Final Study Notes

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Published on 22 Apr 2013
School
McGill University
Department
Geography
Course
GEOG 205
Professor
GEOG 205 Global Change: Past, Present and Future Midterm Notes Winter 2013
UNIT 1: PRESENT
Thomas Maltus populations grow exponentially but power to support them doesn’t
positive checks: things that increase mortality rates (hunger, disease, war)
preventative checks: things that decrease fertility rates (abortion, birth control, celibacy)
fertility rates: average number of children a woman is expected to have based on where they are in
the world
Canada, US & China have low fertility rates due to immigration and the one child rule
3 stages influencing population growth
o stage 1 non-industrial country where birth & death rates high; with industrialization, birth
rates high & death rates drop
o stage 2 high population growth; standard of living increases, more education & family
planning
o stage 3 birth rates drop toward death rates; zero or negative growth becomes normal; few
children in families
sustainability: development which meets needs of current generations without compromising ability
of future generations to meet their own needs
carrying capacity: the maximum number of individuals of a species that can be sustained by an
environment without lessening the environment’s ability to sustain the same number of individuals in
the future
o depends on how we want to live & how we want those who follow to live
o most environmental damage from very large number of people on earth
environmental challenges
o biodiversity species declining
o deforestation 80% original forests cleared/damaged/fragmented
o water industrial wastes dumped into waters of developing countries
o air pollution killing more & more people
amount of people living in urban areas increasing
William Cronon divide between urban dwellers & impacts of major environmental problems
energy consumption increasing over time in past humans lived rural lifestyle (hunting, agriculture)
but now rely on energy to power homes, cars, processes, technology, etc.)
the Gaia hypothesis: a metaphor that the environment at global levels has be changed by life
throughout history & the changes have improved the chance that life on earth will continue life
manipulates the environment for the maintenance of life
James Lovelock argued atmospheric composition can be used to test for presence of life by comparing
gases with those based on biological activity
Daisy world hypothesis: under low temperatures, black daisies have advantage since absorb radiation;
under high temperatures, white daisies have advantage since reflect radiation
weather: day to day variation in the state of the atmosphere combination of temperature, humidity,
cloudiness
climate: weather information & how the atmosphere typically “behaves” over long periods of time
precipitation, expected temperature, etc.
causes and effects of global warming can be changed through adaptation & mitigation
o adaptation: aimed at reducing the effects
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GEOG 205 Global Change: Past, Present and Future Midterm Notes Winter 2013
o mitigation: aimed at reducing the causes
James Hansen began to think about impacts of airborne particles from volcanoes block the radiation
from the sun so darkened earth’s surface & therefore cooled it
Milankovitch theory describes collective effects of changes in earth’s movements on climate
o eccentricity the earth doesn’t orbit around the sun in a perfect circle, period of 100 000
years
o axial tilt changes change of the earth’s tilt every 41 000 years leads to different amounts of
radiation
low axial tilt = small seasonal variation in solar insolation
high axial tilt = large seasonal variation in solar insolation
o precession change in orientation of earth’s orbit every 26 000 years
one square metre of earth directly faces sun & receives 1370 watts of energy but most receive 342
watts
o 6% scattered back to space by atmospheric particles
o 10% reflected back to space by land & ocean surfaces
o 84% remains to heat surface
earth balances incoming & outgoing radiation calculations show planet should be -6C to maintain
balance which is 20C colder than reality
o sunlight attenuated (gradual loss of intensity) by scattering & absorption through atmosphere
o difference due to greenhouse effect greenhouse gas molecules vibrate & absorb heat
gases at top of atmosphere cold so emit less radiation but capture more from earth
radiative forcing: change in average net radiation at top of troposphere due to change in concentration
of greenhouse gases
cloud radiative forcing: change in average net radiation at top of troposphere due to presence of
clouds
feedbacks: factors which tend to increase rate of a process (positive) or decrease it (negative)
albedo: measure of surface reflectivity
possible causes of recent climate change
o astronomic changes in earth’s orbit; increasing solar radiation (not true since sun’s radiation
decreasing & climate increasing)
o volcanic activity episodic & irregular production of ash & chemicals that block solar radiation
