Rainfall has a greater impact than rising temperature on crop yields

From Wiley-Blackwell

Chinese Academy of Sciences
Chinese Academy of Sciences (Photo credit: Wikipedia)

Is rainfall a greater threat to China’s agriculture than warming?

Impact of climate change on China explored in new plant science virtual issue

New research into the impact of climate change on Chinese cereal crops has found rainfall has a greater impact than rising temperature. The research, published in the Journal of the Science of Food and Agriculture found that while maize is sensitive to warming increases in temperature from 1980 onwards correlated with both higher and lower yields of rice and wheat.

The study was carried by Dr. Tianyi Zhang, from the Institute of Atmospheric Physics, and Dr. Yao Huang, from the Institute of Botany, both at the Chinese Academy of Sciences. The paper is part of a special collection of free articles on the links between climate change, agriculture and the function of plants.

“China has experienced significant climate change over the last century”, said Zhang. “The annual mean air temperature increased by 1.1 °C from 1951 to 2001, rainfall in Western China increased by up to 15% per decade and decreased in the North.”

“Projections from climate models predict that mean temperature could rise by 2.3-3.3 °C by 2050 while rainfall could increase by 5-7%,” said Huang. “This could have a major impact on China’s agriculture which accounts for 7% of the world’s arable land but feeds about 22% of the global population.”

The authors turned to China’s provincial agricultural statistics and compared the data to climate information from the China Meteorological Administration. They focused their analysis on China’s main cereal crops, rice, which is grown throughout China, as well as wheat and maize, which are mainly grown in the North.

The results show a significant warming trend in China from 1980 to 2008 and that maize is particularly sensitive to warming. However, they also found that rising temperature collated with both higher and lower wheat and rice yields, refuting the thoughts that warming often results in a decline in harvests.

“Of the three cereal crops, further analysis suggested that reduction in yields with higher temperature is accompanied by lower rainfall, which mainly occurred in northern parts of China,” said Zhang. “This suggests it was potentially droughts, relative to warming, that more affected harvest yields in the current climate.”

“It is often claimed that the rising temperature causes a decrease in the yields of Chinese cereal crops, yet our results show that warming had no significant harmful effect on cereal yields especially for rice and wheat at a national scale from 1980 to 2008,” concluded Zhang and Huang. “However, warming may still plays an indirect role, like the exacerbated drought conditions caused by the rising temperatures.”


This special collection of free articles is featured on the new Life Science pages on wileychina.com, which are being launched from March 2012 to create a Life Sciences Centre for the Chinese research community. New pages will be launched each month and in March the focus is on Climate Change and Plant Science.

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April 5, 2012 1:10 am

Harvest yields are highly volatile and to correlate them with only two already intercorrelated parameters, rain and temperature, is a guarantee for unreliable conclusions.
Plant and soil biology is more complex.

April 5, 2012 1:13 am

Rainfall record from England@Wales since 1766
I never understood what are those babbling about changes in rainfall about. It always changed and present time is not extraordinary at all.
Btw, that alleged 1.1°C warming in China is inflated by 30% by UHI as Phil admitted, AFAIK.

Ian W
April 5, 2012 1:28 am

I don’t suppose these PhD ‘scientists’ ever thought to talk to a few farmers about what affected their crops? It would have been a lot cheaper and no software required.

wayne Job
April 5, 2012 1:40 am

Good grief, who would ever have thought that cereal crops most important ingredient is water.
Crops fail through lack of water, crops fail by being flooded and crops fail by being too cold.
The odd extra degree of warmth is a bonus.

April 5, 2012 2:30 am

Crops as a function if temp. and rain?
I wonder if CO2 affects crops…..

April 5, 2012 2:35 am

Anyone who has a garden in a warm to hot climate as I do, knows that plants grow after it rains. They really grow when it is hot after rain.

Peter Miller
April 5, 2012 3:13 am

There are many, many different varieties of maize, wheat and other cereals – some are more, and some are less, tolerant to rising temperatures and less rainfall. You just choose the variety you need to meet local prevailing conditions.
I always remember – this is a windup for liberals – that South Africa mainly used a drought resistant form of maize with fewer ears of corn than the country to the north which had more reliable rainfall – that was Rhodesia when it was great, before Mugabe made Zimbabwe Ruins – pun intended. ‘Climate Science’ is very similar to Mugabe’s philosophy on life, both: i) have policies which are are economically destructive, ii) are unable/unwilling to tolerate reasonable criticism, iii) are expert in fact and truth distortion, iv) fanatically despise others of different beliefs, v) appeal to the thinking processes of the lumpen proletariat, and hopefully vi) for everyone’s sake, are soon about to die.
We should always remember the world would be unable to feed itself today if it had to rely on the varieties of cereals which were available in the early 1950s.
As with everything to do with ‘climate change’, it is easier and infinitely cheaper to adapt than to try and change things.

