Zeke, this is a great article and comparison between CO2 and CH4 and their time horizons. I think it highlights that time horizons matter, not just for greenhouse gases, but for all aspects of environmental sustainability issues. Thank you!
I appreciated the article, including the graphs, but note that it is a bit unrealistic since it doesn't correctly address drawdown by the natural sinks.
Note that the natural carbon sinks would continue to draw down CO2 at a rate that is directly proportional to the partial pressure of atmospheric CO2. The current drawdown rate is currently a bit greater than 20 GT CO2 per year, which coincidentally works out to be a little more than half the annual CO2 emission rate, but from the physics (eg., Henry's Law, for ocean uptake) we know that it's driven by the difference in partial pressure.
In a more realistic case, say reductions in anthropogenic CO2 emission rates of 1-2% per year, both atmospheric levels and drawdown rates would initially continue to rise but at increasingly slower rates, then peak, and then both would begin to fall.
The proof of this math is annually demonstrated by the convenient fact that natural drawdown rates are seasonally-varying: During the spring and summer each year, atmospheric CO2 levels at Mauna Loa currently decline by a remarkable amount of about 5 ppm (!), despite the fact that anthropogenic emissions continue during these same months. Imagine how much they would fall if, at the start of spring, we really could halt anthropogenic CO2 emissions!
The overall point is that CO2 doesn't simply stay in the atmosphere. We can gain control of atmospheric CO2 and should start talking about where we want it to be in, say, around 50-75 years. This is, IMO, very good news.
More importantly, the warming from CO2 stays well after atmospheric concentrations fall due to the counterbalancing continued warming of the oceans: https://www.pnas.org/doi/10.1073/pnas.0812721106
The climate model used to produce the figures in this article includes both the behavior of the carbon cycle and the relevant timeframes of methane atmospheric chemistry.
Thanks for that response. I've read David Archer's technical publications on the topic and thoroughly enjoyed his book, "The Long Draw", and have also reviewed the AR6 material (as well as previous AR reports) on their treatment of drawdown from the natural sinks.
I'm also aware that cumulative, warming-based, heat uptake by the oceans is about an order of magnitude greater than heat uptake by the atmosphere, but given that the thermal mass of the ocean (mass x specific heat) is about 1000 times that of the atmosphere, we really should not expect that heat will be returned to the atmosphere rapidly after we begin succeeding in reducing atmospheric CO2 levels.
I'm interested in the model that you used. Can you comment on how it addresses dynamic energy and mass transfer within the ocean? IMO, the chief uncertainty, in projecting continued ocean drawdown over a long period of time, comes from uncertainties in our understanding of the ocean's biological carbon pump which removes carbon from the upper ocean more rapidly than lateral transport by currents. But this is less critical for projections over the next few decades and should not substantially affect projections for the earliest years in which we reduce emissions.
Air pollutants including metallic chemical stuff in industrial exhaust has a negative effect on CCN and with the introduction of EM(electro magnetism) in our world, predictions and effects of more or less rain are is being goverened by something new that little study of how EM affects rain and water droplets, size abnd quantity
Clean air works wonders for rain and natural pollutants from the environment spores, etc are much more effective at producing rain. Something to think about. Of course it seems that you have all the answers already
One thing I can’t quite figure out: if methane decomposes into CO2, doesn’t it (at least partly) also stay in the atmosphere forever? Does that get taken into account here?
Yes, you are correct. However, methane's addition to CO2 is a pretty small contribution — it's main contribution is the warming you get when it's in the form of methane.
Zeke, this is a great article and comparison between CO2 and CH4 and their time horizons. I think it highlights that time horizons matter, not just for greenhouse gases, but for all aspects of environmental sustainability issues. Thank you!
Thank you for this useful comparison of CO2 and CH4. It's appreciated.
The third graph says 1 Mton CO2 and 29.4 kton CH4. The graph caption says 29.4 Gton of CH4. Shouldn't these be the same unit of mass?
