Fantastic article! It’s refreshing to see such a balanced perspective, combining hope with the urgency of the challenge. The way you break down complex topics into digestible insights makes it accessible for a wide audience. Thank you for shedding light on such an important issue.
This description of what would happen if we stop emissions of CO2 oversimplifies the problem. The Arctic permafrost is melting and releasing methane in ever increasing amounts. If you stop CO2 emissions, a huge amount of permafrost melting is already committed so these methane emissions will continue to be emitted for decades. Additionally, there is only a finite amount of CO2 that the oceans can absorb and if Co2 concentrations in the atmosphere go down, the CO2 in the oceans will begin to be emitted to remain in equilibrium. Finally, the analysis ignores the heating concentrations of other greenhouse gases. The analysis completely fails if you miraculously stop CO2 emissions but don't stop methane from farms, rice paddies, and other sources, or the increasing CFCs, HCFCs and HFCs from the existing and increasing refrigeration in air conditioning particularly in the emerging economies like China, India, Brazil, Indonesia ...
It's correct that, if we start a carbon cycle feedback, then all bets are off. However, in our present situation, it does not appear that we have done that yet. It's not clear when we will hit that tipping point, and that emphasizes our need to get emissions to zero as quickly as possible.
Ending all fossil fuel extraction is just a starting point. We must direct air capture at least 2,500,000,000,000 tons of the almost 4,000,000,000,000 tons CO2 we have emitted. Otherwise there is no tipping back.
"a huge amount of permafrost melting is already committed so these methane emissions will continue to be emitted for decades."
How huge? There's no reason to think the warming models Prof. Dessler is citing fail to account for thawing permafrost. I'm having trouble finding quantitative estimates of carbon release from permafrost. One constraint is the paleo-record: interglacial warming has not produced runaway emissions from thawing permafrost. Here's an interesting 2018 review paper in AGU's Reviews of Geophysics: "Methane Feedbacks to the Global Climate System in a Warmer World" (agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017RG000559). Another good 2018 paper is in Nature Climate Change: "Methane production as key to the greenhouse gas budget of thawing permafrost" (nature.com/articles/s41558-018-0095-z). As Prof. Dessler points out,
"It's correct that, if we start a carbon cycle feedback, then all bets are off. However, in our present situation, it does not appear that we have done that yet."
AFAICT that's the current consensus position. Not even Jim Hansen knows better.
One more thing, we are already started the process of the positive unstoppable feedback loop. It is unstoppable but as I mentioned 2.5 of the 4.5 trillion times of CO2 must be direct air captured to tip back. That's a heavy lift, prolly......
Andrew, it seems like you have been engaging in a lot of wishful thinking which in the book Overshoot by William R. Catton Jr is called Cargoism, the confidence that new technology will come to the rescue. Removal of CO2 may be done in a pilot plant but the enormous amount of energy required to say nothing of the material requirements of number of facilities make this a non-starter. That's why you don't see governments or even industry moving on this. Notice that this industry conversation does not address how we can live comfortably with much less energy per capita. Notice that this industry conversation doesn't address the simple concept of simply putting less CO2 in the atmosphere to begin with! I think the very respected Peter Carter said it best in the first few minutes of this recent posting, Climate Change Indicators are now Climate Catastrophe Indicators because they are bad and getting worse, faster: https://www.youtube.com/watch?v=Uk9vulmEbqc
The removal of CO2 mentioned in the article is not due to human efforts but rather natural processes—particularly absorption by the ocean and the land biosphere. We know those are happening, so I don't think I'm being unreasonably optimistic here.
Before you conclude that Prof. Dessler is engaging in a lot of wishful thinking, can you explain why Catton's book is more credible than the consensus of physical climate-science specialists in their venues of record? Catton was a sociologist, and that discipline has its own standards of verification. The book wasn't peer-reviewed before publication, AFAIK, though please correct me if you know otherwise. Can you think of any cognitive motivators either Catton or you might be harboring?
"Cargoism" is of course a reference to the Cargo Cult phenomenon in Melanesia after WWII. According to Wikipedia (en.wikipedia.org/wiki/Cargo_cult):
"The term has largely fallen out of favour and is now seldom used among anthropologists, though its use as a metaphor (in the sense of engaging in ritual action to obtain material goods) is widespread outside of anthropology in popular commentary and critique,[6] based on stereotypes of cargo cultists as "primitive and confused people who use irrational means to pursue rational ends".
