1. The IPCC established a list of greenhouse gases in the Kyoto Protocol in 1997. According to this list, water vapor is not a greenhouse gas. To my knowledge, the IPCC has never revisited this issue.
2. In my view, water vapor is not a gas, but if we accept that it is a gas, then we must take into account the fact that it is not a permanent gas. This is crucial from a climate perspective because water vapor acquires latent heat when it vaporizes and releases it when it condenses.
Water vapor transports heat from the tropics to the poles via global atmospheric circulation. This is the greenhouse effect, and it has been working this way for millions of years.
From my legal point of view, water vapor is not a greenhouse gas since it is not included in the list established by the IPCC in the Kyoto Protocol.
From a scientific standpoint, the question of whether water vapor is a permanent gas must be asked. Can we say that a non-permanent gas is a perfect gas?
I observe that the concept of the greenhouse effect does not work. The IPCC realized this a little too late and is trying by all means to prove that it does. So it turned to water vapor for help, but water vapor is precisely the right candidate for the greenhouse effect, which means that CO2 has nothing to do with it.
As a non-lawyer, non-legislator, and non American reader, I wonder why in the first place, authority was given to the EPA to regulate CO2 and other GHGs (except water vapour) on the reason of being a pollutant (which CO2 has never been, particularly in our breathing) in relation with... automobile engines.
Wouldn't it be better to address climate change and its alleged anthropic causality in a new law or article of an existing legislation?
Other point: If the current US government thinks of itself to be a World leading power, then why leave such institutions like UNFCCC or WHO instead of contributing to their change and/or improvement? This behaviour is rather a sign of smallness and of desire to remain so.
Congress never gave (explicitly) EPA or anyone else the authority to regulate GHGs
That was the result of a clever legal strategy taking advantage of ambiguous language in statue and a legal stance of deference to executive branch agencies to interpret ambiguous laws and polices.
That deference has changed (Loper Bright) and we will see how the current EPA approach fares in the courts.
But bigger picture — Congress should obviously be leading on this (along with lots of other stuff!)
The NYT is certainly wrong about extreme weather increasing in terms of cyclones and tornadoes.
Given these are the main extreme weather phenomena that can be cataloged numerically, and have been for hundreds of years, and even better in the satellite era, that's far more important than casual observations of cold snaps, heat waves, rain showers, or "droughts."
But let's do a somewhat casual reality check on the logic of these claims.
CO₂ traps heat like a blanket, slightly warming the whole planet. But it warms the poles faster than the tropics. This shrinks the big temperature gap between hot equatorial regions and cold polar areas (what scientists call the 'meridional temperature gradient'). That's what a blanket would do, and what co2 seems to do, at the margin.
Since that north-south, high vs. low latitude temperature difference is a main engine driving weather patterns—like strong winds, jet streams, and the daily ups and downs in temperature—shrinking it should mean calmer, less variable weather overall, with fewer extremes like super-cold snaps or wild temperature swings. Right?
The cyclone and tornado data lean towards yes as the answer...
It should be noted that the two graphs, "What effect have these regulations listed above had on greenhouse gas emissions?" are mirror-images of each other. Improved fuel economy (more miles per gallon) has reduced real-world CO2 emissions (in g/mi). Burn less gasoline, less CO2.
We all love better gas mileage -- saves us money. But I have never for a moment concerned myself with g/mi of CO2.
I grew up in Los Angeles in the 50s and 60s -- smog was a huge issue and was harmful to health.
The minor increase in atmospheric CO2 did not and does not harm health in animals -- and it is beneficial for plants (more food).
Sunnstein argues that the EF repeal will be overturned for the same reasons that Biden's student debt "forgiveness" program was, i.e., because the Court said the agency did not have the power to make wholesale revisions to a statutorily prescribed program. And he calls the EF repeal a "close analog". But that's whistling past the graveyard.
In the student debt case, the statutory program was nothing like Section 202 of the CAA. Instead, it was a carefully articulated program that permitted only changes only in narrowly defined circumstances. As SCOTUS said, "Congress opted to make debt forgiveness available only in a few particular exigent circumstances; the power to modify does not permit the Secretary to “convert that approach into its opposite” by creating a new program affecting 43 million Americans and $430 billion in federal debt". Biden v. Nebraska, slip op. at 13-14. https://www.supremecourt.gov/opinions/22pdf/22-506_nmip.pdf In fact, in the student debt case, Biden and the Dept of Education lost among other reasons because of the major questions doctrine, which supports the EPA here.
