Do Increasing Temperatures Lower Crop Yields?

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.

grain yields and temperatureFigure 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;

us grain yields and temperatureFigure 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.

grain yields ldcs

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.

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David, UK

But you’re using empirical data, Willis. We mustn’t forget that the models tell a different story (after all, they were made to) and that is why we must continue to be alarmed and wet our beds.

Well done Willis. I spotted another alarmist piece about heat effects on maize production by MET Office scientist Ed Hawkins and Leeds Earth Sciences Prof. Andy Challinor recently which had some obvious flaws:
It was written up in a Guardian piece entitled:
Global food crisis will worsen as heatwaves damage crops, research finds.
So I spoofed the title and wrote a quick review here:
http://tallbloke.wordpress.com/2013/01/14/global-scaremongering-will-worsen-as-revelations-damage-research-funds/
🙂

Mario Lento

Willis: I love your posts. Here’s a question in the form of some thoughts, but please bear with me, maybe you can help answer or correct where I’m going.
I too do not believe an increase in temperature would lead to an overall reduction of plant growth. That’s too broad sweeping a statement from the left. However, I do believe temperature has an affect on the life cycle of plants and may shift growing climates around (more growth in upper latitudes etc. But I digress: My question: Is there a way to separate the causes for increased “production” of crops as related to: advances in agricultural science, demand for more food leads to more supply, subsidies to grow certain crops etc etc. In other words, isn’t some of the increase in crop production due to more farming?
But one more piece here is that has a significant affect on plant growth is available CO2. There seems to be good evidence that extra CO2 increases efficiency of plant growth, Given that CO2 (and H20) are the molecules that plants need for their energy storage –and that their mass (protein, carbs and fats) is made up primarily of these molecules that are essentially rearranged using the energy of the sun.
So, how can we separate temperature from the rest of this puzzle? Your answer would be especially interesting to me.

Around 1975 when AGW was just getting started, Australia’s CSIRO successfully persuaded the Western Australian government that they shouldn’t open up the lands to east of the Vermin Fence (called the Rabbit Proof Fence in the Eastern States) to agriculture, because declining rainfall due to climate change would make wheat growing not viable and would make wheat growing across the whole the Western Australian Wheatbelt less viable.
A couple of years ago I got into a debate on this forum from someone from CSIRO who claimed this was a successful prediction.
Since 1975 the value of WA wheat production has increase more than 5-fold, with no increase in area.
http://members.iinet.net.au/~rgcason/cropsv/wheatvxstait/wawheatvgraf.gif
Couldn’t find a graph for volume, but from memory it’s more than doubled.

Dagfinn

I have another crazy idea: If temperatures become too high for a crop, farmers will change to a different one that’s better suited to higher temperatures. It won’t happen overnight, there will be time to adapt.

Skeptik

massive decline in crop yields due to increasing temperatures?
Obviously the fool that wrote that does not have a lawn,
Mow once in 3 months in winter, mow once every 3 days in spring.

Paulc

Have to agree. It is so obvious that increasing temps lower crop yeild.
Just look at the proliferation of vegation at the poles compared to the equator.
Poles win every time
/sarc

markx

Our plant geneticists have demonstrated a great capacity to adapt plants to areas they are not native to, and now they also have the added and speedier tool of GM technology at their disposal… So warming is the best case scenario, if there must be a change, as I am pretty sure they cannot possibly breed plants to thrive in frozen ground.
Some (really simple!) geography …
The ends of the planet are currently permanently frozen and completely unproductive.
The ‘middle’ of the planet is currently warm, and mostly highly productive.
At the worst a shift towards a warmer world may (possibly, but not certainly) make some warm lands unproductive, but must make some frozen lands productive. (ie, we are buffered).
But, a shift to a colder world would only make the frozen ends bigger, with no possible compensatory buffering effect ….

Ronald

Stupid they are not more not less.
In Holland there are lots of glass boxes were they grow plants, in those boxes its hot and often there is a lot of CO2 up and over 1000 ppm and there is plenty of light.
They do that for an better grow d of the crop and you now that they call it greenhouses? You bet scientist who call CO2 a pollutant greenhouse gas don’t even now what a greenhouse is.
And then they don’t even now what happened in the years long gone when there was a climate optimum.
Sometimes I even wonder how they came to the 2 degrees to be the maximum the temperature may rice.
Higher temperature more CO2 and more water vapor make it only better.

