Bishop Hill Stern's wheat graph
Apr 21, 2012 Climate: WG2 For reasons that I can't quite recall, I found myself looking at Chapter 3 of the Stern report, where I noticed a graph on yield losses in wheat.
;)
The text discussing the figure has this to say:
High temperature episodes can reduce yields by up to half if they coincide with a critical phase in the crop cycle like flowering (Figure 3.4).
The change in behaviour at 30°C seems quite distinct, but it's always good to look at the paper behind the headline. From the minute you read the title, you get a sense that all is not quite well with Lord Stern's work.
Growth and yield of winter wheat (Triticum aestivum) crops in response to CO2 and temperature.
So it's a study on winter wheat. I don't know about you, but I haven't come across any suggestions that winter and spring temperatures in the UK might exceed 30°C, but perhaps I'm wrong.
The abstract is interesting too:
Crops of winter wheat (Triticum aestivum L. cv. Hereward) were grown within temperature gradient tunnels at a range of temperatures at either c. 350 or 700 μmol mol−1 CO2 in 1991/92 and 1992/93 at Reading, UK. At terminal spikelet stage, leaf area was 45% greater at elevated CO2 in the first year due to more tillers, and was 30% greater in the second year due to larger leaf areas on the primary tillers. At harvest maturity, total crop biomass was negatively related to mean seasonal temperature within each year and CO2 treatment, due principally to shorter crop durations at the warmer temperatures. Biomass was 6–31% greater at elevated compared with normal CO2 and was also affected by a positive interaction between temperature and CO2 in the first year only. Seed yield per unit area was greater at cooler temperatures and at elevated CO2 concentrations. A 7–44% greater seed dry weight at elevated CO2 in the first year was due to more ears per unit area and heavier grains. In the following year, mean seed dry weight was increased by > 72% at elevated CO2, because grain numbers per ear did not decline with an increase in temperature at elevated CO2. Grain numbers were reduced by temperatures > 31 °C immediately before anthesis at normal atmospheric CO2 in 1992/93, and at both CO2 concentrations in 1991/92. To quantify the impact of future climates of elevated CO2 concentrations and warmer temperatures on wheat yields, consideration of both interactions between CO2 and mean seasonal temperature, and possible effects of instantaneous temperatures on yield components at different CO2 concentrations are required. Nevertheless, the results obtained suggest that the benefits to winter wheat grain yield from CO2 doubling are offset by an increase in mean seasonal temperature of only 1·0 °C to 1·8 °C in the UK.
The abstract is somewhat unclear, but we seem to have a beneficial effect from CO2 fertilisation offset by temperature increases. The tentative conclusion seems to be that these broadly cancel but that more work is required to prove the point.
Stern seems to have picked up on a fall in seed head numbers. I can't see anything in the abtract to support his claim that that there is a fall in yield, but this may be in the body of the paper. It's not clear from the abstract what the counterbalancing effect of CO2 was on these seed heads.
It seems to me that it must be a perilously difficult problem to predict the effect of temperature changes on crops. The threshold demonstrated in this paper seems clear enough, but do we have the same kinds of data for other crops? Or is the 30°C threshold simply extended to other crops? Presumably you then need to assess the likelihood of the threshold being surpassed in each location that particular crop is grown. And is the good news about CO2 fertilisation factored into the impact assessments too?
Lots of questions. Perhaps readers can help find the answers.
Reader Comments (71)
So you’re getting less yield per crop, but shorter durations presumably mean more crops per season. Sounds like a good deal.
As usual, government by official report (rather than by reasoned argument) means less information per paragraph, but more peer-reviewed source references, and thus a greater yield of obfuscation and propaganda.
Are wheat farmers too dumb to adapt and plant something else? Others in areas currently too cold for wheat will take up the slack.
This just shows Stern's lack of knowledge of the literature on the impacts of climate change.