Is that what you think of the climate-science consensus? Because I told jakerake the paranoid denialist, in the previous thread, that his understanding of the role of intersubjective verification in science was at the "cargo-cult level." Of course, it's just a metaphor, widely over-used. Yet again: "The first rule [of science] is you must not fool yourself, and you are the easiest person to fool" (Feynman). Anyone who tells you "consensus isn't science" is trying to fool you. And it takes more than a rough airstrip hacked out of the jungle and a wooden decoy airplane to deliver any worthwhile technology!
I asked Richard Alley about this, in particular about amplifying feedbacks. He wrote back: “yes, the models do at least attempt to have these feedbacks in. The remaining worry is that some of the uncertainties tend to have a long tail on the bad side—for climate sensitivity, ice-sheet shrinkage and sea-level rise, carbon loss from frozen soils, and maybe a few others, we expect some outcome, there are uncertainties, but those include a little better, a little worse, a slight chance of much worse, but not so much chance of much better. Not sure what to do about that
There's always uncertainty in these kinds of calculations, particularly at very long time scales, when things we don't understand well, like ice sheet disintegration, might be important. The one thing we do know is that the uncertainty increases with temperature, so we should try to stabilize temperature as quickly as possible!
Thanks, Alley did mention that long term things are different: “So, the usual expectation is that stopping the increase in the atmospheric concentration of CO2 and holding atmospheric CO2 constant would allow continuing warming, whereas stopping emissions of CO2 altogether would allow a drop in CO2 with a cooling effect that would offset the continuing warming associated with the ocean, giving near-constant temperature. (Over sufficiently long times, this offset will not continue, and other processes will become important, but initially it takes cessation of emissions to stabilize the temperature.”
The problem with your "Stop emissions, stop warming" claim is that it ignores the physics of:
1) aerosol termination shock (will add +1C to +2C)
2) Earth Energy Imbalance (36-month EEI is ~1.5 W/m², indicating another +1.8C of warming)
3) ECS - Equilibrium climate sensitivity - Hansen et al, calculating 4.8°C ± 1.2°C; Today's CO2e is 560 ppm, double the pre-industrial CO2 level.
4) paleoclimate history indicating the last time GHG levels were this high, Earth was +4C to +5C above pre-industrial
At a minimum, climate physics indicates another 2C to 3C of warming over the next few decades is a given if emissions stop tomorrow. Warming will NOT STOP, due to committed warming, EEI, and aerosol termination shock, which most computer models ignore. This illustrates perfectly the problem with solely relying on models, while ignoring observed data and paleoclimate history.
This "no committed warming upon ZE" misinformation is solely derived from obsolete and problematic computer models. To provide more accurate and credible projections of future warming, scientists MUST stop relying solely on models, and incorporate observed real world data like EEI - the most basic indicator of the true rate of warming. The Earth energy imbalance (EEI) is the most fundamental indicator for climate change, as it tells us if, how much, how fast, and where the Earth's climate is warming, as well as how this warming evolves in the future. Additionally, most models ignore or greatly underestimate aerosol termination shock, which the latest research indicates would add between 1C and 2C upon stopping all industrial emissions.
Climate physics tells us that rather than warming ceasing upon zero emissions, warming would in fact initially accelerate, as EEI net forcing would increase from 1.5 W/m² to 2.5-3.0 W/m² from aerosol termination shock, even while CO2 GHG levels begin to decline. This is why substantial committed warming is a given, and the "Stop emissions, stop warming" claim doesn't hold up to scrutiny.
Andrew - I've been a fan of your substack for a while now and I found this article to be flawed in a couple areas (not characterize the size of the flaws). First, you make a statement about what is "true" and because you are referring to the future, it is flawed because none of us have a crystal ball nor should any of us state what is or is not true about our conjectures about the future. Secondly, you cite the Caldeira paper which is a model study. Aren't models perfect? They're not? So how do we build better analysis that include some modeling but doesn't rely on them solely for the foundation of an argument? Good question, tricky business. Lastly, the carbon sinks are not stable, they are dynamically changing. This makes predictions difficult. As the surface layer of the world ocean becomes supersaturated, or the terrestrial sinks break down, or both, then it won't matter if our anthropogenic emissions are reduced by half in 10 years (unlikely anyway) because the bottleneck in the sinks could result in more GHG in the atmosphere. Someone else already mentioned the feedback loops in the system such as permafrost methane which is poorly modelled and your response is that isn't happening yet. Many scientists disagree with you on that, but sometimes we want to feel hopeful, so its ok to think this is all going to turn out just fine.
