Guest Post by Willis Eschenbach
I keep reading these claims that we’re all going to starve because of global warming. People say it’s going to be the death of agriculture, that increasing temperatures will cause significant drops in crop yields. Here’s a typical bit of alarmism (emphasis mine):
A study by the International Food Policy Research Institute (IFPRI), indicates that climate change would hit developing countries the hardest, leading to massive decline in crop yields and production.
Whoa, a massive decline in crop yields due to increasing temperatures, sounds scary. So I thought I’d review the facts. Here is the global situation, showing the global yields of rice, corn, and wheat, along with the change in global temperature.
Figure 1. Changes in global grain yields and global temperatures 1961-2011. Data Sources: FAO, BEST, Photo
Now call me crazy, but what I see going on there is not a global crisis. Nor is it “massive declines”. Notice that (according to BEST) the global temperature has gone up one full degree centigrade … anyone remember any thermal crises that have resulted from that one degree of warming? Since two degrees is supposed to bring untold sorrows, where are the sorrows of one degree? Where is the lethal sea level rise? Where are the disasters? ¿Où sont les neiges d’antan? And most of all, where are the decreases in yield from that one degree of warming?
Of course, you could say that this is just because it’s a global average, and not all countries produce wheat, so we wouldn’t expect good agreement between global temperature and global grain production. And you might be right. So … here’s the same chart, only this time just for the US;
Figure 2. As in FIgure 1, except for the US rather than for the whole globe. BEST US temperature data.
Again, there is no thermal related decline in yields. According to BEST the US, like the globe, has gone up about a degree since 1960 … where are the climate refugees? Where are the corpses? Where are the thermal catastrophes? And more to the current point, where are the declines in food production? I don’t see them.
Finally, I thought “Well, maybe if I detrend all of the US data and then see how well related the change in annual temperature is to the change in annual crop yields” … no joy there either. Below are the measurements for those relationships. The strength of a relationship between two variables is measured by something called “R squared” (written “R2“), which varies from 0.0 for no relationship between the variables, up to 1.0 for perfectly related variables. Here’s the relationship of US temperature and US crop yields:
R2, US BEST Land Temperature and US Maize (corn) yield : 0.001
R2, US BEST Land Temperature and US Rice yield : 0.000
R2, US BEST Land Temperature and US Wheat yield : 0.022
In other words, no relationship at all. I gotta confess, I don’t see what folks are screaming about. If you believe the BEST data, we’ve seen a full degree of temperature rise in the last half century, and it hasn’t done us any harm—no atolls gone underwater, no millions of climate refugees, no increases in extreme weather. And through all of that temperature rise, the crop yields have kept going up. Will they reach a maximum? Assuredly they will … but it doesn’t seem like that maximum yield is going to be much affected by the temperature.
So I fear that once again we’ll have to postpone Paul Ehrlich’s celebration. He’s been predicting the global Malthusian food crisis for decades now, to no avail. Near as I can tell, according to the Malthusian philosophers like Ehrlich, the problem is that this continued increase in crop yields works in practice, but it doesn’t work in theory …
w.
Further Reading: I put up a post a while ago called “Border Transgressions“, about wheat production and temperature in Mexico. I also discussed how much food people actually have to eat in “I am so tired of Malthus“.
[UPDATE] Some people seem to have understood me as saying that because temperatures were rising and crop yields were rising as well, that the rising temperatures were causing the rising yields. I am not saying that. It may indeed be true that in a warmer world, the general yield would be better, and I see no reason it would not be better … but that’s not what I’m saying.
Some people seem to have understood me as saying that crops are not affected by temperatures above their optimum range. I am not saying that. All crops have preferred temperatures, above or below which they do not produce as well.
People are over-thinking this. What I am saying is simple. It is the answer to the question in the subject of the post—do increasing temperatures lower crop yields? I say no.
Note that I am not saying that increasing temperatures increase crop yields, although they may do so. Instead, I am falsifying the alarmists forecasting things like “massive drops” in crop yields. I’m not saying yields will or won’t go up if it gets warmer … I’m saying they won’t go down.
