Columbia University begrudgingly admits the benefits of CO2 on crops

From the “what took them so long” department….

us grain yields and temperature

Could global warming’s top culprit help crops?
Study looks at how carbon dioxide might cut effects of rising heat


Many scientists fear that global warming will hit staple food crops hard, with heat stress, extreme weather events and water shortages. On the other hand, higher levels of carbon dioxide–the main cause of ongoing warming–is known to boost many plants’ productivity, and reduce their use of water. So, if we keep pouring more CO2 into the air, will crops fail, or benefit? A new study tries to disentangle this complex question. It suggests that while greater warmth will reduce yields of some crops, higher CO2 could help mitigate the effects in some regions, unless other complications of global warming interfere.

The study, by 16 researchers from a half-dozen countries, uses newly available crop models and data from ongoing large-scale field experiments. It appears this week in the journal Nature Climate Change.

“Most of the discussion around climate impacts focuses only on changes in temperature and precipitation,” said lead author Delphine Deryng, an environmental scientist at Columbia University’s Center for Climate Systems Research, the NASA Goddard Institute for Space Studies and the University of Chicago’s Computation Institute. “To adapt adequately, we need to understand all the factors involved.” Deryng cautions that the study should not be interpreted to mean that increasing carbon dioxide is a friend to humanity–only that its direct effects must be included in any calculation of what the future holds.

Many studies say that as temperatures rise, crops across the world will suffer as average temperatures become unsuitable for traditionally grown crops, and droughts, heat waves or extreme bouts of precipitation become more common. Agricultural scientists say that losses could be mitigated to some extent by switching crops, developing varieties adapted to the new conditions, or moving some crop-growing regions poleward. But such adaptations pose daunting challenges.

Due to human activities, average global levels of atmospheric carbon dioxide have risen by more than a quarter since 1960; they now stand at around 400 parts per million, and are expected to keep increasing, along with temperature. At the same time, experiments since the 1980s have shown that higher levels of carbon dioxide in the air helps plants build biomass. The concept is relatively simple; plants take in carbon to build their tissues, and if there is more carbon around, they have an easier time. Leaves take in air through tiny openings called stomata, but in the process the stomata lose water; with more carbon available, they don’t have to open up as much, and conserve moisture.

However, much of the initial evidence for so-called CO2 fertilization has come from lab experiments on isolated plants. These do not account for environmental factors that might affect plants even more powerfully in a warming world, including possibly increased insect and fungus attacks. Thus, suggestions that the greenhouse gas itself might prove a boon to crops have aroused deep skepticism.

In 2014, Deryng and her colleagues published the first global calculation of how heat waves might affect crops, and found that maize, spring wheat and soybeans would all suffer. When they added the effects of carbon-dioxide fertilization, they found that maize yields would still go down–but that spring wheat and soybeans might actually go up. Some media misinterpreted the study to say that climate change might help agriculture overall. The picture is much more complicated, say the authors.

The new study looks at how rising temperatures and carbon dioxide along with changes in rainfall and cloud cover might combine to affect how efficiently maize, soybeans, wheat, and rice can use water and grow. It confirms that heat and water stress alone will damage yields; but when carbon dioxide is accounted for, all four crops will use water more efficiently by 2080.

Based on the current biomass of these crops, water-use efficiency would rise an average of 27 percent in wheat; 18 percent in soybeans; 13 percent in maize; and 10 percent in rice. All things considered, the study projects that average yields of current rain-fed wheat areas (mostly located in higher latitudes including the United States, Canada and Europe), might go up by almost 10 percent, while consumption of water would go down a corresponding amount. On the other hand, average yields of irrigated wheat, which account for much of India and China’s production, could decline by 4 percent. Maize, according to the new projections, would still be a loser most everywhere, even with higher water efficiency; yields would go down about 8.5 percent. The study is less conclusive on the overall effects on rice and soybean yields; half of the projections show an increase in yield and half a net decline.

Deryng says the study is sturdier than past research, because it uses new data from experiments done in actual farm fields, and a half-dozen global crop models, several of which only recently became available. Nevertheless, she says, the uncertainties remain large. Field experiments, which involve blowing CO2 over sizable farm fields for entire growing seasons, have been done only at a handful of sites in the United States, Germany, Australia, Japan and China–not in Africa, India or Latin America, where subsistence farming are mainstays of daily life. She noted that greater yield also might not translate to more nutrition. For example, greater carbon uptake might not be balanced by other nutrients such as nitrogen, and trace elements like zinc and iron that are needed to make crops nutritious.

Bruce Kimball, a retired researcher with the U.S. Department of Agriculture who has studied crop-CO2 interactions, said the paper does “a good job on a huge scale,” though, he said, “more data from more crops from more locations” is needed.” Kimball cautioned also that previous research has shown that the benefits of higher CO2 levels tend to bottom out after a certain point — but that the damage done by heat only gets worse as temperatures mount. “Thus, for greater warming and higher CO2 the results would likely be more pessimistic than shown in this paper,” he said.