April 5, 2012 3:36 am

Than you bring water from places where they have enough of it, Western China . For an economic strong country that should not be a problem. Greenhouses are also a way to save water.You can also pump CO2 into greenhouses to to stimulate growth with the same amount of water or less.

April 5, 2012 4:06 am

Ask an Australian grain farmer which is the most important, rainfall or temperature.
He will just laugh at the absurdity of the question for to Australian grain growers it is rainfall.! rainfall ! rainfall !.
We live and farm in the second driest continent, next to Antarctica, on this Earth.
Some of grain cropping country has just 10″ inches of annual yearly rainfall.
Most of the grain is grown on dryland country ; ie no irrigation as there is no underground water or it is of a quality unsuitable for irrigation.
Researchers are shaped by the environment in which they live and work and for most American, European and perhaps even most Chinese and even a lot of Indian researchers, they live in areas where water and rainfall are rarely in short supply so they just assume it is the same everywhere that water for crops is not a problem.
And their research or perhaps lack of reflects this in the casual acceptance that rainfall and crop water is never a problem so temperature must be!
One of my farming brothers with a mature student Ag degree and four years in the back blocks of Tanzania in the 1970’s getting some 65,000 refugees up to the stage where they could feed themselves has always said; You pay 99 mediocre, average or useless so called researchers to get the 100th one who can and really does make a difference to the world.
Seems like the research of a couple of that 99 are being displayed here.

Brian H
April 5, 2012 4:37 am

dmh didn’t close an italics tag. Please fix or delete the post.
Clue to all taggers: start by typing both open and closing tags, then enter the text or copy between them. That way you can’t f-up.

April 5, 2012 5:02 am

Oops – it looks like among the many recent WordPress changes, fixing the stuck italics bug was not one of them.
One problem I have with studies like this (though this is fatally flawed by apparently not bothering to talk to a single farmer) is that current growing practice is likely somewhere close to optimal, and that any climate change would make things suboptimal. Until farmers (including the ones not consulted) change their crops to adapt to the new conditions.
Any comparison should be between the current optimum crops and the crops grown in the future conditions.

R. de Haan
April 5, 2012 5:06 am

What do you say? The UN IPCC have contracted the Chinese Academy of sciences?
This is terrible.
Expect massive amounts of cheap alarmists reports flooding the West in the same way the Chinese conquered the world with their cheap pots and pans.

April 5, 2012 5:52 am

Brian H says:
April 5, 2012 at 4:37 am

Clue to all taggers: start by typing both open and closing tags, then enter the text or copy between them. That way you can’t f-up.

That’s not the problem. If you don’t close a <i> with </i>, WordPress will do it for you. The problem occurs with a variant that is improper HTML, but passes WP’s check. I forget what it is, I think Anthony posted it once upon a time.
So, the real clue is – proofread your comments and HTML before posting.
Or contact WP and volunteer to fix it for them.

April 5, 2012 5:56 am

As the evidence from the real temperatures, not the crappy anomaly calculation, is that with warming the summers are relatively unchanged and the winters milder, in which case all we have is a longer growing season. How could this possibly be bad? It’s not!
The assumption of alarmingly high temperatures with warming is part of the scare campaign but far from the truth. From 1978 to 1998 our summers warmed incrementally or not at all and the winters warmed. The average rose a bit. So what? Do we care? Being from Iowa, if it is -24.5 deg F and not -25 deg F, my day and life is totally unchanged.
They love to indicate a warm spot over the Arctic during the winter, as when frigid air moves south it must be replaced with some warmer but still very cold air from the south. The warm spot is warmer than the average, but nothing is melting—it just might be -15 and not -20 deg F for a time. Big deal!
It’s all about scaring people. Higher CO2 makes plants more temperature tolerant while they concurrently become more efficient at utilizing water and nutrients. So, higher temperatures are not a problem, even though higher temperatures are not happening. Think about that for a moment. Where’s the beef? A longer growing season is a blessing, not a curse, for those who like to think that everything is bad.

Pamela Gray
April 5, 2012 6:14 am

Lack of sunshine is the pits (ask a vineyard owner). Cold rain, cloudy days, and cold nights are even worse (ask a hay farmer or rancher waiting for pasture). Warm things up and pasture grass takes off like a greyhound dog after a rabbit. grapes get happy, and cows begin to drool over the fence as they try to stretch their necks down towards the alfalfa.
And toms grown in greenhouses are never called “cold house tomatoes”.
Now, do I get a Nobel Prize for saying warm is better?

