New study refutes claims of drought-driven declines in plant productivity, global food security

Aug 25, 2011

A new, comprehensive study by an international team of scientists, including scientists at Boston University in the US and the Universities of Viçosa and Campinas in Brazil, has been published in the current issue of Science (August 26, 2011) refuting earlier alarmist claims that drought has induced a decline in global plant productivity during the past decade and posed a threat to global food security.

Those earlier findings published by Zhao and Running in the August 2010 issue of Science (Vol. 329, p. 940) also warned of potentially serious consequences for biofuel production and the global carbon cycle. The two new technical comments in Science contest these claims on the basis of new evidence from NASA satellite data, which indicates that Zhao and Running's findings resulted from several modeling errors, use of corrupted satellite data and statistically insignificant trends.

The main premise of Zhao and Running's model-based study was an expectation of increased global during the 2000s based on previously observed increases during the 1980s and 1990s under supposedly similar, favorable climatic conditions. Instead, Zhao and Running were surprised to see a decline, which they attributed it to large-scale droughts in the Southern Hemisphere.

"Their model has been tuned to predict lower productivity even for very small increases in temperature. Not surprisingly, their results were preordained," said Arindam Samanta, the study's lead author. (Samanta, now at Atmospheric and Environmental Research Inc., Lexington, MA, worked on the study as a graduate student at Boston University's Department of Geography and Environment.)

Zhao and Running's predictions of trends and year-to-year variability were largely based on simulated changes in the productivity of tropical forests, especially the Amazonian rainforests. However, according to the new study, their model failed miserably when tested against comparable ground measurements collected in these forests.

"The large (28%) disagreement between the model's predictions and ground truth imbues very little confidence in Zhao and Running's results," said Marcos Costa, coauthor, Professor of Agricultural Engineering at the Federal University of Viçosa and Coordinator of Global Change Research at the Ministry of Science and Technology, Brazil.

This new study also found that the model actually predicted increased productivity during droughts, compared to field measurements, and decreased productivity in non-drought years 2006 and 2007 in the Amazon, in contradiction to the main finding of the previous report. "Such erratic behavior is typical of their poorly formulated model, which lacks explicit soil moisture dynamics," said Edson Nunes, coauthor and researcher at the Federal University of Viçosa, Brazil.

The new study indicates that Zhao and Running used NASA's MODIS satellite data products, such as vegetation leaf area, without paying caution to data corruption by clouds and aerosols. "Analyzing the same satellite data products after carefully filtering out cloud and aerosol-corrupted data, we could not reproduce the patterns published by Zhao and Running. Moreover, none of their reported productivity trends are statistically significant," said Liang Xu, coauthor and graduate student at Boston University.

In any case, the trends in plant productivity reported by Zhao and Running are miniscule—a 0.34% reduction in the Southern Hemisphere offset by a 0.24% gain in the Northern Hemisphere for a net decline of 0.1% over a ten-year period from 2000 to 2009. "This is the proverbial needle in a haystack," said Simone Vieira, coauthor and researcher at the State University of Campinas, Brazil. "There is no model accurate enough to predict such minute changes over such short time intervals, even at hemispheric scales."

Any investigation of trends in plant growth requires not only consistent and accurate climate and satellite data but also a model suitable for such purposes. "The Zhao and Running study does not even come close," said Ranga Myneni, senior author and Professor of Geography, Boston University. "Their analysis of satellite data is flawed because they included poor quality data and do not bother to test trends for statistically significance. Our analyses of four different higher-quality MODIS satellite vegetation products that have been carefully filtered for data corruption show no statistically significant trends over 85% of the global vegetated lands."

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Sean_W
1.7 / 5 (3) Aug 25, 2011
"indicates that Zhao and Running's findings resulted from several modeling errors, use of corrupted satellite data and statistically insignificant trends."


Where have I heard of that happening before? Oh, right--in every aspect of climatology. Still, it is anti-science and anti-intellectual to point out that such a thing can happen. Just receive the received wisdom and button it.
ryggesogn2
1 / 5 (4) Aug 25, 2011
What! A computer model is wrong? How can this be? Computers are never wrong.
GSwift7
1 / 5 (1) Aug 26, 2011
who peer-reviewed the original paper? Will the journal continue to use those reviewers? Will the 2010 article be retracted? Has anyone used it as a reference for other studies or reports? How does Science usually handle these things? It's not that rare.

Where have I heard of that happening before? Oh, right--in every aspect of climatology.


According to some organization I heard on NPR recently, who watch and report on journal retractions, the medical journals have way more retractions than any other type of journal. I wonder if that's a good thing because it means they're honest when they make mistakes, or if it is a bad thing because so many articles pass peer review and then get retracted?
omatumr
1 / 5 (4) Aug 28, 2011
Thank you, thank you, Arindam Samanta, coauthors, and editors of Science for bringing some reality back to climate science!

In preparing the following documents (pdf & doc) for today's ACS webinar: "Critical Look at Global Warming Data: Wickedly Complex System Called Climate"

http://dl.dropbox...inar.doc

http://dl.dropbox...inar.pdf

I belatedly realized that all of my former students and associates also became unwitting opponents of official AGW dogma. That was not my intent. In opposing SSM dogma, I had no idea that I was also opposing official AGW dogma, until tip of the iceberg became visible irecently.