so have cooling effect
o land use changes from natural vegetation to grazing land, agricultural crops, bare soil &
urban areas; decreases albedo & increases proportion of radiation transformed into sensible
heat
o circulation patterns El Nino & La Nina
o atmospheric chemistry greenhouse gases warm the earth but also add more reflective &
cloud forming particles that cool the earth
the greenhouse effect: water vapour, carbon dioxide, etc. absorb some of the thermal radiation
leaving the surface of the earth, and in turn heat up the earth
o there is a natural greenhouse effect since all gases there before human beings, but the
enhanced greenhouse effect is due to added effect of human activities
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GEOG 205 Global Change: Past, Present and Future Midterm Notes Winter 2013
clouds reflect radiation from sun back to space, but also absorb thermal radiation two effects
working opposite each other but in general, clouds slightly cool the earth’s surface
runaway greenhouse effect: interior of Venus contains a lot of water vapour which forms the
atmosphere, and creates a greenhouse effect; the temperature rises because of this which leads to
more evaporation and therefore higher increases in temperature; process continues until atmosphere
saturated with water vapour
o Venus closer to sun so started at a warmer temperature won’t happen to earth
temperature anomaly: departure from a reference value or long term average
o positive anomaly: observed temperature warmer than reference value
o negative anomaly: observed temperature colder than reference value
urban heat isle effect: metropolitan area which is significantly warmer than its surrounding rural areas
due to buildings blocking surface heat from radiating into cold sky, thermal properties of materials
absorbing more & lack of evapotranspiration through lack of vegetation
characteristics of rate of growth of proxie materials (ice cores, tree rings, pollen, etc.) influenced by
climatic conditions
future precipitation & storm changes will vary by season & region
aphelion: when the earth is farthest from the sun (July 4th)
perihelion: when the earth is closest to the sun (January 4th)
there is an equatorial surplus of energy which is transferred poleward through atmospheric & oceanic
circulation
atmospheric circulation patterns due to differences in pressure & unequal heating of earth’s
atmosphere air moves to the warmer location (less dense)
latitudinal circulation established as Hadley cells warm air rises at equator & falls at 30 degrees
Coriolis Effect: direction of air motion on a global scale is affect by the earth’s rotation
o flows to the E in northern hemisphere & to the W in southern hemisphere
o strongest near poles & decreases to zero at equator
polar front: where subtropical air meets polar air
land ocean effect: ocean retains temperatures longer than land surfaces; land heats up more quickly;
hot/low pressure air rises & ocean’s low pressure moves in opposite happens in winter
ocean circulation patterns driven by atmospheric circulation
thermohaline circulation = the global conveyor belt
o slow movement of water between Pacific & Atlantic
o transfers warm water from equatorial Atlantic to North Atlantic where it cools & becomes
denser with salt to sinks
o this water then travels to Southern Ocean upwelling & mixing occur to deep waters brought
to surface of Indian & Southern Pacific oceans
o circulation loop moves surface water from Pacific past Australia into Indian Ocean to complete
circuit
o important transfer mechanism for heat from equator to northern hemisphere
changes in circulation patterns = El Nino Southern Oscillation (ENSO)
o occurs every 3-7 years
o cold upwelled waters replaced by warm current
o brings droughts, heavy rain falls, severe spells of heat & cold, high incidence of cyclonic storms
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Document Summary

Thomas maltus populations grow exponentially but power to support them doesn"t. Positive checks: things that increase mortality rates (hunger, disease, war) Preventative checks: things that decrease fertility rates (abortion, birth control, celibacy) fertility rates: average number of children a woman is expected to have based on where they are in the world. Canada, us & china have low fertility rates due to immigration and the one child rule. Environmental challenges: biodiversity species declining, deforestation 80% original forests cleared/damaged/fragmented, water industrial wastes dumped into waters of developing countries, air pollution killing more & more people. Amount of people living in urban areas increasing. William cronon divide between urban dwellers & impacts of major environmental problems. James lovelock argued atmospheric composition can be used to test for presence of life by comparing gases with those based on biological activity. Daisy world hypothesis: under low temperatures, black daisies have advantage since absorb radiation; under high temperatures, white daisies have advantage since reflect radiation.

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