The paper, “Regional Disparities in the Beneficial Effects of Rising CO2 Concentrations on Crop Water Productivity,” is available from the lead author or the Earth Institute press office.


113 thoughts on “Columbia University begrudgingly admits the benefits of CO2 on crops

  1. So, any paleodata on crops raised during the MWP, RWP, Minoan….? Those periods were warmer than we (might) be by the end of the century.

      • Yes, good point.

        Mike Piltdown Mann made all climate variation before the present go away. The climate never changed until mankind invented SUVs. So it has to be CO2, right?


        PS: Sue me Mike.

    • Crops back then were so different from what is being grown today, that I’m not sure how useful such dirct comparisons would be.

      • The steep rise in production is associated with chemical fertilizers under irrigated condition using high yielding varieties. This increased in area. In 2003, I presented a paper [chapter] to a book wherein I showed the paddy yield before green revolution and after green revolution. Before green revolution it was 1300 kg/ha. After green revolution, this has increased to 1800 with high yielding seeds [1300 + 500 kg/ha]. With the chemical fertilizers use this changed to 3800 [1300 + 500 + 2000 kg/ha]. Presently it is around 2600-2800 kg/ha, though research station yields were 5000 to 6000 kg/ha. The soil lost its yielding capacity with year after year on the same piece of land chemical fertilizers are used. Traditionally green manure, farmyard manure are the fetilizers. The chemical inputs has its side effects that are not going in to cost of production are soil, air, water & food pollution and thus water resources and health of life forms are affected.

        Dr. S. Jeevananda Reddy

    • Except that these days, what is patently obvious needs to be ‘verified’ by extensive and expensive study programs in academia, providing numerous opportunities for various individuals to write papers that allow them to add FFD to their name, and strut their stuff as ‘experts’.

      • They’re scurrying around like rats leaving a sinking ship. They’re all just looking for some new way to ride the government funding gravy train (GFGT for those gov. employees that only understand acronyms). They’ve been harping for years that the science is settled and 97% agree. Now that people are taking them for their word why would anyone want to continue spending $1.5 billion a year (or so) on researching a dead topic?

    • Yes ioira, the concept was also taught to me in grade school. And, the DOE FACE studies showed this with real experiments when CO2 was released in fields of cultivated crops. Guess it is possible to reinvent the wheel over and over in climate seance.

      • This false statement was bothersome.
        “However, much of the initial evidence for so-called CO2 fertilization has come from lab experiments on isolated plants”
        Why?, because there have been hundreds of real world studies, encompassing thousands of experiments.
        The biased statement is so misleading. The term “initial evidence” is not cogent to current understanding. It is not “so called” CO2 fertilization. It is CO2 fertilization. A simple look at the web site CO2 science would have answered all their questions, as well as alleviating their fears, and their implicit trust in IPCC estimates of increased droughts and heat waves based on the model mean warming, is not reality, which contradicts the models.

      • A simple look at the web site CO2 science would have answered all their questions, as well as alleviating their fears…

        Yes, but anyone who disagrees with or questions the True Believers’ talking point enviro “science” is obviously evil, in the pay of Big [insert demonized organization here] and deserves to be attacked. Obviously. The fact that anyone questioning their beliefs also potentially threatens their income source is immaterial, they’re Saving The Planet™, don’t you know, why do you hate the planet?

      • DavidA,

        I seem to remember several photosynthesis studies done in corn fields in (I think) Iowa where it was shown that on calm days, photosynthesis shuts down by 11AM due to depletion of available CO2. That is a definite showing of CO2 influences on growth rate and productivity. If photosynthesis is stopped for 3 or 4 hours during the 12 or so hours of sunlight that is a 25-33% reduction in productivity.

        I never saw studies where they released CO2 into the fields to see if they could boost productivity though. It seems to be a logical extension of the CO2 monitor experiments.

      • David A April 21, 2016 at 3:05 am This false statement was bothersome.
        “However, much of the initial evidence for so-called CO2 fertilization has come from lab experiments on isolated plants”

        It is not only what you are saying, David, It is also disregarding the whole chain of causality that biochemistry has been building during the last 80 years. The Calvin cycle, the structure of enzimes like Rubisco, the MIchaelis Menten kinetics, and everything else that biochemist have been doing to understand plant metabolism and physiology.

        It almost reads as if this guy is still in the seventeenth century and he is disagreeing with van Helmont’s five year tree experiment.

  2. I was watching BBC’s documentary “The Truth About Calories” last night and their presenter would not use the term CO2 when 1) discussing how fruit converts sunshine to calories; and 2) he had to use a CO2 canister to foam a dessert — he called it “a gas” because I guess CO2 can never be beneficial. #1 was particularly egregious because he forgot the H2O part of photosynthesis.All-in-all a waste of my time.

