Guest “Torching a Straw Man” by David Middleton
Is CO2 plant food? Why are we still talking about this?
the climate-denier zombie argument that, unlike plants, won’t die
Feb 20, 2025
Recent interviews with Trump administration officials have revived a persistent myth in climate change discussions: “CO2 is plant food”. This is one of those zombie climate-denial arguments that just never goes away because 1) it’s a simple argument and 2) it seems intuitive — after all, plants need carbon dioxide, so more of it must be good, right?
Yes, CO2 enhances photosynthesis. But crops don’t grow in a vacuum, they also need water, temperatures in a particular range, and farmers need predictable seasons. Climate change disrupts all of those.
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Climate change disrupts all of those
Disrupts all of what? Global agricultural data are easily available from the UN Food and Agricultural Organization (FAOSTAT).
Oh! But that’s just wheat and corn! That’s true. There are dozens, if not hundreds, of agricultural products. FAOSTAT also publishes an agricultural Gross Production Index relative to 2014-2016.
Straw Man?
I don’t know of any scientifically literate skeptics who say that more CO2 is better simply because it’s plant food. Nor do I know of any who think that the rise in atmospheric CO2 is the sole reason for improved agricultural output over the past 64 years.
Although, it clearly is plant food. And we know that substantially less CO2 would be very bad for plants. There is compelling evidence that CO2 in the range of 180-220 ppm induced carbon starvation in C3 plants during the Last Glacial Maximum (Ward et al., 2005). While there might be a point at which more atmospheric CO2 could do more harm than good, the rise from 280 to 420 ppm has clearly been beneficial. It’s largely been beneficial due to the exploitation of fossil fuels over the past 160 years,
(Wood for Trees, MacFarling Meure et al., 2006)
From 1800 to 1900, per capita energy consumption, primarily from biomass, remained relatively flat; as did the average life expectancy. From 1900 to 1978, per capita energy consumption roughly tripled with the rapid growth in fossil fuel production (coal, oil & gas). This was accompanied by a doubling of average life expectancy. While I can’t say that fossil fuels caused the increase in life expectancy, I can unequivocally state that everything that enabled the increase in life expectancy wouldn’t have existed or happened without fossil fuels, particularly petroleum.
Our modern society would not exist without fossil fuels and it would collapse in a heartbeat if fossil fuels were made unavailable and/or unaffordable. One of the coolest things about being a petroleum geologist, is that I can give thanks for fossil fuels and say “you’re welcome” in the same sentence.
Funny thing, Andrew Dessler is a professor at Texas A&M University.
The Permanent University Fund (PUF) is a public endowment contributing to the support of eligible institutions of The University of Texas and The Texas A&M University Systems. The PUF was established in the Texas Constitution of 1876 through the appropriation of land grants previously given to The University of Texas, as well as an additional one million acres of land. Additional land grants to the PUF were completed in 1883 with the contribution of another one million acres. Today, the PUF contains over 2.1 million acres of land primarily located in 19 counties in West Texas.
The PUF’s primary investment objective is to maximize investment returns within the risk parameters specified in the PUF Investment Policy Statement without regard to the distribution rate.
The PUF is invested in a broad mix of investments and is actively managed to its policy portfolio or benchmark. UTIMCO allocates the PUF’s assets to internally and externally managed portfolios in accordance with guidelines approved in the PUF Investment Policy Statement.
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References
Lomborg, Bjorn . Welfare in the 21st century: Increasing development, reducing inequality, the impact of climate change, and the cost of climate policies. Technological Forecasting and Social Change. Volume 156, 2020, 119981, ISSN 0040-1625, https://doi.org/10.1016/j.techfore.2020.119981.
MacFarling Meure, C., D. Etheridge, C. Trudinger, P. Steele, R. Langenfelds, T. van Ommen, A. Smith, and J. Elkins (2006), Law Dome CO2, CH4 and N2O ice core records extended to 2000 years BP, Geophys. Res. Lett., 33, L14810, doi:10.1029/2006GL026152.
Ward, Joy K.; Harris, John M.; Cerling, Thure E.; Wiedenhoeft, Alex; Lott, Michael J.; Dearing, Maria-Denise; Coltrain, Joan B.; Ehleringer, James R. 2005. Carbon starvation in glacial trees recovered from the La Brea tar pits, southern California. Proceedings of the National Academy of Sciences of the United States of America. Vol. 102, no. 3 (Jan. 18, 2005): p. 690-694
don’t know why all of the money is wasted pumping CO2 into greehouses.
nurserymen must not know much about growing plants.perhaps they should stop wasting money on water
More plant food in the air has greened near desert areas like the Sahel. With more CO2, plants need leave their stomata open lees time, conserving water.