Here, the statute says nothing about CO2 and the EPA was plainly permitted to forgo regulating it, as four of the Justices (three of whom remain on the Court, while all five of the majority are gone) made clear. If that case is the best argument against upholding the EPA's right to re-think its authority in light of West Virginia and Loper Bright (among others), the nation can rest easy that the repeal will stand firm.
Solid, objective analysis as usual, Dr. P. I personally agree with the Administration’s decision because I do not believe Congress ever granted EPA to near exclusive right to regulate the national, if not global, economy by politically labeling CO2 a danger to mankind. In essence, I agree with you that Congress needs to make such policy and fix the CAA.
I understand and agree with the desire that Congress communicate its mandates clearly and unequivocally. But consider these two facts that are pretty much beyond dispute:
(1) About 90% of global fossil fuel carbon emissions originate from other countries, outside the EPA or Congress's jurisdiction.
(2) In their 2025 letter to the EPA, Lindzen and Happer noted that if the U.S. reduced CO2 and other GHG emissions to net zero immediately, the widely used MAGICC model predicts the effect on global temperatures would only be 0.17° C.
What law could Congress pass that could be reasonably expected to significantly MITIGATE global warming, much less the claimed but unproven dangers of its secondary effects?
It is much easier to imagine Congress passing laws to accelerate the US adaptation to extreme weather, which will occur regardless of the extent of extreme weather caused by carbon emissions. For example, Congress could fund improvements in extreme weather forecasting or phase out federal compensation for damage to structures built in disregard of flood or tidal surge zones. Yet, even the passage of rational adaptation laws would be a long shot.
"What law could Congress pass" is the key question. As we have seen, the science changes, fast and often. Laws are on the books for decades. How do we make the two work together?
I’m sure that the American left, under the cover of “scientific consensus”, will try to have the courts strike down the repelling of the “endangerment” finding. If that would happen, it would essentially mean that no law is what it was meant to be and all of them can be twisted to provide broad, unchecked powers to change the society in ways that voters would never approve. This is not a legalistic issue, which could easily go either way, as Roger seems to suggest in some places, but a fundamental attack on democracy. If a radicalized faction of society, left or right, can “re-interpret” laws to their great benefit, in ways that voters are sure to reject if given the chance, we’re no longer living in a democracy. If you think I’m over-dramatizing this, consider that I’ve lived half of my life under a communist regime that, on paper, had beautiful laws that were permanently interpreted to justify repression. Don’t think it can’t happen here, and under the cover of “protecting our democracy” - where “our” is theirs but not that of the majority.
Good review of the situation. This observation on the whims of climate advocates that "scientific authority trumps the law and democracy, and thus dictates policy" ought to be your callout. Its the most succinct summary I've seen from you of the ridiculous world we've been in these decades.
Excellent article that puts this new development in an unbiased light. None of this is about climate science, it’s all about politics. The question is: do we want to respect laws as they are written (and rewrite them when and if the people vote for it), or should we look for “emanations” and all kind of subterfuges that allow us to get around the will of the voters, expressed through Congress? The hysterical reaction that we see now on the left concerning rescinding the 2009 finding is part of an obvious pattern of rejection of existing laws and forcing a de facto version of the law that suits the left. I don’t want to inject politics here but politics injects itself in every issue. We see that concerning open borders: the extreme-left dominated Democrats know they have no chance of having that approved by voters, so they try to block by illegal means the enforcement of existing laws. Trying to use a law written 60 years ago, when the “consensus on climate change” was more likely to be about entering a new Ice Age in order to “fight” global warming, instead of passing new laws that voters would never approve, is part of the same devious strategy.
Question on coal. I thought i had heard you speak a year ago and suggesting that one of the most important things we could do to reduce CO2 is to reduce coal use around the world. Given my correct or possibly incorrect memory, what is your take on what is happening to coal in this country? Is it possible that the economics simply do not support expansion of coal use. Seems this is more dangerous than the EPA finding.