Here’s what lowers crop yields. Bad weather forecasts lower crop yields. If the farmer knows it will be colder next year, don’t worry, she’ll make money, she’ll plant later, use a different variety, plant beans instead of corn, get a bumper crop, be the envy of her neighbors. Same thing in reverse if she knows it will be hotter, she’ll plant early and have her crop in while the neighbors’ crops are wilting in the field.
But a bad forecast, she puts in hot weather seed and it turns out to be a cold year, the yield will go down.
So increasing temperatures, particularly predicted increasing temperatures, particularly predicted gradual increases over a century, will be lost in the noise of the thousands of changes that farmers do each and every year to account for the much larger interannual variations and interdecadal variations. Every year, the farmers successfully deal with the fact that not next century but next year may be two or three degrees warmer or cooler than this year … do you really think a degree’s rise spread over decades will affect those farmers’ crops? It’s lost in the noise, they’ve got three degrees to think about. Here’s the part that I think many folks don’t understand.
At the end of the day, crop yield is a measure of the farmers, not of the temperature.
In evidence of this, I offer the fact that the above analysis of the detrended US temperature data and detrended US crop yield data showed only an insignificant relationship between the two.
w.
[UPDATE 2] Someone downthread asked about the yields in the poorest countries. Here is that data.
As you can see, progress has been much slower in the developing world. However, even in the worst off countries on the planet, even with the warming of the last 50 years, the yields are still rising. And it is worth noting that the worst countries are all at or above the global average yield rates in 1961. In my lifetime, the poor of the world have moved to where the global average was when I was a kid …
And obviously, of course, at this end of the spectrum even the simplest of improved methods and seeds would double the yield … which is why temperature is not the issue, and never was.
Willis Eschenbach says:
January 31, 2013 at 11:40 am
Ed Hawkins says:
January 31, 2013 at 4:58 am
Said as a farmer; We, the tax payers pay and pay for this academic crap!
Those real and completely unrecognised and unsung heros of all of global mankind, the plant breeders. the men and women on whom ultimately the whole of mankind depends on to feed our numbers far into the future, just get on with their work of breeding new varieties of crops that give higher yields, better tolerance to changing seasonal conditions, better tolerance to drought or heat or cold, better nutrition, better storage longetivity, better disease and insect resistance, easier processing and better baking and cooking characteristics.
All this with a genetic complexity of life that makes analysing the global climate look like a kindergarten exercise.
For that they are rewarded with only a fraction of the income that the climate warming scientists who have contributed nothing to mankind except the promotion of deep fears about the future and the destruction of immense amounts of wealth and the increase in societal conflict.
And for what ?.
Why the hell is our society and civilisation so screwed up and twisted up that the most important people for mankind’s future, the plant breeders are the most neglected group of scientists and regarded by our society as the being at the bottom of the pile in science whilst the most useless and most destructive group of scientists, the global warmers are getting all the big rake off’s and all the gloss?
To Stephen R:
As for 2003 – I should have said the summer as an average was 1.5K hotter than any summer since records began in 1750 (according to the BEST timeseries). And, yes, it was dry in 2003, but not extremely dry as I’ve said elsewhere.
Ed.
I call no rain for 5 mths extremely dry and in the following years we had periods of no rain for 4 mth, 3mths, and 2 x 2 mth periods in one year. The spring and the autumn. The hottest day recorded in SW France was below the highest recorded temperature of 42°C. In 2003 we had June, July and August with every day over 32°C and everyday of july over 37°C. We saw no rain here during the spring and summer and in february of that year I was on the terrasse in my shorts painting the shutters. Sun temperature (open land T) was 26°C.
That year the maïs was good and the wine better.
Curious George says:
January 31, 2013 at 1:20 pm
@Mark Bofill: The IFPRI Food Policy Report relies on “NCAR model” without providing any details. I assume that it is a CAM 5 (Community Atmosphere Model 5). This model has a 2.5% error in heat transfer by water evaporation at 25 degrees C (3% at 30 C). They don’t know the impact of this error – excuse me, an unannounced approximation – and they apparently don’t care.