You made many great points. All the "Warming stops when emissions stop" articles/models I've seen are seriously lacking in all they ways you mention, mostly due to over reliance on models (that underestimate/ignore feedbacks, aerosol termination shock, ECS, paleoclimate history). See my comment I posted above.
"So how do we build better analysis that include some modeling but doesn't rely on them solely for the foundation of an argument?"
Great question. Hansen makes a case for a 3-leg platform for making better climate projections of future warming:
1-models
2-incorporating real world observations like Earth Energy Imbalance - the most fundamental indicator for the true rate of warming
The quickest way to get the temperature down is to stop fugitive methane - oil,gas,coal mining/recovery. Reducing biogenic methane from rice/cattle is more difficult.
Long term CO2 is more important. BEVs are the answer to cars but not the answer to transport.
But the bottom line is renewables could allow a functioning civilisation just not this one - we need to reduce energy consumption.
I can buy Atlantic salmon in the supermarket - from 20,000km away - when NZ produces any amount of Pacific salmon. Money making madness.
Interesting article, but one specific section is confusing to me. "The cooling effect of declining CO2 levels tends to offset the warming caused by heat transfer into the deep ocean." You seem to be suggesting that atmospheric warming would be increased by ocean mixing.
The energy of warming comes from radiation trapped in the atmosphere. So my understanding is that faster mixing with the cooler deep ocean can only act as a heat sink. The consequence of this would be slower heating of the atmosphere (it takes longer to reach equilibrium), but also less atmospheric heating, because some proportion of the radiative energy is being used to heat the deep ocean. Heat transfer with the deep ocean can't add heat energy to either the atmosphere or the surface ocean.
Thanks for your explanation about committed warming and your acknowledgement that if carbon feedbacks are engaged all bets are off. Except that many of us for some time have thought that the proposition that all warming will stop as soon as we get to zero emissions was delusional, a type of denial favoured by those who really didn’t want to confront the fossil fuel industries and actually regulate a wind down of all production.
We’ve known for decades about these possible feedbacks and precautionary guardrails were agreed to because somewhere over a 1C rise in temperature our emissions might cause one or a cascade of feedbacks to kick in. The latest Arctic report confirms permafrost is changing from sink to source. Boreal forest fires in Canada recently have produced three times the GHGs as our domestic economy. Over the past year globally previous sinks absorbed far less of our fossil fuel emissions than usual. We’ve charged past a 1.5C rise and we are in a minefield of potential feedbacks.
Meanwhile emissions are still rising and even ineffectual present mitigation is in danger of stalling. A reasonable person would think that there is no chance of getting to zero emissions for at least decades even as climate change looks to be accelerating reducing our already burnt to a crisp carbon budget.
Think of this the next time you hear hopeful disinformation that warming will stop as soon as we get to zero emissions.
I appreciate that you and Zeke have been trying to cool the waters (haha) somewhat by reminding people that it's not over yet. We can still halt climate change by stopping emissions. But I still don't understand your issue with Hansen's 2023 paper. I think the paper went to great lengths to clarify what it means by equilibrium warming, more so than other academics who just throw around acronyms without properly defining them. He even clarified in the abstract that this warming was not "committed" warming (as you point out). From what I've seen from the discussions on this paper, only you, Zeke, and Michael Mann seem to be confused. I certainly didn't read the paper and think Hansen was suggesting we were committed to 8-10C of warming and simply took away that he is suggesting a higher climate sensitivity than what others are suggesting. If your issue is that the IPCC defines "committed warming" as eventual warming at a fixed CO2 concentration, then I would argue that the IPCC is what is causing the confusion as that definition doesn't make sense. Committed warming should be defined as the warming directly due to our actions if we stopped emissions right now. Equilibrium warming is a better term for warming at fixed CO2 concentration.
