Climate Change Flashcards
What is climate?
“average weather”, the classical period is 30 years, variables include: temperature, precipitation, and wind
What five factos determine the surface temperature of the earth?
- energy balance
- greenhouse effect
- carbon cycle
- radiative forcing
- feedback mechanisms
What is a blackbody?
a material that absorbs all light - 100% absorption, 0% reflection
What is blackbody radiation?
the spectrum of light from an object that does not create light
What is albedo?
fraction of sunlight reflected back into space by an object
what is dE? What contributes to most of the greenhouse effect?
dE = absorption and thermal radiation of GHGs = green house effect
water vapour accounts for most of the effect
What happens to the IR light that is absorbed by GHGs?
- reemitted after absorption
- lost as heat through collisions with other molecules
What is the greeenhouse effect?
absorption of outgoing IR by atmosphere and dissipation of heat
What increases the chance of IR absorbance by molecules?
When the hv approaches the molecular vibrational modes
What are common molecular vibrations?
- bond stretching vibrations: symmetic or asymmeric
- angle-bending vibrations
What condition does IR absorption by molecules require, in terms of vibrations?
requires a change in the dipole moment during the vibration
What happens after vibrational excitation?
molecules move faster –> more collisions –> transfer of E to other molc during collision –> relaxation + release of heat (+emit IR as heat) –> IR absorbed by a neighboring molc
What is radiative forcing?
term used to describe the radiative imbalance caused by species in the atmosphere, based on both concentration and impact (e.g. a poorer absorber at a higher concentration can have a larger impact = greater RF)
> 0 = warming influence
< 0 = cooling influence
Why does the [CO2] have seasonality?
- N. hemisphere is where most vegetation is located
- CO2 build up until growing season begins, then decreases via photosynthesis
Where is most carbon stored? How has human activity changed the carbon cycle?
most C is stored in rocks, sediment (including fossil fuels), then rest in ocean, atmosphere, and living organisms
human activity
- increase release of CO2
- change of land use (deforestation, building over peat bogs) –> less CO2 is removed by photosynthesis
What are major sources of CO2?
combustion: CxHy + O2 –> CO2 + H20
cement production: CaCO3 –> CaO + CO2
Is CH4 a better or worse GHG than CO2?
better - absrobs IR more frequently than CO2
What are common sources for atmospheric CH4?
- anaerobic decomposition: convert cellulose into CH4 and CO2 (occurs at landfills and in livestock)
- biomass burning (from incomplete combustion)
- leaking natural gas lines
- mining of coal
- collecting/refining crude oil releases dissolved CH4 or gens it from incomplete flaring
Describe the role of aerosols on climate forcing
- scattering (increase albedo = negative RF; redirect thermal IR downwards = postivie RF)
- absorption (positive RF)
- can cause increased cloud formation (increased albedo = negative RF)
How is radiative forcing (RF) calculated?
spectral overlay for the absorption of IR by GHGs compared to the spectral emisssion of Earth
What GHG is currently a huge concern?
SF6
What is the Koyoto protocol?
decrease GHG emissions
What is the Montreal Protocol?
phase 1: no more halogenated (e.g. CFCs)
phase 2: phase out HCFC
What is the Kigali ammendment of the Montreal protocol?
phase down HFCs and HFOs
