Study: Global Warming Will Cut Crop Yields – Assuming No Adaption

Obligatory smokestack image for any mention of energy and CO2

Guest essay by Eric Worrall

A PNAS study claims that crop yields will fall by up to 7% for each degree celsius of global warming, assuming no CO2 fertilisation and no adaption measures.

Climate change will cut crop yields: study

August 15, 2017

Climate change will have a negative effect on key crops such as wheat, rice, and maize, according to a major scientific report out Tuesday that reviewed 70 prior studies on global warming and agriculture.

“Each degree Celsius increase in global mean temperature is estimated to reduce average global yields of wheat by six percent,” said the report.

Rice yields would be cut by 3.2 percent, and maize by 7.4 percent for each degree of Celsius warming (almost two degrees Fahrenheit), it added.

Estimates of soybean yields did not change significantly.

Read more: https://phys.org/news/2017-08-climate-crop-yields.html

The abstract of the study;

Wheat, rice, maize, and soybean provide two-thirds of human caloric intake. Assessing the impact of global temperature increase on production of these crops is therefore critical to maintaining global food supply, but different studies have yielded different results. Here, we investigated the impacts of temperature on yields of the four crops by compiling extensive published results from four analytical methods: global grid-based and local point-based models, statistical regressions, and field-warming experiments. Results from the different methods consistently showed negative temperature impacts on crop yield at the global scale, generally underpinned by similar impacts at country and site scales. Without CO2 fertilization, effective adaptation, and genetic improvement, each degree-Celsius increase in global mean temperature would, on average, reduce global yields of wheat by 6.0%, rice by 3.2%, maize by 7.4%, and soybean by 3.1%. Results are highly heterogeneous across crops and geographical areas, with some positive impact estimates. Multimethod analyses improved the confidence in assessments of future climate impacts on global major crops and suggest crop- and region-specific adaptation strategies to ensure food security for an increasing world population.

Read more (paywalled): http://www.pnas.org/content/early/2017/08/10/1701762114

This is a good example of climate hype.

The authors of the study did the right thing, they explained their study ignored real world factors such as adaption, genetic improvement and CO2 fertilisation. There is a place in science for careful studies which seek to adjust just one factor, to study the impact of that adjustment. But their study has been spun into a narrative of failing crop yields.

In the real world, any deficit is more than compensated by the factors the study excluded.

CO2 fertilisation has a dramatic effect on plant growth. The slight rise in CO2 levels to date has measurably greened the world. Commercial greenhouses take this a lot further; they burn vast quantities of natural gas and discard the heat, just to produce enough CO2 for their plants to maximise growth – usually around 1000ppm, more than double current atmospheric levels.

Genetic improvement, production of species such as dwarf rice, can have a huge impact on yield. The world may be on the cusp of truly decoding the genetic blueprint, of an unprecedented level of understanding and control over crops and farm animals. There is plenty of scope for further advances.

As for adaption – down here on the edge of the tropics, we have a simple adaption we use to grow temperate vegetables which can’t tolerate our tropical Summers; We plant them in Autumn. The vegetables grow happily through our very mild winters, and fruit in Spring, before the Summer heat kills them.

I suspect a lot more global warming would be required to allow temperate Northern Hemisphere farmers to plant tomatoes unprotected outdoors in Autumn.

Edit (EW): The following image demonstrates the dramatic effect of CO2 fertilisation on plant growth.

Reproduced with permission, copyright Dr. Craig D. Idso.

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132 thoughts on “Study: Global Warming Will Cut Crop Yields – Assuming No Adaption

  1. Rubbish.

    IPCC assumes that warming causes more water vapor to enter the air, hence more rainfall. A warmer world is less windy, as well, leading to less evaporative loss of soil moisture.

    But even if yield fell, growing seasons would be longer at higher latitudes, producing more wheat.

    Yields won’t fall, however, thanks not just to more moisture but from CO2 fertilization and less water lost to transpiration.

  2. “There is a place in science for careful studies which seek to adjust just one factor” Caeteris paribus. Goes nicely with controlled experiments. Unfortunately, you can’t do such experiments with Earth. You have no control Earths and cannot vary one factor only to see what happens. Those are some reasons why climastrology is a pseudo science.

    • I think you are being way to generous in calling climastrology a pseudo science. It’s more like a religious fanatics superstition. :)

    • Thanks Ted, I would’ve pointed it out if you hadn’t. I’m not normally a grammar n@zi, but that word in the headline is just screaming at me. Please fix it author and/or editor.

    • That study wasn’t on the effect of temperature, but on the effect of CO2. The “less nutritious” food was the result of fertilization *increasing* yields, spreading nutrients over a larger volume in cases where the nutrients are limited. Since this study claims reduced yields, perhaps it should be spun as “Global warming will make food more nutritious”.

      Even apart from ignoring CO2 fertilization, any study that assumes no adaptation is completely unrealistic — and completely irrelevant to the policy issue of whether adaptation or attempted mitigation is a better strategy.

    • Griff,

      another prediction.

      Have a look at how dismal previous predictions of crop disasters were since the 60’s

      https://aleteia.org/2017/08/10/the-end-of-the-world-is-always-10-years-away/

      Then look at the record grain crops in 2016, remember 216, it was the hottest year evah, until 2017 of course. Should have been a disaster for crops, but apparently not.

      http://timesofindia.indiatimes.com/india/govt-revises-foodgrain-output-to-record-275-68-million-tonnes/articleshow/60090001.cms

      • “Then look at the record grain crops in 2016, remember 2016, it was the hottest year evah, until 2017 of course. Should have been a disaster for crops, but apparently not.”

        That’s what I was thinking, too. Here we are in the hottest year evah! and crop yields are up. It’s also the mildest year evah! The greater danger to the crops this year would seem to be early freezes.

    • No he wouldn’t because then there would be no one for him to scare. On the other hand everyone who was dead would have the not to be underestimated advantage of not having to suffer anymore of his extreme alarmist misrepresentations.

      • Griff’s little rants don’t scare anyone except himself.

        It so funny watching him DENY anything that could alleviate his constant chicken-little mentality.

    • Here in the Western Canada grain belt we grow a fair bit of food for the rest of the world. When I was a kid in the 60’s it was not uncommon for late spring or early fall frost to wreck otherwise promising crops. Dry years were not unusual either, and the mid-80’s and mid 90’s were quite hot and dry. I would guess that since approximately the late 1990’s we have had fairly wet weather ( it was supposed to be ongoing drought), almost no crops lost to frost and multiple bumper crops. I read about a year ago that the world had the highest cereal stocks in storage in history. When I was a kid, starvation was taking place somewhere in the world on a massive scale almost continuously. Meanwhile, the population of the earth has grown by about 4 billion people.
      This constant doom mongering is just laughable. Somehow, the solution is for governments to throw money down holes. All they do is lie about reducing CO2. They waste billions that real people could use to actually improve their lives. The associated borrowing drives up costs for everything. The taxes they take out of the economy are diverted from more productive efforts. The CO2 they pretend to reduce has no apparent effect on the environment ( 18 years and counting). The free market will do what needs to be done to provide adequate energy at best price. The mechanisms of government are now owned by the left and utterly self serving and incompatible with individual freedom and responsibility.