———————–
Yup. The paper I read presented NCAR and CSIRO, and just couldn’t make myself talk seriously about the NCAR case, which looked to be a 4 to 5C increase by 2050 in the document. If I’m going to sit around dreaming, I’d prefer to dream happy dreams; that supermodels are going to start throwing themselves at me in 2030 and the I.R.S. is going to give me back every dime I’ve ever paid them with interest by 2043. ~shrug~
For papers with technical details see:
Interactive Effects of CO2 and Temperature on Plant Growth at CO2Science.org
and Terrestrial Plants and Soils at the NIPCC
By contrast, note that Finland lost a third of its population due to famine during a prolonged “cold snap”:
Neumann, J.; Lindgrén, S. (1979). “Great Historical Events That Were Significantly Affected by the Weather: 4, The Great Famines in Finland and Estonia”. Bulletin of the American Meteorological Society 60 (7): pp775–787. doi:10.1175/1520-0477(1979)0602.0.CO;2. ISSN 1520-0477.
Our critically important challenge as a civilization is not global warming, but how to prevent the next glaciation in about 1500 years. i.e. can we generate enough warming to prevent glaciation!
I’ll vote with Minnesotans for Global Warming on the vital importance of warmer weather and catastrophic consequences of colder weather.
Ed Hawkins says:
January 31, 2013 at 4:58 am
“As our paper on French maize has been mentioned, I thought I had better comment briefly”
“1) For those in doubt about whether hot daily maximum temperatures reduce yields, then have a look at 2003 in Europe. The hottest (and presumably sunniest) summer ever in France, and maize yields went down 20% on the year before.
2) It is not average temperature that matters. Studies in laboratory environments have shown there are temperature thresholds beyond which crops start suffering. Also, an increase in average temperature = a change in the number of extremes.”
A 1 – 2 degree World average increase is not a ‘hot’ daily maximum, it’s only 1 – 2 degrees!
You can hardly compare an unusual heatwave and resultatnt drought in France with a 1 – 2 degree average increase in World temperature. Presumably the heatwave conditions to which you refer had local temperatures much higher than 1 – 2 degrees over an unusually long period. Droughts with or without increased temperature are fortunately an unusual occurance and will ruin crops whenever and wherever they occur, but thankfully these are not the norm, otherwise farmers would not grow the crops that suffer in drought conditions. It is a strong bet that even corn growing in France let alone all other crops would benefit from a degree or two of average warmer weather. It would most certainly have benefits here in Britain and across all latitudes of Northern Europe, but occasional heatwaves and droughts will ruin crops in Northern latitudes just as much as they do in any part of the World, but that doesn’t mean that a very slight average warming would not be generally beneficial.
John Russell says:
January 31, 2013 at 5:15 am
STRAW MAN ALERT! Ladies and gentlemen, there is high fire danger, please extinguish all smoking materials, no open flames permitted. STRAW MAN ALERT!!
John, I neither said nor intimated that extreme weather events didn’t affect crops. I grew up on a cattle ranch, I know about weather and crops. What I said was that global warming, the centuries-long increase in the global surface average temperature, would not lower the crop yields.
Instead, farmers will simply plant different crops. But if heat caused low maize yields, how come Yemen and Jordan and Israel have the highest yields in the world?
That’s what I’m talking about, not your fatuous claim that somehow I indicated that extreme hot weather should lead to a bumper crop. I said nothing of the sort. That’s a straw man.
In this regard, folks, please QUOTE MY WORDS if you disagree with what I said. John didn’t, and paid the price.
w.
Sean C says:
January 31, 2013 at 6:26 am
Thanks, Sean. I looked at the global yields as well as the US yields. Since the global yields includes all of the developing nations, they are included in the graph … so how is it that I am overlooking them exactly?
Perhaps it would be valuable for you to point to the nation you are talking about. What nations are you saying make a difference in the corn/wheat/rice yield equation, and what kind of change do they make? Hang on …
OK, here’s the grain yields of the Least Developed Countries (LDCs) and the Landlocked Developing Countries:
As you can see, even in the worst off countries on the planet, even with the warming of the last 50 years, the yields are still rising.