April 5, 2012 6:25 am

Hmmm? Chinese Academy Of Sciences , in other words ……C.A.O.S. ! Where`s agent 86 when You need Him (o:

April 5, 2012 6:26 am

Ric Werme
Ric, don’t ever underestimate the ability of the world’s farmers to adapt and to adapt fast. The academic classes assume that farmers are just ignorant hicks incapable of thinking for themselves.
Nor do the cities and the political and academic elites have the faintest clue of the incredible agricultural research that is continually going on.
There is a almost arrogant belief particularly in the west that very cheap, high quality food in enormous and wastefull quantities and in whatever form is demanded must be supplied by the farmers any time, all the time.
For those academics on here who think that farmers are just ignorant hicks incapable of thinking for themselves, lets see you live on the wages of the mid 1970’s at today’s costs because they are the prices Australian farmers are currently being paid for their grain, the same dollar price per tonne as the mid 1970’s.
In their stupidity the western city elites are destroying the ability of the world’s farmers to produce food as the prices are forced down and down and as the financial cushion that a farmer must have to survive weather and market shocks is destroyed then the farmer’s ability to adapt is also destroyed.
Pay farmers well for what they produce and you will have all the food you need or want.
Destroy their financial base by refusing to pay a fair price for their produce that reflects today’s costs and you will eventually go hungry for there will no longer be the ability to produce and adapt by farmers and probably not that many farmers left either,
Of course the other option which we may be heading for is that the family farmers are eliminated through casual neglect and the elite’s contempt and then only a few huge food producing corporations will be left to produce food and THEN you will know what it is like to pay for food or alternatively, go hungry.

April 5, 2012 7:14 am

The truth about modern farming methods is illustrated by two articles in the Economist in 2010 about Brazilian agriculture:
“THE world is planting a vigorous new crop: “agro-pessimism”, or fear that mankind will not be able to feed itself except by wrecking the environment.”
“In less than 30 years Brazil has turned itself from a food importer into one of the world’s great breadbaskets (see chart 1). It is the first country to have caught up with the traditional “big five” grain exporters (America, Canada, Australia, Argentina and the European Union). It is also the first tropical food-giant; the big five are all temperate producers.”
” Brazil shows a different way of striking a balance between farming and the environment. The country is accused of promoting agriculture by razing the Amazon forest. And it is true that there has been too much destructive farming there. But most of the revolution of the past 40 years has taken place in the cerrado, hundreds of miles away. ”
“…the basic ingredients of Brazil’s success—agricultural research, capital-intensive large farms, openness to trade and to new farming techniques—should work elsewhere…the Brazilian way of farming is more likely to do good in the poorest countries of Africa and Asia. Brazil’s climate is tropical, like theirs. Its success was built partly on improving grasses from Africa and cattle from India.”

April 5, 2012 7:18 am

“Rainfall has a greater impact than rising temperature on crop yields.”
As do soil quality, pests, disease, average insolation, and probably a half dozen other factors.
The idea that slight increases in temperature across an entire year are directly and causally related to growth of, I dunno, say, just hypothetically, tree rings, is an absurd joke and requires serious impairment of critical thinking skills. Thank goodness no-one has ever used tree rings as the basis for overturning long-understood global temperature reconstructions. On a completely and totally unrelated note that couldn’t possibly have any relevance to the question of rainfall and other factors on plant growth, I understand some guy is selling signed hockey sticks for $300 . . .

John F. Hultquist
April 5, 2012 7:22 am

And in the “climate is not average temperature” department it might be helpful to take a look at a couple of climographs. These diagrams show the “pattern” of precipitation and temperature (and sometimes other information). They can be found on the web and in many earth-science textbooks.
In the “Wet-dry tropical” region there is abundant rainfall through the high sun period, and warmth is a year-round aspect:
A less complex climograph – Portland, OR — with low rainfall during the high sun season is here:
The Portland area has ample precipitation except in its 2 hottest months – on average. When there is a “dry year” this summer-dry pattern is problematic. In an inland location, with less rainfall, irrigation is necessary for many crops. Yakima, WA, for example:

