2 ms·

I find the term "half-life" in this context misleading, possibly because I am coming from a nuclear science background where half lives are stable because they

by shkkmo 5y ago

I find the term "half-life" in this context misleading, possibly because I am coming from a nuclear science background where half lives are stable because they are the probabilistic result of nuclear decay. The chance of a given atom decaying doesn't change no mater how many you have or what you do. With CO2, the absorption probability is flexible and can depend on how much CO2 is in the atmosphere (as well as a large number of other factors.) To me this makes "half-life" a poor metaphor for CO2 absorption.

q1w2 5y ago
Good point! The notion of half-life still works - but you are correct that the absorption is likely a product of the concentration. At any particular concentration, the half-life is still roughly representative. A differential equation would be more accurate, but it's not as easy to convey.
- shkkmo 5y ago
  Actually what I am saying is that the absorption rate does not scale linearly with concentration / quantity. While increasing the quantity of CO2 in the atmosphere in many circumsyance will increase absorbtion, there is clearly an upper limit on how high that absorbtion rate can rise. In addition, the absorption rate also depends on how much has already been absorbed, ocean temperature, oceans currents, biosphere health and probably a number of factors of which I am unaware. The half-life of an unstable element is a fixed property of that kind of matter everwhere. The absorption rate of CO2 is in no way a property of CO2 itself, but rather a dynamic characteristic of the complex system that is the planet we live on. Instead of trying to break that down to a single number, I think we need to pay more attention to the actual mechanisms involved and the numbers behind them. CO2 gets sequestered into underground fossil duel deposits very slowly (and possibly not at all anymore given changes in the biosphere.) Vegetative matter is a very shallow reservoir that can only hold so much before the outgassing from decay wipes out the absorption from growth. The biggest source of absorption is (I believe) the oceans. We don't really know how much the ocean can absorb or how the global rise in tempuratures will effect that. I do think that you can't really view CO2 absorbed by the ocean as "gone" in the same way as with CO2 that is sequestered in fossil fuels. (or a decayed atom that has irreversibly become something else.)

by shkkmo 5y ago

q1w2 5y ago

Good point! The notion of half-life still works - but you are correct that the absorption is likely a product of the concentration. At any particular concentration, the half-life is still roughly representative. A differential equation would be more accurate, but it's not as easy to convey.

shkkmo 5y ago
Actually what I am saying is that the absorption rate does not scale linearly with concentration / quantity. While increasing the quantity of CO2 in the atmosphere in many circumsyance will increase absorbtion, there is clearly an upper limit on how high that absorbtion rate can rise. In addition, the absorption rate also depends on how much has already been absorbed, ocean temperature, oceans currents, biosphere health and probably a number of factors of which I am unaware. The half-life of an unstable element is a fixed property of that kind of matter everwhere. The absorption rate of CO2 is in no way a property of CO2 itself, but rather a dynamic characteristic of the complex system that is the planet we live on. Instead of trying to break that down to a single number, I think we need to pay more attention to the actual mechanisms involved and the numbers behind them. CO2 gets sequestered into underground fossil duel deposits very slowly (and possibly not at all anymore given changes in the biosphere.) Vegetative matter is a very shallow reservoir that can only hold so much before the outgassing from decay wipes out the absorption from growth. The biggest source of absorption is (I believe) the oceans. We don't really know how much the ocean can absorb or how the global rise in tempuratures will effect that. I do think that you can't really view CO2 absorbed by the ocean as "gone" in the same way as with CO2 that is sequestered in fossil fuels. (or a decayed atom that has irreversibly become something else.)