I appreciate the write up Zeke, to disambiguate this funky calculation problem, the effects of which are (perhaps) more irritant than reality (?). The reality is we need to reduce emissions and remove CO2 and CH4 / convert CH4 (ISA) as fast and as much as possible, which continues to slide downward on a diminishing hope slope (yeah, I said hope slope). The reality is they are different gases with different dynamics, so treating them differently makes good sense. Recommending a different framework than the CO2e gwp20 vs gwp100 is in line with what my grandmother told me many years ago: stop touching me.
I was not that keen on the title or some of the write-up until we get toward the end: namely that Methane and Carbon Dioxide should be treated separately, as there really is no equivalent and the GWPs can be quite misleading. The conflict is highlighted by the fact that methane has a lifetime of 10 years or so (e-folding) - so it is all gone in about 20 years - and the use of a 100 year time frame for GWP.
It is also very important to separate out fossil methane from biogenic methane. The latter is circular (starts as CO2, goes into grass and plants, is eaten by animals and converted to methane, that ends up as CO2), while fossil methane contributes to more CO2.
We have a serious problem about the claim that CO2 remains in the atmosphere for over 10,000 years. There is some important quantitative data that says CO2 is actually not very long-lived in the atmosphere at all.
The level of CO2 containing the carbon 14 isotope rose dramatically due to atmospheric atomic testing in the 1950s and 60s, reaching a peak in 1966 when atmospheric testing began to be banned by the US, UK and Russia. Since 1966, despite continued testing by France and China, the levels of atmospheric CO2 with C14 isotope are already almost back to the pre 1940 levels.
This means that the majority of that C14 CO2 has already been "consumed" by the earth's natural carbon cycle in only 60 years, which suggests that CO2 essentially remains in the atmosphere for 100 years, not 10,000 years.
In fact, the myth that we breath millions of molecules of CO2 that Genghis Kahn generated is just another urban myth. Like water in a small swimming pool, our atmosphere gets "turned-over" on decadal time scales, some being consumed, some absorbed, some adsorbed and some lost to space, with lots of gases being added to the atmosphere from geological processes and some added from exogenous space weather processes.
As a technical footnote: the C14 isotope has a half-life of 5.730 years so this rapid fall in atmospheric C14 CO2 levels over the 60 year period cannot be caused by the radioactive decay of the C14 isotope.
We live on an extremely dynamic planet. If the earth was not so dynamic and ever-changing, we would not exist. Humans are successful because we can adapt and cope with change so well.
I think you're confusing the lifetime of an individual CO2 molecule (which is probably on the order of years) with the lifetime of a perturbation to atmospheric CO2. While the lifetime of a CO2 molecule is O(years), the lifetime of a perturbation is much longer (centuries to millennia).
Ian, C14 changes in the atmosphere are often mentioned, but in actual fact their are two "labile" reservoirs of CO2: the atmosphere and the ocean and there is an ongoing CO2 exchange between them. A spike in C14 in the atmosphere takes a relatively short time to equilibrate with the CO2 in the ocean, relative to the time the average CO2 molecule resides in these reservoirs. Predictions of current and future CO2 levels in the atmosphere take these and other factors into account. Note increasing temperatures also reduce the reservoir size of the ocean as well.
Yes, I have been doing some experiments recently demonstrating Henry's Law for CO2 exchange between liquids and the atmosphere for my grandsons.
The C14 created in the atmosphere by either cosmic rays or nuclear bombs rapidly oxidizes to CO2 and enters the carbon cycle which, as you say, significantly involves the interaction between the two main labile reservoirs, oceans and atmospheres (and soils, vegetation, rocks etc).
C14 CO2 is created initially at high altitudes and industrial CO2 is created at lower altitudes (closer to vegetation, soils, rocks) but we are told that CO2 disperses quite rapidly. So I can't see how a CO2 molecule emitted from a 100 metre high smoke stack would behave any differently to a C14 CO2 molecule. If industrial CO2 is in fact not rapidly mixed throughout the atmosphere and stays at lower altitudes, then it will equilibrate with the oceans, the biosphere and geological reservoirs faster than C14 CO2 that is created at higher altitudes.
Therefore there is no logical reason for industrial CO2 to linger longer in the atmosphere than C14 CO2 which is less than about 100 years and not 10,000 years.
If in fact we have evidence of CO2 build-ups in the order of 10,000 years, it must be as a result of natural variations such as degassing due to warming oceans, ocean current upwellings, soil erosion and ice melting after the ice age.
Thanks, Zeke. A definite thumbs-up to setting goals for both. And -- hey, here's a wild idea -- to meeting both. One of my two questions as I read your analysis was why it had to be an either-or, but the politics of the New York situation clarified that and your conclusion solved it.