      • John Harmsworth – thank you – an excellent post!

        A few comments:

        a. You wrote:
        “They waste billions that real people could use to actually improve their lives.”
        Actually, the waste from global warming alarmism now amounts to TRILLIONS of dollars every year.
        For a fraction of this amount, we could put clean water and sanitation systems in every village in the world and run them forever. About 2 million children below the age of five die from contaminated water every year. In the three decades that global warming has been a popular obsession, that is ~60 million kids – more than the people of all ages on all sides who died in WW2. That is just one example of this waste.
        Radical environmentalists are the great killers of our time, ranking with Hitler, Stalin and Mao. Another example of this criminal malfeasance is the ban of DDT, which has realty increased malaria in the tropics – another global scale holocaust based on false environmental alarmism.

        b. You wrote:
        “When I was a kid in the 60’s it was not uncommon for late spring or early fall frost to wreck otherwise promising crops.”
        I remember this too – these crop failures coincided with the global cooling period that occurred from ~1940 to ~1975, even as fossil fuel combustion accelerated from the start of WW2. We published a prediction in 2002 for moderate global cooling to start in 2020-2030. I hope to be wrong about this cooling, because humanity suffers in cooling climates. However, the weak SC24 and predicted weak SC25 – neither of which were forecast in 2002 – could very well lead to moderate global cooling.
        Incidentally, this ~35-year global cooling period proves that climate is relatively Insensitive to increasing atmospheric CO2. The global warming hypothesis is thus falsified.

        c. We made eight predictions in our APEGA-sponsored debate with the Pembina Institute in 2002,and all eight have materialized in those states that embraced global warming mania. In comparison, none of the scary predictions of Pembina and the IPCC have happened – the global warming alarmists have a perfect NEGATIVE predictive track record. Hence, nobody should believe anything they say.

        d. Here is my take on the current state-of-play in climate science, published in 2015:

        https://wattsupwiththat.com/2015/06/13/presentation-of-evidence-suggesting-temperature-drives-atmospheric-co2-more-than-co2-drives-temperature/

        Observations and Conclusions:

        1. Temperature, among other factors, drives atmospheric CO2 much more than CO2 drives temperature. The rate of change dCO2/dt is closely correlated with temperature and thus atmospheric CO2 LAGS temperature by ~9 months in the modern data record. [published on icecap.us in January 2008]

        2. CO2 also lags temperature by ~~800 years in the ice core record, on a longer time scale.

        3. Atmospheric CO2 lags temperature at all measured time scales.

        4. CO2 is the feedstock for carbon-based life on Earth, and Earth’s atmosphere and oceans are clearly CO2-deficient. CO2 abatement and sequestration schemes are nonsense.

        5. Based on the evidence, Earth’s climate is insensitive to increased atmospheric CO2 – there is no global warming crisis.

        6. Recent global warming was natural and irregularly cyclical – the next climate phase following the ~20 year pause will probably be global cooling, starting by ~2020 or sooner.

        7. Adaptation is clearly the best approach to deal with the moderate global warming and cooling experienced in recent centuries.

        8. Cool and cold weather kills many more people than warm or hot weather, even in warm climates. There are about 100,000 Excess Winter Deaths every year in the USA and about 10,000 in Canada.

        9. Green energy schemes have needlessly driven up energy costs, reduced electrical grid reliability and contributed to increased winter mortality, which especially targets the elderly and the poor.

        10. Cheap, abundant, reliable energy is the lifeblood of modern society. When politicians fool with energy systems, real people suffer and die. That is the tragic legacy of false global warming alarmism.

        Allan MacRae, P.Eng. Calgary, June 12, 2015

    • heh- it’s not a study if it begins with the premise that reality is impertinent, yo
      “new study finds that, assuming there is no gravity, MODELS forecast a moar UNPRECEDENTED increase in the number of people who float to the moon than EVER in recorded history!”

  3. Yes, adaptation is an important consideration and those plants that have not fully adapted to the historically low CO2 levels (at least compared to when those plants evolved), will benefit greatly from increased atmospheric CO2. I’ll say it again, once we run out of fossil fuels, our biggest concern will be how to boost atmospheric CO2 levels in order to prevent agriculture from crashing. I foresee the solution being many thousands of cement kilns across the world liberating CO2 from limestone. Of course, we’ll still need cheap electricity to run them …

  4. This article utilizes the “stupid people hypothesis” while simultaneously ignoring fertilizer value of CO2. All that remains is propaganda.

  5. The first negative feedback loop is warmer oceans means more clouds that cool the planet.
    The clouds that we see in the sky
    is really the reason for why
    we will not overheat;
    Shields us from solar heat.
    A feedback on which we rely.
    The second negative feedback loop is organic. More CO2 means more plant growth. According to NASA there has been a significant greening of the earth, more than 10% since satellite measurements begun. This results in a cooling effect everywhere, except in areas that used to be treeless where they have a warming effect. The net effect is that we can now feed 2 billion more people than before without using more fertilizer. Check this picture from NASA, (now they can publish real science again) showing the increased leaf area extends nearly everywhere.

    In addition, more leafs changes the water cycle, increases evapotranspiration, and more trees and vegetation reduces erosion and unwanted runoff. Good news all around.

    In short, taking into account the negative feedback occurring the earth will warm up less than 0.5 degrees from now, not at all in the tropics, and less than 3 degrees at the poles. Without the Paris agreement there will be no increase in the death rates in the cities, except from the slight increase of city temperatures due to the urban heat effect. With the Paris agreement we will have to make draconian cuts in our use of electricity, meaning using much less air conditioning and even less heating, and life expectancy will decline.
    More https://lenbilen.com/2017/07/20/rising-co2-more-clouds-a-blessing-or-a-curse-a-limerick/

  6. The authors forecast declines in crop yields due to future warming if other real world factors are ignored. Do they at least note that the real world effect of past warming has been the opposite?

  7. Meanwhile in the real world crop yields continue to inexorably increase. Better methodology, better equipment, better tech’, better practices. How inconvenient.

  8. OT, but saw this today, another benefit of anthropogenic CO2, : “Tsar Bomba had other effects. Such was the concern over the test – which was 20% of the size of every atmospheric test combined before it, von Hippel says – that it hastened the end of atmospheric testing in 1963. Von Hippel says that Sakharov was particularly worried by the amount of radioactive carbon 14 that was being emitted into the atmosphere – an isotope with a particularly long half-life. “This has been partly mitigated by all the fossil fuel carbon in the atmosphere which has diluted it,” he says.