What then should tax payers think of then $625 mn being invested to make it happen or the $175mn to upgrade coal power plants in Kentucky, North Carolina, Ohio, Virginia and West Virginia or the executive action forcing the military to buy coal-generated electricity?
Measures to keep those particular coal fired plants running temporarily is a good idea because the region is short of dispatchable capacity and this is the fastest way to shore up the reliability of the grid. In the long run, the government should not be subsidizing any form of energy, including coal.
I, for one, welcome the revisit of the CAA. It has been used as a cudgel to stop investigation into the real or perceived impacts of climate change since its inception. If this ruling does nothing else it will open up a discussion about what to leave in and what to leave out, and most importantly, why to leave it in or take it out.
On a second note, a pet peeve of mine while working in the Federal government was the subtle and psychological push by my fellow bureaucrats to insert their preferred outcome into forthcoming policy by using clearly biased language into the response to regulatory comments or even the original regulation that guided the reader into believing a worst case scenario. That is the use of phrases like, "This may impact our ability to......." when the science behind that perceived impact is clearly not there or ambiguous at best. I argued unsuccessfully that in those cases, unbiased, clarifying language was the responsibility of the government and phrasing should read, "This may or MAY NOT impact our ability to.......". To me it is a subtle change but when you do not know the real answer it is disingenuous to lead the reader down your personally preferred path. I was heartened to see this language change in the proposal and in the response to comments.
To this layman, the question becomes this: if all US vehicle GHG emissions went to zero overnight, what would be the impact on climate change? If the answer is "negligible," then regulation provides no benefit and should be rescinded. If not negligible, then discussion needs to occur on what the proper response should be.
Two comments:
1. The IPCC established a list of greenhouse gases in the Kyoto Protocol in 1997. According to this list, water vapor is not a greenhouse gas. To my knowledge, the IPCC has never revisited this issue.
2. In my view, water vapor is not a gas, but if we accept that it is a gas, then we must take into account the fact that it is not a permanent gas. This is crucial from a climate perspective because water vapor acquires latent heat when it vaporizes and releases it when it condenses.
Water vapor transports heat from the tropics to the poles via global atmospheric circulation. This is the greenhouse effect, and it has been working this way for millions of years.
From my legal point of view, water vapor is not a greenhouse gas since it is not included in the list established by the IPCC in the Kyoto Protocol.
From a scientific standpoint, the question of whether water vapor is a permanent gas must be asked. Can we say that a non-permanent gas is a perfect gas?
I observe that the concept of the greenhouse effect does not work. The IPCC realized this a little too late and is trying by all means to prove that it does. So it turned to water vapor for help, but water vapor is precisely the right candidate for the greenhouse effect, which means that CO2 has nothing to do with it.
As a non-lawyer, non-legislator, and non American reader, I wonder why in the first place, authority was given to the EPA to regulate CO2 and other GHGs (except water vapour) on the reason of being a pollutant (which CO2 has never been, particularly in our breathing) in relation with... automobile engines.
Wouldn't it be better to address climate change and its alleged anthropic causality in a new law or article of an existing legislation?
Other point: If the current US government thinks of itself to be a World leading power, then why leave such institutions like UNFCCC or WHO instead of contributing to their change and/or improvement? This behaviour is rather a sign of smallness and of desire to remain so.
Yes
Agreed
Congress never gave (explicitly) EPA or anyone else the authority to regulate GHGs
That was the result of a clever legal strategy taking advantage of ambiguous language in statue and a legal stance of deference to executive branch agencies to interpret ambiguous laws and polices.
That deference has changed (Loper Bright) and we will see how the current EPA approach fares in the courts.
But bigger picture — Congress should obviously be leading on this (along with lots of other stuff!)
The NYT is certainly wrong about extreme weather increasing in terms of cyclones and tornadoes.
Given these are the main extreme weather phenomena that can be cataloged numerically, and have been for hundreds of years, and even better in the satellite era, that's far more important than casual observations of cold snaps, heat waves, rain showers, or "droughts."
But let's do a somewhat casual reality check on the logic of these claims.
CO₂ traps heat like a blanket, slightly warming the whole planet. But it warms the poles faster than the tropics. This shrinks the big temperature gap between hot equatorial regions and cold polar areas (what scientists call the 'meridional temperature gradient'). That's what a blanket would do, and what co2 seems to do, at the margin.
