US farmers dodge the impacts of global warming -- at least for now

May 05, 2011
A combine harvester reaps, threshes and winnows its way through a field of corn at harvest time. Yields in the US, Canada and northern Mexico have yet to feel the impact of global warming. Credit: UDSA

Global warming is likely already taking a toll on world wheat and corn production, according to a new study led by Stanford University researchers. But the United States, Canada and northern Mexico have largely escaped the trend.

"It appears as if farmers in North America got a pass on the first round of ," said David Lobell, an assistant professor of environmental Earth system science at Stanford University. "That was surprising, given how fast we see weather has been changing in agricultural areas around the world as a whole."

Lobell and his colleagues examined temperature and precipitation records since 1980 for major crop-growing countries in the places and times of year when crops are grown. They then used crop models to estimate what worldwide would have been had temperature and precipitation had typical fluctuations around 1980 levels.

The researchers found that global wheat production was 5.5 percent lower than it would have been had the climate remained stable, and global was lower by almost 4 percent. Global rice and production were not significantly affected.

The United States, which is the world's largest producer of soybeans and corn, accounting for roughly 40 percent of global production, experienced a very slight cooling trend and no significant production impacts.

Outside of North America, most major producing countries were found to have experienced some decline in wheat and corn (or maize) yields related to the rise in global temperature. "Yields in most countries are still going up, but not as fast as we estimate they would be without ," Lobell said.

Lobell is the lead author of a paper about the research to be published May 5 online in .

Russia, India and France suffered the greatest drops in wheat production relative to what might have been with no global warming. The largest comparative losses in corn production were seen in China and Brazil.

Total worldwide relative losses of the two crops equal the annual production of corn in Mexico and wheat in France. Together, the four crops in the study constitute approximately 75 percent of the calories that humans worldwide consume, directly or indirectly through livestock, according to research cited in the study.

"Given the relatively small temperature trends in the U.S. Corn Belt, it shouldn't be surprising if complacency or even skepticism about global warming has set in, but this study suggests that would be misguided," Lobell said.

Since 1950, the average global temperature has increased at a rate of roughly 0.13 degrees Celsius per decade. But over the next two to three decades average is expected to rise approximately 50 percent faster than that, according to the report of the Intergovernmental Panel on Climate Change. With that rate of temperature change, it is unlikely that the crop-growing regions of the United States will continue to escape the rising temperatures, Lobell said.

"The climate science is still unclear about why summers in the Corn Belt haven't been warming. But most explanations suggest that warming in the future is just as likely there as elsewhere in the world," Lobell said.

"In other words, farmers in the Corn Belt seem to have been lucky so far."

This is the first study to come up with a global estimate for the past 30 years of what has been happening, Lobell said.

To develop their estimates, the researchers used publicly available global data sets from the United Nations Food and Agriculture Organization and from the University of Delaware, University of Wisconsin, and McGill University.

The researchers also estimated the economic effects of the changes in crop yield using models of commodity markets.

"We found that since 1980, the effects of climate change on crop yields have caused an increase of approximately 20 percent in global market prices," said Wolfram Schlenker, an economist at Columbia University and a coauthor of the paper in Science.

He said if the beneficial effects of higher carbon dioxide levels on crop growth are factored into the calculation, the increase drops down to 5 percent.

"Five percent sounds small until you realize that at current prices world production of these four crops are together worth nearly $1 trillion per year," Schlenker said. "So a price increase of 5 percent implies roughly $50 billion per year more spent on food."

Rising commodity prices have so far benefited American farmers, Lobell and Schlenker said, because they haven't suffered the relative declines in crop yield that the rest of the world has been experiencing.

"It will be interesting to see what happens over the next decade in North America," Lobell said. "But to me the key message is not necessarily the specifics of each country. I think the real take-home message is that climate change is not just about the future, but that it is affecting agriculture now. Accordingly, efforts to adapt agriculture such as by developing more heat- and drought-tolerant crops will have big payoffs, even today. "

Explore further: Five anthropogenic factors that will radically alter northern forests in 50 years

Related Stories

U.S. Crop Yields Could Wilt in Heat

Aug 24, 2009

(PhysOrg.com) -- Yields of three of the most important crops produced in the United States - corn, soybeans and cotton - are predicted to fall off a cliff if temperatures rise due to climate change.

Recommended for you

More, bigger wildfires burning western US, study shows

11 hours ago

Wildfires across the western United States have been getting bigger and more frequent over the last 30 years – a trend that could continue as climate change causes temperatures to rise and drought to become ...

