http://www.weru.ksu.edu/new_weru/multimedia/storms/big/duststm4.jpg

Milankovitch Theory of Climate Change

The Earth changes its:

a) orbit (eccentricity), from ellipse to circle at 100,000 year cycles,

b) 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.

Climate Since the Most Recent Ice Age

Does a large, composite volcano affect climate on a global scale?

Effect of Mount Pinatubo Eruption

Note:Volcanoes alsorelease CO2, and warming occursin the long termduring tectonicallyactive periods(eg. Triassic/Jurassicboundary)

TEMPORARYCOOLING

Ice core data

Temperature,CO2 and CH4

are all in phase

Are the gasconcentrationsan effect or acause ofwarming orboth?

The JurassicA much warmer Earth with more CO2

Source: IPCC

The Global Carbon Cycle - 1990sUnits Gt C and Gt C y-1

The KP seeks to reduce net carbon emissions by about 0.3 Gt C below 1990 levels from industrial countries

Atmosphere

Fossil Deposits

6.3

63

91.7

60

90

3.2

Plants

Soil

Oceans

750

500

2000

39,000

About 16,0001.

6

…are leading to a build up of CO2

in the atmosphere.

Fossil emissions

…and land clearing in the tropics...

2xCO2 ENVIRONMENT

Source: IPCC

Enhanced photosynthesis

1950 2006

ClimateModelling

Temporary,regional coolingeffect

Source: IPCC

1. Reduced Biodiversity Rapid change may exceed capacity ofplants and animals to adapt to changingclimate and new interspecies dynamics

2. Sea level rise and coastal floodingThermal expansion + melting ice

3. Expansion of tropical disease range

4. Soil Moisture Decreases and DesertificationEvapotranspiration increases mayexceed increases in precipitation

5. Increased frequency of heat illness

6. Increased frequency of severe events?More energy for tropical cyclones (supports this hypothesis), but reducedlatitudinal temperature gradients couldreduce middle-latitude storm intensity

7. Engineering problem of thermokarst(transportation and housing)

8. Affect on outdoor winter recreationand winter tourism

Alberta’s Fragile Fresh Water Supply•Partially supported by glacial meltwater•Glaciers are retreating•Future ET >> P?

1. Increasing ecosystem productivityHigher photosynthesis rates due to carbon fertilization

2. Increased food productionHigher photosynthesis rates, wider range where soils adequate, longer growing season (depends on soil moisture/depth/nutrients)

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 highertemperatures? (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)

Free Air Carbon Dioxide Enrichment (FACE)

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 C:N ratio?

Source: IPCC

Meanwhile, we are detecting stratospheric cooling !

Why ? Ozone depletionTropospheric [CO2] increases

Further Reading:

Fundamentals of Physical Geography Online7h. The Greenhouse Effecthttp://www.physicalgeography.net/fundamentals/7h.html

Climate Change 2001: The Scientific BasisInternational Panel on Climate Changehttp://www.grida.no/climate/ipcc_tar/wg1/index.htm