Since that north-south, high vs. low latitude temperature difference is a main engine driving weather patterns—like strong winds, jet streams, and the daily ups and downs in temperature—shrinking it should mean calmer, less variable weather overall, with fewer extremes like super-cold snaps or wild temperature swings. Right?
The cyclone and tornado data lean towards yes as the answer...
loved this quote ‘technological chicken and the regulatory egg’..!
It should be noted that the two graphs, "What effect have these regulations listed above had on greenhouse gas emissions?" are mirror-images of each other. Improved fuel economy (more miles per gallon) has reduced real-world CO2 emissions (in g/mi). Burn less gasoline, less CO2.
We all love better gas mileage -- saves us money. But I have never for a moment concerned myself with g/mi of CO2.
I grew up in Los Angeles in the 50s and 60s -- smog was a huge issue and was harmful to health.
The minor increase in atmospheric CO2 did not and does not harm health in animals -- and it is beneficial for plants (more food).
Sunnstein argues that the EF repeal will be overturned for the same reasons that Biden's student debt "forgiveness" program was, i.e., because the Court said the agency did not have the power to make wholesale revisions to a statutorily prescribed program. And he calls the EF repeal a "close analog". But that's whistling past the graveyard.
In the student debt case, the statutory program was nothing like Section 202 of the CAA. Instead, it was a carefully articulated program that permitted only changes only in narrowly defined circumstances. As SCOTUS said, "Congress opted to make debt forgiveness available only in a few particular exigent circumstances; the power to modify does not permit the Secretary to “convert that approach into its opposite” by creating a new program affecting 43 million Americans and $430 billion in federal debt". Biden v. Nebraska, slip op. at 13-14. https://www.supremecourt.gov/opinions/22pdf/22-506_nmip.pdf In fact, in the student debt case, Biden and the Dept of Education lost among other reasons because of the major questions doctrine, which supports the EPA here.
Here, the statute says nothing about CO2 and the EPA was plainly permitted to forgo regulating it, as four of the Justices (three of whom remain on the Court, while all five of the majority are gone) made clear. If that case is the best argument against upholding the EPA's right to re-think its authority in light of West Virginia and Loper Bright (among others), the nation can rest easy that the repeal will stand firm.
Roger, sadly your Substack is turning into quite an echo chamber - e.g. man-made CO2's contrubution to warming. On tipping points, I hope some of your readers will peruse the paper (just out) cited here: https://www.theguardian.com/environment/2026/feb/11/point-of-no-return-hothouse-earth-global-heating-climate-tipping-points?CMP=share_btn_url
Ha! I don’t get that sense given how many critiques I get here (which are always welcome) 👍
Solid, objective analysis as usual, Dr. P. I personally agree with the Administration’s decision because I do not believe Congress ever granted EPA to near exclusive right to regulate the national, if not global, economy by politically labeling CO2 a danger to mankind. In essence, I agree with you that Congress needs to make such policy and fix the CAA.
It seems to me the argument for eliminating the endangerment clause is stronger than the case for having enacted it.
Thanks for reporting on the EPA action.
I understand and agree with the desire that Congress communicate its mandates clearly and unequivocally. But consider these two facts that are pretty much beyond dispute:
(1) About 90% of global fossil fuel carbon emissions originate from other countries, outside the EPA or Congress's jurisdiction.
(2) In their 2025 letter to the EPA, Lindzen and Happer noted that if the U.S. reduced CO2 and other GHG emissions to net zero immediately, the widely used MAGICC model predicts the effect on global temperatures would only be 0.17° C.
What law could Congress pass that could be reasonably expected to significantly MITIGATE global warming, much less the claimed but unproven dangers of its secondary effects?
It is much easier to imagine Congress passing laws to accelerate the US adaptation to extreme weather, which will occur regardless of the extent of extreme weather caused by carbon emissions. For example, Congress could fund improvements in extreme weather forecasting or phase out federal compensation for damage to structures built in disregard of flood or tidal surge zones. Yet, even the passage of rational adaptation laws would be a long shot.