In any case, this is just a semantic argument that bogs down the message that we should be making. If Hansen is right, it means we have even less time to reduce emissions and we need to act even more urgently. I know you're just trying to get ahead of the doomers by saying it's not over yet, we can still stop global warming. But I think this type of messaging is doing the opposite and is feeding into a defeatist mindset. Because you're suggesting if we just do something we all know is impossible (stop emissions tomorrow) we can stop the earth from warming. It's just going to make people throw up their hands and say, "Well that's not going to happen". I understand the point you're trying to make but it's bad messaging. We need to reduce emissions. Full stop.
Potentially a naive question, but in your example of CO2 removal being slow and ocean heat transfer being fast following net-zero, I was wondering whether in the short-term, the enhanced mixing of heat to the deep ocean and thus continued ocean heat uptake from the atmosphere would continue to mask the warming of the atmosphere due to CO2? Or does the cessation of emissions immediately cause the rate of ocean heat uptake to decline meaning ongoing warming as soon as net-zero is reached and for long thereafter? Thank you for a very well written piece by the way!
In the case of rapid oceanic mixing, the surface layer is far below equilibrium because cold water is being mixed up. This means that, even after GHGs are held constant, the climate system has a long way to warm up before it reaches equilibrium. So the warming will continue after you get to constant atmospheric concentrations.
No more "locked in" that the policy set that we have. Taxing net emissions of CO2 unlocks incentives on EVERY decision to emit CO2. Why any other policy that addresses only some of them?
I hear you, although again, I prefer taking a per-tonne fee from domestic carbon producers at the wellhead or import point-of-entry, as well as a per-tonne fee on embodied carbon in imported goods, and allowing the fee payers to raise their prices to customers as much as they dare on the US market. Fee rebates might be arranged for CCS by fossil-fueled manufacturing. Otherwise, dividend the revenue periodically to every everyone who files a federal tax form (even if they didn't earn enough to pay taxes). Those whose annual consumption is below the national per-capita average (slightly more than half of US households) would actually make money, but anyone could save money just by choosing cheaper renewable energy when available. The result would be similar to your proposal, however: market forces would then build out the carbon-neutral US economy.
"Taxing net emissions of CO2 unlocks incentives on EVERY decision to emit CO2. Why any other policy that addresses only some of them?"
Because politics is the art of the possible. Subsidies are an easier sell than direct carbon pricing politically. Apparently even that's not good enough to maintain them following the US elections.
Not necessarily true. Land may continue to absorb (although there is concern that this capacity is being reduced) but as most net zero policy assumes this absorption to get net zero it means we will still emit CO2 that covers what’s being absorbed by land (I assume no country has tried to use sea absorption to get to net zero...). So that leaves sea absorption. I have no idea how much more the sea can absorb and at what point it runs out of capacity but I assume it has a limit which, based on our current progress, I’d guess we are likely to hit before we reach zero emissions.
Sadly I think it's just an academic point and doesn't really matter because:
The temp doesn’t come down much at all for a long time (so bad stuff still occurs for a long time like melting permafrost).
More importantly we are never going to stop emitting CO2. The current round of NDC’s might as well be published on Amazon in the fiction section based on the actual real world policies being implemented. I saw your spiral of doom post as well and I’m not sure we actually have the tech today to get to net zero. e.g. Airplanes (not enough SAF and not sure there will ever be enough), Shipping (various options but none seem to be the leader), Cars/Lorries (more political and economic than tech here), Construction (Couldn't find evidence of a scalable solution for 30B tonnes) power generation (the storage issue. After recent weather in the UK and some of Europe I’m now concerned we don’t really have available solutions for when renewables stop working. We had a long period of heavy cloud cover and very little wind which tanked the renewable output. Just having a 10% backup of fossil based output wouldn’t have been anywhere near enough. The storage needed to power the country for multiple days continuously would be insanely expensive so not sure what the solution to that would be. This was due to odd behaviour with the jet stream which, ironically, may be due to climate change.)
Fantastic article! It’s refreshing to see such a balanced perspective, combining hope with the urgency of the challenge. The way you break down complex topics into digestible insights makes it accessible for a wide audience. Thank you for shedding light on such an important issue.