CO2 is the first link in the global food chain. There isn’t one DNA containing entity that doesn’t require Carbon to produce fresh cells or to reproduce. Plants need Carbohydrates for energy to grow and that carbohydrate is created from CO2, H2O and photosynthesis. CO2 is literally the first link in the food chain, without which ALL life fails
Look at your dinner plate. Except for water and salt, everything else was CO2 not long ago.
says it all, really.
Then the next red-herring they will appeal to is more CO2 makes food less nutritious.
As to Dressler’s comment that a warmer world is a dryer world. There is no real world evidence, both current and geological to support such a belief.
Beyond that more CO2 enables plants to use water more efficiently.
Yep. Locking up fresh water in ice sheets causes a drier world.
Indeed, the planet is 70 percent water, and atmospheric water vapor comes from evaporation, so it is hard to believe that a little increased warming will mean less water.
Th evidence is completely the opposite; cold glacial advances are drier and dustier, inter-glacials are warmer and wetter, allowing more diversity of life! A typical eco-loon, Dessler goes with his feelings and ignores the data!
Antarctica is the driest place on earth.
It also contains the most fresh water….
Both statements above are correct.
God obviously does have a sense of humor.
Bingo, most every crop on the planet now grows about 20 percent more food (more then that, yet just based on CO2 increase) on the same amount of water, on the same amount of land. CO2 warming is at worst, primarily at night, reducing frost damage, and CO2 is expanding growing zones far more then any warming is reducing them.
CO2 warming?
A warmer world should be a wetter world…
While the Clausius-Clapeyron relationship predicts the potential for increased absolute humidity as air warms, that isn’t the only thing that impacts evaporation. In the case of still air, the air immediately above the water can become saturated with water vapor, impeding any further evaporation. Some wind or convection is necessary to strip that saturated layer away to allow more evaporation. As usual, alarmists like Dessler focus on one fact (as with the CO2 experiment by Arrhenius) and ignore the complex interrelationships between all the variables — feedback loops!
There is mixed results in examining the claim. A recent paper ( Recent Decline in Global Ocean Evaporation Due To Wind Stilling – Ma – 2025 – Geophysical Research Letters – Wiley Online Library ) shows that ocean evaporation increased from 1988 through 2007, but has declined from 2008 through 2017.
With enough ship time evaporation rates seem to me nearly as difficult to measure as clouds. Yep! In the paper– “It should be emphasized that substantial gaps exist in the Buoy’s observations, making it challenging to evaluate long-term trends in Eo.” However, in the abstract–“These findings offer crucial insights into diverse responses of global hydrological cycle to climate change.”
That’s been done.
At least twice, so far.
Less nutritious or less tasty or less filling.
The claim any climate change must be for the worse is normal for advocates, despite a lack of evidence. As if “somewhat warmer than the Little Ice Age” is a bad thing?
Historic data seems to indicate that colder periods have more extensive droughts.
I seem to recall tree ring proxy data that there was a rather long drought during the Medieval Warm Period in California. Weather is chaotic.
Not when the historic is replaced by the modelled and computed.
“muddled and confused” seems a better phrase.
So true, Tom! The alarmists, like all sufferers of long term, coercive brainwashing, must find a way to justify their deeply held beliefs; cognitive dissonance is the most common result!
Yeah, Dessler believes in the climate was better myth before modernity.
It may have been better when it was warmer, but for most life on earth and especially for humans, it was definitely worse when it was colder.
They believe in climate stasis. There is a default climate and what it is now is that default and must never change. It seems to me that would be the definition of a climate change denier – n’est-ce pas?
Which is why they embraced Michael Mann’s Hockey Stick “temperature reconstruction”, despite it being contrary to historical records. Any change must be man caused, and therefore Evil.
I wonder how they feel about the temperature range in their environmentally controlled living rooms.
Many of the environmentalists that I have dealt with, believe that any change caused by man is bad and must be opposed.
I asked one young man about what should be done if we found that a big asteroid was going to hit the Earth. He said that nothing should be done, since the asteroid was natural, and if all life on the Earth was wiped out, that would just be nature taking its course.
Not advocates. Activists.
“The Climate Brink” appears to be an outlet for Dressler and Hausfather to expound on their pet peeves. They claim tens of thousands of followers while the number seems to be 15,000 (it’s free). That’s fewer than the number of paying clients at a basketball game when Catlin Clark plays.