So now that you’ve busted me, remind me again … what was I not being “true to accuracy” about? Where am I risking “questions of integrity”?
Folks, making claims is easy. I put the links to the data to encourage you to not just spout off with your brilliant claim, but to go and see if it actually is true before bothering us all with it … how come I gotta do the work on your theory, Sean?
w.
PS—In passing, let me point out that the grain yields of the worst off countries, the LDC and the landlocked developing, are now at or above the global average yields of just a half century ago …
Austin says:
January 31, 2013 at 8:59 am
Fundamentally, this comment is useless. If I have said something you disagree with, QUOTE MY WORDS and tell my why you disagree. Claiming it is “flawed” and then rambling about C3 and C4 plants does nothing.
w.
@CodeTech:
I was mostly just using your statement as a jumping off point…
FWIW, in most places what would happen (IFF warming were real…) is that the “last frost” date would be earlier, so folks would plant earlier, and follow the same temperature / time profile as now, just a day or two earlier. At the end of the growing season, they might have some added growing days, so get more crop, or just harvest early. Some places would get enough added time to add a second crop per year (as is presently done in warmer areas).
Yeah well, alarmists were stampeding governments into initiating force against people in the 1970s – over the disastrous impact global cooling would have on agriculture.
People who can’t adapt quickly will have trouble, but aren’t there a range of plant variations today and much ability to grow more? Within the past year wasn’t there a discusion about wheat in WUWT, which noted it grows from mid-Canada cool to Africa hot?
REf: Ed Hawkins’ paper:
Any crop, whatever the weather the rest of the summer has been, is subject to catastrophic localised events such as flood or hailstorms, so the correlation of an especially hot summer in France with a poor crop cannot be assumed as cause and effect. Very hot summers are often followed by more violent than usual storms at summers’ end, which can devastate a crop. The wide variation of quality and size in wine vintages is testament to that!
As for the overall attempt to relate crop yields to climate, I fear it is meaningless. The vast majority of many staple crops (esp maize /corn, soy and ‘canola’ or rapeseed) in North America is now GM: genetically modified. Records therefore cannot be compared to those of previous years, since strains change in nature over a short period, and in just ten let alone twenty years the crops grown have mutated so far that records are no longer comparable. These foodstuffs are engineered to crop heavily, but are different in kind to those grown in the past.
Monsanto, Dow and their ilk are getting a stranglehold on the food supply with their pesticide-laden and sterile frankenfoods; I’ve been studying this in detail for a few years now and this imo is an even greater problem for our collective future than the AGW scare. Most people don’t seem to understand how far advanced this process has been advanced, least of all consumers in the US and Canada where the advance of GM foods is almost beyond reversal.
If you wish to compare crop yields over the last ten or twenty years, it would be best to limit yourself to Europe or other places where GM crops are not yet the norm. The picture in N America is too distorted by them now for meaningful comparisons.
Charles Dickens made it all up?
Thirty years ago, Marseilles lay burning in the sun, one day.
A blazing sun upon a fierce August day was no greater rarity in southern France then, than at any other time, before or since. Everything in Marseilles, and about Marseilles, had stared at the fervid sky, and been stared at in return, until a staring habit had become universal there. Strangers were stared out of countenance by staring white houses, staring white walls, staring white streets, staring tracts of arid road, staring hills from which verdure was burnt away. The only things to be seen not fixedly staring and glaring were the vines drooping under their load of grapes. These did occasionally wink a little, as the hot air barely moved their faint leaves.
There was no wind to make a ripple on the foul water within the harbour, or on the beautiful sea without. The line of demarcation between the two colours, black and blue, showed the point which the pure sea would not pass; but it lay as quiet as the abominable pool, with which it never mixed. Boats without awnings were too hot to touch; ships blistered at their moorings; the stones of the quays had not cooled, night or day, for months. Hindoos, Russians, Chinese, Spaniards, Portuguese, Englishmen, Frenchmen, Genoese, Neapolitans, Venetians, Greeks, Turks, descendants from all the builders of Babel, come to trade at Marseilles, sought the shade alike—taking refuge in any hiding-place from a sea too intensely blue to be looked at, and a sky of purple, set with one great flaming jewel of fire.
