Climate

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Climate
Change
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Global Climate History
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Milankovitch Theory of Climate Change

• The Earth changes its
• orbit (eccentricity), from ellipse to circle at
  100,000 year cycles,
• wobble (precession), from the north pole pointing
  toward or away from the sun in June at 23,000
  year cycles, and
• c) tilt (obliquity), from 22 to 24.5 at 41,000
  year cycles.

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Climate Since the Most Recent Ice Age
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Does a large, composite volcano affect climate
on a global scale?
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Effect of Mount Pinatubo Eruption
Note Volcanoes also release CO2, and warming
occurs in the long term during tectonically active
periods (eg. Triassic/Jurassic boundary)
TEMPORARY COOLING
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Ice core data Temperature, CO2 and CH4 are all
in phase Are the gas concentrations an effect
or a cause of warming or both?
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The Jurassic A much warmer Earth with more CO2
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Human-induced Climate Change
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Source IPCC
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The Global Carbon Cycle - 1990sUnits Gt C and Gt
C y-1
Atmosphere
3.2
are leading to a build up of CO2 in the
atmosphere.
750
63
6.3
Fossil Deposits
About 16,000
1.6
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Plants
Fossil emissions
500
Soil
91.7
90
2000
and land clearing in the tropics...
Oceans
The KP seeks to reduce net carbon emissions by
about 0.3 Gt C below 1990 levels from
industrial countries
39,000
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2xCO2 ENVIRONMENT
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Enhanced photosynthesis
Source IPCC
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1950
2006
Climate Modelling
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Temporary, regional cooling effect
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Source IPCC
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Climate Change Impacts
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Negative Impacts

• Reduced Biodiversity
• Rapid change may exceed capacity of
• plants and animals to adapt to changing
• climate and new interspecies dynamics
• Sea level rise and coastal flooding
• Thermal expansion melting ice
• Expansion of tropical disease range

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• 4. Soil Moisture Decreases and
• Desertification
• Evapotranspiration increases may
• exceed increases in precipitation
• 5. Increased frequency of heat illness
• Increased frequency of severe events?
• More energy for tropical cyclones
• (supports this hypothesis), but reduced
• latitudinal temperature gradients could
• reduce middle-latitude storm intensity

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7. Engineering problem of thermokarst (transport
ation and housing) 8. Affect on outdoor winter
recreation and winter tourism
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Albertas Fragile Fresh Water Supply

• Partially supported by glacial meltwater
• Glaciers are retreating
• Future ET gtgt P?

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Positive Impacts

• Increasing ecosystem productivity
• Higher photosynthesis rates due to
• carbon fertilization
• Increased food production
• Higher photosynthesis rates, wider
• range where soils adequate, longer
• growing season (depends on soil
• moisture/depth/nutrients)

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• 3. Increased water-use efficiency
• Plants can reduce stomatal aperture,
• yet maintain sufficient internal CO2
• May mitigate desertification and soil
• moisture deficit somewhat
• 4. Increased nutrient-use efficiency?
• Is less Rubisco required at higher
• temperatures? (Contains N)
• 5. High latitude warming
• Both a negative effect (loss of key Arctic
  species, ways of life) and positive effect (crop
  growth ?NPP, soil permitting)

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Free Air Carbon Dioxide Enrichment (FACE)
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FACE Results NPP increases (eg. 40 in cotton
25 for Sweetgum for 550 ppm vs. 370
ppm) Carbon sink increase limited for forests
Increase in wood production is short-lived C
goes mainly to fine roots and leaves affected
by soil fertility No effect on LAI Stomatal
conductance decreases (increased water- use
efficiency) Lower leaf nitrogen concentration
Do they need less? Have less? Due to CN
ratio?
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Source IPCC
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Meanwhile, we are detecting stratospheric
cooling !
Why ? Ozone depletion Tropospheric CO2
increases
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Further Reading Fundamentals of Physical
Geography Online 7h. The Greenhouse
Effect http//www.physicalgeography.net/fundamenta
ls/7h.html Climate Change 2001 The Scientific
Basis International Panel on Climate
Change http//www.grida.no/climate/ipcc_tar/wg1/in
dex.htm