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Doesn't methane dissolve relatively quickly in the atmosphere so it's not a long term threat like CO2 so once you run the numbers amortize it all a tree that le

Doesn't methane dissolve relatively quickly in the atmosphere so it's not a long term threat like CO2 so once you run the numbers amortize it all a tree that leaks methane but eats carbon is a net win so long as the carbon actually stays out of the atmosphere?

the8472 8y ago
It turns into CO2. So all that happens is an initial spike of a more potent GHG turning into a baseline GHG. And the half-life is a ~decade, with constant replenishment that's enough to have a significant effect that the same carbon emitted as CO2 would not have.
ajross 8y ago
Methane oxidizes in the atmosphere with a half life of about 10 years. CO2's equivalent half life (due to ocean absorption) is 27 via a quick google. So they're really not that different. Neither is a "long term" threat -- if we stopped emissions entirely the climate would be expected to return to a pre-civilization equilibrium on the scale of decades.
- whatshisface 8y ago
  That's pretty different from what I have heard elsewhere. Could you please provide some references so I could read further? Here is a link that argues the opposite side: https://www.skepticalscience.com/co2-residence-time.htm https://www.skepticalscience.com/co2-residence-time.htm
  - acqq 8y ago
    Exactly: "What really governs the warming potential is how long the extra CO2 remains in the atmosphere. CO2 is essentially chemically inert in the atmosphere and is only removed by biological uptake and by dissolving into the ocean. Biological uptake (with the exception of fossil fuel formation) is carbon neutral: Every tree that grows will eventually die and decompose, thereby releasing CO2."
- tetraca 8y ago
  > Neither is a "long term" threat -- if we stopped emissions entirely the climate would be expected to return to a pre-civilization equilibrium on the scale of decades. That only can be true if the resultant warming over those decades isn't significant enough to kick off other feedback loops or cause ecosystem collapse. For instance, the caps melting and lowering the planetary albedo, ocean acidification, etc. If these things happen too quickly, you're going to see a serious and nasty extinction event happen. Sure, not all life forms will die - archaea are pretty hearty after all, but it isn't going to be pretty for most complex lifeforms adapted to the climate of the current era.
  - olefoo 8y ago
    Yeah. If the phytoplankton goes and stops renewing free oxygen; it becomes pretty hard to be a mammal in a relatively short time.
  - citrablue 8y ago
    Could it also be possible that the current rate of emissions beefed up the planet's scrubbing capacity, and the climate return to pre-civ levels even faster?
- the8472 8y ago
  The temperature impulse response of CO2 does not seem to have a half-life of 27 years if you look at page 711 of the IPCC report. https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter08_FINAL.pdf https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapt...
  - mirimir 8y ago
    Yes, and on page 712: > Figure 8.29 Development of AGWP-CO2, AGWP-CH4 and GWP-CH4 with time horizon. The yellow and blue curves show how the AGWPs changes with increasing time horizon. Because of the integrative nature the AGWP for CH4 (yellow curve) reaches a constant level after about five decades. The AGWP for CO2 continues to increase for centuries. Thus the ratio which is the GWP (black curve) falls with increasing time horizon. That is, CO2 greenhouse forcing continues for centuries. Back when I worked on this stuff, we used an approximate half life of 250 years. But it's really more complicated. That IPCC report says this, on page 737: > No single lifetime can be given [for CO2]. The impulse response function for CO2 from Joos et al. (2013) has been used. See also Supplementary Material Section 8.SM.11. From Joos et al. (2013):[0] > The CO2 response shows the known rapid decline in the first few decades followed by a millennium-scale tail. For a 100 Gt-C emission pulse added to a constant CO2 concentration of 389 ppm, 25±9 % is still found in the atmosphere after 1000 yr; the ocean has absorbed 59±12 % and the land the remainder (16±14 %). 0) https://www.atmos-chem-phys.net/13/2793/2013/acp-13-2793-2013.pdf https://www.atmos-chem-phys.net/13/2793/2013/acp-13-2793-201...
- consumer451 8y ago
  Thanks for your perspective. > if we stopped emissions entirely the climate would be expected to return to a pre-civilization equilibrium on the scale of decades. Do you have any links to research which backs up this quote? Because I would love to believe it.