    • ” – an isotope with a particularly long half-life”

      So that means is it very LOW activity. If you have a lump of plute, there may be enough mass concentrated in a small volume for this to still be highly active and dangerous.

      At the height of airborne testing C14 was about double typical natural background levels.

    • Yes, plants will thrive in the hottest parts of the word, as long as sufficient water is available. Consider tropical rain forests as a typical example of how much plants like hot and humid, yet many associated heat with deserts. While global rain increases with increased temperatures and evaporation, deserts are more a consequence of topography then temperature. For example, Antarctica is considered the biggest desert on the planet.

      • What categorizes an area as a “desert” is the amount of annual precipitation, not whether there exists water (or ice) on the ground.

    • Want to calculate it – GDU Calculator – (1) Enter postal code for field location. (2) Move the green slider to set plant date. Results show total GDUs and Year-To-Year Comparisons change by date. (3) Move the brown sliders to set daily, weekly, monthly or annual accumulations. (4) Click on any graph line for number estimates. (5) Click on any graph bar for daily details.
      GDU Calculator
      https://www.pioneer.com/home/site/ca/agronomy/tools/gdu/

      http://corn.agronomy.wisc.edu/Management/pdfs/A3265.pdf
      Map shows just across Wisconsin, south to north a variation from 2500-2600 to less than 1800-1900 GDD.

  9. Under the heading of “weather is not climate, but…”

    I, as are most people in the south central United States, are living through a big, real world example of why most average people don’t take weather predictions very seriously anymore. 3 days ago, the forecast for today was sunny and 95 degrees f. But instead, its 71 degrees f and raining – hard! And the thing is it’s been cool and rainy all month long – this is about to be the coolest August in anyone’s living memory.

    So here we all are, supposed to be suffering from ever increasing “Global Warming” that’s going to make it “too hot for humans to live!” and what do we see when we look out our windows? The coolest, nicest summer that most of us have ever seen. Hot Summers? Oh yeah, we had that 6 years ago, and then it cooled back down. Almost like these things are cyclical, imagine that.

    Oh I know, some warmist is about to jump up and say “Weather is not Climate! IN fact Global Warming is what Makes it Wetter and Cooler!!!” And then he will proceed to prove it by a lot of “uhm”, “don’t you see”,
    “errrr”, and “the statistics say”. This will be accompanied by a great deal of waving of hands in the air.

    Thank you, I’ll believe in what I can see.

  10. That sounds like the same thing Lobell & Field did: they assumed farmers are idiots.

    Lobell & Field claimed that a 0.7°F (0.39°C) increase in temperature over the period 1981-2002 should be expected to have reduced crop yields, not overall, but compared to what the yields otherwise would have been, everything else being equal. They admitted:

    “‘…we assumed that farmers have not yet adapted to climate change, for example by selecting new crop varieties to deal with climate change,’ Lobell said. ‘If they have been adapting – something that is very difficult to measure – then the effects of warming may have been lower.'”

    Read that again. It means that their estimate is not based on any measured reduction in crop yields. It’s based on their assumptions about what a +0.7°F temperature change would do to productivity in the absence of other factors, like CO2 fertilization, improved crop varieties, changes in cultivar choices by farmers, etc., etc..

    In the meantime, in the real world, farmers are not idiots, so they grow the crops which grow best in their local climate. In the real world agricultural productivity is soaring. According to World Bank data, global crop yields have almost tripled since chilly 1960. One of the reasons is CO2 fertilization. For example:

    U.S. Wheat:
    https://www.ers.usda.gov/topics/crops/wheat/usda-wheat-baseline-2015-24/

    Wheat, soybeans & corn in ND:

    Here’s a recent article:
    http://brownfieldagnews.com/news/2016-u-s-corn-soybean-crops-biggest-ever/
    Excerpt:

    “The USDA has confirmed record corn and soybean production in 2016.
    Corn totaled 15.148 billion bushels with an average yield of 174.4 bushels per acre, including new all-time high yields for Iowa, Minnesota, South Dakota, and Wisconsin. In 2015, U.S. corn production was 13.602 billion bushels with an average yield of 168.4 bushels per acre. Objective yield data had the third highest ear count on record for the ten states used by the USDA, with a new all-time high in Ohio…”

    1 °C of warming is roughly equivalent to moving about 50 miles south, in the United States, or about 500 feet lower in elevation. If you think that could be a problem, then ask yourself this: are the farms 50 miles south of me less productive than the farms at my latitude? And are the farms 50 miles north of me more productive than the farms at my latitude?

    The chronic shortage of CO2 is the primary factor limiting plant growth on planet Earth. It is possible to contrive growing conditions in which something other than CO2 limits plant growth and health, or in which a shortage of some soil nutrient causes better crop yields to be accompanied by reduced levels of some micro-nutrient, but such contrived conditions are easily avoided through normal fertilization practices. Under real-world conditions, additional CO2 is dramatically beneficial for agriculture, even to CO2 levels far beyond what we can ever hope to reach in the outdoor atmosphere, and the nutrient value of crops grown with extra CO2 is not significantly different from other crops.

    • Well Duhh! If someone plants a cultivar of maize adapted for Minnesota in Jalisco, the yield might be terrible , and vice versa.

      • Indeed.

        C4 plants are generally thought of as warm warm climate plants. Zoysia & Centipede grass are examples, and as everyone around here knows, they brown in the winter. Sugar cane (also technically a grass!) is another, and of course it grows only in very mild climates.

        But the most important C4 plant (also technically a grass!) is corn, and look at its distribution:

        Of course, it is only grown in the summer, up north.

    • Here in Western Canada, dry conditions have not been unusual during the last 140 years or so that grain farming has been common here. After the dry years of the 1980’s many farmers changed practise to zero till or at least minimum tillage. Tillage is one of the major factors that exacerbated the drought and crop losses of the 30’s. So we are now wetter, but also better positioned to continue to get good crops in dry years if they ever return. And they probably will.

    • “It’s based on their assumptions about what a +0.7°F temperature change would do to productivity in the absence of other factors,”

      I think this is ridiculous. Plants are not that sensitive. If the temperature in the room you are sitting in increased, or decreased by +0.7°F, you probably wouldn’t be able to tell it. I don’t know how this small temperature change would be detrimental to crops.

  11. Notice that many of these studies require that you pay to read their lies.

    You’d think that these studies would be available at no charge, just as a measure of transparency to allow the largest possible audience to assess them.

    How clever — keeping the detailed methodologies of the lying process behind a pay wall.