The phenomenon described was known as the "dumb farmer" until Colin Prentice in the mid-1990s remarked that it was analysts incorrectly assuming that farmers are dumb. Since then, it has been referred to as "dumb analyst".
Crop varieties are bred to do very well in a certain range of weather. Outside that range, crops do poorly and yields fall sharply. Clever farmers plant different varieties if circumstances change, and the precipitous drop in yield disappears.
Didn't I read in another blog recently, of the risk of a FALL in temperatures, that could reduce the global wheat belt by 400 miles?
In relation to Dumb Farmers... my Hungarian Parents in Law grow everything and are very aware of what sells and at what time of the year. Here you grow tomatoes and paprikas in the open. Peach, apricot cherry trees abound. So if more places were as hot as an Hungarian summer?
Re markets, the price would go up, giving all sorts of incentives to enter that market: new strains, different crops, new locations, improved farming methods. Until of course the many entrants bring the price down.
Note: in fact as Coeliac myself, there is a growing body of evidence that wheat is not good for us in terms of long term health problems e.g. bowel cancer. It is now only realised how under diagnosed it has been.
Or if we have more precipitation we eat more rice. Hungary has successfully been growing rice since 1946.
Anyway, what do I know, IANAE - just invented in honour of IANAL. Yes it is sarcasm.
Wherever you look in Climate Science adaptation never seems to figure much. Time stands still. The end of world is Monday at 11:00. YHBW.
Even taking CAGW alarmist warming at its current rate, people will fill and leave markets based on demand.
India, which I'm told is a generally warmish sort of place, is heading for its fifth consecutive record wheat harvest.
http://tinyurl.com/c23sfhd
This sort of selective, theoretical, quasi-scientific prediction reminds me of one in the Graun a little while back, which said that UK railways would grind to a halt because of AGW-caused thermal expansion of the track.
Theoretically possible - but easily demolished by simple observation of much hotter countries, like India, with flourishing railway systems.
It always gives me the impression that "climatologists" don't get out much - or, when they do, they don't get further than the nearest beach bar (eg. Mann to Jones "looking forward to seeing you in Tahiti, we can enjoy some nice tropical drinks w/ umbrellas in them").
"So it's a study on winter wheat. I don't know about you, but I haven't come across any suggestions that winter and spring temperatures in the UK might exceed 30°C, but perhaps I'm wrong."
But winter wheat doesn't flower until June.
There are many other factors which have much greater affect the yield of a crop - this strikes me as a typical blinkered statistical outlook - why not try lies and damn lies as well?
Stern's report goes against the grain....... He fails to understand that reduced stomata area from higher [CO2] allows wheat to grow better at higher temperatures because transpiration is lower.
But there is no significant CO2-AGW and, once you strip out the latest temperature fiddling, the World's climate is now cooling. A cold, wet May with snow in the NE and Scotland will concentrate a good many minds in Government as to reality rather than Stern's propaganda aimed at justifying carbon trading to underpin the supranational Euro and Amero currencies.
"So it's a study on winter wheat. I don't know about you, but I haven't come across any suggestions that winter and spring temperatures in the UK might exceed 30°C, but perhaps I'm wrong."
You are not wrong, but winter wheat flowers in summer, not winter or spring. I have known wheat to flower in late May, but early June onwards is typical. The abstract mentions temperature >31C immediately before anthesis. This is a critical time for the crop and could well have a negative effect on pollen maturation and behaviour. Wheat is closed-flowering ie pollen is shed from the anthers within the florets, fertilising the stigma, before floral parts open and the anthers are excerted. So there is a lot of delicate stuff going on - masses of meiotic cell division to produce pollen, maturation of pollen grains, rupture of pollen sacs, growth of single-cell pollen tubes down the stigma. Failure of fertilisation will result in reduced yield.
Contributing factors to yield - genotype, water availability, temperature, light intensity, daylength, pathogens. The requirements are not constant but vary according to the developmental stage of the crop. Warmer, brighter, is better. Winter wheat requires a cold period to initiate flowering - the time x temperature specifics vary with variety. CO2 fertilisation is also good, and is used for some glasshouse crops.