    • I occasionally have reason to point to a tree when someone comes on too strongly about CO2. I ask them what the two predominant chemical components are. Astonishingly few can say CO2 and water. Their eyes often open wide when they actually grasp the fact that ALL the carbon in the tree is fixed from the atmosphere. The water and the minor amounts of nitrogen and trace elements that are present derive from the soil, even though nitrogen is one of the abundant gases in the atmosphere, but by and large that tree is simply water and CO2. I’ve had people, even ones with college educations blurt out, “that can’t be true!” And then – I sketch an approximation of the Geocarb III curve and explain just how very critical the real carbon situation may actually be – and not because of any excess.

      • Trees are also water fountains, almost all of the water passes through and is ejected into the atmosphere. Lets watch this educating video again:

      • Oh well done Duster – I have done exactly this myself – it is extraordinarily satisfying and powerful to see the penny drop. Well done – let’s all keep doing this.

  3. As I understand things, some of the most fecund periods, for both flora and fauna, in earth’s history occurred when the temperature was warmer and the atmosphere had higher CO2 content.

  4. This brings to mind my thoughts on sea level rise “Let us know when data shows that sea level rise is above 7mm per year”. Along the same line of reasoning ” Let us know when the yield of the maize crop drops, along with verifiable evidence that the cause was CO2 related”.

  5. Alarmist Paper:

    Models say it will be bad, so we have to drop emissions…..

    Skeptical Paper:

    Observations say good, but we have to be cautious because the models say bad.

  6. Well, the study gives a thumbs up to 550 PPM.

    Given that the likely peak CO2 is going to be around 460 PPM this is good news.

    • Cue Bill McKibben to form

      ….. ooops, he’s on record as saying that 400 ppm causes disastrous hurricanes, but in climate fuckw!ttery, who cares any more.

    • I and my green friends wants 1200 ppm to be comfortable.
      Remember, photons manufactures plants out of carbon dioxide.

      • No, photons manufacture ATP and NADPH from water! The CO2 phase doesn’t involve photons at all, if the temperature gets too high for most plants (C3s) this second phase starts to fail. Thus evolution developed C4 plants which bypassed this temperature impaired stage. The study referenced in this post compares one C4 plant (maize) with C3 plants (spring wheat, soy).

  7. yes and it assumes all crops grown will remain at the same locations or latitudes.

    The maize discussion amazes me considering that it is grown from Northern Europe to Africa and it does quite well yet a single degree rise will drop production 8%. The temperature spread is 10C over these regions yet the fools in the South continue to waste their lives trying to grow it.

    • Well… yeah.

      Some of these scientists either haven’t seen a farm before or are on crack.

      Anyone who actually has been on a farm before wonders what diploma mill these guys get their degrees from.

      If you look crops like French grapes, the season is starting sooner.

      A faster maturing corn or an earlier planting avoids peak temperatures.

      A slow maturing more heat tolerant variety would get enormous.

      2/3 of the global warming effect is higher low temperatures or a much longer growing season.

      • When I was growing up around cornfields, it was the timing of the rainfall that determined yield, not the temperature. Hot summers with frequent afternoon thunderstorms (minus the tornadoes) made for the highest yields. Very wet springs were a real problem because planting might get put off until late April. (Getting the neighbors horses out to pull the tractors out of the mud was great fun as a kid, but I did learn some colorful language on those days)

        Water is probably the most important element in farming, but I keep hearing people go on about temperature like they know something nature doesn’t. Now if I am going to grow English Peas, I know to plant them in February here in Georgia so I can harvest them in April before it heats up. Corn and Beans go in the ground in March for best results for my kitchen garden. I used to say March 15 for tomatoes around here, but we keep getting late frosts into the first of April so have pushed that back a bit now. This is the first year in the last five that I haven’t lost the early buds on the figs to a late March frost, so I am looking forward to a good crop this year. I am not seeing the effects of global warming here, just weather.

    • You should see the temperature range from South Texas to North Dakota. It’s got to be every bit of 10c and yet corn, wheat and loads of other crops are grown in these states.

      • My daughter is a researcher for Pioneer. Maize has become so important that varieties are now optimized for very modestly sized regions. The varieties grown in Texas are entirely separate from those in North Dakota.

        That means of course that IF the earth warms by a degree, it would be pretty trivial to just switch to varieties optimized for slightly warmer climates. The huffing and puffing by the dubious “expert” scientists is hilarious.

      • Tom, not to mention that a warmer world also opens up 10’s of thousands of acres that are currently too cold.

  8. Not to mention: “Forest growth accelerating in B.C. due to carbon dioxide ‘fertilizer effect'”
    “Rising levels of carbon dioxide in the atmosphere are accelerating the growth of B.C.’s forests by one to three per cent a year, enough to cancel out the impact on the climate from the mountain pine beetle outbreak by 2020, according to a new study from the Pacific Institute for Climate Solutions.” …
    Published on: April 11, 2016 | Last Updated: April 11, 2016 4:36 PM PDT

    • If they would actually practice good forestry and thin the trees by selective cutting (more expensive – but still profitable) they could eliminate the Pine Beetle infestation once and for all.

      • Not saying you’re wrong about that, but my understanding is that this beetle spreads via flight and it normally is killed off by cold winters which BC hasn’t experienced in a while.

