Lecture 3 Flashcards
GHG and feedbacks
Greenhouse gas
gas that re-emits infrared radiation
which is the most abundant GHG, N2, O2, Ar, or H2O
nitrogen, in that order
noar, from h2o
Fourier
recognized earth was warmer than should be, atmosphere is a hotbox
Pouillet
first to math describe GH effect and identfiy h2o and co2 as potential
Tyndall
idnetified GHGs and co2 and h2o as strongest
arrhenius
co2 as regulator of water vapour and determines equilibrium temp
Callendar
compared co2 levels and temp and found they rose together
Seuss Effect
dilution of radiocarbon 14C in atmosphere by CO2 produced by burning fossil fuels
CO2 being produced means higher proportion of that than 14C
up or down tick of CO2 in N hemi summer and why
downtick because there is so much land in N half and all the vegetation is absorbing CO2 in summer
who said the warming of the pipeline
James Hansen
why/how do GHGs work
- polar (charged) means they can absorb and emit
- charge allows re-emission
- motion they absorb as IR rad = warming = warming air around them
- or they re-emit the heat
diatomic molecules are not polar
most of earth’s radiation is emitted at what wavelength
15 um
co2 and water vapour absorb this really well
why co2 over h2o
- long residence time
- absorption band (15um)
- most abundant well mixed GHG,
- directly affected by humans
- highest radiative forcing
GWP
Global Warming Potential
- how strong of a GHG something is
- in reference to a tonne of CO2 (1)
sulphur hexafluoride (SF6)
most powerful GHG
- really long lifetime and crazy high GWP
Forcings
any process or disturbance that drives changes in climate
- does the changing of climate
- pushes something in a certain direction
feedbacks
self-perpetuating mechanisms of change that include a response to that change
- either amplify or moderate changes
- series of interconnected couplings
positive coupling
sign is maintained, cause and effect move in same direction
- increase means increase, decrease means decrease
amplify forcing
negative coupling
more of something means less of another and vice versa, opposing signs
- reverse cause and effect
reduces forcing
negative feedbacks
stabilize, diminish mechanism of change, maintain homeostasis
lapse rate and weathering feedbacks are +/-?
negative
positive feedbacks
amplify mechanism of change
water vapour and ice-albedo feedbacks are +/-
positive
stable equilibrium states
steady-state
- negative feedbacks
- require big forcings to change
unstable equilibirum state
- positive feedback
- small required to push past threshold/tipping point
