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 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 don't know anyone in the climate movement who says lets slow CO2 reduction in favor of methane reduction. I think the emphasis with methane and and HFCs has been on bringing them into the same focus as we have traditionally had with CO2. However, as the graphs show in the short term you get rapid reduction in warming with methane, HFCs and other short-lived climate solutions and every 1/8th degree counts.
I hadn't thought of how using GWP20 might influence people to think reducing methane is more important than reducing CO2.
You don't seem to be critical of GWP*. It has some advantages but also disadvantages, and it is subject to political manipulation by the dairy industry worldwide.
GWP* is a great metric, it just can be combined with bad policy. If you use GWP* you still need a target to reduce methane emissions, not just keep them from increasing.
GWP20 is a conversion factor between CO2 and methane, so under a system that has overall CO2e reduction targets it will determine the relative amount of CO2 vs methane reduced to meet a given target.
In 1983, 43 years ago when modern measurements started, CH4 concentration was 1626 ppb, and now it's 1926 ppb. That gives us a forcing of ~0.14 W/m2, and per IPCC values of 3°C/2XCO2, a warming of 0.1°C.
A tenth of a degree C in 40+, lost in the noise … I'm sorry, but I'm not seeing the problem here.
Disclaimer: I am not a scientist at all. I found this extremely insightful.
If I may use this opportunity to suggest further clarifications of the same caliber, I would like to suggest an analysis of the following:
a) land sector / LULUCF are run as net emissions, taking into account sinks and source;
b) other sectors disregard sinks and look only at sources. One example could be cement - since concrete will later absorb CO2 but that's not reflected, as far as I know.
This was very informative and seems convincing. However, it raises two questions. First, since none of the arguments involve “new” science, why wasn’t there more pushback from the scientific community when this was adopted in New York law. Second, there seems to be support for use of the 20-year GWP in a recent (March 6, 2026) letter to Governor Hochul and other NY state leaders from some scientists, including among others Michael Mann, Richard Horvath, and Mark Jacobsen. Are they simply wrong about this, or can you envision conditions under which their position makes sense.
Howarth and Jacobson are a bit ideological on the methane side of things and may actually prefer short term benefits to long term harms. But I was surprised as well that some of the others put their name on it. I’d hope it’s a misunderstanding of what GWP20 actually entails.
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.
"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.
Plug baby plug
Cap baby cap
Seal baby seal
....
Cool baby cool
Good call Zeke!
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 don't know anyone in the climate movement who says lets slow CO2 reduction in favor of methane reduction. I think the emphasis with methane and and HFCs has been on bringing them into the same focus as we have traditionally had with CO2. However, as the graphs show in the short term you get rapid reduction in warming with methane, HFCs and other short-lived climate solutions and every 1/8th degree counts.
I hadn't thought of how using GWP20 might influence people to think reducing methane is more important than reducing CO2.
You don't seem to be critical of GWP*. It has some advantages but also disadvantages, and it is subject to political manipulation by the dairy industry worldwide.
GWP* is a great metric, it just can be combined with bad policy. If you use GWP* you still need a target to reduce methane emissions, not just keep them from increasing.
GWP20 is a conversion factor between CO2 and methane, so under a system that has overall CO2e reduction targets it will determine the relative amount of CO2 vs methane reduced to meet a given target.
The standard formula for CH4 forcing is:
function(m=1800,m0=750,nmean=300){
a3=-1.3e-6
b3=-8.2e-6
(a3*(m+m0)/2 + b3 * nmean +.043)*(sqrt(m)-sqrt(m0))
where m is current CH4 in ppb, M0 is starting CH4, and nmean is mean N2O concentration.
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2016GL071930
In 1983, 43 years ago when modern measurements started, CH4 concentration was 1626 ppb, and now it's 1926 ppb. That gives us a forcing of ~0.14 W/m2, and per IPCC values of 3°C/2XCO2, a warming of 0.1°C.
A tenth of a degree C in 40+, lost in the noise … I'm sorry, but I'm not seeing the problem here.
Best to all,
w.
Disclaimer: I am not a scientist at all. I found this extremely insightful.
If I may use this opportunity to suggest further clarifications of the same caliber, I would like to suggest an analysis of the following:
a) land sector / LULUCF are run as net emissions, taking into account sinks and source;
b) other sectors disregard sinks and look only at sources. One example could be cement - since concrete will later absorb CO2 but that's not reflected, as far as I know.
This might be a lesser issue.
This was very informative and seems convincing. However, it raises two questions. First, since none of the arguments involve “new” science, why wasn’t there more pushback from the scientific community when this was adopted in New York law. Second, there seems to be support for use of the 20-year GWP in a recent (March 6, 2026) letter to Governor Hochul and other NY state leaders from some scientists, including among others Michael Mann, Richard Horvath, and Mark Jacobsen. Are they simply wrong about this, or can you envision conditions under which their position makes sense.
Howarth and Jacobson are a bit ideological on the methane side of things and may actually prefer short term benefits to long term harms. But I was surprised as well that some of the others put their name on it. I’d hope it’s a misunderstanding of what GWP20 actually entails.
The whole concept of “tipping points” is an unproven hypothesis at best.
Are you suggesting that selling goals for each greenhouse gas should be in lieu of using CO2e or in addition to CO2e?
Doesn't need to be every single species, but separate goals for long-lived stock pollutants (like CO2) vs short-lived flow ones (like methane): https://www.nature.com/articles/s41612-021-00226-2