Oh No! CO2 can't be plant food, say the folk at WUWT

One has to wonder at the thinking process of WUWT fans. A lot of deniers can't accept their own memes when they are supported by scientific research, even though they were originally derived from scientific research. It's a knee-jerk reaction from the scientific illiterati that science must be rejected at all costs. This time a lot of WUWT-ers reject the notion that plants respond to extra CO2. The latest from lots of people in deniersville is that CO2 isn't plant food after all!

Yesterday Anthony Watts copied and  pasted a press release (archived here). (As usual he didn't link to the paper or the press release.)  The paper in Nature Climate Change was by a large team led by Jiafu Mao of the Oak Ridge National Laboratory in Tennessee. The scientists looked at the greening of the extratropical northern hemisphere and compared it with what would be expected with no greenhouse forcing. They concluded that without human activity, the observed amount of extra plant growth would not have occurred.

Earth system models simulate Northern Hemisphere greening. Figure shows the spatial distribution of leaf area index trends (m2/m2/30yr) in the growing season (April–October) during the period of 1982–2011 in the mean of satellite observations (top), Earth system model (ESM) simulations with natural forcings alone (lower left) and ESM simulations with combined anthropogenic and natural forcings (lower right). Credit: Oakridge National Laboratory

From the abstract:

Our findings reveal that the observed greening record is consistent with an assumption of anthropogenic forcings, where greenhouse gases play a dominant role, but is not consistent with simulations that include only natural forcings and internal climate variability. These results provide the first clear evidence of a discernible human fingerprint on physiological vegetation changes other than phenology and range shifts.

The press release points to the importance of the findings, in that the extra plant growth in the northern regions will have a global impact on energy exchanges, water use and carbon budgets. These may variously accelerate or slow the pace of climate change. They also described how they did the analysis:

The team used two recently available 30-year-long leaf area index data sets, 19 ESM simulations and a formal "detection and attribution" statistical algorithm to positively attribute changes in vegetation activity in the extratropical Northern Hemisphere to anthropogenic forcings, or human-induced climate inputs such as well-mixed greenhouse gas emissions.

Leaf area index -- the ratio of leaf surface area to ground area -- is an indicator of vegetation growth and productivity derived from satellite imaging. The remote-sensing-based LAI datasets and ESM simulations showed a significant "greening" trend over the northern extratropical latitudes vegetated area between 1982 and 2011, indicating increased vegetative productivity.

When Mao and his colleagues accounted for internal climate variability and responses to natural forcings such as volcanic eruptions and incoming solar radiation, it was clear that the greening was inconsistent with simulations of purely natural factors and could only be explained by anthropogenic greenhouse gas forcings, particularly elevated carbon dioxide concentrations.

This anthropogenic greening effect has the potential to alter natural processes on a planetary scale. Continent-wide changes in vegetative productivity, such as those in the study, impact energy exchanges, water use and carbon budgets, accelerating or slowing the pace of climate change.

Below is Figure 2 from the paper, with the blue shading showing without AGW, yellow showing AGW only, the brown showing natural plus AGW, and the black line showing observed changes (average).

Observed and simulated 1982–2011 time series of LAI anomalies. The three-year-mean growing season (April–October) LAI anomalies over land of the NEL for both LAI3g and GEOLAND2 satellite-derived observations, for CMIP5 simulations accounting for solely natural (NAT) and greenhouse gas forcings (GHG), as well as CMIP5 simulations accounting for both anthropogenic and natural forcings (ALL).The ensemble (ens.) mean for each set of forcings is given in blue, yellow,and red solid lines for NAT, GHG, and ALL, respectively. Individual satellite-derived observations are indicated with dashed black lines; the observational average is given with a bold solid black line. Blue, yellow, and red shading represent the 5%–95% confidence interval for NAT, GHG, and ALL ensembles, respectively (computed assuming a Gaussian distribution).The grey-hatched area represents the 5–95% confidence interval for the range of variability for the centennial-long pre-industrial unforced control simulations (CTL). Source: Mao16

From the WUWT comments

Anthony Watts' headline wasn't a "claim" headline. He wrote: "Good news! Climate study finds human CO2 fingerprint in Northern Hemisphere greening". Despite this, a lot of the people commenting took issue with the subject, effectively saying "CO2 can't be plant food"!

Mike Jonas decided that the fact that the analysis showed that the greening was not consistent with what would have happened without AGW, it couldn't be AGW. He's the one committing the logical fallacy, not the scientists. Mike's logical fallacy is "personal incredulity":

June 29, 2016 at 8:10 pm
I picked up on the exact same sentence as A. D. Everard. “it was clear that the greening was inconsistent with simulations of purely natural factors and could only be explained by … ” is actually one of the logical fallacies (argument from ignorance). The fact that Sherlock Holmes used it doesn’t make it right. So unless there’s other supporting evidence, or unless there is a detailed correlation other than two things just happening to go in the same monotonic direction, then there is no substance to it. It is just a potentially interesting observation.

Ken claims, with no evidence, that the scientists didn't explore all conceivable causes of the extra greening. He doesn't list even one conceivable cause that the scientists didn't investigate. In his mind it couldn't have been that CO2 is plant food. That would conflict with his "science":

June 30, 2016 at 5:38 am
Tony McCleod — No, if you read the phrase “could only be explained by”, you will clearly see the logical fallacy that is put there on purpose to draw the reader away from the fact that the writer is trying to lead us into the belief that this greening is bad, even though the writer has no proof of that. He has used a couple of simulations to try to pin down the causes of the greening. But these simulations do not cover every conceivable potential cause for the greening.

Basically, he is saying “Trust me. I know what I am talking about”, but clearly he does not.