The universal stare made the eyes ache. Towards the distant line of Italian coast, indeed, it was a little relieved by light clouds of mist, slowly rising from the evaporation of the sea, but it softened nowhere else. Far away the staring roads, deep in dust, stared from the hill-side, stared from the hollow, stared from the interminable plain. Far away the dusty vines overhanging wayside cottages, and the monotonous wayside avenues of parched trees without shade, drooped beneath the stare of earth and sky. So did the horses with drowsy bells, in long files of carts, creeping slowly towards the interior; so did their recumbent drivers, when they were awake, which rarely happened; so did the exhausted labourers in the fields. Everything that lived or grew, was oppressed by the glare; except the lizard, passing swiftly over rough stone walls, and the cicala, chirping his dry hot chirp, like a rattle. The very dust was scorched brown, and something quivered in the atmosphere as if the air itself were panting.
Blinds, shutters, curtains, awnings, were all closed and drawn to keep out the stare. Grant it but a chink or keyhole, and it shot in like a white-hot arrow. The churches were the freest from it. To come out of the twilight of pillars and arches—dreamily dotted with winking lamps, dreamily peopled with ugly old shadows piously dozing, spitting, and begging—was to plunge into a fiery river, and swim for life to the nearest strip of shade. So, with people lounging and lying wherever shade was, with but little hum of tongues or barking of dogs, with occasional jangling of discordant church bells and rattling of vicious drums, Marseilles, a fact to be strongly smelt and tasted, lay broiling in the sun one day.
http://www.gutenberg.org/files/963/963-h/963-h.htm#link2HCH0001
PS To the basic premise of Willis’s article – that warmer weather / climate will increase crop yields: I fully agree with this. Indeed all our our collective observation and experience confirms this to be true. In my reference to the preponderance of GM foods in intensively cultivated developed countries, I was merely pointing out the problem of proving this using yields, since we are no longer able to compare like with like
DesertYote says:
January 31, 2013 at 8:13 am
… the Vermin Fence (called the Rabbit Proof Fence in the Eastern States) …
###
Stupid question I could probably answer myself if I had time to wiki-wiki wiki. Is this the same as the Dingo Fence? Also is the name Dingo Fence real or just something cooked up by an American Activist?
The Dingo Fence is another fence in the East.
The Western Australian Vermin Fence primarily keeps emus out of the wheat areas. There are very large numbers of emus in the forested area on the other side of the fence. A fire burned through in the mid-1990s and an estimated 60,000 emus died.
There was an movie made called The Rabbit Proof Fence, which is why people outside WA call it that.
In the south of WA the land on the other side is quite heavily forested and not hospitable to rabbits. Further north where the country is more open, the fence, which at one time went pretty much the whole length of WA, may have been built to keep rabbits out.
Remember the Medieval English vineyards followed by Frost Fairs on the Thames
The warming since the Little Ice Age is just beginning to return us to the much more productive agricultural conditions in the Medieval Warm Period and the earlier Roman warm period.
Sam the First says:
January 31, 2013 at 5:53 pm
Thanks, Sam. Actually, my basic premise was the other way around—that a warmer climate will not lower crop yields. It may increase them, but that’s not what I have showed.
w.
I’ve added an update at the end of the post to try to clarify some misconceptions that I find floating in the ethernet … plus a graph I posted above of the LDCs.
w.
The threats to crops are five-fold:
1. Lack of sunlight.
2. Torrential rain over long periods, rendering the soil anaerobic.
3. Denuding the soil of essential trace elements.
4. Denuding the soil of essential microorganisms and earthworms.
5. Direct damage to crops through weather events, be that harsh frosts, extreme hailstorms or prolonged drought.
Of course, different crops have different optimum temperatures and some are indeed heat sensitive. You have the option, if it gets warmer, to plant such crops either earlier in the year, in a more shaded environment, outside rather than in glasshouses etc. You have the option of harvesting sooner if the heat comes earlier in the year. You presumably have a longer growing season between the last dangerous frosts of the early spring and the first dangerous frosts of early autumn.