"What law could Congress pass" is the key question. As we have seen, the science changes, fast and often. Laws are on the books for decades. How do we make the two work together?
I’m sure that the American left, under the cover of “scientific consensus”, will try to have the courts strike down the repelling of the “endangerment” finding. If that would happen, it would essentially mean that no law is what it was meant to be and all of them can be twisted to provide broad, unchecked powers to change the society in ways that voters would never approve. This is not a legalistic issue, which could easily go either way, as Roger seems to suggest in some places, but a fundamental attack on democracy. If a radicalized faction of society, left or right, can “re-interpret” laws to their great benefit, in ways that voters are sure to reject if given the chance, we’re no longer living in a democracy. If you think I’m over-dramatizing this, consider that I’ve lived half of my life under a communist regime that, on paper, had beautiful laws that were permanently interpreted to justify repression. Don’t think it can’t happen here, and under the cover of “protecting our democracy” - where “our” is theirs but not that of the majority.
Good review of the situation. This observation on the whims of climate advocates that "scientific authority trumps the law and democracy, and thus dictates policy" ought to be your callout. Its the most succinct summary I've seen from you of the ridiculous world we've been in these decades.
Excellent article that puts this new development in an unbiased light. None of this is about climate science, it’s all about politics. The question is: do we want to respect laws as they are written (and rewrite them when and if the people vote for it), or should we look for “emanations” and all kind of subterfuges that allow us to get around the will of the voters, expressed through Congress? The hysterical reaction that we see now on the left concerning rescinding the 2009 finding is part of an obvious pattern of rejection of existing laws and forcing a de facto version of the law that suits the left. I don’t want to inject politics here but politics injects itself in every issue. We see that concerning open borders: the extreme-left dominated Democrats know they have no chance of having that approved by voters, so they try to block by illegal means the enforcement of existing laws. Trying to use a law written 60 years ago, when the “consensus on climate change” was more likely to be about entering a new Ice Age in order to “fight” global warming, instead of passing new laws that voters would never approve, is part of the same devious strategy.
Question on coal. I thought i had heard you speak a year ago and suggesting that one of the most important things we could do to reduce CO2 is to reduce coal use around the world. Given my correct or possibly incorrect memory, what is your take on what is happening to coal in this country? Is it possible that the economics simply do not support expansion of coal use. Seems this is more dangerous than the EPA finding.
Good memory:
https://open.substack.com/pub/rogerpielkejr/p/low-hanging-fruit
I do not think there is any administrative action that the Trump admin could take that would reverse the headwinds facing coal
Maybe they might cause a blip but coal is on its way out in the US regardless
What then should tax payers think of then $625 mn being invested to make it happen or the $175mn to upgrade coal power plants in Kentucky, North Carolina, Ohio, Virginia and West Virginia or the executive action forcing the military to buy coal-generated electricity?
Measures to keep those particular coal fired plants running temporarily is a good idea because the region is short of dispatchable capacity and this is the fastest way to shore up the reliability of the grid. In the long run, the government should not be subsidizing any form of energy, including coal.
Wasted money in my view.
I, for one, welcome the revisit of the CAA. It has been used as a cudgel to stop investigation into the real or perceived impacts of climate change since its inception. If this ruling does nothing else it will open up a discussion about what to leave in and what to leave out, and most importantly, why to leave it in or take it out.
On a second note, a pet peeve of mine while working in the Federal government was the subtle and psychological push by my fellow bureaucrats to insert their preferred outcome into forthcoming policy by using clearly biased language into the response to regulatory comments or even the original regulation that guided the reader into believing a worst case scenario. That is the use of phrases like, "This may impact our ability to......." when the science behind that perceived impact is clearly not there or ambiguous at best. I argued unsuccessfully that in those cases, unbiased, clarifying language was the responsibility of the government and phrasing should read, "This may or MAY NOT impact our ability to.......". To me it is a subtle change but when you do not know the real answer it is disingenuous to lead the reader down your personally preferred path. I was heartened to see this language change in the proposal and in the response to comments.
To this layman, the question becomes this: if all US vehicle GHG emissions went to zero overnight, what would be the impact on climate change? If the answer is "negligible," then regulation provides no benefit and should be rescinded. If not negligible, then discussion needs to occur on what the proper response should be.