Willis Eschenbach

tallbloke says:
January 31, 2013 at 12:35 am

Well done Willis. I spotted another alarmist piece about heat effects on maize production by MET Office scientist Ed Hawkins and Leeds Earth Sciences Prof. Andy Challinor recently which had some obvious flaws:
It was written up in a Guardian piece entitled:
Global food crisis will worsen as heatwaves damage crops, research finds.
So I spoofed the title and wrote a quick review here:
http://tallbloke.wordpress.com/2013/01/14/global-scaremongering-will-worsen-as-revelations-damage-research-funds/
🙂

That’s great stuff, Rog. I find their claim that warm temps in France are a huge danger to French maize production to be trez bizarre, particularly given the following:

France isn’t even has warmed about a degree, according to BEST, yields continue to rise, and your author is all atwitter … you were right to skewer him.
I just don’t see how there’s anything to support any “global food crises” in there, but hey, what do I know? I was born yesterday …
All the best,
w.

Paulc

So called green house gasses make a hugh difference.
CO2 – Plant food – bring it on
H2O – Add this – the rest is insignificant

Stephen Skinner

The two primary considerations when growing plants and things are: frosts and water. I don’t recall temperature being one. Whenever it gets hot that would indicate plants need more water and if you don’t get the water right the plants die. I don’t suppose those who wish to draw the conclusion that higher temps lower yield have done any gardening or farming, in other words, get their hands dirty?

I wonder whether Wills, it is important measuring yields versus temperature, because it has been shown in a number of papers that temperatures in the Californian and Australian small country towns have not risen as much as in the large cities, if at all.
As I revealed in a previous blog, the temperatures in our tomato growing area of Echuca have actually gone down slightly. Since 1984, our tomato yields have increased three fold, mainly due to better hybrid varieties, better irrigation using underground drip, better fertigation using this drip technology, and better management techniques.
Willis believes that these increases must reduce at some time in the future, but work on soil microbes will continue to produce enormous yield increases.
It might be worthwhile looking at yield versus CO2, but CO2 has not increased threefold since 1984.
Regards, Ian

James Allison

Here’s an even crazier idea. Scientists will continue breeding crop varieties that have better yields in warmer/colder/unchanging climatic conditions.

Gareth Phillips

Agriculture has adapted for thousands of years to meet the needs of changing climates since neolithic times. We currently grow crops across many climates, from cold wet Wales to hot and dry California. I cannot for the life of me see how we cannot adapt to a changing climate as we have done for millennia. We may lose the potential for crops in one area, but gain in another. The change in numbers of bird species in the UK is good example of nature adapting, I’m sure we will do the same. I must admit though, going back to growing traditional Welsh crops like Cabbages, Leeks and root crops on our land works fine, but I do miss growing our own Sweetcorn, French beans and crops more suited to warmer climes. The Met office promised us a warmer and drier climate, we looked forward to being able to grow wonderful crops. In the event it got colder and wetter. We are deeply disappointed.

They say the Sahara was Savannah 6,000 years ago, was that because the rain patterns changed?
I also heard some statistic that Africa has something like 60% of the Worlds arable land, which really surprised me.

Willis Eschenbach says:
January 31, 2013 at 1:13 am
[…]

Thanks Willis.
Their premise seems to be that ‘hot days’ damage the crop, and AGW means there will be more of them. They don’t stop to consider than less frosty days might help even more than hot days hinder though…
But the main flaw is their naive belief in the claims of the fertiliser, pesticide, tractor and seed companies that the increased yields are all down to their products.
Sure, modern methods make for bigger yields, but longer sunshine hours have a lot to do with it too…

Here’s another amusing one for you to check out, Willis. The migratory birds are arriving 4 days earlier, so a wildlife corridor must be set up to save them from climate change or something. 20 years of research too. West Australian Science once again/sarc: http://pindanpost.com/2013/01/31/tell-that-to-the-birds/

George Lawson

Wouldn’t a rise in temperature improve food production further North and South of the Equater? And do recent years’ food production figures take account of the huge areas of land taken out of food production for bio fuel purposes?

Willis, This is 2009 stuff.
They say the areas to be hit the hardest are in the developing world.
Can you bring data from Sahara, Africa, India and such?

Mario Lento

To Ian: I think Willis’ point is this: Just looking at the evidence, shows that the claim that higher temperatures will reduce crop yields is unsubstantiated. It’s to me no different than saying living naturally will lead to a longer healthier life… when in fact the life expectancy of people living in civilization live longer than people living in the wild. Willis’ point is right on, I think.

