Guest Post by Willis Eschenbach
Anthony has posted on a recent study (behind a paywall) of rice production in Rice yields, CO2 and temperature – you write the article. The article claims that rice yields are falling, and will fall further, due to temperature changes.
I said I’d write the article if someone would send me the actual study, and a couple of WUWT readers came through, my thanks to them. Here’s my take on what the authors have done.
First, the good. They have used actual data from farmer’s fields, rather than theoretical data or greenhouse experiments.
Figure 1. Rice Fields in Ha Giang
However, there are some troubling things in the study.
First, it covers a very short time span. The longest farm yield datasets used are only six years long (1994-99). Almost a fifth of the datasets are three years or less, and the Chinese data (6% of the total data) only cover two years (1998-1999).
Now, if they were comparing the datasets to temperature records for the area where the farms are located, we could get useful information from even a two-year dataset. But they are not doing that. Instead, they say:
Data series from the weather stations at the sites were too short to determine trends. Instead, trends in Tmin and Tmax were based on a global analysis of ground-station data for 1979–2004 …
Unfortunately, they have neglected to say which “global analysis of ground-station data” they are using.
But whichever dataset they used, they are comparing a two year series of yields against a twenty-six year trend. I’m sorry, but I don’t care what the results of that comparison might be. There is no way to compare a two-year dataset with anything but the temperature records from that area for those two years. This is especially true given the known problems with the ground-station data. And it is doubly true when one of the two years (1998) is a year with a large El Niño.
For example, they give the trend for maximum temps in the winter (DecJanFeb) for the particular location in China (29.5N, 119.47E) as being 0.06°C per year, and the trend for spring (MarAprMay) as being 0.05°C per year (I get 0.05°/yr and 0.04°C/yr respectively, fairly close).
But from 1998 to 1999, the actual DJF change was +2.0°C, and the MAM change was minus 1.0°C (CRU TS Max Temperature dataset). As a result, they are comparing the Chinese results to a theoretical trend which has absolutely no relationship to what actually occurred on the ground.
To try to find out which “ground-station data” they used, I compared their temperatures for China (29.5N, 119.47E) with the CRUTEM3, CRU TS, and GISS records from KNMI. However, I could not match their numbers, although I could get sorta close. Worrisome.
Next, they have not mentioned autocorrelation anywhere in their study. This makes me think that they have not adjusted for autocorrelation, which is particularly important with short datasets.
Next, they base their predictions for the future on a single computer model of the regional changes. It is widely agreed that computer climate models are not very good at predicting regional changes, so that part of their study seems very weak.
I am most mystified by their use of the 26-year temperature trend. Why not use the actual year-by-year changes in the local temperature? The rice is responding to actual temperatures, not to a mathematical trend … so why not compare yields to actual temperatures?
So once again, we have questionable methods used with uncited data to give alarming results. It is too bad, because their premise is good, and so is their general approach (use actual farm data).
Color me unimpressed …
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They can’t get research funding without torquing the story, the data, the methodology and the News Release announcing their findings.
No big hairy-scary we might all die story means no research funding next year.
What a ridiculous study and ridiculous conclusion. As rice is grown in flooded fields, the moisture year to year is controlled by the farmer and would be, essentially, the same. The other major variables, temperature and CO2 concentration, even if you concede that they have increased to any significant amount during this short study, would only tend to increase crop yields, as has been shown in multiple studies. This is a joke.
Well, we knew it was going to be nothing but hyperbole anyway. Thanks for looking into that for us, and thanks to the readers for supplying the study. I just can’t get to the point to pay for that stuff.
Public release date: 19-Feb-2010
International Rice Research Institute
The Philippines triples its rice yield
Los Baños, Philippines: In the last fifty years, the Philippines has more than tripled its rice yield, while the world average rice yield has increased only about 2.3 times.