She is more interesting and authentic than the D & H duo.
Warming, predictably, make growing season long.
I really good years, for some types of crops, that may mean an extra yield cycle… bonus !
Also expands the area in cold countries, in which crops can be grown… bonus !
The main problem all crops face is late season frosts, which a warming climate may, or may not reduce.
Humpty Dessler is talking from agenda-driven ignorance…. nothing has changed.
// Yes, CO2 enhances photosynthesis.
But CO2 is a necessary ingredient for photosynthesis, not merely an ‘enhancement’. So it would be more accurate to say that CO2 is the source of carbon for photosynthesis. Furthermore, it seems that CO2 is the source for virtually all of the carbon found in substances created in the carbon cycle (Calvin and Krebs cycles etc)
Carbon is cycled through the environment via the carbon cycle, where plants absorb carbon dioxide (CO2) from the atmosphere through photosynthesis, then animals consume those plants, incorporating the carbon into their bodies. When organisms die and decompose, the carbon is released back into the atmosphere as CO2, continuing the cycle.
Key points about the carbon cycle:
Well expressed. As perhaps a minor point, is the chemistry term reactant more appropriate than necessary ingredient?
Both, perhaps. The carbon from CO2 becomes part of the sugars, etc.
Worrying about atmospheric CO2 levels right now is like worrying about the amount of caviar available on the Titanic, after you’ve spotted a large iceberg dead ahead!
The CO2 concentration available for life has been falling for 150,000,000 years; any temporary rise is all to the good! Our REAL problem will be figuring out an economical way to maintain adequate levels despite the continued deposition of calcium carbonate that locks up this fundamental building block of the food chain in mineral deposits! I guess the alarmists must believe that we can eat our marble and limestone countertops once the CO2 level falls below 150ppm!
I agree with the thrust of the article.
I’m not fond of the scaling of CO2 on the graphs from 300 to 440. From 0 to 440 would be better but why not from 0 to 1000 or some other number?
How about from 280 to 440? That’d be the start value to where we are now.
But that’s not the point, the graph describes two things. Actual production and CO2 levels and the point is to relate them together. You could do that with larger ranges in either or both but it’d just have the effect of flattening out the graph to hide the detail.
So you’re right in principle. You need to keep in mind possible issues from scaling and how that might bias the perception of the effect.
Its a bit like how AGW people love to graph the temperature anomalies such that the increase looks steep and dangerous when if plotted on the Kelvin scale, couldn’t even be seen.
Plotted on a typical thermometer scale it’s imperceptible.
This graph is scaled from 200 to 600 because that has been the approximate range over most of the past ~30 million years. It’s a little hard to see because that particular graph is a little cluttered.
The other graphs were scaled 200-440 because that covers the range over most of the Quaternary Period.
Sure. The problem with showing the range of two quantities as both filling the vertical scale is that it visually suggests an equivalence or a correlation between the two quantities.
In the graph area harvested goes from 200k to 800k (four times) on the left hand scale whereas Co2 goes from 320 to 420 (31% increase).
Is that really the visual equivalence you were after?
Looking at that graph more closely, I think David has suggested that the total area harvested for wheat hasn’t changed (at a bit over 200k ha) in the last 60 years. I find that very difficult to believe.
Yes and I picked the wrong scale. When I wrote area harvested I should have written Production.
I can tell you in Kansas wheat acres have not changed appreciably over my lifetime. What has changed is the technology. Better varieties, more technology in land preparationaetc and fertilizer application. A major change is in dual cropping. Wheat/corn or wheat/soybeans. Longer growing seasons allows the use of longer maturation varieties that have better per acre production.
Still unconvinced, I went looking.
From a report from the United States Department of Agriculture on a paper titled KANSAS WHEAT HISTORY we have the following chart showing
Replying to myself, bizarrely for me this supports the idea that the wheat area hasn’t changed much.
I was expecting the growing area to have increased but if major wheat growers (such as Kansas) have decreased in area then that could counter any area increases elsewhere.
Re I don’t know of any scientifically literate skeptics who say that more CO2 is better simply because it’s plant food.
The late-great* Freeman Dyson was fond of this kind of formulation [paraphrasing here]:
the effects of increasing atmospheric CO2 on the biosphere are likely positive, robust and large (or significant),
whereas its radiative effects (viewed by some as a negative) are likely small, uncertain or insignificant.
*& that man was on the 101st percentile (jk) on the scale of ‘scientifically literate skeptics’!