Good catch! I've fixed it to say kilotons.
Thanks for explaining what CO2e really signifies. I’d seen figures before and wondered if they had real meaning.
I appreciated the article, including the graphs, but note that it is a bit unrealistic since it doesn't correctly address drawdown by the natural sinks.
Note that the natural carbon sinks would continue to draw down CO2 at a rate that is directly proportional to the partial pressure of atmospheric CO2. The current drawdown rate is currently a bit greater than 20 GT CO2 per year, which coincidentally works out to be a little more than half the annual CO2 emission rate, but from the physics (eg., Henry's Law, for ocean uptake) we know that it's driven by the difference in partial pressure.
In a more realistic case, say reductions in anthropogenic CO2 emission rates of 1-2% per year, both atmospheric levels and drawdown rates would initially continue to rise but at increasingly slower rates, then peak, and then both would begin to fall.
The proof of this math is annually demonstrated by the convenient fact that natural drawdown rates are seasonally-varying: During the spring and summer each year, atmospheric CO2 levels at Mauna Loa currently decline by a remarkable amount of about 5 ppm (!), despite the fact that anthropogenic emissions continue during these same months. Imagine how much they would fall if, at the start of spring, we really could halt anthropogenic CO2 emissions!
The overall point is that CO2 doesn't simply stay in the atmosphere. We can gain control of atmospheric CO2 and should start talking about where we want it to be in, say, around 50-75 years. This is, IMO, very good news.
CO2 does stay in the atmosphere for quite a bit of time: ~40% of it for >100 years, and ~20% of it for >10,000 years: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2004JC002625
More importantly, the warming from CO2 stays well after atmospheric concentrations fall due to the counterbalancing continued warming of the oceans: https://www.pnas.org/doi/10.1073/pnas.0812721106
The climate model used to produce the figures in this article includes both the behavior of the carbon cycle and the relevant timeframes of methane atmospheric chemistry.
Thanks for that response. I've read David Archer's technical publications on the topic and thoroughly enjoyed his book, "The Long Draw", and have also reviewed the AR6 material (as well as previous AR reports) on their treatment of drawdown from the natural sinks.
I'm also aware that cumulative, warming-based, heat uptake by the oceans is about an order of magnitude greater than heat uptake by the atmosphere, but given that the thermal mass of the ocean (mass x specific heat) is about 1000 times that of the atmosphere, we really should not expect that heat will be returned to the atmosphere rapidly after we begin succeeding in reducing atmospheric CO2 levels.
I'm interested in the model that you used. Can you comment on how it addresses dynamic energy and mass transfer within the ocean? IMO, the chief uncertainty, in projecting continued ocean drawdown over a long period of time, comes from uncertainties in our understanding of the ocean's biological carbon pump which removes carbon from the upper ocean more rapidly than lateral transport by currents. But this is less critical for projections over the next few decades and should not substantially affect projections for the earliest years in which we reduce emissions.
Again, thanks for responding to my comment!
Air pollutants including metallic chemical stuff in industrial exhaust has a negative effect on CCN and with the introduction of EM(electro magnetism) in our world, predictions and effects of more or less rain are is being goverened by something new that little study of how EM affects rain and water droplets, size abnd quantity
Clean air works wonders for rain and natural pollutants from the environment spores, etc are much more effective at producing rain. Something to think about. Of course it seems that you have all the answers already
One thing I can’t quite figure out: if methane decomposes into CO2, doesn’t it (at least partly) also stay in the atmosphere forever? Does that get taken into account here?
Yes, you are correct. However, methane's addition to CO2 is a pretty small contribution — it's main contribution is the warming you get when it's in the form of methane.
If the methane is biogenic (e.g. from cows) the CO2 is not additional – it would have otherwise been emitted by the vegetation the cows ate decaying.
But yes, it matters for fossil CO2 (but is only ~2% of the instantaneous radiative forcing of the CH4!).
Ils veulent nous faire consommer plus, alors qu'il faut consommer moins.