22 Comments
May 25, 2023Liked by Zeke Hausfather, Andrew Dessler

Really interesting, thank you. And encouraging too. This kind of thing - seeing that there is some change in the right direction - is important to communicate, especially when people are getting demoralised at the rate of progress. We are moving too slowly, but at least we can see the movement now.

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Why do we pay more attention to emission estimates instead of a more direct measurement like the Keeling Curve?

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author

Because the Keeling Curve is a lagging indicator since its a function of cumulative emissions. That curve won't flatten out until we get close to net zero, so its not really a good indicator of decadal-scale emissions changes.

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Yes but can’t the ppm jump from year to year tell us roughly whether emissions have increased or decreased? If the jump is the same year over year, couldn’t we say emissions have flattened (assuming ‪CO₂‬ absorption by the planet is constant)?

Or better still, couldn’t we compute a keeling curve into the future for each of the RCP scenarios and compare the real keeling curve against the computed projections to get a good idea which scenario we were tracking?

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Unfortunately there is a lot of year to year variability in ppm changes due to ENSO and other factors unrelated to emissions, so it’s a pretty poor short term indicator.

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https://www.amnh.org/explore/videos/earth-and-climate/keeling-s-curve-the-story-of-co2/dataset-information

I did a quick google search and according to article above, RCP 2.6 says we need a ‪CO₂‬ concentration of 421 ppm in 2100. 8.5 is 936 ppm.

So this is roughly what I’m talking about; comparing the actual keeling curve measurements with keeling curve projections from each scenario. But instead of just the endpoint concentrations like I’m the article above, it would compare the entire curve.

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Not sure how the Keeling curve is relevant. The Keeling curve tells us the historical atmospheric concentration of carbon dioxide (not emissions) and it doesn't tell you anything about the future.

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This article says nothing about the human-caused INdirect emissions - the permafrost thaw, the methane emissions from growing tropical wetlands and Arctic wetlands... and nothing about the tipping points the IPCC keeps ignoring: The Amazon transition to savannah, the boreal forests turning to ashes, the rate-dependent tipping points such as the "compost bomb instability", and the social compounding tipping points, which affect the imagined techno-optimist scenario towards a wonderful future. The IPCC has a long record of having underestimated the damages of the near future (now the past) during its 33 years in existence. It's guided by the pro-growth economics paradigm within the IPCC (and people like economist Richard Tol and his outrageous disinformation on climate) and ignores the basic thermodynamics of civilization. Also, if you want to know how climate will change, don't follow supposed emissions numbers (which are widely acknowledged to be understated for political reasons from various governments), instead follow the Keeling Curve. It shows no change from its exponential form, and the annual increase of CO2 concentrations continues to be 2.5 ppm per year. I'm not impressed by this article.

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Great article, thank you for sharing! It's good to see a little positivity in the numbers however I agree we still have a long way to go. Policymakers (and arguably the system policymakers work within) struggle to have scope for the impacts of long-term self perpetuating feedbacks in the climate system.

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Great article. When you say emissions will remain flat with current policies, are you considering economic growth (people consuming more beef, a larger % of the population flying...)?

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You can read this various ways. Maybe existing policies plus technological change means nothing else needs to be done. In other words, the optimal carbon tax is NOW zero. I don't see it that way. I'd say that existing policies and technological change have reduced the optimal carbon tax, hopefully by enough that politicians will not be too frightened to enact a net emissions tax. After all, we will still need to reduce CO2 concentrations when we reach zero net emissions.

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Is there a graph similar to the total CO2 emissions figure but for CO2 equivalent? What I'm wondering.... could it be that CO2 emissions have flattened but CO2 equivalent has increased from natural sources of methane or carbon sinks now releasing carbon? Is that a reasonable question?

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yes, it's a very reasonable question. Interesting how CO2e is so rarely highlighted. I think it's because we can't control indirect emissions, hence it's scary, hence it is counterproductive to the economic imperative to keep us all complacent that "we're on our way to a great future!". Also worth noting there's two sides to the meme that telling people the climate truth causes utter despair. Individually, when you're faced with the possibility for catastrophe, it motivates drop-everything and deal with the problem. We're far too complacent in this civilization. It'll be our undoing.

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... unless the economy accelerates again.

And where's your methane measurements? That's going to be a lot more materially impactful in the real-world 21st century.

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CO2 provides around 80% of the future warming in all the SSPs. CH4 emissions are certainly important (particularly reducing them to meet our ambitious warming targets), but are not the major driver of future warming due to their short atmospheric residence time.

But CH4 concentrations seem to be more or less track SSP2-4.5, though the rapid increase in recent years is worrying: https://twitter.com/Peters_Glen/status/1597864799978762240

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To me and my son, near-term or near-future warming is more important than a long-term with which you are averaging the effect of methane released today in order to carefully claim it's not "the major driver." Certainly it would be "a" major driver.

The rapid increase in recent years is very worrying because it looks like the beginning of an unstoppable feedback loop whereby natural ecosystems respond to warming by releasing more (and more than we expected) methane, in turn driving warming. Whenever that process reaches the shallow continental shelf of the Arctic ocean, we will get the infamous and too-casually dismissed methane burp. And we will look back on this substack with a sense of tragic nostalgia, a reminder of a time in which we could still believe that it wasn't going to be all that bad, after all.

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Well, methane is not the major driver of near-term warming either. Thats CO2. Here is the increase in radiative forcing due to the three main GHGs (CO2, CH4, N2O) since 1990: https://twitter.com/hausfath/status/1491507813314535424?lang=en

Reducing methane will be key to meet our ambitious climate goals as it can cut warming fast. But methane emissions won't really change which scenario we are heading for under current policies today all that much.

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again it's obfuscation by article

you say The major

I say A major

we talk past each other

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I am very vindicated on this thread by the way

https://www.commondreams.org/news/fossil-gas-leaks

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Methane contribution to global warming has been steadily revised upward in journal papers. You rely too much on the IPCC pronouncements, which are politically tainted by the IPCC's "range of views" together with demand for 100% consensus before publication - that includes therefore the veto power by industry and political members who have a vested interest in NOT letting alarming climate science into the documents, even if they are published in quality journals.

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Great post Zeke.

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