A. Scott

Excellent work Willis … simple common sense tells us warmer temps and increased CO2 are generally beneficial to plant growth – and you show that in the simplest terms.
True as tallbloke notes – some of the gains are an increase in productivity through science, but it seems pretty clear that all things factored crop production is benefited by warmth and CO2.
When we dip back into the inevitable, and looming, descent into the next glacial cold cycle we will want and need all the crop production we can get.
.

CodeTech

In answer to the title question, wouldn’t that depend on the starting point?
I mean, the Prairie Provinces in Canada could easily benefit from a 5-10C rise in temperature for production of almost everything we grow. Can’t say the same would benefit wheat or corn producers in Texas.

Good job again Willis! You might check out AgPHD.com
Those Hefty boys are kind of smart!
Alfred

Another piece of common sense, thanks.
Anyone with half a brain can see that warmer is better as far as food crops are concerned. I do not care about biofuel crops they can die in the fields and let the food prices revert to the level that is affordable to the developing world.

Andrew 4352

This is a situation where averages tell us nothing. Critical events at specific stages of crop development can have a major impact on crop yield. e.g. heat wave during flowering, frost during grainfill, high temperatures during grainfill leading to premature senescence of leaves that provide carbohydrates for grainfill. For winter cereals, high temperatures during stem elongation can accelerate crop development and restrict amount of tillering leading to a constraint on grain production even when more favourable conditions return.
Bottom line is that average temperatures do not necessarily tell us whether the frequency of these “adverse” events is increased or indeed whether these are coincident with critical stages of crop development.
Therefore a more useful metric would be to plot frequency and severity of frost days during flowering, incidence of “heatwave” conditions at stem elongation, flowering (taselling in maize), and grain fill in cereals. Even then, this does not take into account the impact of management practices which allow for a spread of flowering dates (reducing exposure to single extreme events), varietal selection, nutrient management.
The tendency to look at a headline number for temperature is pretty useless as many commenters have pointed out the upward trend in crop yields.

Jakehig

Good post, as always.
You might have noticed that this issue featured in the Stern report which cited a study showing how yields of typical temperate crops declined at higher temps. That was debunked when it was revealed that the study had subjected the crops to constant high temps – as if it stayed at or above 30 degC 24/7.
On the related topic of keeping people alive, I was disappointed but not surprised to note the lack of media clamour over a statement by Bill Gates in a BBC address. He stated that, in his lifetime, the number of children dying before reaching 5 years old has dropped from around 20m per year to 5m. (I would add that is against a background of population growth). While there is a long way to go, that is huge progress which deserves banner headlines.

Nice article.
3 simple points:
1) Plants mature according to ‘degree days’. How many days ABOVE a certain minimum and how many degrees above. For most plants, more degree days is better up to a very high temperature.
2) Phoenix Arizona. How high that ‘very high point’ is can be found by looking at ‘grow season dates’ in the Sunset Garden Book. Only one place has a ‘poor growth’ band in summer. That is Phoenix Arizona. Even then, in exchange, you get growth in all THREE other seasons, so a total longer growing season. So until everywhere is as hot as Phoenix, no worries. (Oh, and in summer they still grow things, just more heat tolerant plants like tomatoes).
3) What you grow matters. Barley grows in Alaska. Oats sprout at 34 F just a hair above freezing. On the other end, Millet grows in the Sahara just on the edge of the sandy bits and tepary beans grow in the Mojave (about as hot as Phoenix, but not irrigated…). So it’s as much what you choose to grow as any given heat level.
Oh, and water maters a whole lot more than heat….
More details here:
http://chiefio.wordpress.com/2013/01/11/grains-and-why-food-will-stay-plentiful/

John West

“Where are the snows of yesteryear?”
They’ll be back.

