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why is the earth warm
ozone, greenhouse gases, sun, albedo, orbital pattern, geothermal flux
Albedo
the light that a surface reflects
Scale of 0-1 - if it is all reflected, the albedo is equal to 1
Earth is about 0.2
Albedo values:
Ocean: 0.05
Forest: 0.1
Ice: 0.8
low albedo
dark-colored surfaces absorb more incoming solar radiation- warmer
Greenhouse gases
Allow thermal energy to escape
Absorb infrared light, re-emit, sending some to surface
Increase in CO2 by decomposition
Decrease in CO2 by photosynthesis
Insolation
Incoming solar energy
IN- UV and visible light
OUT - infrared light
Increase in insolation - increase in plant growth (decrease Co2)
Energy Balance
Outgoing = incoming
Ts = [S/(4σ) *(1-A)] 0.25
Amplifying loops
Enhance a problem
Temp increase causes decrease in sea ice which causes decrease is albedo- leds to more increase of temp
Stabilizing loops
Balance a problem
Increased decomposition leads to more CO2 which then has more photosynthesis which traps CO2
Residence Time
Duration of time something spends somewhere - volume/flux
Carbon Reservoirs
Photosynthesis, respiration, combustion, erosion and weathering, diffusion, and ocean mixing and sedimentation
Steady-state equilibrium
he point at which the flow of different ions inside and outside are equal and opposite, but no single ion is at equilibrium
Stable/unstable equilibrium
Stable equilibrium occurs if after a body has been displaced slightly it returns to its original position when the displacing force has been taken away
Unstable equilibrium occurs if after a body has been displaced slightly it moves farther away from its original position
Infrared radiation
type of radiant energy that is invisible to the eyes; we can only feel it in the form of heat
Sun or fire
Daisyworld
Three main phases- minimum, optimal, maximum
period of rapid growth, reaches temperature limits (stable feedback loop), rapid decrease
white daisy albedo is decreased - temperature of the planet becomes much more similar to that of the dead planet.
soil albedo was increased the planet would also have a longer lifespan - opposite effect of decreased daisy albedo
When the optimal temperature is decreased the lifespan of the planet also decreases- similar to what happens when daisy albedo is changed
Thermohaline circulation
deep-ocean currents driven by differences in the water's density
controlled by temperature (thermo) and salinity (haline)
About a 1000 year process
Example: polar regions ocean water gets cold, forming sea ice. - surrounding seawater gets saltier, because when sea ice forms, the salt is left behind. As the seawater gets saltier, its density increases, and it starts to sink
Oxygen isotopes
O16, O17, O18 - O16 is most common (99.76%)
O16 is lightest
O16 more likely to evaporate while )18 more likely to precipitate
Colder - more fractionation of O16
Lighter (O16) - more positive (colder)
Darker (O18) - more negative (warmer)
Glacial flow
Flow downslope- middle has least deformation
Outward and downward flow
Ice rafted debris
Iceberg calving events (heinrich - cold then warm) creating iceberg armadas
Ice isotope records
Snow - temp 18O
Firn- small circulation
Ice - closed to atmosphere
18O - ice age
CO2 - gas age
CH4- gas age
Lower 18O values indicate colder temperatures.
Higher 18O values indicate warmer temperatures.
Milankovitch cycles
Milankovitch cycles predict a slow cooling trend over the next several thousand years, but human-induced warming is overriding this natural cycle
These cycles are responsible for the timing of ice ages over the past 2.5 million years
Eccentricity
100,000 year cycle
ranging from more circular to more elliptical
When the orbit is more elliptical, Earth receives varying solar energy throughout the year, intensifying seasonal contrasts.
When the orbit is nearly circular, seasonal differences are less extreme.
Tilt
41,000 year cycle
greater tilt increases the intensity of seasons—warmer summers and colder winters.
A smaller tilt results in milder seasons, favoring ice sheet growth in high latitudes.
Precision
20,000 year cycle
Wobble of earth axis
Affects the timing of the seasons relative to Earth's position in its orbit.
Can amplify or weaken seasonal differences depending on whether winter occurs when Earth is closer to or farther from the Sun