      • Arbeegee,

        It is a complicated infestation. Yes they fly, but they prefer to fly short distances. Tree density is probably the most common attribute in these outbreaks, but you can get smaller outbreaks in even the best kept forests. The difference is in how far the outbreak spreads.

  9. I wonder how they teach our children today about CO2, plant life, and oxygen generation? Do they just ignore the whole cycle? Or are they just taught CO2 is a polluting gas and leave it at that? This is another sinister aspect of the AGW scam that’s going to impact us in generations to come.

    • It helps to use the slovenly “carbon” word as a catch all for anything we don’t want to bother to understand.

    • “Or are they just taught CO2 is a polluting gas and leave it at that? ”
      Five years ago at my sons high school open house I asked each of the fie students doing CAGW presentations if they knew of ANY benefits from CO2. Not one could think of any.

    • Earlier I posted about the CO2 studies in corn fields where it was found that on clam days Corn actually uses all available CO2 by late morning and sits there waiting for a breeze to restart photosynthesis. From that, I could see CO2 limiting being a serious problem for corn.

  10. They need to do another study of the effects of CO2 on plants without including the “increasing” warming. What would it look like if the CO2 keeps rising, and the temperature stays the same? Which is what is happening now.

    • no study needed … increased warming leads to more faster growth where I live. Cold temps and the tomatoes don’t grow.

      • In South Western Ontario, Canada the intensive hydroponic greenhouses have been enriching their atmosphere with CO2 for better crop yields for years. Initially they paid for CO2 and latterly they use the scrubbed exhaust from their combined cycle electricity and heating systems. These growers are savvy business people and know how warmer temperatures and higher CO2 concentrations can improve yield and profit. Who would (carbon) credit it?

  11. When I saw “higher levels of carbon dioxide–the main cause of ongoing warming” in the introduction I was tempted to stop reading at that point.

    Ian M

    • Exactly: here we have 16 authors from several different organizations saying “main cause”, so it goes into Cook’s “definite file” for consensus. It also pads 16 lists of publication and provides backing for all the organizations to seek more government funding. Pretty well covers it all.

  12. “Thus, suggestions that the greenhouse gas itself might prove a boon to crops have aroused deep skepticism.”

    By Crikey – Reverse Skepticism!? (:-)

  13. The correlation between yield and temperature is quite weak. For example, temperature stayed roughly constant for the first 15 years in the given graph, before going up, while yield increased at roughly the same rate throughout. The correlation between yield and atmospheric CO2, though, is much stronger (and is similarly strong quite a bit further back than shown in thee graph) in that both increase fairly steadily. A caution is needed, of course: if two factors correlate simply because they both go in a straightish line then there may be no causal link between them at all.

    • Right . I know from seeing it the density of corn planting and hybrid increase in ears versus size of the waste plants in Illinois has virtually eliminated rows you can walk between . That is thoroughly confounded with increased CO2 .

  14. A couple of questions have been buzzing around in my head for some time:

    1. What is the ambient CO2 level in the vicinity of coal fired power plants?

    2. If ambient CO2 in these locations is significantly higher than locations without local CO2 sources, what can be determined about nearby crop yields?

  15. The “food” for plants is sunshine, water, CO2 and soil (Carbon and other elements).

    The higher the CO2, the more plants will grow AND the less water they need to grow more productively.

    It is simply a fact. Climate Science does not like facts and prefers emotional reasoning and peer pressure to conform.

    • Yes, and the alarmists add in questions that hint at negatives to CO2 that have been answered.
      “For example, greater carbon uptake might not be balanced by other nutrients such as nitrogen, and trace elements like zinc and iron that are needed to make crops nutritious.
      CO2 has been found to also make plants more nitrogen efficient. It is desperation for funding, and nothing more.. All their predicted harms happened in areas they did not do studies and are based on IPCC models that predict far more warming and droughts then are occurring.

      The benefits of CO2 are KNOWN and manifesting, the predicted harms are MIA. Currently about 15 percent of the GLOBAL populations food supply is due to the benefits of CO2 growing more food, with zero additional water or land requirements! If atmospheric CO2 content was instantly reduced to 280 PPM, global famine and war would result.

  16. The best way to see how well crops of all types are doing is to look at the costs of said crops on the commodities exchange. As best as I can tell the world is awash in most crops.

    • Warmists value precision over accuracy. That’s the problem. They often get good groupings (could be from poking holes afterwards, though) at 50 yards but they’re hitting the wrong barn door.

  17. A few crops here, a few crops there, pretty soon we’re talking real food.

    How off message is that?
    Blasphemy really.
    Can’t have more food to feed the masses because of fossil fuel emissions.

    Heck, Bernie is still griping about fracking.

    Where’s this all heading?
    We have to just wait. Maybe another 12 years or so for the sheep and charlatans to acknowledge there is nothing calamitious happening with our climate.

    Then it will be known that all of the watching, monitoring, measuring, pondering, pontificating, publishing and hysteria will have been for nothing.