My other question is why you would assume that methane reductions have to be temporary. If a gas peaker plant is replaced by energy efficiency, heat pumps, or renewables, and those alternatives are quicker to build and cheaper to operate and maintain, why would we assume that anyone will go back to gas?
This paper argues against using a GWP approach, and finds that animal agriculture is the main cause of warming observed to date.
Wedderburn-Bisshop, G. (2025). Increased transparency in accounting conventions could benefit climate policy. Environmental Research Letters, 20(4), 044008.
True, perpetual ch4 increase would put it in a "source" category. It's scary with perma melt and leaks everywhere and garbage galore. Don't light a smoke around cows and thawing tundra.
I agree that separate targets for each GHG would be desirable, and that the GWPs are imperfect and problematic for any time frame. However, I think we might be stuck with GWPs and CO2eqs for the simple reason that money is limited and policy makers want to choose from their menus of options based on getting the biggest bang for their buck. For methane, the bang for the buck is bigger if GWP20 is used rather than GWP100, thus possibly moving up methane mitigation options on their priority list.
I disagree with Hausfather's assertion that that those of us advocating for using GWP20 for methane are necessarily discounting the future. First, by obtaining a relatively quick impact on climate, we can avoid warming-induced emissions of both short-lived and long-lived GHG that result from positive feedbacks to climate change. Specifically, near-term CH4 abatement will likely slow down positive feedback processes, thus reducing CO2 and N2O emissions as well as CH4, which will have long-term impacts. This is true independent of the "tipping point" criticism that Hausfather gives (which I agree with). Second, we aren't suggesting that CO2 and N2O emission abatement should be forgotten -- I think we all are in favor of a "yes-and" approach, but CH4 and N2O are often neglected because CO2 gets more press attention. Using GWP20 for CH4 brings needed attention to what might otherwise be overlooked, thus potentially increasing overall GHG mitigation efforts. Finally, I don't see how we can neglect the suffering of the people already living or soon to be born. If CH4 abatement can make their suffering less in the next few decades, that seems like an immediate priority. That doesn't necessarily discount the value of generations to come, because making progress on fighting climate change now can help achieve momentum and provide hope that the long-term battle can also be won if more effort were forthcoming. We need some wins now, and CH4 abatement is a relatively low hanging fruit.
Eric A. Davidson, Spark Climate Solutions and University of Maryland Center for Environmental Science
The problem is that any CO2e target that includes a conversion factor between CO2 and CH4 inherently introduces a tradeoff between the two. And using GWP20 massively inflated the value of methane compared to CO2 in a way that’s not aligned with the relative climate impact of methane - particularly when applied to ongoing emissions over time. Using GWP20 might make it slightly harder to meet the 2030 target in NY by increasing the overall emissions to be reduced, but could make it much easier to meet future targets (by prioritizing methane over CO2) and sets a bad precedent of using GWP20 elsewhere in GHG accounting. After all, when applied to 20 year stream of emissions GWP20 doesn’t result in much more cooling during those 20 years than just reducing CO2 (and much less cooling thereafter).
Correct me if you think I'm wrong because I'm not a climate scientist (merely a pharmacist) but from what I've read, ERF is a better measurement for different emissions compared to GWP, because it measures the heating that's occuring now
GWPs are just a measure of the average ERF of a gas compared to CO2 over an arbitrary time period (e.g. 20, 100, or 500 years). But they don't really work well when integrating emissions over time rather than looking at a single pulse.
I think NY is finally starting to realize that their net zero commitments aren’t possible if they want a reliable electric power system and they’re trying to finagle numbers to somehow justify that to the climate community. These theoretical calculations are interesting but the issue all along has been how to realistically transition to “renewable” power. You can’t just start building wind and solar units and adding batteries and then see what you got. This has been the direction up until now and people are starting to realize there are numerous significant collateral effects such as grid reliability and actual generating capacity when wind and solar aren’t available. There needs to be a comprehensive plan that looks at more than just reducing CO2 and CH4 and other emissions at any cost. The current and past direction has been a ready fire aim approach and NY has backed itself into a hole.
"I think NY is finally starting to realize that their net zero commitments aren’t possible if they want a reliable electric power system and they’re trying to finagle numbers to somehow justify that to the climate community. "
We're all entitled to your opinion, and mine. IMHO, your intent is to obstruct collective decarbonization, on behalf of fossil fuel producers and investors. Good luck proving me me wrong here ;^)!