ROM

As an old and now retired farmer, one who was very interested in and mixed up in agricultural research for many years, we have a much, much greater danger from whack job city politicians and bureaucrats reducing their support and funding for agricultural research because they are out ,of money due to it all being spent on non visible climate warming research and the massive subsidies for hot air mitigation and going to the wealthy city scammers with their completely useless and inefficient so called renewable wind and solar power generators.
And no doubt they will take the attitude that there is plenty of food so we can cut back on agricultural research
And I don’t mean agricultural subsidies which to all intents and purposes don’t exist in Australia at all.
Australian farmers depending on the type of crop, put in 1% of their gross income each year towards research which is matched by the federal government.
This is distributed in grants to Ag researchers.
State governments generally support the various Agricultural research institute’s basic infrastructure and salaried researchers and support staff.
Through the Gene mapping and now the very rapid ability to access the various genetic specifications of plant material via the internet and genetic sources of plant material in the seed banks of a surprising number of countries around the world, the world’s plant and crop breeders can rapidly sort through their needs in genetic material, locate as to where some of this material might be stored in the 40C below zero vaults of the various international seed banks and get usually only 2 or 3 seeds posted to them within days so that the new material can be incorporated into the new season’s plant crosses.
From those crosses will come in perhaps ten years time after selecting from perhaps as many as 15,000 initial plant crosses, a new variety might emerge for farm commercial production to finish up somewhere on the plate of the consumer in a form they will never recognise as coming from a plant, let alone from a seed used to grow a single plant some ten or more years ago, a single seed that came from somewhere half a world away.
The curators of these global seed banks all know one another very well and the interchange of plant genetic material goes on by devious channels even through low level conflicts between nations. Like all agricultural researchers, there is a deep knowledge that if they let their international system of swapping genetic material and information and technology fall apart then all nations will eventually suffer as genetically controllable diseases become uncontrollable due to the lack of access to genetic material which would have natural resistant genes to those plant diseases and which a transfer of perhaps 2 or 3 seeds with natural resistance to that disease / insect / fungal pathogen and etc from a national seed bank of one country to the plant breeders of another country where the problem has arisen, would lead to resistance being incorporated into new crop plant material within perhaps some 5 to 7 years.
And the devastating crop losses would be almost halted from that disease or even the ability to again grow the crop would be re-established .
Exactly the situation here in Australia in the mid 1990’s with our chick pea industry when a highly virulent fungal pathogen developed through a genetic shift of the fungal pathogen and the growing of chick peas almost ceased until the plant breeders using overseas plant genetic material, bred full resistance to that pathogen back into the new generation of chick pea plant material.
We have far, far more fear of stupid politicians and bureaucrats interfering and stopping funding for that quiet, absolutely essential to future world food supply, international plant and genetic material swapping system than we will ever have from a degree or so change or shift in the temperature of the local climate.
A shift that occurs in any case with every individual and different in climate season and usually by much more than a degree.

Vince Causey

Well, Willis, as you are surely aware, the alarmist claim is about the catastrophes that they reckon will occur in the future, just as soon as the temperatures get stoked up a bit. So while I share your view that it is all nonsense, your logic will have no effect on such a mindset.

@Markx:
Generally, yes, the ‘first frost date’ determines the end of the growing season. However… for only minor cold / frost there are a few plants folks can grow. Spanish Winter radishes, turnips, kale (that can be harvested from under snow!) all come to mind. The rate of growth is still temperature proportionate, so faster when warmer….
Don’t really need to GMO or develop any more heat tolerant plants. They are fine up to about 110 F for most things. Since most of the planet will get nowhere near that temperature, simply shifting plant types a bit north will cover most anything possible.
Since most ‘warming’ is not higher highs, but higher lows, warming is pretty much universally a benefit.
@Julian in Wales:
It was Savanna because at higher temperatures, the rising air pulled water laden winds inland, and rained more.
http://chiefio.wordpress.com/2010/08/10/cold-dry-sahara-hot-wet-savanna/
IFF the world really warms (which I sorely doubt) the Sahara becomes one giant garden…
Look on a Globe. Look at the size of the USA, and Brazil. Look at the part of Africa not a desert… I think that 60% is way off… I think you are echoing this quote, but without the modifiers and caveats:
http://blogs.worldwatch.org/nourishingtheplanet/the-fertile-continent-agriculture%E2%80%99s-final-frontier/

But in an article in the November/ December 2010 edition of Foreign Affairs magazine, titled The Fertile Continent, Roger Thurow—Senior Fellow on Global Food Policy at the Chicago Council on Global Affairs—says, “The continent that has been fed by the world’s food aid must now help feed the world.”
The article highlights Africa as agriculture’s final frontier. “More than half of the earth’s unused arable land that can still be exploited without endangering forests and other ecosystems is in Africa…In contrast to much of the rest of the world, land and water resources in Africa have been largely underused.”