User comments : 29

Adjust slider to filter visible comments by rank

Display comments: newest first

Sanescience
3.4 / 5 (9) May 05, 2011
Full disclosure: I'm a science enthusiast, and I'm unconvinced that AGW is either not a problem, or a problem.

I don't like reports that as a foundation for their claims use words like: Likely, unlikely, largely, relatively, suggests, etc.

I suspect these are the effects of an inherent lack of understanding and/or details of what climate change is. The mere fact that such a "broad" coverage term of "climate change" is used is probably a sign that the levels of guessing makes this more "art" than "science".

Yes, yes, the true believers on either side of AGW will howl at what is so obviously apparent to them. But science is fairly specific about how you need an understanding of all inputs to a system, able to build a model that uses those inputs to generate predictions that can be evaluated for "correctness".

That is not where we are at with AGW.
emsquared
2.3 / 5 (6) May 05, 2011
"They then used crop models to estimate what worldwide crop yields would have been had temperature and precipitation had typical fluctuations around 1980 levels."
This gets me to: do they have reason to believe that temp and precip levels SHOULD stay "around" 1980 levels? Why not 1950? Why not use an average of levels spanning back to earliest reliable records? Maybe they address this in the paper, but if not then theyre using a basesless assumption for the premise of their study. Which would make it idle speculation.

"We found that since 1980, the effects of climate change on crop yields have caused an increase of approximately 20 percent in global market prices," said Wolfram Schlenker
...
He said if the beneficial effects of higher carbon dioxide levels on crop growth are factored into the calculation, the increase drops down to 5 percent."
I wonder if this change in crop yields only looks at that amount going to food market, or if it counts that produced for ethanol too...
Fig1024
2.8 / 5 (6) May 05, 2011
What I find amazing is the strong negative reaction so many people seem to have against the idea of global warming. It's as tho they have been personally insulted. Of course all research done by others should be taken with grain of skepticism, not blind acceptance, but these reactions are way out of line.

I think someone should conduct a psychological study to determine reasons for this unusual behavior.
emsquared
2.1 / 5 (8) May 05, 2011
I don't think it's the idea of it that people have a problem with, Fig. It's the fact that policy is being forced upon entire nations, without due democratic process, via unilateral actions of agenda-driven agencies, that create damaging economic circumstances, without absolute scientific proof. I don't think any rational person would disagree that "we're probably having some effect", that's my belief, and IMHO that's all that's been proven, but is that good enough reason to take the extreme economic actions that are being taken? No votes, no legistlation. EPA hands down regulations with near impunity. That's where the strong negative reaction is.
NotParker
1 / 5 (5) May 05, 2011
"The United States ... experienced a very slight cooling trend and no significant production impacts."

So the Global part of Global Warming IS NOT GLOBAL.

CO2 is plant food. More CO2, more plants. Thats good for humans who like food.
NotParker
1 / 5 (6) May 05, 2011
What I find amazing is the strong negative reaction so many people seem to have against the idea of global warming.


That could be because warming is normal. There is a clear 1000 cycle in the ice core data.

1000 years ago it was the Medievil Warm Period.
2000 years ago it was the Roman Optimum.
3000 years ago it was the Minoan Warming.

Its just our turn ... and nothing to do with humans.

Warm is good. Warm is life. Cold kills.
ryggesogn2
1.1 / 5 (7) May 05, 2011
"Outside of North America, most major producing countries were found to have experienced some decline in wheat and corn"
Did they dare to account for the failures of socialism?
Zimbabwe used to feed itself before the govt redistributed the land.

but these reactions are way out of line.

You have not been paying attention have you? Anyone who questions the science is attacked and ridiculed.
Whose reactions do you consider out of line?
Quantum_Conundrum
1 / 5 (3) May 06, 2011
He said if the beneficial effects of higher carbon dioxide levels on crop growth


I think this is the first time I've ever seen an AGW believer actually admit that increasing CO2 actually increases plant growth and production...

emsquared:

It's a deliberate, systemic bias. The 1980's were a relatively quiet decade for world weather disasters, so it is a convenient decade to bias other decades against.

Take for example, major tropical cyclones. The 1980's was the second weakest decade on modern record, second only to the 1970's. And ironically, the 1900's to 1925 was the second STRONGEST 25 year period lining up with an actual century. However, if you take a 25 year running total of category 4 hurricanes, the second highest peak is in the 60's, again before any alleged AGW would have mattered. The highest peak is the period we are in right now*

Quantum_Conundrum
1 / 5 (4) May 06, 2011
Since 1992, we have new types of infrared, microwave, and spaced-based radar satellites which help detect short lived intensification, etc, so storms that may not have been classified as a major storm in the past are now classified as such since they are immediately seen to be so powerful with non-stop 5 spectrum satellites viewing them...