    And the billions……

  18. “Many studies say that as temperatures rise, crops across the world will suffer as average temperatures become unsuitable for traditionally grown crops, and droughts, heat waves or extreme bouts of precipitation become more common.”

    Temperatures have already been rising; not much, in fact precisely how much is unknown, but temperatures have risen. Crop yields, on average, have not suffered. A simple google search will yield plenty of data on crop yields to date. Here’s one:

    When does the temperature rise start to make crops across the world suffer and what temperature is unsuitable for traditionally grown crops? Because so far, no such effect has been observed. And it is getting hotter. Not much hotter, but it has gotten a bit hotter.

    And when are heat waves or extreme bouts of precipitation going to become more common? Because, again, Google it, they are not more common. And note, there have always been heat waves, bouts of precipitation, and even cold snaps, hot Februarys, cool summers etc.

    Slightly warmer weather and more CO2 fertilizer would only stand to reason that more plants would grow. How is this a problem?

    • If it does get much hotter, then Canada and Russia in particular will be able to produce dramatically more food.

  19. No mention of other advances in agricultural practices, fertilizer application, crop rotation, tilling practices. In any case, it is all good news that CO2 is an added benefit amongst other modern crop management improvements.

    Also earlier first frost and later last frost will only increase the growing season. If it every gets to the point of multiple crop plantings in temperate climates, then the per hectare yield rates will increase again – thanks AGW (in moderation) – a true friend to crop yields.

    Sadly the authors will be banished/shamed by the AGW “in group” and grants rescinded. No good news goes unpunished.

  20. So basic biology is no longer understood by “scientists”?
    Some old fable about life being limited by the least available input.
    But then I guess the cult can not admit that photosynthesis requires carbon dioxide.
    I wonder what they eat.
    Got to admit I am running out of sympathy for the Cult of Calamitous Climate, seems only reasonable that persons obsessed about “carbon pollution” might be fools.

  21. The paper is a collection of whinges about possible risks that are not in evidence. Why not write a paper with the negatives, all rooted in questionable models without demonstrated skill, surrounded by caution and state outright that CO2 fertilization is a plus. That at least is known. The rest, kowtowing to the CAGW meme. Why bother?

  22. LA Times also picks up on the Duke/NYU study Guardian wrote about in Reasonable Skeptic’s comment above. funny how behind every CAGW silver lining there is always a cloud!

    20 Apr: LA Times: Sean Greene: Global warming has made the weather better for most in U.S. – but don’t get used to it, study says
    Since Americans first heard the term global warming in the 1970s, the weather has actually improved for most people living in the U.S. But it won’t always be that way, according to a new study…
    Research shows Americans typically — and perhaps unsurprisingly — like warmer winters and dislike hot, humid summers. And they reveal their weather preferences by moving to areas with conditions they like best.
    A new study in the journal Nature has found that 80% of the U.S. population lives in counties experiencing more pleasant weather than they did 40 years ago.
    “Virtually all Americans are now experiencing the much milder winters that they typically prefer, and these mild winters have not been offset by markedly more uncomfortable summers or other negative changes,” write Patrick Egan, a political scientist at New York University, and Megan Mullin, professor of environmental politics at Duke University.
    It’s hard to complain about sunny days, but the researchers foresee a problem. If Americans think climate change has benefited their lives so far, they’ll have little motivation to demand action or overcome apathy in responding to global warming, the scientists write…

  23. “The first results from the field station, known as the Soybean Free Air Concentration Enrichment—SoyFACE for short—were jarring. Under these realistic field conditions, elevated carbon dioxide boosted yields of soybean and corn only half as much as it did for plants in enclosures. “Higher carbon dioxide does lead in an agricultural context to more production,” DeLucia says. “But that increase in production has been greatly overestimated by experiments done in enclosures.”


    more carbs AND more proteins. We’re doomed

  24. All biological production comes from photosynthesis. CO2 and H20 provide all the mass, the sun provides all the energy to combine the mass into glucose. All the CO2 comes from the atmosphere into the leaf stomata, all the H2O comes to the leaf via the roots.
    If the wiki page is correct, about 115 gigatonnes of biological mass is produced every year by photosynthesis. Photosynthesis removes about 170 gigatonnes of CO2 from the atmosphere to create that biomass.

    Some life, such as fungi or bacteria get their energy indirectly via the autotrophs.

  25. I made a comment about the beneficial effects of a higher CO2 level re crop increases and so being healthier and a plus for us, the attack was the: Oh that is not true! I was told the warmer and the more CO2 it gets plants would shut down ( they do during the hottest part of the day no matter what the CO2 or H2O levels are). but the attack was scary. I had to block the sender eventually.

  26. …higher levels of carbon dioxide–the main cause of ongoing warming–…

    Hey, Columbia University. Please prove this statement with actual data. Thanks in advance.

  27. Oh – I get it: Crop yields in the US have increased over the last 55 years. So has CO2

    So?? – Agricultural efficiency has not??

    Trash science

    • Not exactly. While they probably should have mentioned that there were other factors involved, still, they didn’t say that CO2 was the only reason for the increased crop yields.