"It seems to me that it must be a perilously difficult problem to predict the effect of temperature changes on crops."
Yes and no. There are always variety specific nuances. In wheat, although all varieties of bread wheat belong to the same species, there is great inter-varietal variation in just about every characteristic. For instance, wheats from southern europe flower very early in the UK, but then ripen prematurely without filling the grain, even in apparently ideal growing conditions. Not entirely predictable - you just have to grow them to find out.
Considering the variables listed above: the effects are testable in controlled environments, so while prediction is complicated it is possible to build general models of crop growth based on repeatable, real-life experimentation. Then there are varietal interactions to deal with. But - these can be tested and repeated and confirmed, unlike models in some other fields of endeavour.
Charlie
Thanks, that's helpful. The study was of UK wheat, so I'm guessing 30°C is would still represent quite a leap over normal temperatures. I wonder how long the hot spell would have to last to have the effect noted in the paper.
Also, presumably there are varieties of winter wheat that are more heat-tolerant and therefore suitable for hotter climates? What do they grow in France?
Wheat flowering (anthesis) occurs in June in the UK (early or late part of the month depending on whether autumn- or spring-sown), so temperatures of 30°C are possible but unlikely to be maintained consistently, as they were in these experiments. If we ever do get these conditions regularly in the UK, then we simply switch to a tropical C4 crop such as maize. It works well and outyields wheat comfortably.
Whilst we still have a winter(and that's not going to change), we won't be able to crop more than once per season with cereals, so no benefit from them dying prematurely, unfortunately - even the shortest season cereals need about 4-5 months of decent growing conditions, which is a bit of a stretch and will mean harvesting in short days and wet conditions for a second crop in October/November.
Nice comment from Richard Tol about 'dumb analysts' - but my experience with crop varieties suggests they're not as fussy as we're often led to believe - inter-season weather variation can be substantial and it's very rare for crops to fail significantly - even last year we were warned by hyperventilating journalists and politicians http://www.telegraph.co.uk/earth/agriculture/farming/8517376/Lack-of-rain-already-causing-crop-failures-Defra-warns.html that UK wheat crops had been damaged 'irreversibly' by drought - this was drivel of the first order - yields were little changed from previous years.
The only widespread cereal crop failure I'm aware of in the UK was indeed caused by environmental conditions - a leading new wheat variety, 'Moulin' failed to set seed properly in 1987, leading to 90% yield losses. The cause was not 'warming' of any sort, rather a period of cool, dull and wet weather which resulted in poor pollen production.
Strange to need to reiterate once more that biology is favoured by warmth.
This graph shows average maximum temperatures in June for England was 18°C. It's hard to see 30°C as much of a threat.
As we develop higher cloud cover from lower solar magnetic field, the heat stored in the Pacific during the mid 20th Century grand maximum will decay. Predictions are for the 2030s, 2040s or 2050s as the coldest decade, the latter corresponding to the 1690s in the LIA.
If we have that ~2 K temperature fall, it'll be quite serious. In the 1690s, a quarter of the population of Scotland died from the poor harvests and cold winters.
"Nevertheless, the results obtained suggest that the benefits to winter wheat grain yield from CO2 doubling are offset by an increase in mean seasonal temperature of only 1·0 °C to 1·8 °C in the UK."
In other words, if climate sensitivity is below 1 to 1.8 degrees, winter wheat yield would go up; if it is above 1 to 1.8 degrees, it would go down. In any case, the changes would be minimal, even for a cold weather crop. Chances are, you could grow something else in a warmer climate that would have a higher yield anyway, especially if CO2 had also increased. And that is apart from the fact that new areas that are currently too cold to grow anything would become productive.
So this is typical Stern spin. The potential global gain in agricultural productivity from both warming and higher CO2 sticks out a mile, and has been documented for decades, but you would never know it from the presentations of the orthodox.