This description of what would happen if we stop emissions of CO2 oversimplifies the problem. The Arctic permafrost is melting and releasing methane in ever increasing amounts. If you stop CO2 emissions, a huge amount of permafrost melting is already committed so these methane emissions will continue to be emitted for decades. Additionally, there is only a finite amount of CO2 that the oceans can absorb and if Co2 concentrations in the atmosphere go down, the CO2 in the oceans will begin to be emitted to remain in equilibrium. Finally, the analysis ignores the heating concentrations of other greenhouse gases. The analysis completely fails if you miraculously stop CO2 emissions but don't stop methane from farms, rice paddies, and other sources, or the increasing CFCs, HCFCs and HFCs from the existing and increasing refrigeration in air conditioning particularly in the emerging economies like China, India, Brazil, Indonesia ...
It's correct that, if we start a carbon cycle feedback, then all bets are off. However, in our present situation, it does not appear that we have done that yet. It's not clear when we will hit that tipping point, and that emphasizes our need to get emissions to zero as quickly as possible.
Yes there's a need to get them to zero as quickly as possible. Yet, emissions are still increasing.
I'm not despairing- all things must die, even human 'civilisation'- but do you really think a net zero could happen in the next 30 years?
I don't.
Ending all fossil fuel extraction is just a starting point. We must direct air capture at least 2,500,000,000,000 tons of the almost 4,000,000,000,000 tons CO2 we have emitted. Otherwise there is no tipping back.
The piece blowing smoke up somebody's ass ....
"a huge amount of permafrost melting is already committed so these methane emissions will continue to be emitted for decades."
How huge? There's no reason to think the warming models Prof. Dessler is citing fail to account for thawing permafrost. I'm having trouble finding quantitative estimates of carbon release from permafrost. One constraint is the paleo-record: interglacial warming has not produced runaway emissions from thawing permafrost. Here's an interesting 2018 review paper in AGU's Reviews of Geophysics: "Methane Feedbacks to the Global Climate System in a Warmer World" (agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017RG000559). Another good 2018 paper is in Nature Climate Change: "Methane production as key to the greenhouse gas budget of thawing permafrost" (nature.com/articles/s41558-018-0095-z). As Prof. Dessler points out,
"It's correct that, if we start a carbon cycle feedback, then all bets are off. However, in our present situation, it does not appear that we have done that yet."
AFAICT that's the current consensus position. Not even Jim Hansen knows better.
One more thing, we are already started the process of the positive unstoppable feedback loop. It is unstoppable but as I mentioned 2.5 of the 4.5 trillion times of CO2 must be direct air captured to tip back. That's a heavy lift, prolly......
How huge? The entire Arctic. Good God
Andrew, it seems like you have been engaging in a lot of wishful thinking which in the book Overshoot by William R. Catton Jr is called Cargoism, the confidence that new technology will come to the rescue. Removal of CO2 may be done in a pilot plant but the enormous amount of energy required to say nothing of the material requirements of number of facilities make this a non-starter. That's why you don't see governments or even industry moving on this. Notice that this industry conversation does not address how we can live comfortably with much less energy per capita. Notice that this industry conversation doesn't address the simple concept of simply putting less CO2 in the atmosphere to begin with! I think the very respected Peter Carter said it best in the first few minutes of this recent posting, Climate Change Indicators are now Climate Catastrophe Indicators because they are bad and getting worse, faster: https://www.youtube.com/watch?v=Uk9vulmEbqc
The removal of CO2 mentioned in the article is not due to human efforts but rather natural processes—particularly absorption by the ocean and the land biosphere. We know those are happening, so I don't think I'm being unreasonably optimistic here.
Before you conclude that Prof. Dessler is engaging in a lot of wishful thinking, can you explain why Catton's book is more credible than the consensus of physical climate-science specialists in their venues of record? Catton was a sociologist, and that discipline has its own standards of verification. The book wasn't peer-reviewed before publication, AFAIK, though please correct me if you know otherwise. Can you think of any cognitive motivators either Catton or you might be harboring?
"Cargoism" is of course a reference to the Cargo Cult phenomenon in Melanesia after WWII. According to Wikipedia (en.wikipedia.org/wiki/Cargo_cult):
"The term has largely fallen out of favour and is now seldom used among anthropologists, though its use as a metaphor (in the sense of engaging in ritual action to obtain material goods) is widespread outside of anthropology in popular commentary and critique,[6] based on stereotypes of cargo cultists as "primitive and confused people who use irrational means to pursue rational ends".