  28. The Climate Change Fever should break once a few of its shaman priests go to the nether world.

  29. Huge uncertainties in CO2 improving plant growth, but they’re dead-set certain that temperatures are rising and it’s all because of man.

    • Mike T. I have not seen much on “Huge uncertainties in CO2 plant growth”. Do you have information on field experiments, satellite data on greening areas of Earth, etc. which show these huge uncertainties? Everything that I have shows a rather low uncertainty on the CO2 – plant growth data.

  30. In the 1970s or very early 1980s I was reading some book saying something about when an uncomfortable heatwave hits Iowa. There was said to be nights in such heatwaves when people had trouble sleeping due to temperature in degrees F and relative humidity both being in the 80s. So people who were kept up at night said they could hear the corn growing. Consider what the daytime temperatures were/are in such Iowa heatwaves. Apparently, such heat does not hurt the kind of corn that is grown there or anywhere nearby.
    And what about crops grown in the Dakotas? America’s crazy weather gets crazier there. For one thing, the highest temperature recorded in USA east of the Rockies occurred in 1936 (121 degrees F) in two states, and one of them was North Dakota. It is a good idea to look up what the highest temperature ever recorded in each of the 50 states was, and when it occurred. Please find this (easy web search), and know what the alltime record highs were in the two states where these are lowest, and what states these are. Hint: Both have had someplace getting accumulating snow in July in a recent year, and one of them is more south than New Hampshire is.

    Manmade climate change seems to be making weather milder, with extreme extratropical heatwaves not getting worse in terms of extreme high temperatures. I consider this expectable, since a driver of weather is temperature gradient between the tropics and the polar regions. The Arctic has warmed much more than anywhere else – that is one thing the models got right. Part of the Arctic warming from the mid 1970s to around 2005 was from the north-warming upswing of the Atlantic Multidecadal Oscillation – which most of the models do not consider, so after 2005 global temperature did not keep up with what most of the CMIP5 models predicted – even excluding the bad-case RCP 8.5. Keep in mind that the north-warming phase of the AMO is a global-warming phase due to surface albedo positive feedback being mostly a northern hemisphere thing due to greater land area with snow variability and greater year-to-year carryover of surplus/deficit from “normal” of sea ice in/near the Arctic than the Antarctic.. Likewise with the north-cooling phase of the AMO.

  31. Has someone decided what the world’s perfect temperature is? Was it 1880 when the average temperature was 13 degrees C, or 1950-80 at an average of 14 degrees, or 2015 (hottest ever) when the temperature averaged 15 degrees C? In Singapore the average temperature is about 27 degrees, yet people and plants seem to survive quite well. On the other hand in Montreal the average temperature is about 6 degrees, while in London the average is 13 degrees C, and plants and people prosper.
    So if the world warms by a further 1 degree, will Singapore become unlivable? Will London and Montreal prosper? Surely crops can be grown in whatever proves to be the optimum locations? Haven’t people and plants been adapting ever since civilization began? Yes, hit by the odd famine and plague and flood, but life goes on and gets better.

  32. “Earth Institute” ! … WTF ! … more like “Grant Theft-a-lot and The Bedwetters’ Bullshit Band”.

    I want mi money back; all of it.

  33. The Alarmist backpedaling continues. They tried to frighten people, and it didn’t work. So now, they have to resort to saying “well, ok, things aren’t scary NOW, but they will be. Because we say so, and because we’re the experts. Just trust us, dammit. Why would we lie?”

  34. “Soybean seed yield was always increased by elevated CO2 Allen et al. (1987)”

    Welcome aboard Columbia intellects.

  35. Paradox seems to revolve around how CO2 elevation cause leaves to partition where increased carbon is shunted inside.
    The relative proportion of carbon made into protein does not keep happening at the same ratio as when leaf under less CO2.

    Elevating al t

  36. Elevating CO2 shunts more carbon into leaf starch. At night, given benign conditions, starch is mobilized for use by the plant.
    This is why we see the yield go up; yet at the same time hear how
    pollen & grain protein is lower when CO2 higher.

    • Some of this CO2 dynamic might (?) be from some way elevated CO2 inhibits the enzyme (cytokinin oxidase) that naturally degrades the plant hormone cytokinin. Cytokinin (phyto- hormone) up-regulates 2 enzyme levels (glucose-6-phosphate ddhydrogenase & 6-phosphogluconate dehydrogenase) integral to leaf using it’s oxidative pentose phosphate pathway, which equates to greater starch metabolism.

      Cytokinin abundance under higher CO2 also partly might explain some other factors. It increases cell cycles (from G1 to S phase &
      possibly G2/M transition … crucial in meta-phase to achieve synchronized cell division after the lag period), integrated in chloroplast maturation, sustains turgor via influencing more cellular water potential leading to less water uptake required, reduces cells uptake of oxygen, conditions DNA leading to initiation of a shoot(s).