    • … and another thing, Without CO2 fertilization … what? … no implication that each degree rise is BECAUSE of more CO2, hence CO2 rise that ACCOMPANIES (in fact, CAUSES) the temperature rise, hence UNAVOIDABLY causes CO2 fertilization?

      So, what is the study suggesting? — the possibility of temperature rise WITHOUT CO2 rise?

      Okay, is THIS sort of temperature rise caused by humans too? Are we supposed to somehow fix ALL instances temperature rise, regardless of whether our CO2 causes the rise?

      I don’t get it — what is the subtext of this study? If not global warming is caused by human CO2, then what? — Global warming is caused by humans, but we’re not really saying how, but it’s still up to humans to stop global warming anyway??

    • Would it be reasonable to presume that most of the studies were funded by public money, thereby making this practice of limiting access to the study reports less tenable?

  12. IMO , it is time to call out these kinds of “studies ” as the lies they clearly are .
    Propaganda . ” Pure ” and simple…

  13. So called experts report global warming will be caused by anthropogenitic co2 emissions resulting in additional growth. CO2 is a fertilizer used to increase growth of plants. If warming trend is supported by nature that would open additional land for farming. No reason to expect a reduction in overall farm productivity.
    Global warming alarmists have a frightening future to sell supported by invalid climate models that has made the bell ringers wealthy and society poorer.

    Macpherson

  14. In the spring farmers try to plant crops the earliest they can without the emerging plants being damaged by frost. In the fall they plant so that the crop is up and hardy prior to the first frost. If climate warms, farmers will plant earlier in the spring and later in the fall. A warmer climate would make it easier for temperate climate farmers to make two crops in a single growing season.

  15. Climate change will cut crop yields…

    Climate change will cut crop yields… When this happens again:

    Little Ice Age

    by Edna Sun

    February 15 , 2005 — It was only a few hundred years ago that the earth experienced its last ice age. Global temperatures started falling during the 1300s and hit their lowest points in the late 1700s and early 1800s. New Yorkers could walk from Manhattan to Staten Island across a frozen harbor, while Londoners held “Frost Fairs” on a solid Thames River. Glaciers advanced in China, New Zealand, and Peru, and snow covered Ethiopian peaks. Diseases, aided by the change in climate, spread quickly throughout Europe and Asia. Iced waters delayed shipping from ports, growing glaciers engulfed farms and villages, tree lines receded, and agriculture deteriorated, leading to centuries of poor harvests, famine, and social unrest. Though the average global temperature dropped only one to two degrees Celsius below what they are today, the cold spell nevertheless drastically affected life at this time.

    – – – – – – – – – – – –

    Global temperatures naturally fluctuate slightly from year to year. However, in the past 10,000 years, there have been three relatively long global cold spells. The Little Ice Age (LIA) is the most recent and best documented, especially in Europe

    It may have had a greater effect on history than its predecessors because it immediately followed several centuries of unusually warm temperatures. Between 800 and 1200, Europe basked in a warm spell known as the “Medieval Warm Period” (MWP); temperatures were 2 to 3 degrees Celsius higher than they are today.

    […]

    Fatal Harvest

    During the LIA, summers were wet and unusually cold and the growing season was shortened. Widespread crop failure resulted in famine that killed millions of people. To avoid starvation, people would eat the planting seed for next season, which created more of a shortage the following year.

    During the MWP European farmers primarily grew cereal grains such as wheat, barley, and rye, which flourished. But the long thin stalks of these crops made them vulnerable to the strong winds and heavy rainfall that came during the LIA. The temperature drop in northern Europe made it difficult to raise these grains and many farmers gave up trying. Less grain was produced, creating a severe shortage and raising prices.

    […]

    PBS

    • David Middleton

      Illustrations and text that even a thicko like me can understand, thank you for that.

      I also read somewhere that most Cathedrals in Great Britain, and across Europe were built during the MWP. Food was plentiful so people didn’t have to spend their time grubbing around for minimal sustenance, instead they could afford time to work for money on major projects of the time.

      • Ya, forget minor things like the highs are not getting higher, the northern latitudes would get more temperate opening up huge tracks of land that can’t be cultivated now. More BS even if the premise was correct.

      • Yes, most Gothic cathedrals were indeed built during the High Middle Ages, c. AD 1130 to 1492 (for Spain; the Middle Ages ended at different times in other countries). Seville was begun during Medieval time, but not finished until the 1520s. I don’t know the last Gothic cathedral, but at least one of the latest was Segovia, built 1525-77. By that time, the style was old hat in most of the rest of Europe.

        The end of the Medieval Warm Period is variously dated, but arguably lasted until 1400. The 14th century had a mixed climate, during the transition from WP to the Little Ice Age. Population crashed from the Black Death of 1347, et seq. Hard to think of a better LIA cathedral than new St. Paul’s in London, built after the Great Fire of 1666.

      • De nada.

        First Gothic cathedral was begun in Paris at the Basilica of St. Denis (an abbey church rather than cathedral), c. 1130 and finished c. 1144. From France, the architectural style spread to England, Germany, Eastern Europe, Italy, Portugal and Spain, where it seems to have lingered longest.

        Some credit England with the key innovations, however.

      • The building work was started with great enthusiasm, hundreds of workmen on site but in many cases the work slowed during the late 13th – 14th centuries and the buildings were never completed to the original ambitious plans — crossing towers west front spires etc. — due to civil strife and the like, examples: Chartres, Amiens, Laon, Beauvais.

      • Chris Hanley

        from what I can gather from Sixto Vega and some of the reading I did on the period, much of the building work might have been disrupted by climate change (moving from the MWP into the LIA when the weather was disruptive) the plague (which it seems was a recurring event as the climate worsened, [coincidence?]) and the 9th Crusade, followed by the Scottish war of independence.

      • Chris,

        You are surely right about Beauvais, which was built in fits and starts over centuries, both due to structural and financial issues. No to mention war, famine and pestilence.

        The others IMO however were all finished in the 13th century, albeit perhaps not to original plans, if such ever existed. I could of course be wrong about that. Some had design problems, too.

        The 14th century has with some merit been called the worst century. It began with famine, continued with the 100 Years’ War and Black Death, then finished off with peasant revolt, proto-Protestant rebellion and usurpation.

      • HotScot,

        The Scottish Wars for Independence (1296–1328; 1332–57) don’t seem to have interfered much with the English Gothic cathedral building program.

        As you know, Scotland has no Gothic cathedral, although St. Magnus on Orkney was built in the 12th century.

        It might however have been divine intervention which caused the ferocious and highly competent King Edward I to die en route to Scotland in 1307, leaving the wars in the incompetent hands of his foppish son Queen Edward II. Hence, Bannockburn, 1314. The effeminate Fast Eddie however can’t be blamed for the Great Famine of 1315.