"... average maximum temperatures in June for England was 18°C. It's hard to see 30°C as much of a threat."
It wouldn't be for most of the life of the crop, but the period around anthesis is critical. No fertilisation, no grain. Also, in the graph reproduced from Stern, not much happened at 30°C, but there was a sharp fall in numbers of grains per ear at temps above that. The potential number of grains per ear, and ear number, is fixed weeks before flowering, almost before stem elongation. So a reduction in grains per ear is a result of failure of pollination for one reason or other. Best go back to the original Wheeler paper - could be misrepresented in Stern, who knows?
SNTF suggests switch to maize - a C4 crop - if it gets too warm. Nah, don't fancy cornbread, beans and black molasses, or - worse - mealie mealie! Polenta is bad enough.
There are two giant biomes sat side by side in a clay pit at at Austell receiving equal amounts of energy from the environment. Surely it must be possible to double the amount of the trace gas CO2 in one of them and monitor the effects. That's if they want to of course.
It seems an utter requirement of alarmists to assume that humans will stay stock still like rabbits in the headlights waiting for the end of days and not adapt to anything. The alarmists show no cognitive ability to think of humans in a positive light at all. I despise them for wanting power and control over human development i.e. no development.
Looks like, this year, the UK could grow winter wheat in May.
The IndexMundi website has plenty of information about wheat production, among other things:
http://www.indexmundi.com/agriculture/?commodity=wheat&graph=production
Bishop on BBC News 24 repeat right now theres a throwaway headline coming up
Greenpeace say that cloud computing is too energy intensive
They say that if it was a country it would be the 5th biggesr polluter
This is disputed by Apple
Worth getting on this one
Surprized chief BBC Censor Richard Black let that one through
Sorry thats my Dyslexic typing
Thats CLICK with Spensor Kelly
Here's a follow-up to the Wheeler paper quoted in Stern. The variety was Chablis, a spring wheat, field grown, with polythene temperature gradient tunnels moved over the plots to increase temperature at flowering time.
Effect of High Temperature Stress at Anthesis on Grain Yield and Biomass of
Field-grown Crops of Wheat, Ferris et al, Annals of Botany 82 : 631–639, 1998.
From the abstract: "... the number of grains per ear at maturity declined with increasing maximum temperature recorded over the mid-anthesis period (76–79 DAS) and, more significantly, with maximum temperature 1 d after 50 % anthesis (78 DAS). Grain yield and harvest index also declined sharply with maximum temperature at 78 DAS. Grain yield declined by 350 g/m2 at harvest maturity with a 10°C increase in maximum temperature at 78 DAS and was related to a 40 % reduction in the number of grains per ear. Grain yield was also negatively related to thermal time accumulated above a base temperature of 31°C (over 8 d of the treatment from 5 d before to 2 d after 50 % anthesis). Thus, grain fertilization and grain set was most sensitive to the maximum temperature at mid-anthesis."
@Janner
I think the Eden biomes display something important already - the big one showcases a humid tropical environment (held around 30°C) whilst the smaller of the pair houses a warm temperate environment (Mediterranean-ish, a few degrees warmer than ambient). Guess which one the staff spend much of their time hacking back so that visitors don't need their own machetes?
@Filbert Cobb
Totally agree regarding maize vs wheat, but it's a decent illustration that we've got at least 10°C warming headroom in terms of highly productive food crops - best not look at the downside though - even barley doesn't grow too well on ice...
@Filbert Cobb
So the Chablis paper says we lose 350g/m2 (3.5 t/ha) if we raise temperatures by (an insane) 10°C over ambient - we're well into maize territory there, but nonetherless, UK wheat yields would be in the region of 4t/ha which is still better than most of the world does now... Amazingly resilient stuff, isn't it? Anybody would think it originated from a hot dry sort of place, like the Levant.
Cough.
@SNTF
"Amazingly resilient stuff, isn't it?" Yes - you only have to look at its latitude range.