Is that what you think of the climate-science consensus? Because I told jakerake the paranoid denialist, in the previous thread, that his understanding of the role of intersubjective verification in science was at the "cargo-cult level." Of course, it's just a metaphor, widely over-used. Yet again: "The first rule [of science] is you must not fool yourself, and you are the easiest person to fool" (Feynman). Anyone who tells you "consensus isn't science" is trying to fool you. And it takes more than a rough airstrip hacked out of the jungle and a wooden decoy airplane to deliver any worthwhile technology!
I believe there is a word in psychology for "belief perseverance" but:
https://research.com/education/why-facts-dont-change-our-mind
https://en.wikipedia.org/wiki/Belief_perseverance
I asked Richard Alley about this, in particular about amplifying feedbacks. He wrote back: “yes, the models do at least attempt to have these feedbacks in. The remaining worry is that some of the uncertainties tend to have a long tail on the bad side—for climate sensitivity, ice-sheet shrinkage and sea-level rise, carbon loss from frozen soils, and maybe a few others, we expect some outcome, there are uncertainties, but those include a little better, a little worse, a slight chance of much worse, but not so much chance of much better. Not sure what to do about that
There's always uncertainty in these kinds of calculations, particularly at very long time scales, when things we don't understand well, like ice sheet disintegration, might be important. The one thing we do know is that the uncertainty increases with temperature, so we should try to stabilize temperature as quickly as possible!
Thanks, Alley did mention that long term things are different: “So, the usual expectation is that stopping the increase in the atmospheric concentration of CO2 and holding atmospheric CO2 constant would allow continuing warming, whereas stopping emissions of CO2 altogether would allow a drop in CO2 with a cooling effect that would offset the continuing warming associated with the ocean, giving near-constant temperature. (Over sufficiently long times, this offset will not continue, and other processes will become important, but initially it takes cessation of emissions to stabilize the temperature.”
The problem with your "Stop emissions, stop warming" claim is that it ignores the physics of:
1) aerosol termination shock (will add +1C to +2C)
2) Earth Energy Imbalance (36-month EEI is ~1.5 W/m², indicating another +1.8C of warming)
3) ECS - Equilibrium climate sensitivity - Hansen et al, calculating 4.8°C ± 1.2°C; Today's CO2e is 560 ppm, double the pre-industrial CO2 level.
4) paleoclimate history indicating the last time GHG levels were this high, Earth was +4C to +5C above pre-industrial
At a minimum, climate physics indicates another 2C to 3C of warming over the next few decades is a given if emissions stop tomorrow. Warming will NOT STOP, due to committed warming, EEI, and aerosol termination shock, which most computer models ignore. This illustrates perfectly the problem with solely relying on models, while ignoring observed data and paleoclimate history.
This "no committed warming upon ZE" misinformation is solely derived from obsolete and problematic computer models. To provide more accurate and credible projections of future warming, scientists MUST stop relying solely on models, and incorporate observed real world data like EEI - the most basic indicator of the true rate of warming. The Earth energy imbalance (EEI) is the most fundamental indicator for climate change, as it tells us if, how much, how fast, and where the Earth's climate is warming, as well as how this warming evolves in the future. Additionally, most models ignore or greatly underestimate aerosol termination shock, which the latest research indicates would add between 1C and 2C upon stopping all industrial emissions.
Climate physics tells us that rather than warming ceasing upon zero emissions, warming would in fact initially accelerate, as EEI net forcing would increase from 1.5 W/m² to 2.5-3.0 W/m² from aerosol termination shock, even while CO2 GHG levels begin to decline. This is why substantial committed warming is a given, and the "Stop emissions, stop warming" claim doesn't hold up to scrutiny.
Well said, I wrote an essay and should have read yours first.
Andrew - I've been a fan of your substack for a while now and I found this article to be flawed in a couple areas (not characterize the size of the flaws). First, you make a statement about what is "true" and because you are referring to the future, it is flawed because none of us have a crystal ball nor should any of us state what is or is not true about our conjectures about the future. Secondly, you cite the Caldeira paper which is a model study. Aren't models perfect? They're not? So how do we build better analysis that include some modeling but doesn't rely on them solely for the foundation of an argument? Good question, tricky business. Lastly, the carbon sinks are not stable, they are dynamically changing. This makes predictions difficult. As the surface layer of the world ocean becomes supersaturated, or the terrestrial sinks break down, or both, then it won't matter if our anthropogenic emissions are reduced by half in 10 years (unlikely anyway) because the bottleneck in the sinks could result in more GHG in the atmosphere. Someone else already mentioned the feedback loops in the system such as permafrost methane which is poorly modelled and your response is that isn't happening yet. Many scientists disagree with you on that, but sometimes we want to feel hopeful, so its ok to think this is all going to turn out just fine.