My point is that NY passed the Climate Act in 2019 with much fanfare as Gov Cuomo stood next to Al Gore at the signing in a pep rally atmosphere at Fordham U. The party’s over now and since the Act is all hype, and the plan was basically shutdown all the fossil and nuke and build wind and solar with no regard for anything else except GHG, it is a failure. Since the goals were codified and the only way to reach the 2030 40% reduction (currently at 14%) is to Hochul has to deal with the poo poo sandwich Because there was no plan to get to the goals in the Act, Gov Hochul has to deal had to The roadmap to get to the 2030 goal in the legislation was to shutdown fossil fuel and nuke
Sorry wasn’t done. Suffice to say you can’t get there from here and changing esoteric theoretical calculations like the 20 vs 100 is one way to get there. Proceeding without changes may cause - according to AI -
A New York State Energy Research and Development Authority (NYSERDA) memo estimates that rigidly meeting the 2030 targets could add significant costs to households—potentially over $4,000 annually for some upstate oil- and natural gas-heated homes, around $2,300 for NYC natural gas households, and higher gas prices overall.
This is a state agency not a far right wing climate denier analysis.
These are real negative short term effects and not extrapolations to disaster in 2100.
Public money is usually required to pay for the cleanup caused by businesses. ‘Make the polluter pay’ is gaining popularity around the world, but this is the age of deregulation in the US.
it is crazy how surrogates seem to take over the whole narrative, and how grammar can be used to dance around it all. That said, if we could use methane and carbon dioxide credit markets to do things to support the role out of better land and water cycle management practices, then I am okay with that since those things will increase property value and improve access to heathy air, soil and water.
I appreciate the write up Zeke, to disambiguate this funky calculation problem, the effects of which are (perhaps) more irritant than reality (?). The reality is we need to reduce emissions and remove CO2 and CH4 / convert CH4 (ISA) as fast and as much as possible, which continues to slide downward on a diminishing hope slope (yeah, I said hope slope). The reality is they are different gases with different dynamics, so treating them differently makes good sense. Recommending a different framework than the CO2e gwp20 vs gwp100 is in line with what my grandmother told me many years ago: stop touching me.
I was not that keen on the title or some of the write-up until we get toward the end: namely that Methane and Carbon Dioxide should be treated separately, as there really is no equivalent and the GWPs can be quite misleading. The conflict is highlighted by the fact that methane has a lifetime of 10 years or so (e-folding) - so it is all gone in about 20 years - and the use of a 100 year time frame for GWP.
It is also very important to separate out fossil methane from biogenic methane. The latter is circular (starts as CO2, goes into grass and plants, is eaten by animals and converted to methane, that ends up as CO2), while fossil methane contributes to more CO2.
Thawing permafrost provides two different sources of methane:
1. Production of new methane as anaerobes consume the thawed organic carbon.
2. Weakening of geological caps over subterranean reservoirs (of varying ages), allowing for leaks and/or creating blowouts.
In the first instance, the "circular" nature is on a long timescale (last glaciation or maybe even dating from the start of this ice age).
In the second instance, we could probably group those releases as fossil methane.
"Everything should be made as simple as possible, but not simpler"
Yeah, let's not combine apples and oranges just to get a nice single number.
Tangential note:
MethaneSAT is an organization that is working to track the greatest sources of methane emissions on the planet.
https://www.methanesat.org/data
(I wonder what the attack on the Qatari gas field looks like.)
We have a serious problem about the claim that CO2 remains in the atmosphere for over 10,000 years. There is some important quantitative data that says CO2 is actually not very long-lived in the atmosphere at all.
The level of CO2 containing the carbon 14 isotope rose dramatically due to atmospheric atomic testing in the 1950s and 60s, reaching a peak in 1966 when atmospheric testing began to be banned by the US, UK and Russia. Since 1966, despite continued testing by France and China, the levels of atmospheric CO2 with C14 isotope are already almost back to the pre 1940 levels.
This means that the majority of that C14 CO2 has already been "consumed" by the earth's natural carbon cycle in only 60 years, which suggests that CO2 essentially remains in the atmosphere for 100 years, not 10,000 years.
In fact, the myth that we breath millions of molecules of CO2 that Genghis Kahn generated is just another urban myth. Like water in a small swimming pool, our atmosphere gets "turned-over" on decadal time scales, some being consumed, some absorbed, some adsorbed and some lost to space, with lots of gases being added to the atmosphere from geological processes and some added from exogenous space weather processes.
As a technical footnote: the C14 isotope has a half-life of 5.730 years so this rapid fall in atmospheric C14 CO2 levels over the 60 year period cannot be caused by the radioactive decay of the C14 isotope.
We live on an extremely dynamic planet. If the earth was not so dynamic and ever-changing, we would not exist. Humans are successful because we can adapt and cope with change so well.
