45:211: Environmental Geography Module 8 Atmosphere and Climate.
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Transcript of 45:211: Environmental Geography Module 8 Atmosphere and Climate.
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45:211: Environmental Geography
Module 8
Atmosphere and Climate
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45:211: Environmental Geography
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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45:211: Environmental Geography
Atmosphere
• The layers of air masses surrounding the Earth are collectively referred to as the atmosphere.
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45:211: Environmental Geography
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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45:211: Environmental Geography
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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45:211: Environmental Geography
Atmospheric Layers
• Stratosphere – Extends from about 20-50
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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45:211: Environmental Geography
Ozone: the Good and the Bad
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45:211: Environmental Geography
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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45:211: Environmental Geography
Greenhouse Effect
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45:211: Environmental Geography
Trace Gases
• Most of Earth’s atmosphere is climatically neutral– the important
gases are present in trace amounts only
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45:211: Environmental Geography
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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45:211: Environmental Geography
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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45:211: Environmental Geography
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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45:211: Environmental Geography
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 1998. A. Neftel et al, Historical CO2 Record from the Siple Station Ice Core, Physics Institute, University of Bern, Switzerland, September 1994. See http://cdiac.esd.ornl.gov/trends/co2/contents.htm
Atmospheric carbon dioxide (CO2):1750 to present
270
280
290
300
310
320
330
340
350
360
370
1750 1800 1850 1900 1950 2000
part
s pe
r m
illio
n vo
lum
e
Siple Station (1750-1970)
Mauna Loa (1958-present)
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45:211: Environmental Geography
The Historical Data
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45:211: Environmental Geography
Cumulative Radiative Forcing of GHG Emissions
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45:211: Environmental Geography
Temperature Change, 1400-2000 (Northern Hemisphere)
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45:211: Environmental Geography
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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45:211: Environmental Geography
… is spatialClimate change is not uniform over the Earth.
Magnitude varies with location
And with season ….
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45:211: Environmental Geography
Canada: Temperature Changes
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45:211: Environmental Geography
• Higher temperatures (wider extremes?)
• Changes in precipitation - wetter and drier
• Rising sea level (e.g. Fig. 17.16 in text) and melting of ice bodies
• Changes in food production and ecosystems– Longer growing seasons
– Range of tolerance
– See Figure 17.18 in text
Possible Effects of A Warmer World
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45:211: Environmental Geography
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45:211: Environmental Geography
Ecozones
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45:211: Environmental Geography
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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45:211: Environmental Geography
Change in Arctic Ocean: Summer Ice Cover
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45:211: Environmental Geography
Permafrost in Canada
2xCO2
Present
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45:211: Environmental Geography
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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45:211: Environmental Geography
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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45:211: Environmental Geography Data Source: Marland et al, 1999. Carbon Dioxide Information Analysis Center.
Cumulative carbon emissions, 1950-1996
7,415
8,504
11,651
15,715
4,235
4,054
2,331
1,361
966
50,795
1,557
2,080
2,118
0 10,000 20,000 30,000 40,000 50,000 60,000
United States
Indonesia
Korea, Rep.
Brazil
Australia
Mexico
South Africa
Canada
India
United Kingdom
Japan
Germany
China
Million tons of carbon
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45:211: Environmental Geography
Data Sources: United States Department of Energy, Energy Information Administration, International Energy Outlook, 1998 and 1999.
How much will the Kyoto Protocol reduce emissions?
8.0
5.8
7.6
6.4
0
2
4
6
8
1990 1995 2000 2005 2010
Bill
ion t
ons
of ca
rbon
Business-as-usual
Kyoto Protocol scenario
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45:211: Environmental Geography
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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45:211: Environmental Geography
Problem:
• In the 1970s, it was discovered that CFCs were reducing the concentration of ozone in the stratosphere.– CFCs take 10-20 years to diffuse up into the
stratosphere, but they are long-lived.
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45:211: Environmental Geography
• 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
Cl + O
Cl + O3 = ClO + O2
Unstable
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45:211: Environmental Geography
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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45:211: Environmental Geography
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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45:211: Environmental Geography
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.