  16. Climate models do not regionally downscale. Therefore any crop impact esrimates are pure speculation. That statement is true for all 72 papers. I dug into corn, where there are two prominent negative impact papers. One uses a glaringly faulty statistical model to analyze US county level data. The other analyzed CIMMYT data for Kenya on test plots trying to develop drought resistant corn. Its flaw is that none of the test plots had optimum conditions, so the null hypothesis is flawed.

    • Did research in Kenya myself. Can’t list all the ways that research findings may be flawed or deliberately manipulated in that environment, though to be fare, I found those working on agricultural work were perhaps more rigorous than our medical research.

      • I recall a rangelands paper from that area ca. 1960’s that acknowledged

        “the local witch doctor, who, being both potent and resident next door, added greatly to the experimental error”

      • The CIMMYT yeild data is probably pretty good. Norman Borlaug’s Institute. The egregious error made by Stanford’s Lobell in analyzing the data was not recognizing that all Kenyan corn is grown under suboptimal moisture conditions. The MAM (March April May)rainy season is a month shorter than the 4 month minimum for rapid maturing maize cultivars. So all Kenyan corn is drought stressed. Corn does fine in high heat IFF it has enough water. This is never true for part of the Kenyan growing season.

  17. Total nonsense with respect to their conclusions and implied risks to agriculture. Models and limited field warming studies do not account for the expansion of arable land with warming as agricultural belts expand toward the poles, the increased water efficiency of crops with increased CO2 or the increased growth rate of plants with increased CO2 and longer growing seasons. The study also seems to ignore real world experience which suggests just the opposite conclusions. Such a report gives the distinct impression of a scary conclusion around which they tried to build a study.

    • Grant money in search of a preferred conclusion. Par for the course in Climate “science”.

  18. So… assuming reality is totally different from what is observed.. we might have a problem.. What a spectacular bunch of crap.

  19. **IF** Fossil..fuelled power is wholly replaced by Renewables, we will move from Agricultural Production to Electrocultural Production requiring vast transfers of land..base from the former to the exigencies of the latter … did I read here an area equivalent to the total N and S American continents, with much of Africa thrown..in?
    So, Mega..Morons On the Green side, where is the agricultural land lost to Electrocultural primacy going to be replaced??
    “Ah! The solar ranches are lost to ag. production, BUT we can farm round the windmill towers!!”
    Wrong …. by the time the tower density has been mazimized, and the access easements set..aside, and the network of connectivity and telemetry cabling set..aside in alienated strips, and the massive Musky Battery Storage Warehouses located, and the concomitant Switchyards added, there will be precious little ag. land left for substantive and efficient production.
    The countryside as we know it today will be horizon..to..horizon Electroculture with nary a farmer or a wheat..stook or a peasant, rabbit, pheasant, or other avian creatures to be seen. In other words, an Electrocultural natural disaster and Industrial Park covering former idyllic ‘scapes of pastoral bliss, hills, moors, and mountains.
    In retrospect, people will ask why we spread Electroculture all over the landscape, drastically reducing ag. productivity. Why don,t we revert to producing power in centralized locations in things called Power Stations, using nuclear power, and restoring the countryside to its Park..like amenity for all.

    • Ross King tienes razón en casi todo lo que comentas,te equivocas en lo de la energía nuclear…..hay una mínimo posibilidad de desastre nuclear pero si se llega a producir las consecuencias son desastrosas,ya comprobamos con Chernovil y Fukushima,la contaminación y los residuos radioactivos nos afectan por miles de años,,por esto la energía nuclear no es recomendable. La SOLUCIÓN es un novedoso e interesante SISTEMA para producir abundante energía eléctrica y barata,sumamente barata.Para fin de año se lanza al mercado esta manera de generar electricidad.No afecta a nada ni a nadie,puede funcionar las 24 horas del día no importa que no haya sol o viento.no importa que haya sequía o llueva mucho y NO CONTAMINA….ES EXTRAORDINARIO.

    • I think that’s pretty accurate extrapolation there, Ross. I intend to grow vines up the sides of the windmills and hire midgets with ladders to look after harvest. Midgets so they don’t lose their heads to the blades and ladders so they can get to the top fruit. Just don’t give away my secrets, Ross! Those Green guys are always looking for mitigation! Mitigation, man! That’s all we need!
      That shoulda been a John Lennon song. Mitigation is all we need! Not overly catchy, I admit.

  20. Ya, forget minor things like the highs are not getting higher, the northern latitudes would get more temperate opening up huge tracks of land that can’t be cultivated now. More BS even if the premise was correct.

  21. Here’s an idea if we are really worried about food crop production. Why not stop the inefficient nearly valueless program to convert corn into fuel ethanol? It might also make it appear that we really care about food scarcity in those regions of the world unfortunate enough to know what it means to go hungry.

  22. The following article which highlights record crops in India says everything you need to know about the future of crop yields. I’ll back the real world against models any day.

      • Although pteridophytes and certain conifers do better in humid atmospheres with 5000 ppm. I was speaking of most crop plants. We don’t need to go above 1000 ppm to optimize most important plants.

      • Unfortunately, we’ll never get there. Outdoor CO2 levels are unlikely to ever get much above 600 ppmv, because fossil fuel supplies are not limitless, and because there are powerful negative feedbacks which remove increasing amounts of CO2 from the atmosphere, as CO2 levels rise.

        I’ve read that most greenhouse operators run their greenhouses at 1200 to 1500 ppmv, because that’s optimal for C3 plants. That’s most crops, including wheat, rice, all vegetables, all nuts, and nearly all fruits except pineapples.

        CAM plants (mainly pineapples & cacti) also benefit from extra CO2, but I don’t know what the optimal level is.

        C4 plants don’t benefit much from extra CO2 except when under drought stress. The C4 plants are corn, sugar cane, sorghum, millet, some warm-climate turf grasses, and some weed grasses (like the dreaded Japanese Stiltgrass).

      • Dave,

        CAM and C4 plants might not benefit from levels higher than now at all. Not sure about that, but they can survive and thrive on remarkably low concentrations of CO2.

        Commercial greenhouses can be as low as 1000 ppm, depending upon the plants. I suppose a tree nursery might run higher.

        Depends upon species, but the marginal gain in going from 800 to 1000 ppm isn’t usually all that much. But 800 is way better for C3 plants than 400 ppm.

        I too doubt that we’ll ever get much above 600 ppm, if at all. Even burning all currently economically recoverable known FF reserves over the next three centuries probably wouldn’t do it.