At any rate, there is no "trend" in the number or severity of tropical cyclones, and the greatest previous peak before this one, which is almost as big as this peak, took place before AGW could have caused it, and in a time when instrumentation was not as common or as good to detect short-lived intensification. Which is to say, in the past, a major hurricane was only classified as such if someone was actually in the thing with an anemometer measuring it, which only happened a fraction of the time.
Quantum_Conundrum
1.2 / 5 (6) May 06, 2011
More recently, Australia's "Historic flooding" and of course the "historic Cyclone Yasi" were both over-hyped by the media. It turns out, Australia had TWO much worse floods in the past, well over 100 years ago, in which the water levels were 13ft higher...and it turns out Australia has been hit by several stronger cyclones, both before AGW could have had any influence, and including one nearly a hundred years ago.

Ultimately, it turns out when you actually do long-term research instead of swallowing everything the media or TWC alarmists say, weather and climate disasters were, in general, far worse in the past, 50 to 150 years ago, than they have been in recent decades.

It is also true that the two strongest landfalling tropical cyclones in history: Labor Day and Camille, happened 1 to 4 decades before AGW could have been any influence, indeed, Labor Day happened when CO2 levels were barely above ambient, and is undeniably the strongest landfall on record in the world.
Quantum_Conundrum
1 / 5 (4) May 06, 2011
The point I'm making with all of this is that major disasters happen so seldom that any time it happens, there is a knee-jerk reaction by the media and the local victims to instantly claim it is the "worst ever" and therefore something must be going wrong, etc.

In reality, it isn't the worst ever, and is just a 30 year or 50 yar event most times.

Katrina was allegedly rated as a 1 in a couple hundred years event, yet on some cyclone intensity scales it's landfall intensity does not even rank as high as Betsy (though over the water it was at one time stronger than Betsy ever became.) Betsy was both larger and stronger at landfall, according to some intensity scales. In fact, the levees failed in exactly the same way, and in exactly the same places in Betsy. But because people did not heed warnings, and because people expect the government to do everything for them, and have the wrong idea about the purpose and capabilties of levees, the loss of life was much greater in Katrina.
GSwift7
1.3 / 5 (6) May 06, 2011
The obvious flaw here is that changes in crop yields are also influenced by economic factors. The cost of water, electricity, deisel fuel, fertilizer, heavy equipment, etc, as well as projected prices of the grains themselves, taxes and subsidies. In order to associate a cause and effect relationship to any one factor, you have to control for all the other factors which might have a substantial influence. Of course I deliberately left some of the most important factors out of my list here. Those are average rainfall, length of growing season, amount of daily cloud cover, distribution over time of the rainfall. One of my Uncle's best years in the past couple decades was a year that started out with a late growing season and a spring drought. The amount and timing of summer rainfall in combination with the perfect timing of conditions favorable to harvest led to an almost double yield that year. Farming is very chaotic and hard to predict systematically.
GSwift7
1.2 / 5 (6) May 06, 2011
One oddball day with a late freeze can really do a number on yield.

You also really should break down the types of grains they are growing. The yield per acre isn't the same for one type of corn as it is for another. Same goes for wheat. If the proportion of one type of corn versus another type of corn has changed over time then you would need to account for that here too, before you could draw any cause and effect relationship between temperature and yield.

Maybe this guy is completely wrong and the impact on yield has been substantially negative but all the other factors combined have hidden what he's looking for in such a huge pile of noise that he's not able to discerne a noticable signal in the data. Or maybe he's right and there hasn't been very much of an effect at all.
Sanescience
2 / 5 (4) May 07, 2011
Somebody must be quite offended for people to have the *AUDACITY* do debate this issue, and blanket assigned a 1.
deepsand
3 / 5 (12) May 07, 2011
More likely one who is just appalled at what passes for "rational discourse" here.

Or, as is said at USNA, by those who seem to be given more to a woman's intuition than a Midshipman's erudition.
GSwift7
1 / 5 (3) May 09, 2011
They talked about this story on NPR this morning on my way into work. The spokesperson that NPR interviewed stated the following: "of course, the value of the US dollar is the biggest influence on the price of food". Which is part of what I was saying. The idea that global warming may have caused a 1-2% increase in the price of food over the past few years is pure speculation. It is impossible for them to prove that. The complicating influence of other factors makes it impossible to quantify any such thing. It could be either worse or better than what they are saying, and the uncertainty in their estimate is so large that their estimate is meaningless. You people do know what the term "statistically insignificant" means, don't you?
deepsand
3 / 5 (10) May 09, 2011
"of course, the value of the US dollar is the biggest influence on the price of food".