I am not denigrating his simulations. They certainly suggest avenues of further investigation. I am, however, denigrating his misleading choice of words when he says “could only be explained by”. Such hyperbole is political, not scientific.

Tom Halla seems to be suggesting that it's the temperature rise that's causing CO2 to increase. He doesn't explain the mechanism for how temperature is going up. Oddly, this is the same Tom Halla who doesn't think it's warmed since 1998, and who thinks that climate science is a communist plot.

June 29, 2016 at 1:09 pm
Didn’t NASA do something similar within the last few weeks? Mao does assume CO2 rise is anthropogenic, though, and not a result of warming.

Pat Frank doesn't "believe in" attribution studies. He must not know about the valid and long understood greenhouse effect. He's just another WUWT "climate hoax" conspiracy theorist:

June 29, 2016 at 4:13 pm
You hit the centrally important point, Janice. There is no such thing as a “formal “detection and attribution” statistical algorithm to positively attribute changes…”(my bold)
Attribution — the assignment of a causal source — can be done only by means of a valid scientific theory. Never by statistics. Never ever by statistics.
Climatologists have totally run off the boards with statistics. They misuse it all over the place to assign causality. It is a fatal error of method and of thinking. Doing so not science. Climatology is no longer science. It is mere narrative.

Peta in Cumbria lists all the possible causes of greening in an attempt to show that CO2 can't possibly be "plant food". Peta hasn't heard of acid rain either, but does seem to agree that the planet has warmed enough for more people to sow winter crops:

June 29, 2016 at 1:46 pm
So no chance at all that greening is caused by…
a.Shed loads of nitrogen fertiliser being thrown around by farmers – hey come on, we all know the ever increasing amount of food being grown to feed extra mouth just falls down out of the sky.
b. No chance that sulphur dioxide from power statioons and vehicles exhausts is making things grow – we all know UK farmers just throw extra sulphur at their crops because its fun to do.
c. No chance that it extra NOx from all the extra diesel vehicles on the road – remember? – those high mpg & fuel efficient ones effectively mandated by government 20 or 25 years ago?
d. No hope that the extra greenery came from a widescale move to winter-sown arable crops, from spring sown crops – where the fields are brown/bare for maybe Septemebr compared to being brown from September to May inc. previously.
e. No hope that all the extra soot from diesel vehicles is having a fertilising effect – yes – soot is a *very* good soil conditioner. Mother Nature knows trick or two when it comes to starting wildfires and thats before she launches all that CO2 NOx and SO2 up with the smoke
So what have we got – preconceived notions from smallminded brains.
You can’t really blame them though, they, like most of the rest of the world, are addicted to carbohydrates – and Thats What That Stuff Does to People. 

Cliff Hilton finds it hard to believe that an extra 50 to 70 ppm of CO2 could cause plants to grow more. Could CO2 possibly be plant food after all? Good grief. That will put the cat among the WUWT pigeons.

June 29, 2016 at 2:32 pm
CO2 has gone up about 50-70ppm in this time frame. Is it possible to get this kind of greening? A greenhouse should be able to duplicate the greening…no? Is that small of an increase capable of contributing to that much greening? Or are the simulation an exaggeration? Is it really that green? 

Tom in Florida has a conspiracy theory. He's skeptical of the fact that CO2 is plant food and thinks it's just a ploy to "gather the acceptance of skeptics":

June 29, 2016 at 7:51 pm
This is a Trojan Horse report. They slip in the “fact” that they can distinguish the effect of human produced CO2 inside a report that has a conclusion that will gather the acceptance of skeptics. If this “fact” goes unchallenged it will be used over and over as if it were indeed proven to be so. 

rishrac is another conspiracy theorist who agrees with Tom and thinks it's a "smoke screen" for something else. Those dastardly scientists!

June 29, 2016 at 8:12 pm
+1.. I have a lot of problems with the co2 story. This is a feel good story and we ( the skeptics) are buying into it. It’s a smoke screen for something else. It has the CAGW qualities of a set up. I’m not buying a cook book here. I think you’re right Tom.

tadchem is another "climate hoax" conspiracy theorist who sees nefarious intent behind every bit of scientific research:

June 30, 2016 at 8:05 am
After witnessing years of statistical malpractice by environmentalists and climate ‘scientists’, I see little reason to trust ‘a formal “detection and attribution” statistical algorithm’ without further details. 

There was also a lot of discussion about the lead author's name which, as you'd expect from WUWT, got ugly, so I won't bother with it.

References and further reading

Jiafu Mao, Aurélien Ribes, Binyan Yan, Xiaoying Shi, Peter E. Thornton, Roland Séférian, Philippe Ciais, Ranga B. Myneni, Hervé Douville, Shilong Piao, Zaichun Zhu, Robert E. Dickinson, Yongjiu Dai, Daniel M. Ricciuto, Mingzhou Jin, Forrest M. Hoffman, Bin Wang, Mengtian Huang, Xu Lian. "Human-induced greening of the northern extratropical land surface." Nature Climate Change, 2016; DOI: 10.1038/nclimate3056

• Climate study finds human fingerprint in Northern Hemisphere greening - press release at ScienceDaily.com

From the HotWhopper archives

• CO2 is plant food? Not on your nellie, sez Anthony (Pavlov) Watts and his dogs! - October 2013
• WUWT claim? CO2 is NOT plant food. How WUWT rejects chemistry, biology and photosynthesis - June 2014
• Denier for Hire: Sick, crazy and weird - CO2 is plant food book touted at WUWT - April 2014
• Denier weirdness: Plant food and ice ages at WUWT - May 2015
• Matt Ridley loses the plot, falls back on "CO2 is plant food" - September 2013
• "Expert" David Legates tells US Senate Committee that CO2 is animal food - June 2014