Today support for AGW seems to be waning in the American Chemical Society, and I suspect that support for SSM will also be diminishing in the American Physical Society.

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
Howhot
2.3 / 5 (3) Aug 29, 2011
Unfortunately for the ignorant deniers this is just technical commentary. It doesn't stop the coming freight train of a disaster that is real global warming.
GSwift7
1 / 5 (1) Aug 29, 2011
Unfortunately for the ignorant deniers this is just technical commentary. It doesn't stop the coming freight train of a disaster that is real global warming


Care to explain what you didn't like about my comment? I'm willing to discuss anything you think I said that was wrong, as always. My comment didn't have anything to do with global warming. Do you really think that the peer review process is working? There has been a seriously worrying trend of increasing detractions in recent years. The percentage of articles which pass peer review and are later proven to be flawed has increased greatly. As I tried to say in my previous post, climate change is not the area of science with the biggest problem in this regard. Some posters here seem to want to make it sound like that's the case, but it isn't.
antialias_physorg
5 / 5 (2) Aug 29, 2011
Do you really think that the peer review process is working?


I think we need to clear up what 'peer review' really means (as someone who has peer reviewed a couple of papers himself maybe I can shed light on this). Peer review in journals (and conferences) works like this:

The paper is anonymized and handed out to a number of researchers in the field with a certain track record (usually by 'points' given for books, journal articles)

Now the thing to understand is: Research never has any peers. It's research. You NEVER find anyone who is an expert because research is, by definition, original. The peers can look at the paper and check whether the methods used are applicable (correct statistical methods, etc.)

Reviewers don't, usually, have access to the raw data and don't have the time to check it if they did (being researchers themslves they have other things to do). They certainly don't have the time (or money) to fly out to the rainforest and do spot checks on the ground.
antialias_physorg
5 / 5 (2) Aug 29, 2011
Now from my experience the peer reviewer oftentimes doesn't do the review himself but hands it down to his PhD students to read through, make comments and hand it back.

This may sound bad at first but often the head of an institute is already more into the managerial side of science and is a bit removed from the nitty-gritty of doing actual science - so PhD students are, in reality, the ones who are the most 'hip' to the subject, anyways.
Still: They will only ever be working in related fields (closely related with any luck) but never on EXACTLY that same subject.

The more specialized a paper is the more the reviewers will come from scientific areas with backgrounds that do not encompass all the specialties needed to make a perfect assessment.

Is the peer review process perfect? Certainly not.
Is there anything better? I have yet to see anyone make a proposal that would be.

Increased retractions may simply be a result of the explosion of papers due to 'publish or perish'.
antialias_physorg
5 / 5 (2) Aug 29, 2011
'Anonymization' is also very relative in highly specialized fields. The number of researchers in such a field is a few hundred (globally) and the number of groups with any serious output is maybe a dozen. People know who is working on what to a certain extent. So if you get a paper with a certain subject you mostly already know who it's from. (being that people publish mostly work that is based on their earlier work. Scanning through the references will often tell you who authored the paper)

This may seem like it leads to personal favoritism or that animosities between researchers could lead to papers being arbitrarily blocked. Not so (apart fom the fact that I've never run accross such inter-group hatred).

Since the paper is handed out to several people (and you never know to whom else) it would look suspicious with everybody coming back with an: "minor revisions needed" (which is the usual 'grade' the first time) and one professor handing back an "unacceptable".
Howhot
5 / 5 (2) Aug 29, 2011
Yeah, G7, peer review can be a real hassle for folks posting Bull, shit. Does that say it clear enough.
GSwift7
2.3 / 5 (3) Aug 30, 2011
Howhot:

Yeah, G7, peer review can be a real hassle for folks posting Bull, shit. Does that say it clear enough.


Are you trying to say that I post BS? I always back up my posts with links to good sources. You always post nonsense that is easily refuted with five minutes on google.

For example, I just looked up some of your recent comments and refuted two of your BS claims with less than 5 minutes on google on the following thread:

http://www.physor...her.html

lmfao

to Antialias:

I appreciate your informative posts on peer review. Thanks for the insiders' point of view.
Howhot
5 / 5 (1) Aug 30, 2011
G7, your arguments are always irrelevant wordy stuff that always has a global warming denier persuasive tone to them. Sometime it's not BS, but every time I've followed one of your posts (on google) it always points to some goofy anti-AGW argument.

Look, I apologize if I've just been reading you wrong all this time, and you really do have a concern about the bleak picture science is painting for us with respect to AGW. I certainly will admit when I'm wrong.

