Guest Post by Willis Eschenbach (@WEschenbach on eX-Twitter)
The usual font of misinformation, the Guardian, has an article claiming the following:
In 2023, the hottest year ever recorded, preliminary findings by an international team of researchers show the amount of carbon absorbed by land has temporarily collapsed. The final result was that forest, plants and soil – as a net category – absorbed almost no carbon.
Hmmm, sez I as my bad number detector starts ringing … sounds fishy. Something on the order of 55% of emitted CO2 is sequestered and 45% remains airborne. Of this, some 75% is sequestered on land. So if land sequestration has “collapsed”, we should see an immediate jump in airborne CO2 of about 75% * 55% ≈ 41%. But I don’t recall seeing that in the data … hmmm.
And indeed, this jump in atmospheric CO2 is what the “preliminary findings” paper linked above uses as the basis of their claims about the carbon sinks, viz (emphasis mine):
In 2023, the CO2 growth rate was 3.37 ± 0.11 ppm at Mauna Loa, 86% above the previous year, and hitting a record high since observations began in 1958, while global fossil fuel CO2 emissions only increased by 0.6 ± 0.5%. This implies an unprecedented weakening of land and ocean sinks, and raises the question of where and why this reduction happened.
…
The CO2 growth rate in the decade 2013-2022 has averaged at 2.42 ± 0.08 ppm yr -1 . In 2023, it increased to a record high value of 3.37 ± 0.11 ppm yr -1 at the Mauna Loa station (MLO).
Whoa, biggest jump in the record, which “implies an unprecedented weakening of land and ocean sinks“! EVERYONE PANIC!!
So as is my habit, I went to the Mauna Loa site and got the CO2 data. It’s monthly, so I converted it to annual data. Here is the result, showing the growth rate for a given year as the average value for the previous year subtracted from the average value for the given year.
Figure 1. Annual change in atmospheric CO2
Hmmm, sez I once again… the change from 2022 to 2023 looks perfectly average, and at 2.5 ppmv, it’s certainly not the 3.37 ppmv they claim. Why would that be? They can’t be calculating the difference in annual averages.
A closer look at what the NOAA folks are doing when they calculate what they call the “annual mean rate of growth” explains the mystery.
The annual mean rate of growth of CO2 in a given year is the difference in concentration between the end of December and the start of January of that year. If used as an average for the globe, it would represent the sum of all CO2 added to, and removed from, the atmosphere during the year by human activities and by natural processes.
There is a small amount of month-to-month variability in the CO2 concentration that may be caused by anomalies of the winds or weather systems arriving at Mauna Loa. This variability would not be representative of the underlying trend for the northern hemisphere which Mauna Loa is intended to represent.
Therefore, we finalize our estimate for the annual mean growth rate of the previous year in March, by using the average of the most recent November-February months, corrected for the average seasonal cycle, as the trend value for January 1. Our estimate for the annual mean growth rate (based on the Mauna Loa data) is obtained by subtracting the same four-month average centered on the previous January 1.
Now, that all sounds perfectly legit, but doesn’t explain the large 2023 value. So I looked at the monthly data. Figure 2 below shows the more recent of the four-month November-February periods that they are averaging.
Figure 2. Year over year difference, monthly CO2 data. Blue bars highlight the periods from November to February used in their calculations
Following their instructions, I can replicate their calculations exactly. And in Figure 2, we can see why they’ve gotten such a high number—by chance, the data centered on Jan 1, 2024 occurred during a peak time of annual CO2 rise, and the data centered on Jan 1, 2023 occurred during a low time.
What difference does that make? Well, they’ve taken a four-month average starting in November, and compared that to the same period of the previous year … but they could just as easily have started their four-month average in January or June and done the same calculation of annual change.
But here’s the thing. If they’d chanced to start their four-month average in January rather than November, instead of the difference from 2022 to 2023 being the largest jump in the record, it would only be the 24th largest out of the 64 years. If they’d started in February, 11th largest. And if they’d started in June, it would be the 7th largest jump in the record.
And of course, this means that their claim that the carbon sink “is failing” is a totally falsified artifact of their calculation method. It depends entirely on the random choice of the month they’ve used to start their four-month average, and if they’d started in January, they’d have been forced to conclude that there’s nothing unusual going on with the carbon sink in the slightest.
Having been caught by confirmation bias more than once, I can only have compassion for the authors. They were looking for a climate disaster, they thought they’d found one, and unfortunately, because that confirmed their preconceptions, they didn’t look any deeper.