Despite being criticized as a poor rice producer because of its status as the world’s biggest rice importer, the Philippines has actually done remarkably well in raising its rice yields from 1.16 tons per hectare in 1960* to 3.59 tons per hectare in 2009**.
In 2009, Philippine rice yields were actually lower than the previous two years due to the damage done by the tropical storms “Ondoy” and “Pepeng”. In 2007, average rice yields topped 3.8 tons per hectare and in 2008 they were 3.77 tons per hectare**.
Rice yields in the Philippines are also higher than those in Thailand, the world’s biggest exporter of rice, where yields over the last few years have been around 3 tons per hectare*.
According to estimates from the United States Department of Agriculture, the average world rice yield in 1960 was 1.84 tons per hectare and in 2009 it was forecast at 4.24 tons per hectare.
http://www.eurekalert.org/pub_releases/2010-02/irri-tpt021910.php
More non-science (close to the word “nonsense”) from the CAGW’s.
How can they posit a change in rice yields in response to global temp changes rather than the temps the rice plants directly experience?
Hi Willis,
Thank you for the review and write up!
Do I understand correctly that this was a peer reviewed study that was then published by the US Nat’l Academy of Sciences? If so, might be quite appropriate to mention in your review with a question of why these clear problems you’ve noted were not caught by peer review – and even if not peer reviewed, why in the world is NAS allowing things like this past their editor on to publication? Do they publish anything??
Next, might I suggest/ask that you add a few sentences explaining autocorrelation and its import with short data series?
Regardless, as you note – to try to draw ANY conclusions wrt temperature effect on crop yields using two years yield data compared to a few decades of temperature trends is just ludicrous. I’m increasingly dismayed at what is passing for ‘science’ these days.
Thanks again, keep up the great work!
You have not touched on very many of the deliberate errors. The precipitation is not controlled. The CO2 at the fields is not measured. They don’t have a control group for the study which I know is hard to create. Even when rice is in water, the light, humidity and CO2 levels of the plant above the water affects the crop.
We have no control over fertilizer , or soil conditions.
The student is an economist and this is not close to a plant science study.
I really like your picture. If the student was smart, he would have taken sample yields from 5-10 dozen of the individual teracces and seen what kind of varience there was from one little puddle to the next. If the natural yield variability is 18%, then that alone is outside the range of normal variation.
So, they “found” a possible problem. Now they need additional funding for a more exhaustive study … something to tide them over for a decade or so. Then they can “study” a new facet of agriculture/climate and discover a new area requiring additional study that’ll take them through another decade.
What a racket! Talk about job security.
Rice in southeast Asia is fairly labor intensive as a crop.
Walking through a rice paddy there several years ago was a fairly dangerous proposition although not as dangerous as walking on the berms. I hope never to do that again.
In Arkansas they plant it by airplane. Lots of water moccasins as well. It would be interesting to see what the difference in yields per acre is. Like I said on the other thread, the study falls under the category of warmist propaganda.
Good job Willis.
How does the chinese demand for rice compare with state controlled chinese birthrate/population and that with global average temperature and change in rice production? Is temperature statistically relevant?
How could the records of nearby weather stations be to short? We are talking of two to six year datasets. It must be a very rare weather station with a shorter lifetime than that.
It would seem that for some unfathomable reason these “scientists” think that the rice is somehow teleconnected to climate trends in the past and/or the future rather than the weather during the growing season. It is true that the weather of the last few years will have some influence by way of soil moisture, the number of weed seeds in the soil etc, but no more than that.
KW You must have missed the advances made by the dendro gang in science. They discovered a process called teleconnection in which tree ring width responded to, and was therefore a proxy for, temperatures elsewhere than at the place the tree was growing, and was in fact more directly influenced by those distant temperatures than by other aspects of growing conditions in the trees’ localities. The rice theory is simply a corollary.
In other words:
The obvious flaw is that local rice yields respond to local conditions ONLY. If no local conditions are used, there is no actual study.