@George Lawson:
Yes. Effectively, everything cooler than Phoenix Arizona ( I was there one day when the shut down the airport as the tarmac was melting in the sun… 128 F or so in the shade… and there’s no shade…) will gain growing days until they have a full 4 season growing window. Then the summers start to be limited to ‘hot temperature crops’ as they warm to match Phoenix.
That means the 45 and 60 day growing periods of the “Frozen North” have about 300 growing days to add (and about 2 or 3 more crops per year…) before it’s an issue. Now look at how big the land is in Russia, China, Mongolia, Canada, Alaska, …
@Code Tech:
Look at south slightly west Texas. More sorghum, less corn. As Texas gets hotter, (and dryer) they shift to sorghum (or millet) at similar yields. (Though AGW theory says we ought to be warmer and wetter… for that, look at Brazil with spectacular growth of corn and soybeans…)

Peter in MD

isn’t this testable? Setup 2 greenhouses, one with higher CO2 and higher temps and no fertilizer, the other with lower CO2 levels and lower temps and all the fertilizer they want. Keep H2O the same.
Wouldn’t this be an appropriate test?

John West

@ Eyal Porat
Data is a little older, but interesting.
http://www.nationmaster.com/graph/agr_cro_pro_ind-agriculture-crop-production-index
“Crop production index shows agricultural production for each year relative to the base period 1999-2001. It includes all crops except fodder crops. Regional and income group aggregates for the FAO’s production indexes are calculated from the underlying values in international dollars, normalized to the base period 1999-2001. “
Plucking a few:
# 2 Morocco: 148.6 % 2004
# 13 Algeria: 128.4 % 2004
# 25 Ghana: 121.2 % 2004
# 30 Angola: 119.2 % 2004
# 38 Chad: 115.7 % 2004
# 41 Maldives: 115 % 2004
[must be a lot of underwater agriculture]
# 50 Rwanda: 113.1 % 2004
# 50 Botswana: 113.1 % 2004
# 58 United States: 111.3 % 2004
# 182 United Arab Emirates: 57.4 % 2004

Jimbo

Developing countries??? I thought most of the warming would be felt as you moved towards the poles??? Anyway, I digress.
What is the result after the recent global temperature rise, hottest decade on the record with highest levels of atmospheric co2 in 800,000 years?
The biosphere has been greening as well as the Sahel & Sahara I wonder why?
It’s always the bad things they promote and avert their eyes at the good things about global warming such as an expansion of food growing areas northwards and the introduction of crops which used to grow further south.

Dr. Michael Mann [Medieval Warm Period]
“It is evident that Europe experienced, on the whole, relatively mild climate conditions during the earliest centuries of the second millennium (i.e., the early Medieval period). Agriculture was possible at higher latitudes (and higher elevations in the mountains) than is currently possible in many regions, and there are numerous anecdotal reports of especially bountiful harvests (e.g., documented yields of grain) throughout Europe during this interval of time. Grapes were grown in England several hundred kilometers north of their current limits of growth, and subtropical flora such as fig trees and olive trees grew in regions of Europe (northern Italy and parts of Germany) well north of their current range.”
http://www.meteo.psu.edu/holocene/public_html/shared/articles/medclimopt.pdf

Now let’s look at the effect of far higher temperatures and levels of Co2 than we have today in a poor, third world country.

Effects of Rapid Global Warming at the Paleocene-Eocene Boundary on Neotropical Vegetation
Abstract
Temperatures in tropical regions are estimated to have increased by 3° to 5°C, compared with Late Paleocene values, during the Paleocene-Eocene Thermal Maximum (PETM, 56.3 million years ago) event. We investigated the tropical forest response to this rapid warming by evaluating the palynological record of three stratigraphic sections in eastern Colombia and western Venezuela. We observed a rapid and distinct increase in plant diversity and origination rates, with a set of new taxa, mostly angiosperms, added to the existing stock of low-diversity Paleocene flora. There is no evidence for enhanced aridity in the northern Neotropics. The tropical rainforest was able to persist under elevated temperatures and high levels of atmospheric carbon dioxide, in contrast to speculations that tropical ecosystems were severely compromised by heat stress.http://www.sciencemag.org/content/330/6006/957

Just my 2 cents.

Doug Huffman

An attempt at humor here (I, retired, have quit my day job). Is there any chance this whole kerfuffle is due ab initio to misreading greenhouse glasses as greenhouse gasses, a simple typographic error?
Yes, our local greenthumbs use coldframes and de facto greenhouses. Mine, a legacy of my greenthumb builder/owner is about 50 sq. feet, head-high, and made of plastic scrap. We have also a triangular room, that squares up an odd angle, with a window, and a 500 Watt strip heater where he started tomato seedlings. He also transplanted native Cypripedioideae, Lady’s slipper orchids!
Back to climate change; our builder/owner sailed the Great Lakes when he was sixteen years old – evidenced by his AB Seaman’s Card that I found while cleaning. Now Lake Michigan is at a historical low level. Our ferry company has put an alternative deeper water dock in service.