As for "an insane" 10°C rise over ambient - we don't need climate change to provide a rise from a dull overcast 17 to a flaming 28 in England in June, just our typical changeable temperate maritime stuff.
I am sure I read somewhere that the rise in average temperature is mostly due to higher night time lows rather that higher daytime peaks. Intuitively, this should mean fewer frosts and thus an enhanced growing season, also a NH northward extension of cultivable land, all of which seem, together with enhanced CO2 fertilisation, like a win-win.
I will have to learn how to read, as I can't see why a dog-leg should be the best fit for the data points on that graph. How did they do that?
On a different matter, can anyone clarify if Lord Stern takes his name from a love of authoritarianism, or from the back end of a ship?
@Pharos
I'd heard that too - seems to fly in the face of GHG theory that the heating effect happens when there's far less outgoing radiation to be intercepted, no? I'd be interested to hear a (sophistry-free) explanation of this.
Or maybe it's because climate psyence is too corrupt to pay attention to the UHI effect that's contaminating much of its data. Even the BBC now tell us nightly that rural areas are far colder at night than urban ones. Unusually, they're not lying.
@Luther
Broken sticks were very fashionable at Reading in the late '90s. Some folks also managed to execute PCA correctly there too - something to do with having a top class Applied Statistics department. If UEA had one too then it's pretty certain that the Hockey Team's filth would have been strangled at birth.
I see the graph title is 'yield loss caused by high temperature in a cool-season crop' and then shows the effect of temperatures roughly double what might be expected. How much warming was Stern anticipating?
Hi sayno: climate science has as much of a clue as the guy pickling cucumbers in Swift's 'Gulliver's Travels'.
I was in south Brittany in 1987 when there were fears that the Moulin variety of wheat would fail owing to the lousy summer. Ilived for a few years about 50 miles south of Toulouse where winter(durum) wheat was the main crop, harvested in July. Temperatures were on average 4 degrees higher than in the English Midlands annually and 30° was common enough any time between early May and late October.
Need England tremble?
'The cultivation of wheat (Triticum spp.) reaches far back into history. Wheat was one of the first domesticated food crops and for 8000 years has been the basic staple food of the major civilizations of Europe, West Asia and North Africa. Today, wheat is grown on more land area than any other commercial crop and continues to be the most important food grain source for humans. Its production leads all crops, including rice, maize and potatoes.
Although the crop is most successful between the latitudes of 30° and 60°N and 27° and 40°S (Nuttonson, 1955), wheat can be grown beyond these limits, from within the Arctic Circle to higher elevations near the equator.'
http://www.fao.org/docrep/006/y4011e/y4011e04.htm
Although the discussion has focussed on winter wheat, the other half of the figure shown at the top (part 'b', cut off) shows the temperature effects on groundnut in India. While that might be of little interest to readers in the UK, we are after all talking about global warming, not just UK warming. The billion people in India surely have an interest in outcomes there.
Perhaps someone with experience of Indian weather patterns and food production could comment on the likely effect of a rise in temperature of a few degrees in India.
The essence of this thread is if you want to know about crop yields, ask a farmer, not a climate scientist.
OT - but I just read on Real Science that Steve Goddard passed away last night - aged 81.
He was so sharp and endlessly productive that I always imagined him as half that age.
There is reference from a commentator that he was "raided" by law-enforcement shortly before he suffered a fatal heart attack.
http://www.real-science.com/attention-scientist-steven-goddard-dies-at-81
I always thought that Steven's technique of drawing attention to contemporary historical reports of climate anomalies was one of the most effective ways of deflating the alarmist "consensus" - I think this post of his summed that up:-
http://www.real-science.com/below350-org
He will be missed.
@ Jiminy Cricket; 9:46 pm. Please don't spread scare stories like this. Yes, there is some evidence of increased incidence of bowel cancer amongst people with Coeliac/gluten enteropathy/IBD/IBS, but it is probably secondary to the effects these disorders cause to the gut, rather than wheat itself.
