CHM310 – Lecture 6
The Carbon Cycle
1. Biogeochemical Cycle.-
2. Box models
a. Assume something is flowing into the box and something’s are flowing away from the
b. Rate if intake =R
c. Rate of loss = kC (concentration of material in the box, k= constant)
d. How the concentration of material changes aong as a function of time.
e. This is a first order rate law
f. You will arrive at a steady state. R=kCss
g. Css = R/k
h. dC/dt= -kC
i. lm C/C o -kt
j. half lives – time taken for a species to decay with a starting point
k. half lives = ln (1/2) = -kt 1/2
m. ln(1/e) = -kt e
n. t =e/k
o. life time for a material in a box = t = aeount of X/ rate of loss
p. C/(-dc/dt) = 1/k 3. Carbon cycle
a. Water is the most important greenhouse gas, then Carbon Dioxide
b. Going down towards places where ice accumulates slowly, drill down, and store them.
Literally, you bring a km of ice.
c. And they mel them, and measure the amount of CO 2
d. Interestingly, is the oscilations you see in blue (slide)
e. Past we would have being under a few km of ice (Toronto)
f. It is not entirely known why that ice moved
g. We are now 390ppm in CO 2
h. The black line are
4. In the past co2 has being tightly coupled in with the climate
5. Summar y of the Radiative Forcing Components
6. IPCC –www.ipcc.ch intergovernmental panel on climate change
7. Radiative units are Wm- W =J/s Power
8. Estimate of how much additional energy is coming into the climate system relative to the pre-
industrial times as a result of change which occurs since that time.
9. Co2 is indicated in red. Comes around to 1.60-1.7 Wm- It says that how much additional energy
is coming to the climate system since the pre industrial atmosphere. There is more C now than
in the past.
10. Area estimated with Co2 is relatively small. Then why study?
11. The answer is that it’s small for estimated how much additional radiative forces now in the
system. But what really matters is 50 years from now, or 100 or further. To make that estimate we have to know where we are now, and then make the predictions. By figuring out where it’s
going to go.
a. For that we need to know the C cycle.
12. The amount of C in the atmosphere is 800x10^15 g of C. 800giga tons of C.
a. Flux = flows , we will be talking about flows of C
13. The C in the atmosphere is overwhelmingly as CO2. – 390ppm
a. Next is Methane – CH4 – 1ppm
14. Once co2 is in the atmosphere, where does it go?
15. mass = 10 15
16. Flux =10 15/yr
17. Once Co2 is in your atmosphere where does it go?
18. Photosynthesis Co2 +H2o +sunlight organic matter +oxygen
19. 53% of the C in the biosphere has moved into the atmosphere.
20. Then it changes track in the biosphere.
a. Land biosphere – 800 (there is much C in the trees and plants as there is in the
b. Flux of C from the atmosphere to the Biosphere – 110 eons. 110 giga tons
c. We can calculate what is the rough life tims/time scale that is ging to take the C atom
from the atmosphere to the biosphere?
d. You can do this