What proof that exchange rates are greatest factor?

The idea that global warming may have caused a 1-2% increase in the price of food over the past few years is pure speculation.

Are you saying that supply volume is not a factor?

Or, that it is independent of growing conditions?
lengould100
3 / 5 (2) May 10, 2011
Bottom line is, "Increase earth atmosphere's CO2 content, and the global temperature should rise, according to all known physics". It's up to you deniers to explain (with 100% certain proof, as you demand of everyone who may disagree with you) why that may not be the case.

I just love to watch as the deniers pile on to every possible opening with a barrage of opinion and possibilities. Not even any pseudo-science anymore, since that's all been so thoroughly debunked. Any chance there's a PR firm being paid to maintain such vigilance?
lengould100
3 / 5 (2) May 10, 2011
Quantun Conundrum: I think this is the first time I've ever seen an AGW believer actually admit that increasing CO2 actually increases plant growth and production...

Of course we've all long known that the potential benefits to plant growth of increased atmospheric CO2 has been taken into account, it's only you who are finally becoming aware of that.

So now, does that mean you can FINALLY stop re-posting again (and again and again......) such a silly little factoid? Please?
emsquared
1 / 5 (2) May 10, 2011
No rational skeptic of AGW theory argues against the physics. It's undeniable that CO2 creates radiative forcing. This is known. The skepticism comes in when the assertion is made that we know what's going on, and what's going to happen, with the system when we are not able to quantify all of the relavent parameters in the system.

If a theory is to be proven true, it is up to the theory to withstand all attempts at falsification. AGW Theory: Manmade contributions to atmospheric CO2 since ~1950 are going to cause the global temperature to raise, on average X degrees C. To prove this is not falsifiable, you must quantify ALL OTHER contributing CO2 sources (biotic, geologic), ALL CO2 sinks, ALL OTHER parameters that affect avg global temp, and see if it holds water. AGW theorists haven't done that. They haven't done that, they say, well we assume it's going to be like it was in this convenient data set. That's not valid as a scientific assumption, as it is not falsifiable itself.
emsquared
1 / 5 (2) May 10, 2011
i.e. you cannot prove that what's going on now "should" be like what was going on for the past 100,000 years (since the beginning of modern oceano/geologic climate patterns, i.e. inter-glacials), as we only have what is going on now to reference, no earth duplicate to reference and no models capable of accurately representing the complex system. Therefore, AGW Theory is not a falsifiable theory, so it is not a valid scientific theory, so IMHO, it is not worthy of taking extreme action upon.

This is an oversimplification of my problem with AGW theory, due to constraints of physorg comments, but please show me how I am wrong here and I will sign-up with AGW theorists everywhere.

My mind is wide open on this, but I am a scientist first, and if the theory can't meet scientific criteria, I can't subscribe to it.
deepsand
3 / 5 (10) May 10, 2011
No rational skeptic of AGW theory argues against the physics. It's undeniable that CO2 creates radiative forcing. This is known.

Knowing this alone is sufficient for knowing that man's dumping of CO2 into the atmosphere must increase radiative forcing, which cannot do other than force temperatures upward.

That there may or may not be other factors is immaterial to the effect of this particular factor.
deepsand
3 / 5 (10) May 10, 2011
... AGW Theory is not a falsifiable theory ...

Falsifiability is a PROPOSED - as opposed to a universally accepted - solution to the problem of INDUCTION.

The basis of AGW findings, however, is DEDUCTION.

"Falsifiability" has become a word tossed about carelessly by far too many.
emsquared
1 / 5 (2) May 10, 2011
Knowing this alone is sufficient

And as I said in another thread, I would never argue that we don't do SOMETHING, the physics are the physics. You must remember at the same time then, the accompanying physics like CO2s logrithmic effect on forcing.

http://brneurosci.org/co2.html :is an AMAZING fact sheet on the full CO2 physics, give it a look won't you? It's pretty dense, so you may want to have some time, but it's well worth the read.

The uncertainty of the magnitude is the thing here. Not to mention the debateability of it's negative effects... but that's a whole 'nother topic.

The basis of AGW findings, however, is DEDUCTION.