      The data discrepancy for crops under elevated CO2 might also
      be a cytokinin feature. Dicotyledon & monocotyledon plants, as well as different strains of the same plant, make different amounts of cytokinin; plus dicotyledons’ sequence pulses of cytokinin & auxin phyto-hormone usually different. It’s RNA (t-RNA) can be found in chloroplasts & cell cytoplasm or it can be in the form of free molecules. Plants make cytokinin in their roots &that moves upward in xylem; the % in leaves is modulated by daily temperature & light (both photo-period & irradiance).

      Higher temperature reduces the level of cytokinin (& raises the ratio of auxin) which may be why maize (already a better CO2 “fixer”) responds less impressively to elevated CO2 in “hot” conditions; while woody bushes/trees have different responses. Expanded range for plants may(?) also have less to do with “theoretical” warmth & more a factor of CO2 level impact on cytokinin which is itself then responding to water vapor. Although cytokinin is not affected by red light intensity (photon
      fluence) it does respond to far red, white & blue fluence; under low fluence of far red light cytokinin holds down the elongation of plant shoots. My surmise is the reported greater moisture content above sub-saharan trees/bush might (?) refract greater
      far-red (pulses of far-red are used to increase bio-mass, which outdoor plants get toward sun down) onto leaves & that allows the CO2 augmented cytokinin to work without inhibiting the shoots it initiated from subsequently elongating; diffused light reflection (rather than direct light) into leaf canopy increases growth.

      Cytokinin reaction to elevated CO2 also can explain the way levels of available nitrogen influence crop yields. This phyto-hormone increases the transcription of nitrate reductase messenger RNA; which improves nitrogen utilization (as earlier commentator pointed out) but does not in itself lead to better protein made from carbon.

  37. It is not mentioned here, but the reason why maize is not so effected by increased CO2 concentrations, is that it is a C4 photosynthesis plant, while the wheats and barleys are all C3 plants.

    C4 plants have a two-step photosynthesis which internally boosts CO2 concentrations in the leaf. Thus C4 plants are reletively impervious to variations in CO2 concentrations, and can also survive in very low CO2 environments.

    So why did C4 varieties not take over the world during the last ice, when CO2 concentrations went down to 180ppm?? Because C4 plants are adversely affected by cold temperatures, which is why sugar-cane and maize prefer tropical and warm regions, rather than the wilds of Ireland or Scotland.

    Not sure if the actual paper mentions this, but it is a bit of an ommission if it does not.


    • C4 plants evolved to deal with high temperatures. Normal photosynthesis is a two step process, the first step is the light dependent stage where the energy from the light is used to break down water into O2 and H+. The O2 is a waste product and the H+ is used to create energetic molecules to be used in the Calvin cycle to produce sugars from CO2. If the temperature gets too high the stomata close to prevent water loss, but this causes O2 to accumulate in the leaf. At the higher temperature and increased O2 the first step in the Calvin cycle stops because of a competitive reaction with O2 instead of CO2. C4 plants evolved to avoid this by adopting a three step process whereby the Calvin cycle is carried out in cells at the center of the leaf away from the cells where the first step occurs and where the O2 increases. They do this by converting the CO2 into 4-carbon compounds and these are transferred to the cells where the Calvin cycle occurs and the CO2 is regenerated to enter the Calvin cycle.

      • Since C4 plants expanded during ice ages, it is more likely that they evolved to endure low moisture and low CO2 conditions. They will, as a by-product of this, also endure higher temperatures, but mostly because they have lower moisture losses. (They have thick cell walls, almost like cacti.)

        It is clear from Tieszen et al that more C4 plants inhabit the low altitude regions of savannah Africa because of the low moisture conditions there, rather than because of the high temperatures. See Tieszen, Distribution of C3 and C4 grasses in Kenya, fig 4.

        In addition, all woody trees are C3, so all the tropical rain forests are C3. So C3 plants can endure and thrive in higher temperatures, even though their photosynthetic efficiency drops off. Note that the efficiency of tropical C3 plants increases markedly with increasing CO2 concentrations, so the tropical C3 trees should be doing better, as well as the African savannah trees.


      • ralfellis April 21, 2016 at 12:16 pm
        Since C4 plants expanded during ice ages, it is more likely that they evolved to endure low moisture and low CO2 conditions. They will, as a by-product of this, also endure higher temperatures, but mostly because they have lower moisture losses. (They have thick cell walls, almost like cacti.)

        No, the pressure to evolve C4 plants is the enhancement of photorespiration in C3 plants which requires high temperature, even during glacial periods the tropics, where C4 plants developed, were still hot and arid.
        Cacti evolved in response to the same stimuli but using a different method, separating the light dependent mechanism from the Calvin cycle temporally by opening the stomata at night and fixing the CO2 overnight and releasing for processing it in the morning. The evolution was relatively recent, within the last 30 million years. At the same time the tropical forests receded allowing more hot arid space where C4 could flourish.