Re Nor do I know of any who think that the rise in atmospheric CO2 is the sole reason for improved agricultural output over the past 64 years.
Right. For one major exception / example: One indirect (+) effect of hydrocarbons (CO2 production) on the biosphere is that, in production of synthetic nitrogen fertilizers, they supply the di-hydrogen (H2) for the Haber-Bosch process.**
Cheers, — RLW
————————
**Schematically, in two stages are, first steam-reforming CHx + 2 H2O => CO2 + H2 ; second, ammonia synthesis: dinitrogen N2 + 3 H2 —> 2 NH3
The nitrogen fertilizers are applied directly to agriculture.
[ Recall that Pimentel estimated that, in modern or industrial scale agriculture, the caloric (energetic) value of food produced is comparable to that of the petrochemical input!?! Quite aside from the photons / solar input …]
The CO2 (byproduct) has other uses (refrigerant, extinguishers, well injection) but may also be released into the biosphere, in which case it enhances carbon fertilization. Note that the hydrogen (H2) is intermediary — it is produced & consumed on-site like in other petrochemical processing — so it doesn’t need to be stored, transported etc. as in the proposed ‘hydrogen economy’ scenarios.
Perhaps Dessler doesn’t know what the ‘A’ stand for in Texas A&M. $ PUF, Robert A Welch Foundation &c &c he seems to be working in the wrong place…
Dessler is the formerly infamous climate scientist whose seminal 2010 paper using clear sky/all sky ‘proved’ cloud feedback was positive. Except he published his data in the paper, with an r^2 of 0.02! Which Steve McIntyre promptly took apart. An almost perfect random ‘shotgun’ proves nothing except that Dessler was mathematically ignorant.
Nothing has changed since. He is still a TAM full Prof. and still ignorantly wrong.
“mathematically ignorant”
Seems to be a common trait of climate scientists.
essentially an “Aggie Joke”
He fell on his head too many times raking leaves.
I’m an Aggie with a minor in oceanography before the department split (spit?) out meteorology. Taught us stuff like this.— “A surprising feature of these results is that, even with a significantly improved dataset, the exact time of separation of a ring remains elusive……It is well known that determining the true uncertainty of geophysical spectra is fraught with problems.. ” From–
Sturges, W. and R. Leben. 2000. Frequency of ring separations from the Loop Current in the Gulf of Mexico: A revised estimate. Journal of Physical Oceanography. 30:1814-1819.
https://doi.org/10.1175/1520-0485(2000)030<1814:FORSFT>2.0.CO;2
Give them some credit—- https://www.cfact.org/2025/02/16/texas-takes-giant-steps-toward-nuclear-energy-dominance/
Didn’t mean for anyone to take it personally. When I was in school just up the road in bear land during the mid 60’s, everything was an Aggie joke.
Rud, Dessler is just one of many compensated liars: Climate disaster ladder-climbing academics and their grant-seeking institutions, venal politicians of both the Left and Right, entrenched bureaucrats building empires (Deep State), crony capitalist rent-seekers, Leftist/Socialist/Marxist ideology-driven NGOs and the ever-present sensationalist media empires. And there’s always the useful idiots class to back them up.
In his debate with Koonin Dessler said something along the line that he is not too worried about blackouts since he has a little generator. Not only is it an inefficient way to use fossil fuels it is also a means of escape for the privileged from a problem he helped creating! How about everybody gets such a device or well let´s just avoid the problem of destabilizing the grid, which would be the most efficient solution!
Was it also him lecturing everybody else how he gets from his (supposedly impressively sized) house near campus to work by bike?
Uh and then there is him “proving” by modeling that the Tonga eruption did not cause any global warming in contradiction to strong empirical correlation.
CO2 related global greening is a well documented fact!´I find it very astonishing that some one is willing to print Desslers rambling that it would be a strawman.
When a so called Professor can pen such hopelessly unscientific opinion as Dressler has here, it is no surprise the quality of our educational institutions are increasingly being questioned.
Can this really be the view of a person expected to set an example to the students and other academics, looking for inspiration and considered opinion.
What has happened in our higher education institutions?
Have they become so wedded to the easy funds from state tax payers, they no longer feel the need to be honest, sceptical or inquisitive any more?
Screwtape was in Thomas Robert Malthus’s ear.
Watch the Soho Forum debate on CO2 between Dessler and Steve Koonin from a couple of years ago. Koonin comprehensively demolishes the fraud Dessler. it is worth watching to the end when Koonin confronts Dessler with his having signed a letter to the Unscientific American magazine attacking Koonin qualifications.