However … they’re still totally wrong. The data doesn’t show any change in the carbon sinks. It’s just an artifact of the odd way that they are calculating the “annual” change.
My very best to everyone, I’m going outside to see the moon.
w.
As Usual: When you comment, I ask that you quote the exact words you’re discussing … it avoids endless misunderstandings.
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As always Willis, common sense and a little bit of maths comes to the rescue. Thank you. But will this help those unfortunates that believe the sky is falling? I fear not.
I think you’re being too kind and generous letting them off with the excuse that it was just a random choice. I’m betting on nefarious.
NOAA wrote “In 2023, the CO2 growth rate was 3.37 ± 0.11 ppm at Mauna Loa, 86% above the previous year…” Publishing instead a change in CO2 growth rate for a 4 month period in 2023 instead of all of the 2023 data is simply fraud. Of course the creators of the fraud knew which 4-month period to choose. That is why they picked it.
This is the kind of “methods” problem that should be flagged and corrected in peer review. I’m betting it won’t, because it would invalidate the entire premise of their “study” and reduce the breathless hyperbole to just “meh.” We’ll see what the final published paper looks like.
I’m betting on stupidity.
“….I’m betting on nefarious.”
Me too. I bet they choose the months to get the most dramatic result.
Chris
Yes, definitely scientific fraud. Nothing new there.
[ Enter “lofty pontification” mode … ]
Erm, the GML “Trends in CO2” webpage also contains an annual version of their data directly.
https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_annmean_mlo.txt
[ Exit “lofty pontification” mode … if possible … ]
Lofty pontification…
<LP Mode>
Mark, given the bizarre mathematical machinations done by NOAA in their calculation of the annual increase in CO2 … I’d be a fool to trust them to average the years.
</LP Mode>
w.
I wonder why the method is so convoluted. When I see the term “annual” I assume it represents the whole year.
So did I, Fran, which was why I was surprised when their numbers were so different.
w.
It is (or course) fraud.
Totalmente de acuerdo con Fran y con Willis.
Bravo to both of you !!!
Gracias, jovencita.
w.
— “We need to get some broad based support, to capture the public’s imagination… So we have to offer up scary scenarios, make simplified, dramatic statements and make little mention of any doubts… Each of us has to decide what the right balance is between being effective and being honest.” – Prof. Stephen Schneider, Stanford Professor of Climatology, lead author of many IPCC reports.
— “It doesn’t matter what is true, it only matters what people believe is true.” – Paul Watson, co-founder of Greenpeace.
We don’t need or want agenda driven or “The Cause” driven “science”.
We need and want “the real McCoy”.
Some of us actually very much doubt that figure of 45% attributed to humankind. In fact, most of it just disappears into thin air – or water….
https://breadonthewater.co.za/2024/07/28/the-mystery-of-the-missing-human-generated-carbon-dioxide/
Henry, I have no idea what you are calling “that figure of 45% attributed to humankind”. Certainly I said nothing of the sort.
w.
Sorry. My mistake. You did not say that. I thought it was implied.
The text says “Something on the order of 55% of emitted CO2 is sequestered and 45% remains airborne”. Are you saying that “emitted” does not refer to emitted by humans?
David, the 55/45 ratio comes from comparing estimates of human CO2 emissions to the gain in total atmospheric CO2. Otherwise, according to the carbon cycles, natural sinks have about 50 times the amount of carbon as the atmosphere. And the annual CO2 fluxes are 96% natural and 4% human.
Now we know why their findings are preliminary. They were waiting for Willis to correct them.
And, calculating a four month ‘difference’ when the full year is available just guarantees more random fluctuation in the smaller window result. As here.
And they failed to mention that the 4-month window resulted in a dramatic decrease between 2022 and 2023, offsetting the 2023 to 2024 increase. Liars.
Thank you Willis, good work!
Grievous harm is being done with numbers, but not with the actual emissions of CO2.
“temporarily collapsed”
Dramatic words are destroyed by the undramatic contexts people drag them into.
Like F-bombs in Chris Rock standup… by the end of an hour I don’t even hear them. This post would be incomplete without double exclamations!!
“temporarily collapsed”
Like the drunk stumbling from lamppost to lamppost.
But I don’t recall seeing that in the data … hmmm.
Exactly !!