You made many great points. All the "Warming stops when emissions stop" articles/models I've seen are seriously lacking in all they ways you mention, mostly due to over reliance on models (that underestimate/ignore feedbacks, aerosol termination shock, ECS, paleoclimate history). See my comment I posted above.
"So how do we build better analysis that include some modeling but doesn't rely on them solely for the foundation of an argument?"
Great question. Hansen makes a case for a 3-leg platform for making better climate projections of future warming:
1-models
2-incorporating real world observations like Earth Energy Imbalance - the most fundamental indicator for the true rate of warming
3-paleoclimate data
I feel a song coming on....
Stop, in the name of science, before you break the climate!
Think it oh, oh, over!
Thanks! I've read Hansen, and did not realized the difference between committed and equilibrium. Feeling much more optimistic!
The quickest way to get the temperature down is to stop fugitive methane - oil,gas,coal mining/recovery. Reducing biogenic methane from rice/cattle is more difficult.
Long term CO2 is more important. BEVs are the answer to cars but not the answer to transport.
But the bottom line is renewables could allow a functioning civilisation just not this one - we need to reduce energy consumption.
I can buy Atlantic salmon in the supermarket - from 20,000km away - when NZ produces any amount of Pacific salmon. Money making madness.
I see some issues already mentioned. However, you might emphasize sea level rise as an issue that continues...
Kevin
Yeah, that's a good point. SLR will go on for a very long time after emissions cease.
Interesting article, but one specific section is confusing to me. "The cooling effect of declining CO2 levels tends to offset the warming caused by heat transfer into the deep ocean." You seem to be suggesting that atmospheric warming would be increased by ocean mixing.
The energy of warming comes from radiation trapped in the atmosphere. So my understanding is that faster mixing with the cooler deep ocean can only act as a heat sink. The consequence of this would be slower heating of the atmosphere (it takes longer to reach equilibrium), but also less atmospheric heating, because some proportion of the radiative energy is being used to heat the deep ocean. Heat transfer with the deep ocean can't add heat energy to either the atmosphere or the surface ocean.
Am I missing something?
Thanks for your explanation about committed warming and your acknowledgement that if carbon feedbacks are engaged all bets are off. Except that many of us for some time have thought that the proposition that all warming will stop as soon as we get to zero emissions was delusional, a type of denial favoured by those who really didn’t want to confront the fossil fuel industries and actually regulate a wind down of all production.
We’ve known for decades about these possible feedbacks and precautionary guardrails were agreed to because somewhere over a 1C rise in temperature our emissions might cause one or a cascade of feedbacks to kick in. The latest Arctic report confirms permafrost is changing from sink to source. Boreal forest fires in Canada recently have produced three times the GHGs as our domestic economy. Over the past year globally previous sinks absorbed far less of our fossil fuel emissions than usual. We’ve charged past a 1.5C rise and we are in a minefield of potential feedbacks.
Meanwhile emissions are still rising and even ineffectual present mitigation is in danger of stalling. A reasonable person would think that there is no chance of getting to zero emissions for at least decades even as climate change looks to be accelerating reducing our already burnt to a crisp carbon budget.
Think of this the next time you hear hopeful disinformation that warming will stop as soon as we get to zero emissions.
I appreciate that you and Zeke have been trying to cool the waters (haha) somewhat by reminding people that it's not over yet. We can still halt climate change by stopping emissions. But I still don't understand your issue with Hansen's 2023 paper. I think the paper went to great lengths to clarify what it means by equilibrium warming, more so than other academics who just throw around acronyms without properly defining them. He even clarified in the abstract that this warming was not "committed" warming (as you point out). From what I've seen from the discussions on this paper, only you, Zeke, and Michael Mann seem to be confused. I certainly didn't read the paper and think Hansen was suggesting we were committed to 8-10C of warming and simply took away that he is suggesting a higher climate sensitivity than what others are suggesting. If your issue is that the IPCC defines "committed warming" as eventual warming at a fixed CO2 concentration, then I would argue that the IPCC is what is causing the confusion as that definition doesn't make sense. Committed warming should be defined as the warming directly due to our actions if we stopped emissions right now. Equilibrium warming is a better term for warming at fixed CO2 concentration.
