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Lec 2 - Geog 205

readings if you missed the first two lectures

consider earth's orbit, solar strength, the amount that makes it through, how much is absorbed, and how much is reflected
these systems interact:

know the chart really well
109% absorbed (accumulation)

if we look from 1940 to 1975, there is a cooling trend
the cause: sulfur dioxide : is an aerosol that reflects sunlight
around mid 70's, legislation reduced mat of sulfer dioxide

external forcing: greenhouse gases, tropospheric aerosols (reflect sunlight), land use change, long-term solar radiation (how close earth to sun, angle, energy emitted by sun)
internal variation: thermohaline circulation (i.e. conveyor belt) ( change the balance), and el nino (short term)
29.1why do we care about short-term? perturbation, feedback, land use. we also need to make sure that our short term knowledge is predictable¶

must understand theory bfore we make relationships

look for correlation (external force changed in a similar way as observed climate?
scientific explanation?
dominate cause?

ppm composition of earth's atmosphere (will be on exam)
need to look at lifetime of gases,
lifetime: i.e. respiration, recycling multiple lifetimes
methane lasts 12 years,
global warming potential: if co2 is one, ch4 has larger impact
co2 is dominate, i.e. it has most effect + most numerous

natural hydrological cycle
but as climate changes, the amount of water vapor increases
has to do with the amount of energy in atmosphere to evaporate water from the oceans

breathing, fossil fuels, livestock
also natural sources, like soils

anaerobic respiration, microbes release methane
cattle farts

fertilizer

when produced in troposphere, is bad (for some reason)

ideally replaced

replaced CFCs

3 major: carbon dioxide, methane, nitrous oxide

warming at the top at the troposphere

isotopes. c12, 99%. c14, radioactive, used for carbon dating, are decaying
c14 is decreasing. c12 is increasing. this means that c14 hasn't been used in a long time
c14 possibly from fossil fuels or volcanos
c13 possibility. plants have lower c13 than geological sources.
there are more sources of organic carbon in atmosphere
thus, we deduce that cause of increase of carbon is fossil fuels

which planet in the solar system has a runaway greenhouse effect? i.e. positive feedback
answer: venus
venus doesn't absorb very much energy
96% atmosphere is co2, and greenhouse gases are 265 deg f

sulfates, soot, organic carbon, dust
tend to be short lived
esp in troposphere, precipitated out by rain
but when reach stratosphere, they can last for years
aerosols form a haze
they reflect the sunlight away (or something)
volcanic activity, dust from desert, manufacturing

mount pinatubo
- spread around the globe, for several years
- decrease in 4 w/m^2, decrease in 1% of solar radiation globally

at about 100,000 year cycle from circular orbit to elliptical earth orbit
but this doesn't match our sudden increase of temperature
tilt and wobble- changes in earth axis
-- right now we're in the middle
-- distribution of temperatures would change
-- wobble changes the time that the season occurs
time scale: 20,00 - 100,000 years, not responsible for short time scale

increase over time.
less sunspots, less solar radiation
sunspots: change 2% of radiation. compare to mt petuba, is 1/8th

major movements of energy from tropics to poles
some other stuff

between 3 and 7 years, it happens
heating and cooling
when it occurs: southeast trade winds revere or weaken, cold upwelling reduced or absent, high pressure over austrilia, rain over south america
changes weather patterns across the world
also, La Nina, like El Nino, but less strong
about a redistribution of global climate, but not a signal.

dry and wet seasons
warm water is nutrient poor, wreaks havoc on marine ecosystems

total radiative forcing, co2 and ch4 have the greatest effect