In my early work life as understudy to the internal auditor in a large foodstuffs producer organization, scanning pages & pages of reported numbers was the main part of my (mostly agonizingly boring) job.
But after a couple of years in this role, those anomaly numbers do start to jump up out of the columns at you.
Then the interesting part of the job kicks in – how / what / why / who / when / where did this number come to be reported?
(Initially gobsmacked at the regularity by which “aw, should be about” values were being reported)
If the Probity, Provenance and Presentation (3 Ps) of climate “science” numerical constructs (risibly called “data”) are to be rendered acceptable (i.e. vastly improved from where they are now), constant auditing of the reported constructs such as Willis does are critically essential.
If for no other reason that future generations will be able to see that rationality was not completely abandoned by at least some people during the 21st century’s “Extraordinary Popular Delusions and the Madness of Crowds“
“pro·bi·ty /ˈprōbədē/ noun
the quality of having strong moral principles; honesty and decency.”
Because I wasn’t sure.
And, in context –
Also needed –
A Probity auditor: A probity auditor works independently to the procurement team and will report on how regulations and standards are followed.
https://www.cips.org/intelligence-hub/ethics/probity
We need to move some of these math geniuses away from computer ‘science’ and have them teach real statistics to all these failing professions. Evidently none in climate ‘science’ but I played chess with one long ago in a college dorm. Never were enough statisticians or we would be having earthquakes from all the grave rolling. We have a family doctor who probably has saved lives with his stat knowledge but not so sure about some others.
You have to be adept at several things—linear algebra, calculus, probability—to even begin to be good at statistics for some underlying topic area. Most aren’t (Mann being a notable example). So the over-reliance on and frequent misuse of available statistical packages. Start with garbage in, and the statistical package reliably produces garbage out.
A glaring example from some years ago was a ‘famous’ paper using an 8 term multivariate regression on (IIRC) twenty years of US corn yield (by county!) to ‘prove’ global warming would reduce corn yields. The problem was, there should have been a 9th term (temp x soil moisture) because corn does fine when hot and wet, poorly when hot and dry. The paper specifically discussed intentionally omitting that term, falsely arguing there was no statistical weather correlation between the two independent variables. Tell that to corn yields! Was the topic of my very first post at WUWT back in 2011. Authors got caught when the paper got so famous that one of the authors released the actual (aggregated by state) underlying data by state in a graphical ‘boast’ format. Easy to visually prove the underlying error.
Hilarious, Rud. Thanks.
w.
The main thing to remember is additional CO2 giving better crops…
True in general, because most crops of all types are C3. Corn is one of only 3 significant C4 (the others are sugar cane and millet).
WE, I went and looked up the original post here. Worse than ‘hilarious’. The actual corn data was 60 years, the published aggregated state data was 40 years. Superficially compelling.
And I first picked it up from an NRC ‘report’ to Congress while researching my first ebook ‘Gaia’s Limits’ concerning food (a very complicated topic). NRC represented it to Congress as coming from a NSF ‘consensus’.
You go to the underlying NSF summary, it clearly says the worst of all model projections.
So an NRC lie to Congress about an NSF ‘worst’ that was clearly also wrong.
My regards to you and your beautiful ex-fiancée.
Old fundamental required ecological principles about limiting factors even before multivariate regression. Also I guess exponentials are in there somewhere. They have there place but I see too many papers using them that skew the data. Stats are not the only thing missing, I must have pages of references going back at least to 1966 about “ocean connectivity.” These must be the ‘last to know.’
https://www.earth.com/news/reef-fish-populations-are-boosted-by-ocean-connectivity/
Maybe we should more expose “Affirmative Action” as grave rolling going around there also.
Well done, as always.
BTW, if anything, 2023 – 2024 are proving that global temperatures are not driven by CO2 : where is the CO2 spike supposedly inducing the T spike of the last 2 years ?
Seems there is always a surge in CO2 rate of increase at strong El Nino events.
Another way of approaching it is to look at the 12 month change, thus removing the seasonal aspect.
When scaled and graphed against the UAH ocean atmospheric temperatures we get the rate of CO2 increase following the ocean atmospheric temperatures.
The rate of CO2 increase has a spike just after El Nino events, and even steps up with the step change in temperature from major El Ninos.
So it is NOT that sinks have collapsed.. it is that the source has suddenly surged.