Doug Huffman

There are two measuring devices that I believe could provide meaningful drought/climate change data were they formally distributed and operated; (non-weighing) lysimeters and pan evaporators.
The general reduction in pan evaporation rates may be evidence of solar and/or global dimming.

markx

ROM says: January 31, 2013 at 3:24 am
“……. we have a much, much greater danger from whack job city politicians and bureaucrats reducing their support and funding for agricultural research because they are out ,of money due to it all being spent on non visible climate warming research and the massive subsidies for hot air mitigation and going to the wealthy city scammers with their completely useless and inefficient so called renewable wind and solar power generators. And no doubt they will take the attitude that there is plenty of food so we can cut back on agricultural research…”
Truly well said ROM …. Agricultural research funding seems to get cut back every year, but the success stories are everywhere … these are the people who are the saviours of humanity!
(Sorry to disappoint Michael Mann and James Hansen, that title is not reserved for you, though you will be held up to students in the future as a laughable example of how policy and noble cause corruption can hijack science).

Stephen Richards

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
In this note they do the crafty “climate change” meme. So no temperature increase there then ?
Also, the big problem in recent years in france has been the droughts. Rainfall has been below average for maybe 10 years BUT that is now changing. I have found that if I can get enough water for my legumes they grow very well indeed with average temps 5°C higher than the southern UK.. The comparison is with the UK where, with temperatures lower and rainfall higher the crops still don’t grow as well as here in france with less water.

Latitude

We grow corn in Canada…and corn in Florida
…tomatoes in Alaska….and tomatoes in Mexico
beans in Siberia…and beans in Cuba
…where are these delicate crops these scientists keep finding

John West

cRR Kampen says:
“climate change just dropped your economy into contraction”
1:

“Much of the fall in gross domestic product was due to a big reversal in business inventories and a plunge in federal defence spending which each knocked 1.3 percentage points off growth.

http://www.ft.com/cms/s/0/32ca94f2-6ae1-11e2-9670-00144feab49a.html#axzz2JYYaCnTZ
2:
Sandy wasn’t caused by climate change.
http://wattsupwiththat.com/2012/11/05/an-inconvenient-truth-sea-surface-temperature-anomalies-along-sandys-track-havent-warmed-in-70-years/

markx

cRR Kampen says: January 31, 2013 at 3:57 am
“..the disaster? Check it out: http://www.barchart.com/commodityfutures/Grains .
Learn what a factor of three means, start with corn and remember last year’s cattle slaughter worldwide….”

Sorry, you will have to be a little more specific regarding your meaning …. are you trying to point out that putting 40% of the US crop into biofuels is affecting prices? Or that futures fluctuate on every report, weather and financial? Forgive me if I am a little slow, I last traded agricultural commodity futures about 12 years ago…
“…O and climate change just dropped your economy into contraction….” ….
…and here you point to an article on the effects of the storm ‘Sandy’…??!!
Hang on, do you hold the position that storm was purely the result of climate change? Even Trenberth noted that even he could attribute only a few percent of the effect to warming to date, being more of the opinion that this was just an indicator of things to come… (but, lets give him the benefit of the doubt and say the storm WAS 5% worse due to climate change…lets see, if the economy slowed down 0.4% and the climate change contribution was 5% of that, then I guess we MAY have seen a climate induced effect of 0.02% on the economy).

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.
3) Maize yields have increased (by a factor of ~4) over the past 50 years because we have become better at growing crops, better irrigation (as discussed in our analysis) etc – technology has played a a large part in this, and long may it continue. But, that yield trend has slowed.
4) CO2 is plant food, but not so much for crops which use the C4 photosynthesis pathway, like maize – laboratory experiments demonstrate this. These details matter.
5) Our projection of a 0-12% drop in maize yields by 2016-2035 assuming no technology development is not exactly alarmist! It gives the crop breeders information they need.
6) I am not a ‘Met Office’ scientists as Rog has suggested – I am at the University of Reading.
The paper is available here for anyone that wants to read the whole study:
http://www.met.reading.ac.uk/~ed/home/hawkins_etal_2012_GCB.pdf
Ed.

Jer0me

¿Où sont les neiges d’antan?

The words are French, but the punctuation is Spanish!

H.M.