April 5, 2012 7:50 am

Not a bad article – gently smoothing over some of the ‘catastrophic’ concepts of CAGW, pointing out that more rain is usually a good thing, and working quietly between the constraints of getting heard on the subject.
As state above in comments, never underestimate the ability of farmers to adapt..
… and more importantly, NEVER underestimate the ability of plant breeders to solve problems.
Why is Brazil the biggest soybean grower in the world? (in spite of ‘green’, read hegemonic campaigns to curtail their rise)?
Because of an intense 50 year program to adapt the high latitude soybean varieties to Brazil’s soils and climates:

Soybean varieties introduced from the USA and varieties rescued from early introductions in Brazilian territory were part of the Brazilian soybean-breeding programme which spread the crop from high to low latitudes. Disease-resistance, pest-resistance, tolerance to low fertility soils, as well as production of plants with pods sufficiently high above the ground for efficient mechanical harvesting, were all aims of the programme.

further: “Breeding Soybeans to the low latitudes of the Brazilian Cerrados (Savannahs)” Carlos Roberto Spehar

April 5, 2012 7:56 am

Heat per se is irrelevant to crop yields, at least up to the point where they are literally burned by e.g. UV from the sun. They call summer the “growing season” for good reason. Heat without adequate water, on the other hand, is a disaster, as is water without adequate heat.
However, “Climate Change” — the reworking of “Global Warming” now that the Earth isn’t cooperating by warming — continues to be bullshit. Sure, the climate is always changing because the Earth is a dynamic system. However, nobody knows how much of the change is anthropogenic in origin, and the most probable fraction is perhaps 1/3 or 1/4.

Henry chance
April 5, 2012 7:56 am

My land is in wheat
We have lost more to late frost and no one talks about frost damage for winter wheat in the heading stages.
Our wheat is early this year in addition to it being an earlier variety by choice.

April 5, 2012 8:18 am

Now the good news, expect more rain.

These results are substantially consistent among the three IPCC (Intergovernmental Panel on Climate Change) scenarios.
The increased probability of heavy rainfall events in China is closely connected with increased transportation of water vapour from the Arabian Sea and the South China Sea. Additionally, atmosphere stratification has become increasingly unstable, which has provided a favorable background for the initiation of heavy rainfall at the end of the 21st century.

Now the bad news, expect less rain.

The projected decline in rainfall over most of China is substantial in numerical experiments that include the effects of sulfate aerosols.

Deforestation and rainfall.

As early as the 1950s deforestation in China attracted attention, but it was not until the 1960s that it assumed alarming proportions.

North and northwest China, where the average annual precipitation has decreased by one third between the 1950s and the 1980s,2 has been experiencing just such a desiccation process. Evidence is clear and abundant. For example, lake Lobnor vanished in 1972, and lake Kukunor, since the beginning of Holocene period, has dwindled in area by one third and in depth by 100 m.3 Finally, the depth of lake Ohlin, at the head of the Yellow River, has been dropping by over 2 cm annually.4

April 5, 2012 8:24 am

Good lord. When you read any ancient stories, the cycling of drought and rain is prominent. Seven lean years, seven fat years. It’s all about rain. Nothing about temperature.
I don’t know the Chinese equivalent, but I’d bet their old legends are even wiser and more specific than ours. They’ve been around longer and they’re smarter.

Hugh Pepper
April 5, 2012 8:28 am

Every farmer knows that plants need both rain and appropriate warmth to germinate and grow to maturity. The authors of the article point out that warming “exacerbates” drought conditions, with potentially devastating consequences for the hundreds of millions who depend on this food for their survival.The Chinese are already buying land in Africa to replace the crops which are being lost in their own country.
Another food crisis is looming as a result of the rapid glacial melt (7% decline per year now) in the Himalayas, which threatens the available in stream flows of all major rivers in Asia and SE Asia. Flooding is wiping out crops in Bangladesh, for example, thereby threatening the livelihoods of millions, and the Indus River has recently flooded displacing millions more and threatening food supplies in Pakistan.
Warming (climate change) is having devastating impacts everywhere, but especially in areas where billions of the world’s populations live, and where much of global commerce is conducted.
REPLY: “Another food crisis is looming as a result of the rapid glacial melt (7% decline per year now) in the Himalayas”
Hugh, are you brain damaged? The Himalyan Glaciers 2035 scare has been exposed as an error, and even the IPCC admits it now. By your figures, it is even worse!
at 7% per year, they’ll be gone in about 14 years (7%x14= 98%) or in the year 2026. You are even wronger than wrong.