In any case, this is just a semantic argument that bogs down the message that we should be making. If Hansen is right, it means we have even less time to reduce emissions and we need to act even more urgently. I know you're just trying to get ahead of the doomers by saying it's not over yet, we can still stop global warming. But I think this type of messaging is doing the opposite and is feeding into a defeatist mindset. Because you're suggesting if we just do something we all know is impossible (stop emissions tomorrow) we can stop the earth from warming. It's just going to make people throw up their hands and say, "Well that's not going to happen". I understand the point you're trying to make but it's bad messaging. We need to reduce emissions. Full stop.
Potentially a naive question, but in your example of CO2 removal being slow and ocean heat transfer being fast following net-zero, I was wondering whether in the short-term, the enhanced mixing of heat to the deep ocean and thus continued ocean heat uptake from the atmosphere would continue to mask the warming of the atmosphere due to CO2? Or does the cessation of emissions immediately cause the rate of ocean heat uptake to decline meaning ongoing warming as soon as net-zero is reached and for long thereafter? Thank you for a very well written piece by the way!
In the case of rapid oceanic mixing, the surface layer is far below equilibrium because cold water is being mixed up. This means that, even after GHGs are held constant, the climate system has a long way to warm up before it reaches equilibrium. So the warming will continue after you get to constant atmospheric concentrations.
No more "locked in" that the policy set that we have. Taxing net emissions of CO2 unlocks incentives on EVERY decision to emit CO2. Why any other policy that addresses only some of them?
I hear you, although again, I prefer taking a per-tonne fee from domestic carbon producers at the wellhead or import point-of-entry, as well as a per-tonne fee on embodied carbon in imported goods, and allowing the fee payers to raise their prices to customers as much as they dare on the US market. Fee rebates might be arranged for CCS by fossil-fueled manufacturing. Otherwise, dividend the revenue periodically to every everyone who files a federal tax form (even if they didn't earn enough to pay taxes). Those whose annual consumption is below the national per-capita average (slightly more than half of US households) would actually make money, but anyone could save money just by choosing cheaper renewable energy when available. The result would be similar to your proposal, however: market forces would then build out the carbon-neutral US economy.
"Taxing net emissions of CO2 unlocks incentives on EVERY decision to emit CO2. Why any other policy that addresses only some of them?"
Because politics is the art of the possible. Subsidies are an easier sell than direct carbon pricing politically. Apparently even that's not good enough to maintain them following the US elections.
Not necessarily true. Land may continue to absorb (although there is concern that this capacity is being reduced) but as most net zero policy assumes this absorption to get net zero it means we will still emit CO2 that covers what’s being absorbed by land (I assume no country has tried to use sea absorption to get to net zero...). So that leaves sea absorption. I have no idea how much more the sea can absorb and at what point it runs out of capacity but I assume it has a limit which, based on our current progress, I’d guess we are likely to hit before we reach zero emissions.
Sadly I think it's just an academic point and doesn't really matter because:
The temp doesn’t come down much at all for a long time (so bad stuff still occurs for a long time like melting permafrost).
More importantly we are never going to stop emitting CO2. The current round of NDC’s might as well be published on Amazon in the fiction section based on the actual real world policies being implemented. I saw your spiral of doom post as well and I’m not sure we actually have the tech today to get to net zero. e.g. Airplanes (not enough SAF and not sure there will ever be enough), Shipping (various options but none seem to be the leader), Cars/Lorries (more political and economic than tech here), Construction (Couldn't find evidence of a scalable solution for 30B tonnes) power generation (the storage issue. After recent weather in the UK and some of Europe I’m now concerned we don’t really have available solutions for when renewables stop working. We had a long period of heavy cloud cover and very little wind which tanked the renewable output. Just having a 10% backup of fossil based output wouldn’t have been anywhere near enough. The storage needed to power the country for multiple days continuously would be insanely expensive so not sure what the solution to that would be. This was due to odd behaviour with the jet stream which, ironically, may be due to climate change.)
It all looks a bit bleak really :(