// lecture 07

Question 1

molecules with

Answer 1

one atom or two of the same atoms aren’t GHGs. the primary gases in our atmosphere are thus transparent to longwave radiation.

Question 2

polyatomic molecules are GHGs:

Answer 2

water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), and CFCs. they rotate and vibrate, so that means they can absorb the right frequencies of longwave.

Question 3

all GHGs are rather a small fraction of the atmosphere:

Answer 3

water vapor 0.4%, CO2 0.04%, and methane 0.0002%.

Question 4

“trace gases”

Answer 4

have a remarkable effect on the atmosphere. such as ozone

Question 5

water vapor

Answer 5

gas form of water (humidity); #1 GHG. powerful because of its molecular structure and because there’s a lot of it. not controlled by humans so its a feedback. increasing global warming. bent triatomic molecule: H2O.

Question 6

CO2

Answer 6

primary contributor to the antropogenic GHE (63% of it so far). extremely long-lived. increases primarily due to fossil fuel burning (80%) and deforestation (20%). 50% of what we emit quickly gets taken up by the ocean or land. most else sticks around for over 100 yrs.

Question 7

methane (CH4)

Answer 7

natural gas; much more potent on a per molecule basis than CO2. lifetime is 8 yrs. natural sources: marshes (swamp gas) and other wetlands. increase anthropogenically due to farm animals, landfills, coal mining, gas leakage, and rice farming.

Question 8

nitrous oxide (N2O)

Answer 8

laughing gas; more potent on a per molecule basis than CO2. global warming potential: 310. comes from agriculture, chemical energy, and deforestation. small concentrations of only 0.3 ppm.

Question 9

ozone (O3)

Answer 9

occurs in two places in the atmosphere:

• in the ozone layer: good ozone, protects us from ultraviolet radiation and skin cancer.
• near earth’s surface: bad ozone, caused by air pollution.

Question 10

bad ozone

Answer 10

a GHG and is more potent on a per molecule basis than CO2, but it’s very short-lived.

Question 11

CFCs

Answer 11

ozone depleting chemicals and are strong GHGs. almost phased out. some replacements like HFCs are still strong GHGs though. global warming potentials of up to 11,000.

Question 12

the natural GH contributions:

Answer 12

H2O (water vapor): 60%, (but less than 1% of mass of atmopshere), CO2: 26% (but 400 ppmv, ~0.04% of mass), and all others: 14%.

Question 13

unnatural GHE

Answer 13

increasing levels of CO2 and other GHGs leads to a strong GHE. with more GHGs, it’s harder for outgoing radiation to escape to space.

Question 14

contributors to the “anthropogenic” GHE

Answer 14

CO2: 63%, methane: 18%, CFCs and HFCS: 12%, and nitrous oxide: 6%.

Question 15

global warming potential (GWP)

Answer 15

how much GHE emission of a given gas causes over a fixed amount of time.

Question 16

methane’s GWP

Answer 16

25

Question 17

CO2 gets absorbed by the ocean, but

Answer 17

slowly. decay in atmosphere is nearly 200 yrs, but 20% remains longer.