A rice plant doesn’t care what happens in the next field, let alone in the glaciers of Greenland.
Ed
No matter how poor the science of those he critiques, we can rely on Willis to brighten the story with a great choice of images. 🙂
Was that rice yield study peer-reviewed? If so, shame on the peers! Even to a non-scientist like me the following remark by Eschenbach alone:
” they are comparing a two year series of yields against a twenty-six year trend. I’m sorry, but I don’t care what the results of that comparison might be. There is no way to compare a two-year dataset with anything but the temperature records from that area for those two years”
would have been enough to reject the study and return it to sender.
The problems you cite are so obvious that even a child should be able to see it since you pointed it out. That level of logical challenged studies has become so common in climate science that it is practically the norm. You are being way to kind and giving them far too much credit. These are supposed to be scientists making these “studies”. There is no concept of cause and effect. They can’t even establish correlation. It is nothing but pure advocacy and I am getting sick of seeing science being so completely corrupted by it.
So the Green Revolution continues to improve yields in China although at a slower rate. The initially more impressive gains from new hybrids of rice and better fertilization have now slowed to a more modest increase. However, better farmers with better knowledge STILL get better yields than their neighbors…
And these “scientists” think THEY can filter out ALL this noise and come up with an AGW signal!!??? They truly think they can figure out what the farmers yields SHOULD HAVE BEEN had only the temperatures been different?
What a HOWLER!!! LOL!
This is too small a sample size.
Nothing in the study that tells us anyone visited Asia. Use of the word “controlled” is incredibly misleading. Not speaking to a single farmer? This is as bad as the other thread that uses one thermometer for one country.
I found a great link to a rice yield study here:
http://www.fao.org/docrep/003/x6905e/x6905e05.htm
The next issue is very serious. When they say it increased 10-20 % less than it could have or would have if the temps were cooler, how did they know what it WOULD have been? They have no accesess to audited reports of number of plants per acre at planting time. We have no honest way of knowing how accurate their actual number of plants per acre were planted. 227 farms in 6 countries requiers a lot of observers. They appear to have none.
Crop yields vary from year to year from field to field based on so many variables. I have seen one field give 150 bu of corn and the one next door give 120 and then they flip the next year. There are just too many variables. The best years for corn are a cold wet start and then warm, sunny days with intense nightime storms timed every other week. Then dry, calm weather when in bloom, then a couple of heavy rains. Then hot conditions and then very dry conditions for harvest.
So many variables – sun, wind, rain, temps, harvest conditions, pest conditions, etc. You just cannot control for these nor could you measure them at any granularity or exactness to know.
It would be easy to verify CO2 response in a lab for rice.
Who is paying these guys ? The IPCC ?
Thanks Willis for another excellent critique of what turned out to be yet another poor attempt to generate more climate alarm.
This is a worthless study which tries to link change in climate to crop yields, which, in fact, depend not just on weather, but on many other other biological factors. I can’t understand how it managed to get through the peer review process, let alone be passed for publication.
It is cargo cult ‘science’ par excellence!
k winterkorn says:
August 11, 2010 at 2:49 pm
“How can they posit a change in rice yields in response to global temp changes rather than the temps the rice plants directly experience?”
Just like Michael Mann thinks trees respond to global and hemispheric temperatures rather than the local climate they grow in.
My next comments. Welch is an Econ grad student. So was I a long time ago. I also have degrees and education beyond a bachelors in 4 additional fields. I am also a farmer.
Correct me if I am wrong, but UC SD doesn’t have a school of Agriculture. So he does google ag research? Wouldn’t we expect this kind of research to come from a school with an ag department and actual field tests under control?
Texas A & M has tracked rice for 100 years. They may track precip and several other inputs but not daytime high and night time low temps. If he claims his flimsy study was peer reviewed, was it with greenie weenies ? Surely not some Ag Phd’s.