        See, for example:
        Tansley review, “The evolution of C4 photosynthesis”, Rowan F. Sage, Department of Botany, University of Toronto.
        “High temperature is a major environmental requirement for C4 evolution because it directly stimulates photorespiration and dark respiration in C3 plants (Brooks & Farquhar, 1985; Sharkey, 1988). The availability of CO2 as a substrate also declines at elevated temperature due to reduced solubility of CO2 relative to O2 ( Jordan & Ogren, 1984). Aridity and salinity are important because they promote stomatal closure and thus reduce intercellular CO2 level, again stimulating photorespiration and aggravating a CO2 substrate deficiency (Guy et al., 1980; Schulze & Hall, 1982; Adam, 1990). Relative humidity is particularly low in hot, arid regions, which will further reduce stomatal conductance, particularly if the plant is drought stressed (Sage & Sharkey, 1987). Together, the combination of drought, increased salinity, low humidity and high temperature produces the greatest potential for photorespiration and CO2 deficiency (Ehleringer & Monson, 1993), so it is not surprising that these environments are where C4 photosynthesis would most frequently arise.”

  38. I am surprised that green-house growers never comment on this subject. There is a whole industry supplying equipment to add CO2 to closed green-houses, up to 1000 ppm just to ensure that growing veggies have all the CO2 they need to maximize their growth.

  39. .
    This extract also does not explain why water efficiency of wheat will rise so much, with increasing CO2.

    Wheat is a C3 plant, and reacts well to greater concentrations of Co2, and it does so by closing up its stomata and forming less stomata (because it does not always need all that extra CO2). And a smaller stomatal area means less transpiration and water loss. So increased Co2 is highly beneficial to C3 plants growing in arid regions, which is why the African savannah especially is greening so rapidly. Although you will not find this info in the mainstream press.

    CO2 fertilisation of desert lands.

    More CO2 fertilisation on the African savannah. This study is interesting, as they are saying that improved tree growth due to increased Co2 is now a threat to wildlife, and are thinking of how to limit the increased tree growth.

    Picture gallery – some interesting picture comparisons with 90 years ago, demonstrating the dramatic extent if CO2 fertilisation. (There may be elements of reduced grazing, but a study would sort out the differences.)


    Please send these pictures to your local and national newspapers, and ask them why they are not running stories on the benefits of increased CO2. Why are they only pandering to the scare stories of Big Green?


  40. Kimball cautioned also that previous research has shown that the benefits of higher CO2 levels tend to bottom out after a certain point — but that the damage done by heat only gets worse as temperatures mount.

    As far as I can tell, nobody expects the CO2 level to exceed 800 ppm. Extra CO2 is beneficial up to as much as 1000 ppm. See graph Figure 1 in the article liked below.

    Increasing the CO2 level from 340 ppm to 500 ppm increases the growth by 15-25%, while an increase from 340 ppm to 700 ppm potentially increases plant growth by 30 to 40%. Beyond 700 ppm, the effect of more CO2 gets smaller. Beyond about 1,000 ppm, the line is nearly horizontal, … link

    As for temperatures, it has been warmer than now during the Minoan, Roman, and Medieval warm periods. Plants and people prospered. link CO2 is good and we don’t have to worry about “the damage done by heat”.

  41. My freshman ag teacher was telling me this was probably why corn yields in low lying area’s of fields was higher than the hill tops in 1962, I’ve seen nothing to refute that since.

  42. It is truly amazing that the authors of this study consider projections of doom and gloom from the IPCC to be more credible than “evidence for so-called CO2 fertilization has come from lab experiments on isolated plants.” Actual data from experiments is not as credible as unproven projections by the IPCC. Simply amazing!

  43. So crops are better with warming and a new study in British Columbia found forest regeneration better than expected as a result of elevated CO2 . Gee all they had to do was talk to some greenhouses . What’s next fewer of those tens of thousands of fuel poverty deaths caused by the poor no longer able to pay their goofy feed in tariff rip off heating bills ? What scary global warming ? Time for a costume change Kermit .

  44. You folks all carp about the scientific model that predicts the effects of climate change, yet you all get elated over a report of a model that predicts climate change events that will come to pass in 2080. Why is one model, that you disagree with, any better or worse than another model, that you agree with? Where’s the logic?

    • Robert B Bregman commented : “…You folks all carp about the scientific model that predicts the effects of climate change, yet you all get elated over a report of a model that predicts climate change events that will come to pass in 2080. Why is one model, that you disagree with, any better or worse than another model, that you agree with? Where’s the logic?…”

      Because one model is verified by empirical evidence and the other fails. Is this a trick question?

  45. The Australian Grains Free Air CO2 Enrichment (AGFACE) program has been running since 2007 and has found many positives, results are summarised here with links to detailed reports,
    Increased yields were often accompanied by reduced protein, but this is a normal situation in real world cropping, wetter years generally see higher yields, but lower protein content, whilst drier years see reduced yields and higher protein content.
    What I think is important is that in the AGFACE trials, whilst % protein may decline in the grain, when the higher yield is taken into account, the amount of protein produced per hectare increases meaning more people can have their protein supplied from the same area of land.

Comments are closed.