On Youtube https://www.youtube.com/watch?v=4gICW2VL434
Wow, Koonin wiped the floor with him and made him look like a lying fool.
Dessler. Heh. If he looks like a duck, sounds like a duck, and acts like a duck, then he’s a quack.
Greenhouse Carbon Dioxide Supplementation
In general, CO2 supplementation is the process of adding more CO2 in the greenhouse, which increases photosynthesis in a plant. Although benefits of high CO2 concentration have been recognized since the early 19th century, growth of the greenhouse industry and indoor gardening since the 1970s has dramatically increased the need for supplemental CO2. The greenhouse industry has advanced with new technologies and automation. With the development of improved lighting systems, environmental controls and balanced nutrients, the amount of CO2 is the only limiting factor for maximum growth of plants. Thus, keeping the other growing conditions ideal, supplemental CO2 can provide improved plant growth. This is also called ‘CO2 enrichment’ or ‘CO2 fertilization.’
https://extension.okstate.edu/fact-sheets/greenhouse-carbon-dioxide-supplementation.html
According to Mann, only temperature affects tree ring growth.
That is why it is so hard to see Death Valley. All the huge trees get in the way.
There is no debate whatsoever that CO2 is plant food. Why even argue it with the climate denier deniers?
Green plants convert solar energy and CO2 into cellulose, which make up the vast majority of the biomass of any plant species and the world of plants world wide, and oxygen. This has only been known scientifically for hundreds of years after chemical science described CO2 and its role in the biosphere.
The fact that plants need other things does not negate the essential thing that plants need is CO2 without which life would be impossible. The amount of water, or the amount of nutrients, or the quality of soils that plants also need is important to maximize plant growth … but there are plant species that need very little water, or nutrients, or even soil to grow and reproduce. That climate change will somehow remove water from the earth, or will remove nutrients from the earth, or will denude the earth of soils is ridiculous beyond all belief. The climate has always changed, it will always change … and those changes will favor some species over others, while many species will adapt if not be replaced by others.
https://skepticalscience.com/renewables-dont-need-expensive-backup-today.html
dresser has an extremely dishonest article on Renewables posted at skeptical science
Does anyone think dresser is going to be honest with the co2 fertilizer discussion?
His flawed assessment misses on a key point. The Climate Syndicate initiate is to eliminate gas, coal, and oil generators in toto. His assumption that there will always be a hydrocarbon/coal failsafe is no part of the plan.
crops don’t grow in a vacuum, they also need water, temperatures in a particular range, and farmers need predictable seasons. Climate change disrupts all of those.
We’re still waiting for evidence that global warming, er, “climate change” is causing any noticeable “disruption” of water, temperatures, or predictable seasons that harms agriculture. So is the IPCC, which really wants to convince us that it’s an imminent, existential threat. It must drive them nuts to have to accurately report in the “Observations” chapter each time that there is no measurable impact; no trend of more or worse drought, precipitation, wildfires, extreme weather, “unpredictable” seasons, declining agriculture production, etc. They assure us that bad things will happen, though, if we don’t knock it off, because the climate models say so. That silly qualifier is probably the only thing that keeps them from drinking themselves into a stupor over the anguish that reality isn’t complying with their religion.
Perhaps Dressler is competing with Paul Erhlich as to who can make the most erroneous predictions based on unfounded assumptions!!! Dressler has some catching up to do but maybe he can close the gap if he can maintain his foolishness for a while longer.
The difference is that everyone knows Paul Erhlich was wrong. Dresser is being more subtle in his fraud by couching the same Paul Erhlich prediction as “climate science”. Ah! its climate science so the science is solid!
It has electrolytes! *non-descript hand gesture*
“Yes, CO2 enhances photosynthesis. But crops don’t grow in a vacuum, they also need water, temperatures in a particular range…”
But plants require less water – lose less from their leaves – with high C02 levels, which is why “greening” is happening around the margins of deserts which are shrinking.
Commercial greenhouses/nurseries keep C02 levels at around 1 000ppm to 1 200ppm precisely because C02 is plant food. Plants grow quicker and healthier requiring less water and fertiliser… otherwise why go to the cost of installing equipment and buying the gas?
Temperature rage – yes! Range with quite wide latitude.
I used to work in a commercial greenhouse. We kept the CO2 at about 1200 ppm. No, I could not even tell it even when working in it every day. I rode submarines for 8 years in the Vietnam era, where CO2 got to 5000 ppm before the scrubbers were activated.
We rooted cuttings on pea gravel, with misters above. No soil needed until they had their root system going.