I think you're confusing the lifetime of an individual CO2 molecule (which is probably on the order of years) with the lifetime of a perturbation to atmospheric CO2. While the lifetime of a CO2 molecule is O(years), the lifetime of a perturbation is much longer (centuries to millennia).
Thank God for carbon isotopes!
Ian, C14 changes in the atmosphere are often mentioned, but in actual fact their are two "labile" reservoirs of CO2: the atmosphere and the ocean and there is an ongoing CO2 exchange between them. A spike in C14 in the atmosphere takes a relatively short time to equilibrate with the CO2 in the ocean, relative to the time the average CO2 molecule resides in these reservoirs. Predictions of current and future CO2 levels in the atmosphere take these and other factors into account. Note increasing temperatures also reduce the reservoir size of the ocean as well.
Thank you John.
Yes, I have been doing some experiments recently demonstrating Henry's Law for CO2 exchange between liquids and the atmosphere for my grandsons.
The C14 created in the atmosphere by either cosmic rays or nuclear bombs rapidly oxidizes to CO2 and enters the carbon cycle which, as you say, significantly involves the interaction between the two main labile reservoirs, oceans and atmospheres (and soils, vegetation, rocks etc).
C14 CO2 is created initially at high altitudes and industrial CO2 is created at lower altitudes (closer to vegetation, soils, rocks) but we are told that CO2 disperses quite rapidly. So I can't see how a CO2 molecule emitted from a 100 metre high smoke stack would behave any differently to a C14 CO2 molecule. If industrial CO2 is in fact not rapidly mixed throughout the atmosphere and stays at lower altitudes, then it will equilibrate with the oceans, the biosphere and geological reservoirs faster than C14 CO2 that is created at higher altitudes.
Therefore there is no logical reason for industrial CO2 to linger longer in the atmosphere than C14 CO2 which is less than about 100 years and not 10,000 years.
If in fact we have evidence of CO2 build-ups in the order of 10,000 years, it must be as a result of natural variations such as degassing due to warming oceans, ocean current upwellings, soil erosion and ice melting after the ice age.
Plug baby plug
Cap baby cap
Seal baby seal
....
Cool baby cool
Good call Zeke!
Thanks, Zeke. A definite thumbs-up to setting goals for both. And -- hey, here's a wild idea -- to meeting both. One of my two questions as I read your analysis was why it had to be an either-or, but the politics of the New York situation clarified that and your conclusion solved it.
My other question is why you would assume that methane reductions have to be temporary. If a gas peaker plant is replaced by energy efficiency, heat pumps, or renewables, and those alternatives are quicker to build and cheaper to operate and maintain, why would we assume that anyone will go back to gas?
Zeke,
I hope there is a common ground rooted movement to mitigate these ungodly ghgs to levels that are less odious to us kinfolk.
May the day of ghgs be over!
This paper argues against using a GWP approach, and finds that animal agriculture is the main cause of warming observed to date.
Wedderburn-Bisshop, G. (2025). Increased transparency in accounting conventions could benefit climate policy. Environmental Research Letters, 20(4), 044008.
https://doi.org/10.1088/1748-9326/adb7f2
Do they account for the upturn in CH4 emissions that correspond with the shale fracking boom that started around 2008?
https://gml.noaa.gov/webdata/ccgg/trends/ch4_trend_all_gl.png
True, perpetual ch4 increase would put it in a "source" category. It's scary with perma melt and leaks everywhere and garbage galore. Don't light a smoke around cows and thawing tundra.
I agree that separate targets for each GHG would be desirable, and that the GWPs are imperfect and problematic for any time frame. However, I think we might be stuck with GWPs and CO2eqs for the simple reason that money is limited and policy makers want to choose from their menus of options based on getting the biggest bang for their buck. For methane, the bang for the buck is bigger if GWP20 is used rather than GWP100, thus possibly moving up methane mitigation options on their priority list.
I disagree with Hausfather's assertion that that those of us advocating for using GWP20 for methane are necessarily discounting the future. First, by obtaining a relatively quick impact on climate, we can avoid warming-induced emissions of both short-lived and long-lived GHG that result from positive feedbacks to climate change. Specifically, near-term CH4 abatement will likely slow down positive feedback processes, thus reducing CO2 and N2O emissions as well as CH4, which will have long-term impacts. This is true independent of the "tipping point" criticism that Hausfather gives (which I agree with). Second, we aren't suggesting that CO2 and N2O emission abatement should be forgotten -- I think we all are in favor of a "yes-and" approach, but CH4 and N2O are often neglected because CO2 gets more press attention. Using GWP20 for CH4 brings needed attention to what might otherwise be overlooked, thus potentially increasing overall GHG mitigation efforts. Finally, I don't see how we can neglect the suffering of the people already living or soon to be born. If CH4 abatement can make their suffering less in the next few decades, that seems like an immediate priority. That doesn't necessarily discount the value of generations to come, because making progress on fighting climate change now can help achieve momentum and provide hope that the long-term battle can also be won if more effort were forthcoming. We need some wins now, and CH4 abatement is a relatively low hanging fruit.