the8472 8y ago

It turns into CO2. So all that happens is an initial spike of a more potent GHG turning into a baseline GHG. And the half-life is a ~decade, with constant replenishment that's enough to have a significant effect that the same carbon emitted as CO2 would not have.

ajross 8y ago

Methane oxidizes in the atmosphere with a half life of about 10 years. CO2's equivalent half life (due to ocean absorption) is 27 via a quick google. So they're really not that different. Neither is a "long term" threat -- if we stopped emissions entirely the climate would be expected to return to a pre-civilization equilibrium on the scale of decades.

whatshisface 8y ago
That's pretty different from what I have heard elsewhere. Could you please provide some references so I could read further? Here is a link that argues the opposite side: https://www.skepticalscience.com/co2-residence-time.htm https://www.skepticalscience.com/co2-residence-time.htm
- acqq 8y ago
  Exactly: "What really governs the warming potential is how long the extra CO2 remains in the atmosphere. CO2 is essentially chemically inert in the atmosphere and is only removed by biological uptake and by dissolving into the ocean. Biological uptake (with the exception of fossil fuel formation) is carbon neutral: Every tree that grows will eventually die and decompose, thereby releasing CO2."
tetraca 8y ago
> Neither is a "long term" threat -- if we stopped emissions entirely the climate would be expected to return to a pre-civilization equilibrium on the scale of decades. That only can be true if the resultant warming over those decades isn't significant enough to kick off other feedback loops or cause ecosystem collapse. For instance, the caps melting and lowering the planetary albedo, ocean acidification, etc. If these things happen too quickly, you're going to see a serious and nasty extinction event happen. Sure, not all life forms will die - archaea are pretty hearty after all, but it isn't going to be pretty for most complex lifeforms adapted to the climate of the current era.
- olefoo 8y ago
  Yeah. If the phytoplankton goes and stops renewing free oxygen; it becomes pretty hard to be a mammal in a relatively short time.
- citrablue 8y ago
  Could it also be possible that the current rate of emissions beefed up the planet's scrubbing capacity, and the climate return to pre-civ levels even faster?
the8472 8y ago
The temperature impulse response of CO2 does not seem to have a half-life of 27 years if you look at page 711 of the IPCC report. https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapter08_FINAL.pdf https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapt...
- mirimir 8y ago
  Yes, and on page 712: > Figure 8.29 Development of AGWP-CO2, AGWP-CH4 and GWP-CH4 with time horizon. The yellow and blue curves show how the AGWPs changes with increasing time horizon. Because of the integrative nature the AGWP for CH4 (yellow curve) reaches a constant level after about five decades. The AGWP for CO2 continues to increase for centuries. Thus the ratio which is the GWP (black curve) falls with increasing time horizon. That is, CO2 greenhouse forcing continues for centuries. Back when I worked on this stuff, we used an approximate half life of 250 years. But it's really more complicated. That IPCC report says this, on page 737: > No single lifetime can be given [for CO2]. The impulse response function for CO2 from Joos et al. (2013) has been used. See also Supplementary Material Section 8.SM.11. From Joos et al. (2013):[0] > The CO2 response shows the known rapid decline in the first few decades followed by a millennium-scale tail. For a 100 Gt-C emission pulse added to a constant CO2 concentration of 389 ppm, 25±9 % is still found in the atmosphere after 1000 yr; the ocean has absorbed 59±12 % and the land the remainder (16±14 %). 0) https://www.atmos-chem-phys.net/13/2793/2013/acp-13-2793-2013.pdf https://www.atmos-chem-phys.net/13/2793/2013/acp-13-2793-201...
consumer451 8y ago
Thanks for your perspective. > if we stopped emissions entirely the climate would be expected to return to a pre-civilization equilibrium on the scale of decades. Do you have any links to research which backs up this quote? Because I would love to believe it.