Global warming I

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AGEC/FNR 406
LECTURE 20
Average Temperature at Earth's Surface, 1866-1998
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Data/Graphics from the Midwest Climate Data
Center http//mcc.sws.uiuc.edu/climate_midwest/mwc
limate_change.htm
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Pollution Problem

• Greenhouse gases are stock pollutants
  environment has little or no assimilative
  capacity.
• Dynamic problem Persistence of greenhouse gases
  and continued use will add will likely increase
  global warming.
• Potentially significant impacts on social,
  economic and ecological systems.
• Even with remediation, effects will continue over
  an extensive time period.

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Global Warming
Truth or fiction?
Intergovernmental Panel on Climate
Change(international group of scientists)... Wa
rming of the climate system is unequivocal Globa
l warming of 3-8 degrees Celsius over the next
50 years
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Evidence
1. More warm days steady rise since
1982 1995-2006 rank as warmest since 1850 2.
Melting of snow and ice 3. Record number of
icebergs 4. Sea level rise (high confidence) 5.
Changes in Gulf Stream 6. Changes in
precipitation patterns 7. Coral reef damage from
algae
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• IPCC 4
• 4th assessment report _at_ http//www.ipcc.ch

Eleven of the last twelve years (1995-2006) rank
among the twelve warmest years in the
instrumental record of global surface temperature
(since 1850)
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What are the Greenhouse Gases?

• Carbon dioxide (CO2) 50
• Methane (CH4) 18
• Nitrous oxide (N2O) 6
• Hydrofluorocarbons (HFCs)
• Perfluorocarbons (PFCs)
• Sulphur Hexafluoride (SF6)

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Carbon Dioxide

• Nature Cycled through various atmospheric,
  oceanic, biotic and mineral reserves.
• Anthropogenic activities
• Burning of fossil fuels (oil, natural gas and
  coal) for power generation and transportation.
• Industrial processes.
• Forest clearing.
• Natural gas flaring.
• Biomass burning.

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Methane

• Nature Produced through anaerobic decomposition
  of organic matter in biological systems.
• Anthropogenic activities
• Municipal solid waste landfills.
• Wetland rice cultivation.
• Livestock digestion.
• Waste production.
• Production and distribution of fossil fuels.
• 20 times more effective at trapping heat than
  carbon dioxide.

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Nitrous Oxide

• Nature Microbial processes of nitrification and
  denitrification in biological systems.
• Anthropogenic activities
• Addition of nitrogen to soils agriculture.
• Industrial production activities.
• Solid waste combustion.
• Fossil fuel combustion.
• 300 times more effective at trapping heat than
  carbon dioxide.

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HFCs, PFCs, Sulphur Hexafluoride

• Anthropogenic activities
• HFCs are replacements for ozone-depleting
  substances.
• PFCs and Sulphur Hexafluoride emitted in
  industrial processes
• Aluminum smelting.
• Electric power transmission and distribution
• Magnesium processing
• Semiconductor manufacturing
• Very long atmospheric lifetimes. Concentrations
  can irreversibly accumulate in the atmosphere.

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Why Focus on CO2?
Source IPCC 4th Assessment Report
http//www.ipcc.ch/pdf/assessment-report/ar4/syr/a
r4_syr_spm.pdf
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Sources of CO2
Main source is fossil fuels (burning of coal
coincided with the industrial revolution)
Supply of CO2 in the U.S.1/3 Electricity and
industry 1/3 Transport (cars) 1/3 Other
(biomass burning, etc.)
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Potential effects on
1. Agriculture forestry
2. Human health (disease transmission)
3. Fish, wildlife, and ecosystems
4. Coastal environments water supplies
Human-managed systems may adapt more readily
than natural (non-managed) systems. Currently
stressed systems may be at special risk.
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Consequences for Ag
1. Higher temperature will shift
agricultural production2. Variation in
temperature US 8 in winter 3 in
summer 2. Moisture reduced from East to
West 3. More rainfall variability 4.
Increased pest populations
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Consequences for FishWildlife

• Changes in temp and precip. could cut breeding
  populations of ducks in half.
• Cold water fish habitat could be reduced or lost
  in many states
• Migration/breeding cycles may be disrupted for
  species that depend on temp signals (studies show
  some species of birds and amphibians are
  migrating and breeding earlier than expected).

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Two ways to get rid of CO2
1. Reduce emissions (reduce energy use)2.
Lock-up carbon somehow (in forests?) What is
the cheapest way to do this from an economic
perspective? 1. Moral suasion (unlikely) 2.
Carbon taxes (unpopular) 3. Tradable permits
(shows promise)
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Benefits and costs
1. Aggregate damage estimates range from 1-1.5
of GDP (industrialized countries) to 2-9 of GDP
(developing countries)2. Estimates of annual
costs of stabilizing CO2 emissions at 1990 levels
range from 0.5 to 2 of GDP.Is Benefit-Cost
analysis the right tool?
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Precautionary motive
Future impacts are uncertain Magnitude of
problem is unknown Catastrophic and
irreversible effects are possible Is there a
need for precautionary action now?