Exactly what I was thinking. And the annual increase of CO2 in the atmosphere is deemed to be 45% of the human emissions that is not absorbed, even though natural emissions are approximately 20 times the human emissions. The 45% assumes that the natural emissions have stayed constant. Certainly some or most of the increase in CO2 levels comes from increase in 20 times larger natural emissions due to an increase in temperature?
“assumes that the natural emissions have stayed constant.”
Anyone that thinks sources of CO2 don’t grow quickly as the planet warms…
… needs to find a second brain neuron. 🙂
A sponge can absorb water. More water can be poured on than the sponge can absorb.
That’s true.
But they seem to think that the Earth is a sponge that can’t absorb any more CO2 (or the latest GHG that gets headlines).
A sponge’s ability to absorb more water can’t, but the Earth’s ability to absorb more CO2 can and does.
The Earth is presently “greening”. (More food produced is a bad thing!?)
I’ve noticed TV channels are playing more “scary” movies than usual as we approach Halloween. Annoying.
This “study” is just another example of, “So we have to offer up scary scenarios,”.
( https://wattsupwiththat.com/2024/10/22/no-the-carbon-sinks-arent-sinking/#comment-3984174 )
But they do it year round.
Ninos (or warmer temps generally) tend to be associated with more dryness on land. More dryness is associated with less sinking action (more net emission – whatever). Moisture levels on land are not well monitored, but a good proxy might be atmos CO2 change.
dryness in some areas, yes.. but wetter in other areas.
Atmospheric CO2 would be very likely closely correlated with, and caused by Ocean temperatures, as that would relate to the solubility of CO2 within those waters, resulting in either emission or absorption of CO2 for higher and lower temperatures respectively. This is clearly visible in the temperature and CO2 ice core proxies where the close correlation of CO2 and temperature (with CO2 lagging temperature by ~700years due to the thermal mass of the Oceans). Smaller variations with much less lag time could be caused by changes in just the surface layers of the Oceans, or regional changes, as seen in El Ninos.
Ron Clutz agrees and goes further with the explanation and calculations.
Mid 2024 More Proof Temp Changes Drive CO2 Changes | Science Matters
Technically, as literally phrased above, the claimed sample was for anywhere between 0 seconds to 24 hours.
But for any period of time they might choose, it would seem kind of foolish to take CO2 readings on the side of a volcanic mountain over a seismically active volcanic field, at least without some effort at normalizing for dispersion.
Actually, dk_, it was a good choice of where to measure CO2. Keeling was no dummy. Here’s why.
w.
Thanks, Willis.
Somehow, I’d not seen that piece before.
I don’t know if this makes a significant difference, but from the link provided by Mark BLR
above:
https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_annmean_mlo.txt
There is this:
“# NOTE: Due to the eruption of the Mauna Loa Volcano, measurements from Mauna Loa Observatory
# were suspended as of Nov. 29, 2022 and resumed in July 2023.
# Observations starting from December 2022 to July 4, 2023 are from a site at the
# Maunakea [sic] Observatories, approximately 21 miles north of the Mauna Loa Observatory.”
I was going to raise this issue myself. The question has to be how close are the trends at each site to each other? Would an F-Test conclude that they were from an homogeneous sample?
Over the past 10+ years, I and others have pointed to the information about measuring CO2 emissions, as W.E. does again. Measurements are taken at several different locations and compared. Researchers do, in fact, know what they are doing.
This “on a volcano” trope is like the game “Whac a Mole“. 🤠
WE says:” It’s just an artifact of the odd way that they are calculating the “annual” change.”
You kindly give them the benefit of the doubt about their calculations.
I would have thought they went through several ways of calculating then accepted the one with the worst picture.
Good man.
mk, I’m generally averse to speculating on peoples’ motives, for a simple reason.
I’m rarely aware of my own true motives for what I do.
w.
Per mkelly, I’m guessing they picked a conclusion then calculated the fairest-looking way to reach it. I get it, they have bills to pay.
“However … they’re still totally wrong.”
Seems so. That might explain why the paper hasn’t found a Journal publisher.
Now that’s funny…
Being “wrong” has never stopped 97% of “climate science” journal publications. !
They don’t need no stinkin’ journals, Nick
They’ve got, as Willis correctly highlights –
The usual font of misinformation, the Guardian.
