M3L1 - Energy & Feedback Loops Flashcards
Emissivity
The proportion of energy received to emitted
Black body
Something that emits 100% of energy it absorbs (emissivity = 1)
Planck’s law
For a given object, the energy at any specific wavelength is dependent on temperature (measured in kelvin)
Stefan-Boltzmann Law
There is a direct relationship between an object’s temperature and how much radiation it emits
What does EMR scattering in the atmosphere depend on
- Wavelength of the EMR compared to particle size
- Amount of particles/gasses
- How far the EMR travels through the atmosphere
Three types of scatter
- Rayleigh scattering
- Mie scattering
- Nonselective (geometric scattering)
Rayleigh scattering
- Shorter wavelengths of visible spectrum are scattered by particles smaller than the wavelengths of light (including dust, NO2 and O2)
- Explains why sky is blue
Mie scattering
- Occurs when the wavelength of EMR is similar to the particles in the atmosphere (or particles are larger)
- Driven by presence of aerosols
Aerosols
Mixture of gasses, dust, water vapour
Nonselective (geometric scattering)
- Scattering by particles much larger than the wavelength
- Water vapour and clouds
- Why clouds are white (scatter all wavelengths equally)
Why do contributions to greenhouse effect vary
Based on characteristics of the gas, how much there is, and what indirect effects it has
Water vapour
- High relative contribution to greenhouse effect
- Humans not influencing the amount directly
- Residence time is short (~9 days)
New and emerging compounds
- Sulphur hexafluoride is a growing concern
- 23,500 more potent than CO2
- Used in high voltage electrical applications
- Often unaware of implications of new compounds until they have been around for a while
Carbon sources and sinks
- Most things are in balance
- Known out of balance (burning fossil fuels faster than they are forming)
- Unknowns (permafrost flux, methane hydrate amount)
What is global warming potential standardised to
CO2
Methane hydrate
Formed when water and methane gas come together at
high pressures and low temperatures in oceans
Ocean acidification
- Oceans absorb ~1/3 of co2 released in atmosphere
- Increases concentration of hydrogen ions, decreasing pH
- Carbonic acid acid formation and subsequently dissociates releasing hydrogen ions (H+) and bicarb (HCO3-)
Radiative forcing
- Measure of influence a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system
- Internal forcings: atmospheric, surface
- External (solar forcing)
Feedback loops
- Positive adds to initial change
- Negative reduces initial change
Environmental stability
- Stable: Deviations up to a certain point from equilibrium end up returning to equilibrium, or new
equilibrium - Unstable: Small perturbations result in larger shifts and a lack of ability to return to equilibrium
Resiliency
- Ability for a system to keep functioning after being subjected to disturbance
- Not always a positive
- Examples: Soil resilience in agriculture; overfishing; deforestation; electrical grids