      • I was surprised recently when I searched on the co2science.org web site and found that studies show that pineapples and cacti do apparently benefit a lot from extra CO2. Here’s a paper:

        http://onlinelibrary.wiley.com/doi/10.1046/j.1365-3040.2000.00588.x/full
        The Abstract begins:

        Crassulacean acid metabolism (CAM) species show an average increase in biomass productivity of 35% in response to a doubled atmospheric CO2 concentration. Daily net CO2 uptake is similarly enhanced, reflecting in part an increase in chlorenchyma thickness and accompanied by an even greater increase in water-use efficiency. The responses of net CO2 uptake in CAM species to increasing atmospheric CO2 concentrations are similar to those for C3 species and much greater than those for C4 species…

        Here’s a paper about pineapples:
        http://journal.ashspublications.org/content/122/2/233.full.pdf

        Excerpt from the Abstract:

        “Pineapple plants were grown at CO2 levels of ≈330 (ambient) and ≈730 µmol/mol in open-top chambers for 4 months… Average plant dry mass at harvest was 180 g per plant at elevated CO2 and 146 g per plant at ambient CO2…”

        Note: “µmol/mol” == ppmv.

        Here are some papers about cacti:
        1. Nobel & Hartsock. Short-term and long-term responses of Crassulacean acid metabolism plants to elevated CO2. Plant Physiology, 82: 604–606. (1986)
        2. doi:10.1016/0168-1923(91)90095-8 (1991)
        3. PMID:12231958 (1993)
        4. doi:10.1111/j.1365-3040.1994.tb00322.x (1994)
        5. PMID:12226228 (1996)
        6. doi:10.1006/jare.1996.0100 (1996)
        7. doi:10.1093/aob/mci034 (2005)
        8. doi:10.1104/pp.107.103911 (2007)

        Here’s an excerpt from the abstract of the first reference:

        …net CO2 uptake over 24-hour periods and dry weight productivity of these two CAM succulents is predicted to increase an average of about 1% for each 10 microliters per liter rise in ambient CO2 level up to 650 microliters per liter.

        Note #1: “Microliters per liter” == ppmv.
        Note #2: From the paper it appears that they didn’t test above 650 ppmv.

      • Dave,

        I stand corrected as to CAM. I was a little unsure when including those plants in with C4.

  23. What is the best answer for the problem of man-made climate change? Renewables? A carbon tax? Geoengineering? Forced life-style reductions? Carbon trading treaty’s? A stronger centralized authority overseeing decisions? Absolutely not! In fact, all of the solutions that are always talked about will likely make everything worse and have no measurable effect on climate.

    From the very beginning, the most effective, efficient, rational and inexpensive thing to do about man-made climate change is for everyone to have the freedom and power to adapt!

    Perhaps the biggest issue with AGW is that no one can know just how much of it there will be, or how it may manifest. Adaptation is the only method of dealing with the issue that simple takes the unknown in stride. We are always adapting to our world all of the time anyway, especially economically and politically. We must, if we are going to survive. Adapting to a few degrees of warming over 100 years would be a piece of cake! And in the very likely event that it doesn’t warm that much or not at all, we would not have wasted a second or a single penny on preparing for something that was never going to happen.

    Adaptation also opens the door to a vast amount of opportunity for life enhancement! The U.S. was the world’s shining example of the opportunity that lies in adaptation (in an environment of relative freedom). People came here by the millions trying to escape the status quo. It was different, but they adapted and the vast majority thrived. Usually, the actual climate was also much different, but they adapted very quickly to the new weather pattern; and thrived!

    Climate change, as projected, is almost imperceptible, compared to the vast amount of change we adapt to through the course of our lives. This is true for individuals, neighborhoods, cities, states and countries. We adapt as we need to, based on what is actually happening. This is done most efficiently when each layer of society has freedom to choose what is best for them. The great socialism experiment (that is still going on), has shown conclusively that a powerful centralized authority will always be worse than a society built on individual liberty. It is not about good or evil. It is about adaptability and efficiency! A powerful, central authority will always be slower and far less efficient in dealing with changes than free individuals choosing what is best for them (under the rule of law), through a free market.

    This article looks at what would happen if we assume no farming adaptability. This is very much like the rest of the discussions of climate change action. The solutions put forth are largely based on an assumption of no adaptability to climate change, and, therefore, a need to prevent those change at great cost. This is a false basis for the discussion! Not only do these solutions ignore our greatest asset, but they promote the type of centralized decision making processes that usually lead to great harm of the very thing they were created to protect. In the end, local people will adapt to their local conditions anyway, but if they have given up part of their wealth and power to a centralized government, they will be less able to adapt to actual changes in real time, and they will suffer greatly and needlessly.

    • Jclarke 341 se producen fallas cuando el que dirije NO SABE Y SOLO SUPONE y lo peor…..se enoja cuando alguien QUE SABE LE CORRIGE. Todo lo que los científicos del clima están hablando hoy sobre las causas del Calentamiento Global – Cambio Climático es en base a nuestra TEORIZA pero cuando lo compartimos en 2012 los científicos de clima nos criticaron,nos ofendieron. En nuestra TEORÍA demostramos que el Calentamiento Global empieza 15-20 años antes de fin de siglo y termina en los primeros 15-20 años del nuevo siglo y la causa son las ERUPCIONES VOLCÁNICAS 60% SOL 30% HOMBRE 10% se termina el calentamiento y el clima del planeta es controlado por SOL 60 % ERUPCIONES VOLCÁNICAS 20% HOMBRE 20% Todo es cíclico,cada fin de siglo se produce el Calentamiento Global pero cada vez es mas fuerte. Las GRANDES ERUPCIONES VOLCÁNICAS se producen a fin de siglo.

    • You’re right.
      James Lovelock’s Gaia hypothesis and Daisyworld model apply just as much to humans as to any other organisms. Our hubris likes to imagine that we are godlike creatures elevated above the mortal world. But we are not.

  24. I can only assume organisations paywall research to avoid widespread analysis and review of their research findings. The commercial value of the science or pay per view must be utterly trivial. This is not how science should work but but has the makings of a a secret society accessible only to the ordained.

    If the time to adapt was measured in decades, there may be an argument for mitigation action now.

    But crops like wheat, rice etc can be changed annually in theory. Allowing (say) 5 years for a transition would be entirely adequate – farmers are a conservative breed generally, genetic changes take time,and changes to varieties planted.

    The report can only be regarded as utterly pointless as it ignores adaptation and mitigation which is entirely feasible and likely, could potentially increase crop yields.

  25. The USDA publishes “Crop Production Historical Track Records” every year. The report includes virtually any crop you can think of, and the records date back to the 1800’s.
    http://usda.mannlib.cornell.edu/usda/current/htrcp/htrcp-04-13-2017.pdf

    The yield for most crops has increased dramatically since 1950. That’s the same period in which atmospheric CO2 has increased significantly. As an example, the yield for corn has risen as follows:

    Year Yield
    1950 38.2 bu/acre
    2000 136.9 bu/acre
    2016 174.6 bu/acre

  26. They’re right – the climate change that is ahead will indeed cut crop yields. Famine always follows the heels of climate cooling.