But, it was good enough for the Guardian. And it was thought worthy of publication here:
https://www.fs.usda.gov/nrs/pubs/jrnl/2024/nrs_2024_pan_001.pdf
What explanation do you have for that? Read the Guardian piece, its a classic:
https://www.theguardian.com/environment/2024/oct/14/nature-carbon-sink-collapse-global-heating-models-emissions-targets-evidence-aoe
The paper is made a central exhibit for the claim that natural carbon sinks are ceasing to absorb, hence doom, and this is another item in the Guardian Age of Extinction series
https://www.theguardian.com/environment/series/the-age-of-extinction
The Guardian did the same as the authors, they found a paper which supports their predictions of doom, subjected it to no critical evaluation at all, took it at face value, and did a major doom laden piece substantially based on it.
We are in the middle of one of the great mass delusions of all time. This is a nice instance of the symptoms, but there are more every week. And yet the curious thing is, none of the promoters ever draw the logical conclusions which follow from their supposed beliefs: they never want China to take its emissions to zero. Or India.
The summit of their ambitions is for a country doing 1% of global emissions to take the one third of its emissions that come from electricity generation to zero, ASAP. Without ever asking what difference doing this will make. Its mass hysteria on the part of the media and most politicians. Though a few are now starting to wake up.
“ And it was thought worthy of publication here:”
No, that is a different paper, which is actually quite positive about carbon sinks.
Sorry, yes, if I have it right the paper is here (reference from this latest Guardian outburst of climate hysteria)
https://arxiv.org/pdf/2407.12447
I’m not sure about its publication status from this.
Re-reading that Guardian piece again, and I have the same reaction, it really is an exercise in climate hysteria. What ifs, possibilities, dire consequences if… With no account of how likely any of this doom laden narrative is.
And as someone in another comment says, all this against the background lunatic idea that erecting huge numbers of wind turbines in the North Sea can have some effect on the temperature of the planet.
Every so often in human affairs we seem to get people with one of these mass religio-political manias coming to power, endorsed by the intellectual establishment. Climate mania is unfortunately one of a long series, which is not going to stop here.
They are seeking headlines…different kind of “publication.”
Notice they are using the Mauna Loa annual growth rate for 2023AD which today is 3.36ppm/yr. https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_gr_mlo.txt
This gives a higher growth than the global value.
The global annual mean growth for 2023AD is 2.79 ppm/yr.
https://gml.noaa.gov/webdata/ccgg/trends/co2/co2_gr_gl.txt
When they calculate the global mean growth they use the difference between the December/January mean from the Dec/Jan mean from the previous year.
By using the Mauna Loa data rather than the Global, they get a more scary number.
They wanted another “Hockey Stick” to reach the Tipping Point in order to create panic and bedlam.
Harold the Organic Chemist Says:
At the MLO in Hawaii, the concentration of CO2 in pure dry air is 422 ppmv. One cubic meter of this air has 0.839 g of CO2 and a mass of 1.29 kg at STP. For sunny day at 70 deg. F and with 70% RH, the concentration of H20 is 14,780 ppmv. One cubic meter of this air has 14.3 g of H20 and a mass of 1.20 kg , but contains only 0.780 g of CO2.
To the first approximation and with all things being equal, the proportion of the
greenhouse effect (GHE) due to H20 is given by:
GHE for H20 = moles H2O/moles H20+moles CO2 = 0.79/0.81=0.98 or 98%
This calculation assumes that a H2O molecule and a CO2 molecule each absorb about the same amount of IR light. Actually H20 absorbs more IR light than CO2. H2O is the major GH gas by far and CO2 is a minor trace GH gas. About 71% of the earth’s surface is covered by water.
On the basis of the above data and rough calculations, I have concluded that the small amount of CO2 in the atmosphere can only heat up such a large amount of
air by a very small amount if at all. I have further concluded that the claim since 1988 by the IPCC and a coterie of unscrupulous scientists that GH gas CO2 causes “global warming” and is a deliberate fabrication and a lie.
The purpose of this fabrication and lie is to provide for the UN a justification for the distribution, via the UNFCCC and the UN COP, of the donner funds from the rich countries to the poor countries to help them cope with “global warming” and
“climate change”. The funds for these two organizations and the IPCC are many, many millions of dollars. At the recent COP29 conference the poor countries have requested about a trillion dollars.
This is what all this rhetoric about the emission of GH gases, global warming and climate change is really all about: the money. Hopefully, this fraud can not go on too much longer. We really do not have to worry at all about the minor trace greenhouse gas CO2.