And deduction requires a statement of certainty, based upon the statistics used to make said deduction. I don't think I've ever seen an honest, statistical assessment of certainty. They give the range they predict, sure, but again, the methods they use to obtain this range are themselves quite uncertain, just read the link.
deepsand
3 / 5 (10) May 10, 2011
Knowing this alone is sufficient

And as I said in another thread, I would never argue that we don't do SOMETHING, the physics are the physics. You must remember at the same time then, the accompanying physics like CO2s logrithmic effect on forcing.

Linear or non-linear, direct proportionality is maintained. More atmospheric CO2 --> increased radiative forcing --> increased thermal energy retained by Earth system.

The basis of AGW findings, however, is DEDUCTION.
And deduction requires a statement of certainty, based upon the statistics used to make said deduction.

No statistical data involved in the underlying controlling physical laws re. radiative forcing.

And, no inductive reasoning either.

Thus, falsifiability is not applicable.
emsquared
1 / 5 (2) May 11, 2011
Linear or non-linear, direct proportionality is maintained.

Actually no, you have a law of "diminishing returns". There's a concentration where no matter how much more CO2 there is, the forcing cannot increase any further. Now, of course we're not near that concentration, but we are at a point where the concentration has to double for each same step in temperature. Seriously, just skim that link above if you want an objective look.

No statistical data involved in the underlying controlling physical laws re. radiative forcing.

But there are most definitely statistics involved in applying those physics to the global climate. Those basic thermodynamic properties are as applied in and of themselves. Put them into a complex system and it is not cut and dried. Different atmospheric characteristics react differently (are more or less sensitive) to that forcing, see: climate sensitivity. There are interferents to the forcing, and much uncertainty to how they interact.
deepsand
3 / 5 (10) May 11, 2011
Actually no, you have a law of "diminishing returns".

Still direct, as opposed to inverse, proportionality.

I.e., the relationship [ More atmospheric CO2 --> increased radiative forcing --> increased thermal energy retained by Earth system ] still holds.

There's a concentration where no matter how much more CO2 there is, the forcing cannot increase any further.

Hm-mm; nope. May be a non-linear response, but it's not a hard cut-off. The "saturation" myth ignores the facts that 1) IR absorbed becomes IR re-radiated; and, 2) a finite number of CO2 molecules cannot absorb an infinite number of photons.

But there are most definitely statistics involved in applying those physics to the global climate. Those basic thermodynamic properties are as applied in and of themselves. Put them into a complex system and it is not cut and dried.

Does not render said relationship moot.
emsquared
1 / 5 (2) May 11, 2011
May be a non-linear response, but it's not a hard cut-off
There is a cut-off at 100% CO2, heh, but seriously it is most definitely a logarithmic line; to use that illustratively, if we could have 1,000,000ppm CO2 atmosphere, the temp would only increase 10% for the last 750,000 ppm. The majority of the temp increase occurs in a very small percentage of the concentration increase.
Arm yourself with some facts:
http://brneurosci.org/co2.html
Does not render said relationship moot.

I didn't say it renders the relationship moot. In fact I have acknowledged the relationship multiple times. But it does dictate that the physics are not occuring in a vaccuum, it occurs in a system with mitigating factors. Factors not fully understood or quantified. You're saying it's cut and dried at the physics, I'm saying it's not. You want to sweep real conditions under the rug, I say they're necessary to understand to make the best decision for our country and people. Agree to disagree?
deepsand
3 / 5 (10) May 15, 2011
The information presented at http://brneurosci.org/co2.html re. "saturation" is, at best, misleading; at worst, incorrect.

What the author calls the "extinction coefficient," measured per unit of distance, is here actually the "MASS attenuation coefficient," measured in units (length-squared) per unit MOLAR MASS.

Additionally, author fails to account for the fact that such attenuation includes SCATTERING, which is precisely what happens when a CO2 molecule absorbs and spontaneously re-radiates an IR photon.

Additionally, the density () of CO2 is not constant throughout the atmosphere, so that the mass attenuation coefficient ( / ) is not a constant.

Said coefficient here only determines what FRACTION of the input beam is SCATTERED over a given area density, aka mass thickness.

More news stories

There's something ancient in the icebox

Glaciers are commonly thought to work like a belt sander. As they move over the land they scrape off everything—vegetation, soil, and even the top layer of bedrock. So scientists were greatly surprised ...

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

Clean air: Fewer sources for self-cleaning

Up to now, HONO, also known as nitrous acid, was considered one of the most important sources of hydroxyl radicals (OH), which are regarded as the detergent of the atmosphere, allowing the air to clean itself. ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...