I read "Science" and they have a great editorial staff and pier review process. But occasionally there are corrections. Right now, I think the correction is bogus.
Howhot
not rated yet Aug 30, 2011
Look G7, the reason I say I think the correction is bogus, is due to the droughts of the south last year and the drought of 2011 for much of the mid-south interior (Texas, Oklahoma, SW-Kansas). Geeze, 100 F for months. That is significant and convincing IMHO.
GSwift7
1 / 5 (1) Aug 31, 2011
That's a local drought caused by la nina. Just a little farther south, in Colombia South America for example, they have had ample rainfall and the crops have been doing fine over the same time period. I was engaged to a girl from there, so I saw the news stories about flooding and landslides that don't get airtime here in the US. Don't be fooled into thinking that the conditions in Texas are some kind of global trend. The study described above was published in the very same journal as the original article and was peer reviewed. They can't both be right. I don't know how it works, but I would guess that a paper attempting to refute a previous paper would be met with serious peer review scrutiny.

If the previous paper gets retracted by the journal, will you accept that it is wrong, or will you disagree with the editors of Science?
antialias_physorg
not rated yet Aug 31, 2011
is due to the droughts of the south last year and the drought of 2011 for much of the mid-south interior (Texas, Oklahoma, SW-Kansas). Geeze, 100 F for months. That is significant and convincing IMHO.

Weather vs. climate. Two different things.

AGW is a climate phenomenon, so you can't argue it by giving anecdotal evidence of single datapoints. You can argue it with long term trends and models (which is what scientists have done). The global trend is pretty obvious (and statistically significant) if you look at the data.
omatumr
1 / 5 (4) Aug 31, 2011
is due to the droughts of the south last year and the drought of 2011 for much of the mid-south interior (Texas, Oklahoma, SW-Kansas). Geeze, 100 F for months. That is significant and convincing IMHO.

Weather vs. climate. Two different things.

AGW is a climate phenomenon, so you can't argue it by giving anecdotal evidence of single datapoints. You can argue it with long term trends and models (which is what scientists have done). The global trend is pretty obvious (and statistically significant) if you look at the data.


Thanks for the advice.

I looked at global temperature trends and concluded AGW is a scam.

So did several other scientists, including 8,000 physicists at CERN:

www.theregister.c...results/

So did well-known environmentalists:

http://opinion.fi...settled/

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
barakn
4 / 5 (4) Aug 31, 2011
Care to explain why you lied about the 8,000 CERN physicists?
jsdarkdestruction
3 / 5 (2) Aug 31, 2011
cern said no such thing. you tried posting that before except you said 4000. like i said before when you posted that article you claimed proved your point was nothing more than a personal attack and rant about conspiracies and was obviously negatively biased from the start. stop lying and saying people agree with you when they clearly dont.
Howhot
5 / 5 (1) Aug 31, 2011
Weather vs. climate. Two different things.

AGW is a climate phenomenon, so you can't argue it by giving anecdotal evidence of single datapoints. You can argue it with long term trends and models (which is what scientists have done). The global trend is pretty obvious (and statistically significant) if you look at the data.


Agreed. They are however extreme events (record breakers 20 degrees F hotter than typical) that would be expected additional moisture in the atmosphere. See it was also very humid. According to NASA, the jetstream the normally would drag down cooler air simply floated over the top giant heat bubble.

Last year, it was also similar. The point being, it doesn't take centuries for climate change. Decades can show the change too.

GSwift7
1 / 5 (1) Sep 01, 2011
Agreed. They are however extreme events (record breakers 20 degrees F hotter than typical) that would be expected additional moisture in the atmosphere. See it was also very humid. According to NASA,


That's really changing the subject away from the article here. You know, if the article here is correct and the previous journal paper was faulty, that doesn't say anything about any other paper about GW. There are bad papers you know. People make mistakes.
GSwift7
1 / 5 (1) Sep 06, 2011
Last year, it was also similar. The point being, it doesn't take centuries for climate change. Decades can show the change too


By definition, climate is the average of weather over a period of 30 years or more, so at least three decades are required before you can declare "climate change". Natural variations can average out on scales smaller than 30 years, and some happen on longer time scales that will not even show up at the 30 year interval. Any given 30 year period might only have three phases of the AMO or PDO, so it could have two positive and one negative or visa versa. You need four at the bare minimum, and more would be even better. We've only had satellite observations since the 70's, so we're just seeing the tip of the iceberg right now.
deepsand
5 / 5 (6) Sep 06, 2011
Satellite observations are not the sole source of material data.
GSwift7
1 / 5 (1) Sep 06, 2011
Yes, but the older records were never meant to be used for the current purpose, and they are not suited for it.
deepsand
5 / 5 (5) Sep 07, 2011
So, for times preceding said satellite observations, we cannot "declare climate change?"

I doubt that that is what you mean to say; but, that is what your words present.
Howhot
not rated yet Sep 07, 2011
G7, Ok after a careful read, I agree with the substance of this article. It's a flawed model, and the criticism seems to be accurate that the model did not take into account cloud effects on the plant growth.

However,

This new study also found ... increased productivity during droughts, compared to field measurements, and decreased productivity in non-drought years 2006 and 2007 in the Amazon, in contradiction to the main finding of the previous report


In other words, with new satellite data and analysis, non-drough year 2006 and 2007 where in-fact drought years, and the others where just normal. It's kind of like asking the question; HOW DO YOU LIKE YOUR MEDICINE? Bad tasting Cherry or Bad tasting Orange.