I haven't studied the Stern report but of the rest of his analysis is as poor quality as that presented here, I don't think that reading it will be the most likely domestic usage chez Alder.
Somehow I have a persistent image of cute labrador puppies that are called 'Andrew' or something very close..........
If Google "Effect of High Temperature Stress Ferris" you can find the original paper - which I won't attempt to analyse.
Further to my earlier post - it appears that Steve Goddard isn't dead - his site was maliciously hacked.
http://stevengoddard.wordpress.com/2012/04/21/real-science-was-hacked/#comments
This just about sums it up: if you grow the wrong crop, it goes down. Pick one that is adapted to the environment and it goes up (instead of finding an environment where wheat is already under stress as most other papers have done).
It's pretty obvious really, ... and it's pretty obvious that the unscrupulous can get any result they like!
Conclusion
The simulations in this study took into account the effects of COz, air temperature, incident solar radiation and soil moisture on crop growth, water-use and development. They indicated that while doubling present atmospheric CO2 concentration would lead to increases of between 28 and 43 % in above-ground biomass at anthesis and potential crop yield, a simultaneous increase in air temperature of just 3 "C would cause a reduction in above-ground biomass at anthesis and potential grain yield by up to 60 % for Cultivar Egret and 25 % for Cultivar Matong. This effect was mainly due to shortened vegetative growing periods, with no significant change in water deficit. In contrast the late-maturing cultivar UQ189, which is adapted topresent conditions in southern Queensland, was predicted to have a higher above-ground biomass at anthesis and potential grain yield under the enhanced greenhouse conditions. Therefore selection of suitable
cultivars will be one of the key strategies to cope with climate change.
Sensitivity of wheat growth to increased air temperature for different scenarios of ambient COz concentration and rainfall in Victoria, Australia - a simulation study. wang et al
Steve Goddard is fine and posting here: http://stevengoddard.wordpress.com/
His other site was hacked: http://www.real-science.com/
A write-up of the alleged revolt in NASA against the frauds attributed to Hansen: http://johnosullivan.wordpress.com/2012/04/11/nasa-in-mass-revolt-over-global-warming-fraud/
My Dogs, and everyone -
Yes, but www.real-science.com IS still under control of the hacker who is moderating all realist and factual comments. Nasty and sad that an extremist warmist has succombed to such a low level. But the important thing is that Steve is still with us, and will still be spinning his chainset for many a mile.
The simulated increase in grain yield due to increasing CO2 concentration in most cases exceeded the simulated responses to changes in climate variables.
Sensitivity of field-scale winter wheat production in Denmark to climate variability and climate change (Olesen et al 2000)
It is not only wheat that is hyper-sensitive to 30 degrees. Maize also seems to have this issue. See “Nonlinear heat effects on African maize (corn) as evidenced by historical yield trials”, Lobell et al. in Nature : Climate Change 2011.
The Economist
fell for itgave a favourable report, whilst Willis Eschenbach at WUWT debunked it.http://manicbeancounter.com/2011/03/21/the-economist-on-corn-production-over-30-degrees/
@Salopian, I let my post stand... no other comment.
World temperatures are not going up but World Grain Harvests are booming thanks to greater CO2 availability and better farming practices. Plants just love that CO2!
Any plant will grow better with more sunlight, more atmospheric CO2 (Plant Food) and sufficient water.
It's called Photosynthesis....Plants need fertile soil....sunlight....CO2....water. And they return O2 to the atmosphere, which we need, and we exhale CO2 that Plants need. Simple Facts are way above the comprehension of mad greenies.
Apr 21, 2012 at 10:59 AM | Filbert Cobb - NTF suggests switch to maize - a C4 crop - if it gets too warm. Nah, don't fancy cornbread, beans and black molasses, or - worse - mealie mealie! Polenta is bad enough.
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You mean, "mealie meal" but you're right in that it is fairly course stuff.