    BTW the equatorial ocean heat content is falling at an unusual speed, some kind of La Nina might be on the way:

    And the relentless cold anomaly emanating from Antarctica will eventually turn global temperatures into decline:

  27. Yet another “scientific” study showing that if your grandmother had wheels, she could be a taxi cab.

  28. Since 1950 Indian grain production has increased five-fold, thanks to better farming methods, better transport and storage and thanks to increased levels of CO2. This PNAS study is quite in line with Paul Ehrlich’s failed alarmist end-of-times predictions of Global Famine and deaths. For the same reasons in Ethiopia, and because of increased political stability and peace, the current drought has not resulted in the starvation of millions as seen in past droughts.
    The PNAS Study is real, only in the Computer Model World.

  29. A bit of science might be worth considering about this subject. See Sage & Kubien’s (2007): “The temperature response of C3 and C4 photosynthesis”; free full text = http://onlinelibrary.wiley.com/doi/10.1111/j.1365-3040.2007.01682.

    I suggest laymen interested in C3 plants first try to find paragraph about how heat impacts the enzyme Rubisco activase leading it’s dynamic form to degrade into non-dynamic forms (monomers & dimers) & thus leaf experiences poor levels of ready for work Rubisco. There is an example of how a plant (wheat) can compensate somewhat by splicing from the gene a more heat tolerant form of the enzyme (laymen could look for “isoform” & the abbreviation “kD”).

    And furthermore can suggest laymen then try to find paragraph about how heat impacts the electron transport chain leading to light harvesting antennae drawing away from photo-system 2 (PSII). There are other dynamics there as well, like less electron transiting PSII & deficit of NADPH for toggling balanced reactions.

    Since original post is not about CO2 I am not attempting to parse that myself. There is incidentally some mention on certain stomata response variability for those who are thinking about how elevated CO2 influences stomata.

    • Since now reviewed some other comments think this is my logical place to add details of a popular C4 crop, maize corn. It’s optimum temperature for Rubisco bring fully activated is around 28°C & yet because of how C4 deal with CO2 internally (concentrates) total photosynthesis holds steady up to 37.5°C.

      If temperature goes up little by little to 45°C maize can still perform 50% of it’s optimal total photosynthetic capability. But quickly raising temperature to 40°C (where C4 Rubisco activase enzyme “denatures”) knocks down total photosynthesis to only 58% of what it would be at 28°C; while quick jump to 45°C causes drastic Rubisco inactivation.

      See on-line free full text of (2002) ” Sensitivity if photosynthesis in a C4 plant, mauze, to heat stress”. And the authors do address the factor of elevated CO2 as well.
      Quote: “… increasing … CO2 around maize leaves to 1,200 microbars did not affect the Rubisco activation state or altrr the effect of high temperature ….” Which leads me address the common
      observation here how greenhouse growers ramp up CO2 for productivity – in greenhouses they manipulate temperature to match their crop’s temperature optimum.

  30. It’s pretty amusing. The paper says, “Crops are sensitive to climate change, including changes in temperature and precipitation, and to rising atmospheric CO2 concentration (1, 2). Among the changes, temperature increase has the most likely negative impact on crop yields … Meteorological records show that mean annual temperatures over areas where wheat, rice, maize, and soybean are grown have increased by ∼1 °C during the last century…

    So, how did crop yields change over the last century of rising temperature? Merely up by factors of 2-4.

    See also, G. F. Warren Spectacular Increases in Crop Yields in the United States in the Twentieth Century Weed Technology 12(4) (Oct. – Dec., 1998), 752-760.

    Here’s how the paper starts out, “ About 15 years ago, I heard several speakers saying that our crop yields were “leveling off.” This stimulated me to assemble data on the subject. The result is shown in Table 1, which gives the U.S. average yields for 10- yr periods during this century for nine crops. The increases are spectacular, varying from two- to sevenfold.

    So, according to Zhao, et al., “ Results from the different methods consistently showed negative temperature impacts on crop yield at the global scale, …,” despite the evidence that a centennial temperature increase of 1 C — pretty typical of AGW scariness — saw huge increases in crop yields.

    There’s no accounting for no accounting.

  31. “Although pteridophytes and certain conifers do better in humid atmospheres with 5000 ppm. I was speaking of most crop plants. We don’t need to go above 1000 ppm to optimize most important plants.”

    A lot of these comments focus on increased Carbon Dioxide in the atmosphere. No doubt if Earth warms 7 degrees Fahrenheit particularly in the Northern locations it will cause more growth and CO2 and heat stored in crops and trees in Siberia for example. This could lead to an increase in fires and decreased rain in southern locations could off set gains in Northern locations.

    With increased Carbon Dioxide comes increased heat and decreased rain in southern locations in USA and Africa. We should save gas for a rainy day and use as fertilizer when good options like lower cost solar and gravity motors are cheaper in the long term. Looking at 1 variable like CO2 levels the atmosphere might too simplistic. I hope I wrong. Thousands of people were killed in a heat wave in Russia in 2010 and it can get too hot. A lot of Carbon Dioxide has been put into the atmosphere since 2000 and there is a lag in heating and it keeps getting hotter. So we need to find out if studies of global warming accounted for increased plant growth due to increased CO2 and if crop gains in the North will make up for decreased crop gains in southern location in USA and Africa due to drought. There are many variables in global warming. Bugs and plant diseases will move North and caused increased spraying and amount of refuge acres…..

    “Russian President Dmitry Medvedev declared a state of emergency in seven regions, and 28 other regions were under a state of emergency due to crop failures caused by the drought.” 55,736 killed in 2010 heat wave in Russia from smoke and fires. I would think studies on global warming account for increased plant growth due to increased carbon dioxide and do these posts account for droughts heading north and being more often there too. If someone was part of those studies or can get that information please post. https://en.wikipedia.org/wiki/2010_Russian_wildfires

  32. As much as I’m enjoying three summers in a row with no need for an air conditioner running up my electric bill, I’m not real keen on running the furnace in the summer, either. I track the daily temps, weather (rain/sun/snow/whatever), and when the furnace goes on and when I turn it off. I have had to run it to mid-June during the past three years.
    This debate is nonsensical, wastes money that could be spent on developing better crop yields with less fertilizer, and does not about improving trash disposal by burning it to produce cheap electricity.
    Why don’t we debate the issue of trash disposal? There are several manmade mountains of trash that are being mined now for methane, which is used to generate electricity for nearby communities. Recycling is a big deal around here: bring your unwanted electronics, metal stuff, etc., to the recycling drive. The area is cleaner than it was 50 years ago, by a long shot. So when is that kind of thing going to be recognized, and these idiotic panicky papers cease and desist?