My view is the greatest dangers come by destroying soil fertility rather than changing temperature.
Philip Bradley
January 31, 2013 at 6:59 pm
DesertYote says:
January 31, 2013 at 8:13 am
###
WOW, thanks for the information! I found it fascinating. On a side note, when I first heard of the Dingo Fence, I actually owned a Dingo and thought the idea of someone trying to building a fence to control her movements was kind of funny. She was scary smart and more agile then a cat. Owning her was very instructive.
And thanks again. This is why I come here to read, one of the few places where the comments are usually more interesting then the article being commented on.
Slightly off thread. Our activist friends the Greens last year broke into a Canberra CSIRO trial plot of GE modified wheat and shredded the lot.Thanks to all the Ag scientists who have contributed here. It helps explain why MSM arts/humanities educated journos (i.e. most) do not understand or care about agriculture (or science). Dingos (wild dogs) are native to Australia. The dingo or dog fences were constructed to keep sheep country free of dogs. They are still maintained for this purpose. PS It’s obvious more should be spent proportionately on ag.science research than on climate change stuff. Cheers from soggy (again) Sydney.
@John Russell says:
January 31, 2013 at 5:15 am
“Sure; up to a point warmth can increase plant growth. But speaking practically?
The USA had its hottest year on record in 2012 (1). So following Willis’s logic, perhaps we should expect crop yields to be the best on record? ”
++++++++++
Actually, the US had a drought, caused by colder than average temperatures of the Pacific West Coast. Note colder. Colder air holds less moisture. The normal Easterly winds naturally blew this dry air over the middle of the country where the cloudless skies made it hot. Dry air holds much less latent heat and so warms up faster. The drought was the problem –not global average temperature.
If you are trying to lead people to believe Willis suggested that drought-caused higher temperatures should lead to increased crop growth, then you are just looking for an argument.
“So I thought I’d review the facts.”
Willis, really, this is climate science, there’s no need to get carried away……..
Global warming is supposed to manifest itself gradually over this century. Farmers have plenty of options such as planting drought / heat resistant strains or planting new crops. Cold and wet can also cut yields in ONE summer. What does that tell me about man-made global warming?
Mark Bofill says:
January 31, 2013 at 9:38 am
[bunch o’ stuff, and ‘still I’m somewhat suspicious of findings that show +9% increases for rainfed wheat across the board in 2050 under these projections and yet shows a 21% decrease for irrigated wheat; I’d like to see the mechanics of that.’]
———————–
Okay, I feel justifiably stupid. The explanation for this is right there in the paper clear as day, it says ‘the Middle East and North Africa and Sub-Saharan Africa regions both experience (average IRW) reductions of about 4 percent’. Basically the argument is that irrigated crops suffer because the water available from precipitation goes down in these places.
I don’t know if this is TRUE, but that’s the explanation at any rate. Kudos to Paul_K’s comment on Lucia’s the Blackboard (Lower Crop Yield for AGW?) for prompting me to re-read the darn thing and pay better attention. 🙂
Mario Lento
January 31, 2013 at 11:48 pm
Actually, the US had a drought, caused by colder than average temperatures of the Pacific West Coast. Note colder. Colder air holds less moisture. The normal Easterly winds naturally blew this dry air over the middle of the country where the cloudless skies made it hot. Dry air holds much less latent heat and so warms up faster. The drought was the problem –not global average temperature.
###
I wish I could have said this as well as you, and I hope, even though this thread is a bit old, others read and remember it. In the past, I have tried, unsuccessfully to make this point. I had even thought to do so in this thread, yesterday. But, I was so crazy busy that I did not want to withstand the frustrations of trying to communicate even moderately complex concepts.
I grew up in the shadow of the Hohokam along the Salt River, had a few O’odham (the Hohokam’s descendents) friends, and learned a little bit about their history. Almost all the periods of drought (and high land temps) happened during times of globally cool climate. Not only that, but the Hohokam culture had its golden age, with cool temps and plenty of rain ( and sometimes too much) during the MWP!