April 5, 2012 8:56 am

There is no terrestrial place on Earth where it is too hot to grow plants. Too dry, too cold, absolutely. But not too hot. (Except for fresh, still cooling lava flows — there, happy now nitpickers?)
The most productive agricultural regions are also the warmest. Fancy that.
Maize is originally a tropical plant. Varieties have been developed that will grow farther north, but the tropics are home. Ditto staples such as rice, wheat, manioc, taro, edible beans, yams, cassava, sorghum, amaranth, millet, and even potatoes (though at high altitudes).
Why is this? Because, dear friends, plants evolved in much warmer times. The last ~1.8 million years have been the COLDEST on Planet Earth in the last quarter of a billion years. Plant genera are much older than 1.8 million years.
The Goreans claim global warming will damage agriculture. Nope. Just the opposite.
I’ve said it before and I’ll say it again

Bob Diaz
April 5, 2012 10:41 am

“Projections from climate models predict …”
Oh my gosh, next they’ll be telling us that children in England won’t know what snow is… :-))
I guess we all know how accurate climate models are.

April 5, 2012 1:29 pm

Philip Bradley said @ April 5, 2012 at 2:35 am

Anyone who has a garden in a warm to hot climate as I do, knows that plants grow after it rains. They really grow when it is hot after rain.

It’s the same in cooler places like Tasmania, too. There are two reasons rainfall generates more growth than irrigation.
Rain carries ammonia created by lightning into the soil. Rain also contains dissolved CO2. Once in the soil, this produces free hydrogen ions that can then displace cationic nutrients, such as calcium and magnesium from the clay particles and humus.
Robert Brown said @ April 5, 2012 at 7:56 am

Heat per se is irrelevant to crop yields, at least up to the point where they are literally burned by e.g. UV from the sun.

Not so, Robert, though it’s not entirely starightforward:

Number of days for completion of germination, height of plant, leaf area index, grain, straw and total dry matter yield were found to be related to the sunshine hours. Grain and straw yield were negatively related with the heat units accumulated at the seeding stage. Grain yield alone was positively related to accumulated heat untis at flowering stage, while grain and straw yield were not related with heat units at growth, bootleg and maturity stage. Total accumulated heat units during the entire growth period of the crop was positively related to the grain and straw yield.


Eric in CO
April 5, 2012 2:13 pm

I live in Colorado. I could have told you this based on my front yard, or even hops plants in the back. Though Denver isn’t too hot, the sun is powerful and radiation is way up there compared to other places. Grass lives if it rains, and does not if there is a drought.

April 5, 2012 2:21 pm

What China look at Britain
Millions of householders across southern and eastern England are being hit by a hosepipe ban as drought grips parts of the country.
East Anglia saw just 426mm of rain during 2011, which is a third less than the annual average for the region.

Gail Combs
April 5, 2012 4:38 pm

Philip Bradley says:
April 5, 2012 at 2:35 am
Anyone who has a garden in a warm to hot climate as I do, knows that plants grow after it rains. They really grow when it is hot after rain.
Understatement. I just went from 6″ high abrussi rye to rye that is so high I can not see my 13 hand ponies not even their heads. And it happened in about a week. Darn stuff bolted faster than I have ever seen before ~ CO2 + warmth + rain
All this stuff was studies in the 1800’s and earlier. http://www.k12.hi.us/~ckuroda/history_of_hydroponics.html

Stephen Skinner
April 6, 2012 4:38 am

Death Valley has recorded one of the worlds hottest temps, and yet it has a golf course with green grass.
Today it appears that many disciplines are taught without understanding the importance of observation. With some it is as if observation is unreliable.

Alan Watt
April 6, 2012 7:27 am

Not to worry, the Chinese are so advanced they already adapted to rainfall changes before computer models projected the crisis.
The predominant food grain in China has always been rice, which requires more water than other grains (wheat, corn [maize]). However, the average per-capita rice consumption has been
declining since 1995. According to this reference ( An analysis of Food Grain Consumption in Urban Jiangsu Province of China ), annual per-capita rice consumption went from 71.3 kg in 1995 to 56.2 kg in 2000 and 50.2 kg in 2007. That’s a reverse hockey stick with a whopping 21% reduction in just 5 years from 1995 to 2000, and an overall 30% reduction in 12 years.
Are the Chinese in Jiangsu Province starving? No. The Chinese are eating more meat and poultry and planting other grains as livestock feed.
So if the climate dries out, China will just grow less rice and use grains needing less water to feed livestock for food. On the other hand if rainfall increases (which is not inconsistent with Climate Change Theory), China will just raise more ducks and geese in vast artificial ponds. So they’re fine either way: drier climate means more chicken and pork; wetter climate means more waterfowl, fish and rice.
Problem solved by adaption, and they started doing it back before 2000.
[A certain amount of sarcasm here, but the reference is real]

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