  33. This study is nothing more than the standard paul erlich – doomsday projection

    It goes against the long term trend of ever increasing yields.

    Skeptical science ran this same study a few weeks ago – with the typical justification ” it was peer reviewed”

  34. In India Rice is grown in Summer, in Monsoon season and in Winter in which temperature vary by more than 10 oC. It is cultivated under high inputs under irrigation.

    Dr. S. Jeevananda Reddy

  35. I am a farmer in north Iowa, so I can tell you what is happening in the “real world of farming.” We have what we call trendline yields for all major crops. For corn and wheat the trendline yield is rising. In the real world of farming in our nation, the yields of these crops are slowly rising in a predictable and consistent manor. Is it possible that global warming is putting a drag on yields? Maybe, but all the other factors outweigh the “possible drag” meaning that it is not that big a factor. There is no current evidence that we need to worry about grain production in at least the near future or even in the long run. We are really good at producing grain in this country and can easily adapt to any changing conditions that might affect it. We humans are very creative in solving problems especially if we have the incentive (profit) to do it. We are not going to run out of food, unless we put the government in charge. Then I would worry.

    • Hi MikeB, – Think you’ll be interested in this late comment.

      Maybe no more than 9% of the trend of greater yields for maize/corn in the last “… 50 years of increasing CO2 (73 ppm increase) …in dry conditions …” can be attributed to CO2; for soybeans CO2 bump good for possibly 12% of soy yield increase from 50 years ago (presumably related to legume nitrogen dynamic). The rest is related to various agronomic factors.

      % for maize & soybeans stated above are from McGrath & Lobel’s “…combination of historical yield & climatic data & field experiments that do not require elevated CO2 …” extrapolations. Source is research titled (2011) ” An independent method of deriving the carbon dioxide fertilization effect in dry conditions using historical yield data from wet and dry years”

      • Google finds this abstract for McGrath & Lobel (2011):
        http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2486.2011.02406.x/abstract
        Full text here:
        http://sci-hub.bz/10.1111/j.1365-2486.2011.02406.x

        The authors note that F.A.C.E. (Free-Air CO2 Enrichment) experiments tend to show smaller carbon dioxide fertilization benefits than do container-based studies, and they guessed that the FACE experiments are better than the container experiments, and that the container experiments overestimate the benefits.

        I doubt that is true. The problem with F.A.C.E. experiments is their unnaturally large fluctuations in CO2 levels. Bunce (2012) found that the FACE methodology results in an underestimate of the agricultural productivity improvement from higher CO2 level:
        https://link.springer.com/article/10.1007/s11099-012-0041-7

        It’s explained by Prof. George Hendrey here:
        http://pages.citebite.com/d1r3n6l1c4vft
        (or here: http://web.archive.org/web/20110717100621/http://www.qc.cuny.edu/Academics/Degrees/DMNS/sees/People/Pages/FacultyResearch.aspx?ItemID=26 )

      • I wrote at 6:24pm (currently in moderation), “The authors note that F.A.C.E. (Free-Air CO2 Enrichment) experiments tend to show smaller carbon dioxide fertilization benefits than do container-based studies, and they guessed that the FACE experiments are better… and that the container experiments overestimate the benefits… I doubt that is true. The problem with F.A.C.E. experiments is their unnaturally large fluctuations in CO2 levels. Bunce (2012) found that the FACE methodology results in an underestimate of the agricultural productivity improvement from higher CO2 level… It’s explained by Prof. George Hendrey here…”

        Here’s an excerpt from Hendrey:

        “All FACE experiments tend to underestimate ecosystem net primary production (NPP) that may occur at a particular increased concentration of CO2. This is because of the sensitivity of photosynthesis to rapid and poorly controlled variation in CO2 concentrations that are an inevitable result of the FACE technique.”

      • Hi Dave Burton, – The physical characteristics of plant containers is known to influence plant growth. This was identified as an issue for CO2 enrichment studies over 20 years ago (“Limitations to CO2 induced growth enhancement in pot studies”).

        A good idea of issues surrounding container growing can be found in (2012) “The art of growing plants for experimental purposes: a practical guide for the plant biologist”; free full text = http://www.publish.csiro.au/fp/Fulltext/FP12028 . There is a brief subheading for CO2 itself & a notable statement was that “… At the beginning of an experiment, when plants are small, CO2 control is more challenging and necessitates some CO2 scrubbing of the air ….”

        As for free air CO2 enrichment FACE tactical issues I find the following synopsis interesting & think container pot growth would be impractical for studying these environments. Quote below is regarding grasslands from (2006) “Plant CO2 responses: an issue of definition, time and resource supply”; free full text link = http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.2006.01886.x/full

        “Kansas.  No response in wet years, significant gain in dry years, largely because of the responses of Cyperaceae and forbs. There was clearly no disadvantage of C4 grasses, most likely because they profited similarly from soil moisture savings as C3 taxa.

        “Montana.  The mean +40% response in biomass production was the result of one C3 grass species (Stipa comata) and was clearly driven by moisture savings, which permitted greater seedling establishment.
        “Swiss lowland.  No response in wet years, but a significant response in dry years, arriving at a mean +18% yield, largely because of Cyperaceae. The effect was almost completely explained by soil moisture effects of elevated CO2.

        “Swiss alpine.  Clearly no response, irrespective of season or nutrient addition. This site at 2500 m elevation has a dense, late successional heath operating under naturally low nutrition and at 25% reduced partial pressure of CO2. It came as a surprise that nutrient addition, which doubled biomass, did not facilitate a CO2 effect over 4 year.

        “California.  No overall CO2 effect, when tested across all combinations with warming, nutrient addition or watering treatments. When tested alone, CO2 enrichment exerted a 33% peak biomass increase. Surprisingly when CO2 was added to any of the other treatments, it reduced their stimulating effect drastically.

        “Negev.  The peak season biomass response was +17%, but resulted almost exclusively from the response of a single species out of 25 (one out of five legume species, Onobrychis crista-galli). Without Onobrychis, which is the most mesic element in this system, the CO2 effect was zero.

        “Nevada.  This desert system operates far from complete ground cover, and hence may expand. There was a small CO2 effect on a native, but a massive effect on an exotic Bromus ( ×2.3) because of the combination of density and individual growth (+50%) responses; forbs were stimulated by +40%. In shrubs, there was no response in relatively dry years but a massive effect in an exceptionally wet year (shoots extension c. ×2). Root responses to CO2 were negative (fewer roots).

  36. Well I know my vegetable plants do worse when CO2 increases and the heat increases. Sarcasm. We need to pull federal funding from this nonsense.

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