Eric A. Davidson, Spark Climate Solutions and University of Maryland Center for Environmental Science
The problem is that any CO2e target that includes a conversion factor between CO2 and CH4 inherently introduces a tradeoff between the two. And using GWP20 massively inflated the value of methane compared to CO2 in a way that’s not aligned with the relative climate impact of methane - particularly when applied to ongoing emissions over time. Using GWP20 might make it slightly harder to meet the 2030 target in NY by increasing the overall emissions to be reduced, but could make it much easier to meet future targets (by prioritizing methane over CO2) and sets a bad precedent of using GWP20 elsewhere in GHG accounting. After all, when applied to 20 year stream of emissions GWP20 doesn’t result in much more cooling during those 20 years than just reducing CO2 (and much less cooling thereafter).
Zeke, do you get a paycheck from Exxon. Your wrong. Eric Davidson is spot on.
Eric Davidson you are right. Zeke has it all wrong for those living on this extremely rapidly warming scenario we are already in.
Correct me if you think I'm wrong because I'm not a climate scientist (merely a pharmacist) but from what I've read, ERF is a better measurement for different emissions compared to GWP, because it measures the heating that's occuring now
GWPs are just a measure of the average ERF of a gas compared to CO2 over an arbitrary time period (e.g. 20, 100, or 500 years). But they don't really work well when integrating emissions over time rather than looking at a single pulse.
I think NY is finally starting to realize that their net zero commitments aren’t possible if they want a reliable electric power system and they’re trying to finagle numbers to somehow justify that to the climate community. These theoretical calculations are interesting but the issue all along has been how to realistically transition to “renewable” power. You can’t just start building wind and solar units and adding batteries and then see what you got. This has been the direction up until now and people are starting to realize there are numerous significant collateral effects such as grid reliability and actual generating capacity when wind and solar aren’t available. There needs to be a comprehensive plan that looks at more than just reducing CO2 and CH4 and other emissions at any cost. The current and past direction has been a ready fire aim approach and NY has backed itself into a hole.
"I think NY is finally starting to realize that their net zero commitments aren’t possible if they want a reliable electric power system and they’re trying to finagle numbers to somehow justify that to the climate community. "
We're all entitled to your opinion, and mine. IMHO, your intent is to obstruct collective decarbonization, on behalf of fossil fuel producers and investors. Good luck proving me me wrong here ;^)!
My point is that NY passed the Climate Act in 2019 with much fanfare as Gov Cuomo stood next to Al Gore at the signing in a pep rally atmosphere at Fordham U. The party’s over now and since the Act is all hype, and the plan was basically shutdown all the fossil and nuke and build wind and solar with no regard for anything else except GHG, it is a failure. Since the goals were codified and the only way to reach the 2030 40% reduction (currently at 14%) is to Hochul has to deal with the poo poo sandwich Because there was no plan to get to the goals in the Act, Gov Hochul has to deal had to The roadmap to get to the 2030 goal in the legislation was to shutdown fossil fuel and nuke
Sorry wasn’t done. Suffice to say you can’t get there from here and changing esoteric theoretical calculations like the 20 vs 100 is one way to get there. Proceeding without changes may cause - according to AI -
A New York State Energy Research and Development Authority (NYSERDA) memo estimates that rigidly meeting the 2030 targets could add significant costs to households—potentially over $4,000 annually for some upstate oil- and natural gas-heated homes, around $2,300 for NYC natural gas households, and higher gas prices overall.
This is a state agency not a far right wing climate denier analysis.
These are real negative short term effects and not extrapolations to disaster in 2100.
Public money is usually required to pay for the cleanup caused by businesses. ‘Make the polluter pay’ is gaining popularity around the world, but this is the age of deregulation in the US.
this is how business profits, pushing costs of to the future.
Eric Davidson is spot on. Zeke is absolutely wrong.
it is crazy how surrogates seem to take over the whole narrative, and how grammar can be used to dance around it all. That said, if we could use methane and carbon dioxide credit markets to do things to support the role out of better land and water cycle management practices, then I am okay with that since those things will increase property value and improve access to heathy air, soil and water.