas emissions in half, but double the population - we do not help the problem.
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29. Cumulative carbon emissions, 1950-1996
In terms of historical contributions to the atmospheric buildup of emissions, the industrialized countries like the US have contributed roughly 80 percent of the carbon dioxide buildup in the atmosphere to date. On a country-by-country basis, the comparisons between the rich and poor countries are even more stark. Since 1950, the US has emitted a cumulative total of roughly 50 billion tons of carbon, while China (4.5 times more populous) and India (3.5 times more populous) have emitted only 15 and 4 billion tons respectively.
Data Source: Marland et al, Carbon Dioxide Information Analysis Center.
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Data Source: Marland et al, Carbon Dioxide Information Analysis Center.

30. How much will the Kyoto Protocol reduce emissions?
How Much will the Kyoto Protocol Reduce Global Emissions?
According to global carbon emission projections, even with the implementation of the Kyoto Protocol, emission levels in 2010 are still expected to be more than 30 percent higher than 1990 levels, largely due to increases from rapidly growing developing countries that are not bound by emission limitations under the Kyoto Protocol.
Data Sources: United States Department of Energy, Energy Information Administration, International Energy Outlook, 1998 and 1999.
Data Sources: United States Department of Energy, Energy Information Administration, International Energy Outlook, 1998 and 1999.
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31. Ozone Depletion
Ozone is formed in the Stratosphere when high-energy solar ultraviolet radiation splits molecular oxygen (O2) into atomic oxygen (O+O).
The atomic oxygen may then combine with another oxygen molecule to form triatomic oxygen (O3, ozone). 
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32. Problem:
In the 1970s, it was discovered that CFCs were reducing the concentration of ozone in the stratosphere.
CFCs take years to diffuse up into the stratosphere, but they are long-lived. 
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33. In the stratosphere, UV radiation breaks down CFC molecules, releasing atomic chlorine. A free chlorine atom reacts with an ozone molecule, converting it from O3 to O2.
Cl + O3 = ClO + O2
Unstable
Cl + O
Cl + O3 = ClO + O2
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34. Consequences of Ozone Loss
More UV radiation will reach Earth’s surface.
More/worse sunburns - leading to increased rates of skin cancers
Suppression of immune system
Lower crop yields
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35. Montreal Protocol (1987)
Reduce production of CFCs and phase out their use by 2000
82 nations have signed the agreement
U.S. stopped production of CFCs in 1996.
As a result of these efforts, the levels of CFCs in the atmosphere will stabilize and should decline in the future.
But CFCs will remain in the atmosphere for several decades (residence time)
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36. Summary Global warming is due to increased levels of greenhouse gases.
Impacts of climate change are varied and may be viewed as positive and negative.
Kyoto Treaty calls for emissions reductions.
CFC’s are thought to lead to the destruction of the ozone layer.
Increase of UV radiation poses a health risk.
Their use is being curtailed through the Montreal Protocol.
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