The simple correlation of yields and temperature would not prove Willis’ point, because other factors also intervene, chiefly technological change (new crop varieties, new farming practices, geographical dispersion of crops, etc. More sophisticated methods are needed, but the general conclusion roughly coincides with Willis.
Crops (like maize) are not a homogeneous set of identical plants, from maize in the Highlands of Peru to maize in Iowa. There are a large number of varieties, and each variety has a large number of “cultivars” (lineages of plants). There are also some genetically modified varieties, besides ordinary selection by breeding. Each cultivar of a variety of a crop, in turn, may be cultivated in different manners (e.g. no tilling, limited tilling, traditional tilling; with or without fertilizer; with different amounts of fertilizer; with or without pesticides; on soils having a varied composition; etc.
Each cultivar, cultivated in a certain manner at a specific site, has an average yield that is a function of temperatures and precipitation. Not just annual temps or annual rainfall, but their distribution at key phases of the crop cycle. There is variation around that average yield, not only from year to year but from field to field, etc.
Each cultivar/variety/crop has thus a RANGE of climatic conditions (say, combinations of temp and rain at different stages of crop cycle) in which the average or expected yield is economically convenient at a certain market price for the output and for inputs. The same yield that makes maize unsuitable in Iowa would be perfectly acceptable in Oaxaca (Mexico), or for that matter, on either side of the US-Mexican border where vastly different yields of maize prevail.
Agriculture is unlike natural vegetation, because agriculture is itself an adaptation of human activities to natural conditions. Farmers plant crops suitable for their fields, and do so in a manner that is, to the best of their knowledge, the most adequate. Perhaps not the optimum, but the best they can do at the moment. And they adapt when conditions change, even in the short term (e.g. rain-fed farmers advance or delay the date of planting in relatively dry areas, depending on the rainfall they get in a particular year). In a longer term, other adaptive changes are introduced (new cultivars/varieties/crops, different farming practices, etc.).
Just as one cannot conceive of a plant not ‘responding’ physiologically to a changed climate, one cannot conceive of a farmer not ‘responding’ behaviorally to changes in environmental conditions. Her job as a farmer is precisely that: responding to changes in the environment.
Suppose that normal climate at a certain place gradually changes along 50 or 100 years. This would change the mean and distribution of expected yields of all cultivars in that area.
The most common way to ascertain the expected change in yields for a certain change in climate is to compute an agronomic ‘crop model’, making yield a function of all relevant variables. Once the “maize production function” is statistically obtained (for one or more cultivars at one or more sites), the analyst SIMULATES a change in climate by forcing the crop (on paper) to undergo a higher temperature or, say, a reduction in rainfall. The usual result, of course, is a reduction in yields, because the original cultivar or variety is perhaps no longer as suitable as it was before, especially because no change has been introduced (‘forced’) in farming practices, let alone the cultivar itself. Now, a few hundred miles South (or North, depending on your hemisphere) the crop has been planted for years in a warmer climate, only the cultivar or variety was different (slightly more adapted to warmer or drier or wetter or colder conditions). Once soil composition is considered, changing the cultivar or variety would ordinarily do the job (keep or increase the yield under the new climate, compared with the situation before). There is ample time to do that by trial and error along 50 or 100 years, involving three or four generations of farmers.
Besides the effect of changed temperature and rainfall, AGW is supposed to occur due to increased atmospheric concentrations of CO2. Now, as plants synthesize their tissue taking carbon from the atmosphere through photosynthesis, more CO2 means more photosynthesis, and ordinarily produces a rise in yield. In some crops (the A4 variety, including maize) the effect on yields is less important, but more CO2 has the curious effect of greatly reducing the plant’s water requirement (by reducing water loss in leaf stomata). According to various experiments, this factor alone may cause an increase of 20-40% in yields (in C3 plants like wheat) and/or a 20-50% reduction in water needs (in C4 plants like maize).
Warming in very hot areas (say the Sahel) and especially if at the same time they become drier, may suffer indeed a reduction in yields, not considering CO2 fertilization, and not considering farmer’s response, a reduction variously estimated from 0% to -40% in various studies. But at the same time, enormous amounts of land in temperate zones (say, in North America or Eurasia) would have an expansion of the no-frost period, and a general improvement of plant suitability. There would also be a large expansion of arable land as more land becomes suitable that previously wasn’t. The net effect is not easily ascertained. The best studies considering these factors (even if including them in an extremely conservative manner) do not foresee a very large net effect. The best evaluations come from so-called “integrated assessment” models (IAM) combining agronomic crop models, agro-ecological zones, soil maps, climatic models, and socio-economic models predicting behavior of people and economic/technological development (including displacement of crops to new areas, changes in crop mix and crop schedule, introduction of double cropping with short-cycle crops where the no-frost period expands, and so on). IAM studies have been mainly carried out at IIASA, the International Institute for Applied Systems Analysis, Laxenburg (Austria), by a team led by Dr Gunther Fischer. The global effects they have calculated are ordinarily based on the ‘worst’ climate scenarios, and often do not take account of all the factors (e.g. may not include new cultivated areas, or may assume a very small or no CO2 effect on plants), but in all cases, under a variety of models and scenarios, the effects are relatively small (say from +5 to -5% effect, to be observed on a FUTURE agricultural production that will be four or five times as large as it is today, due to modest improvements in agricultural practices, as farmers in developing countries catch up with existing technology, or allowing for some extent of technological progress in the meantime). The net effect on hunger is that by 2080 the percentage of humankind suffering hunger (now 12.5% according to FAO) will be reduced to about 1-6% depending on scenarios (figures below 5% as regarded by FAO as not significantly different from zero, due to the method used). The most recent IIASA study (Fischer 2011) can be found at:
FAO, 2011. Looking ahead in World Food and Agriculture: Perspectives to 2050. Edited by Piero Conforti. FAO, Rome. http://www.fao.org/docrep/014/i2280e/i2280e00.htm.
(Fischer’s study looks farther ahead to 2080, and is based on FAO very prudent projections of farm output, plus effects of climate, and also considering the effect of crop-based biofuels that are likely to be introduced according to current targets).