Some strongly supporting ‘numbers’. The ECS of CO2 without feedbacks is calculated from first principles as ~1.1 (Curry blog, 2010), 1.2 (Lindzen address to Parliament 2011), or more precisely 1.16 (Monckton’s Irreducible Equation paper, about 2016). The climate models have 3-3.2 depending on which CMIP. Since Dessler proved in his mistaken conclusions 2010 paper that cloud feedback is about zero, and even IPCC says all else sums to zero, the large ~2.5x discrepancy must be from the modeled positive water vapor feedback.
Supporting factoid. The ONLY CMIP6 model NOT producing a spurious tropical troposphere hotspot was INM-CM5. This was so striking that INM published a paper on it. Their ‘secret’ was, they used actual ARGO observations to parameterize ocean rainfall, thereby reducing ocean water vapor feedback by about half. INM-CM5 also produced the lowest CMIP6 ECS, at 1.8 closest to the EBM observational about 1.7.
Messing with those “fact” thingies again, are we, Rud?
Don’t you know that will get you banned from polite company?
w.
What is ECS? What are you trying to say? I do not know anything about these fancy climate models. I recall this quote: Models are always wrong, but sometimes they are useful.
My message is quite simple. There is too little CO2 in the air to cause global warming, water is the main GH gas by far, and the UN and the collaborating and unscrupulous scientists (aka, the welfare queens in white coats) are perpetrating the greatest scientific fraud in recent human history since the Piltdown man. The objective of this fraud is to transfer immense wealth from the rich countries to thee poor countries.
The proposed “positive water feedback” is nonsense. Since 71% of the earth’s surface is covered by H20, it does not any help from CO2. Moreover, the wind is a major force for transporting H20 into air. On land water is released by the transpiration and respiration by plants. All the animals including insects release vast amounts of water via respirations.
Please go to: “Science of Climate Change 4(1)” and read the review by
Roy Cark. This review is 78 pages, and is highly technical, and has extensive bibliography. He reviews a number of research papers reporting on the role of wind on transporting H2O into the air.
Finally, look what has all this global warming and climate change nonsense has done to the UK. The last thermal power plant has just been shut down and winter is coming. In California, Gov. Gavin N. wants to ban all ice cars and trucks by2035. In NY, the Climate Act mandates that by 2023 70% of the electricity be generated by renewables, such solar panels and wind turbines.
I’ll stop for now.
Typo correction: 2023 should be 2030.
The CO2 growth rate from year to year is so erratic even as calculated 2023 doesn’t signify anything, yet another Guardian ‘climate-crisis’ beat-up.
“the amount of carbon absorbed by land has temporarily collapsed. The final result was that forest, plants and soil – as a net category – absorbed almost no carbon.”
Totally insane.
Ohoh. All that adding organic bio-char propaganda people keep claiming will improve soil must have reached its saturation point.
We know that the earth is greening. Therefore land-based carbon sinks are expanding not contracting. The earth is never in equilibrium but always struggling to achieve it. At some point the rise in co2 will plateau, at which point earth will probably overshoot and atmospheric concentrations will decline.
The first paragraph in the above article gives a quote from The Guardian that starts off with “In 2023, the hottest year ever recorded . . .”
Oh, please! . . . can’t we once and for all dismiss this phrase as a being quite idiotic and really meaningless?
The first practical thermometer is generally considered to have been invented around 1714 by Daniel Gabriel Fahrenheit, when he developed the mercury-in-glass thermometer, providing a much more precise temperature measurement than previous designs. Moreover, such thermometers began to be widely used in meteorology starting only in the early 1800’s.
So, let’s assume we should consider Earth temperatures as being “meaningful” since the time life is believed to have first appeared on Earth, which is about 3.7 billion years ago (ref: https://naturalhistory.si.edu/education/teaching-resources/life-science/early-life-earth-animal-origins ). Therefore, the hottest year “ever recorded” actually represents a sampling of at most 225 years/3.7 billion years, or 0.000006% of the appropriate interval of concern.
As an alternative way to look at this, the current Ice Age (the “Quaternary”) began about 2.5 million years ago, so “recorded temperatures” have never considered “Hothouse Earth” conditions and recovery from such!
(ref: https://climate-xchange.org/2018/08/hothouse-earth-what-is-it-and-what-can-we-do-about-it/ )
Talk about a classic case of being myopic!
My immediate guess would be CO2 outgassing of the oceans. Perhaps from higher temperatures but also just in-out cycles I read about years ago for the South Pacific and English Channel(?), on this (I think) site.