lecture 6: human environment relations Flashcards
Climate is a function of the interaction of many spheres:
atmosphere: gases
* hydrosphere: oceans, large bodies of water
* lithosphere: plate tectonics
* cryosphere: glaciers, ice sheets, snow cover
* biosphere: vegetation, animals, humans
the last glacial period:
all of Canada covered in ice expect for northern yukon
lower sea levels at that time exposed the bering land bridge
causes of climate change:
- variations in solar radiation
- changes in composition of the atmosphere
- changes in earths surface
- variations in earths orbit
variations in solar radiation
the sun tends to emit more energy during periods of high sunspot activity
sunspot:
a cool ration of high magnitude on the sun (dark and black)
* Sunspots occur in cycles and reach a maximum every 11 years
* sunspots are cool areas on the sun that are surrounded by faculae
* solar output changes on the order of 0.1 - 0.2% in relation to sunspot cycles
* more sunspots = increased solar output
faculae:
bright areas with high amounts of energy
Maunder Minimum:
a period with no sunspots; this corresponds to a time known as the little ice age
changes in composition
greenhouse gases
addition of greenhouse gases (CO2, water vapour, methane) increases global temperature
* CO2 has long residence time in the atmosphere – even though we are reducing CO2 effects will not be felt for decades
* A warming climate appears to be inevitable during our lifetimes
Ice cores
- width of an layer provides insight on the temp and snowfall of that year
- Each year a new layer of ice forms
- bubbles of air trapped in the ice
- Ice cores can provide data for up to 600,000 years in the past
denderochronology
- the study of tree rings
- wider rings = warmer or wetter years
- tree rings provide data up to 1000 years in the past
theory of plate tectonics
- the continents have moved over time
the collision of converging plates = an uplift and the creation of mountains - implications: affects wind, temp and precipitation patterns on surrounding landscapes
variations in earths orbit
The greenhouse effect: why does it exist?
greenhouse gasses allow solar radiation to pass through, but they also absorb infrared radiation from earth
* Main greenhouse gases: carbon dioxide, water vapour, methane
Milankovitch theory:
three seperate phenomena relating to earths orbit contirbute to climate change (3 cycles)
1. eccentricity: changes in the shape of the earths orbit from circular to elliptical, 100,000 year cycle (accounts for ice ages)
2. precession: wobble of earths axis, 23,000 year cycle
3. obliquity: changes in the tilt of earths axis, 41,000 year cycle
enhancement of the greenhouse effect:
the greenhouse effect itself is not a concern however the enhancement effect by humans is a concern.. why? - adding greenhouse gas = climate change
* increasing the amount of CO2 enhance the greenhouse effect.. why? Because more infrared radiation from the earth is absorbed in the atmosphere
* CO2 emissions are increasing in China and India as the economies in these countries continue to industrialize
ozone
- gas composed of oxygen with a pungent smell
- forms naturally in the stratoshpere
- forms in the troposphere by chemical reactions with other gases