John Russell

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? Well in fact yields in almost all sectors—including livestock—saw significant reductions, with a consequent rise in prices (2).
In 2012 the UK had average temperatures which, using the same rationale, would suggest—if temperature were the-be-all-and-end-all—that we should have seen average crop yields. In fact, most likely because of increasing rainfall (3), year-on-year the UK’s agricultural yields are slowly falling (4).
So overall what does this tell us? Could it be that—speaking practically—while both are important, the optimum amount of water has a greater impact than the optimum temperature when it comes to agricultural production? The evidence suggests that due to climate change the unreliability of rainfall—with, at the extremes, an increase in both drought and flooding events—will be the greatest headache for farmers. (5)
So note the specific question Willis uses as the title for this post and beware any extrapolation to the suggestion, “climate change is good for us”. If in doubt, why not actually ask the question of a farmer?
References
1: http://www.climatewatch.noaa.gov/video/2012/the-making-of-the-hottest-year-on-record-usa-temperature-update
2: http://www.ers.usda.gov/topics/in-the-news/us-drought-2012-farm-and-food-impacts.aspx
3: http://www.metoffice.gov.uk/news/releases/archive/2013/2012-weather-statistics
4: http://www.thecropsite.com/reports/?category=87&id=1385
5: http://www.metoffice.gov.uk/climate-change/guide/impacts/food

Bruce Cobb

Willis, in order to see what Alarmists see, you just need to have the reality-suppressing, fear-inducing Warm-O-Vision © goggles they wear. Not sure if they’re still available, but perhaps on ebay.

CodeTech

E.M.Smith, you replied to my admittedly brief comment with the obvious statement that in higher temperature areas it’s trivial to switch crops.
I guess the part I skipped out was that we could continue to grow the same crops as we do now if the temperatures were higher, since the Canadian Prairies aren’t exactly known for overall warmth. However, in areas that are already nearing the upper limits for a type of plant then sure, increasing temps could be a problem. And no, I don’t know the average temps in Texas or the exact tolerance of the kinds of wheat and corn we grow here, so maybe Texas wasn’t a great example.
Apparently the obvious thing missing in the original article is that people don’t just continue to blindly do the same things when conditions change, and making that assumption when attempting to project the results of “climate change”, whatever that means, is just stupid. It’s like saying that a monotonous, slow rise in sea level would be catastrophic when we KNOW that people won’t just sit and chew their nails watching it happen. Sea walls would be built, existing structures might be altered, future designs in the area would be adjusted.
Again, lower crop yields might be the result if people plant the same crops in the same place where climate is “changing”, and make no other changes to account for this alleged “change”. However, people are just not that stupid (with the possible exception of “climate scientists”…)

Graham W

For God’s sake everyone. Plants hate additional CO2 and warmer climates, they told me so and I published it in a paper. Arctic ice! Radiative properties of CO2! Peer review!

Graham W

P.S: Ultra-thunder-mega-super-hurricane Sandy!