Memo to Doubters—I was Tempted to say “Deniers”—CO2 is Plant Food!

Guest post by Indur M. Goklany

This illustration from a recent article in Science magazine shows that CO2 is plant food.  It is based on both empirical data and model results (not “data”).  I know that looking at empirical data might seem like a novel idea to some people, but for some perverse reason, I find it more compelling.

image

On the right: Empirical Data. Growth of 21-day-old rice and S. viridis seedlings at different ambient CO2 concentrations ranging from 30 to 800 parts per million. NOTE: The very last set of pots on the extreme right is out of sequence. They are for 390 ppm, while the next to last pots are for 800 ppm.

On the left, Modeled Data:

Modeled changes in CO2 assimilation rate in response to changes in leaf intercellular CO2 partial pressure for C3 and C4 photosynthesis and for a hypothetical C4 rice. Curves 1, 2, and 4 have Rubisco levels typically found in a C4 leaf (10 μmol m−2 catalytic Rubisco sites). Curve 3 shows a typical response for C3 leaves with three times the Rubisco level of C4 leaves. Curve 1 shows the response of a C4 leaf with C4 Rubisco kinetic properties. Curve 2 models how a C4 leaf with C3 Rubisco kinetic properties would respond (a hypothetical C4 rice with C3 Rubisco kinetics). The comparison of these two curves shows the increase in CO2 assimilation rate achieved with C4 compared with C3 Rubisco kinetic properties within a functional C4 mechanism. Arrows to curves 1 and 3 show intercellular CO2 partial pressures typical at current ambient CO2 partial pressures for C4 and C3 photosynthesis. To generate the curves, model equations were taken from (11) and comparative Rubisco kinetic constants from (12). (B) [Reference numbers per source.]

Source: Susanne von Caemmerer, W. Paul Quick, and Robert T. Furbank (2012). The Development of C4 Rice: Current Progress and Future Challenges. Science 336 (6089): 1671-1672.

Finally, note that the top photograph on the right is for rice.  According to Wikipedia, not always a reliable source, but in this case probably trustworthy:

[Rice] is the most important staple food for a large part of the world’s human population, especially in Asia and the West Indies. It is the grain with the second-highest worldwide production, after maize (corn), according to data for 2010.

Since a large portion of maize crops are grown for purposes other than human consumption, rice is the most important grain with regard to human nutrition and caloric intake, providing more than one fifth of the calories consumed worldwide by the human species.

In other words, not only is CO2 plant food, CO2 makes human food.  Guess some folks skipped that biology class.

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I’m by no means an expert, but doesn’t the question about whether or not it is universally beneficial have something to do with the respiration model used by the plant in question, where not all plants are the same? The argument as I have heard it given is that one kind of plant benefits, but another does not or can even be hurt by it. One species of plant does not a sweeping generalization make either way…
rgb

the Mark of the Alarmist is the obsession in deleting from history (=”denying”) everything that was known before, even the most uncontroversial stuff like CO2 being “plant food”.
this is in order to demonize the molecule, so no positive can be described as coming out of it.

Alvin

Robert, do you have a plant in question that is negatively affected by CO2?

polistra

I love the Living Histogram! Best data representation ever. Let the plants be their own graph.

Gary Hladik

Thanks for this article. I had seen C3 and C4 photosynthesis mentioned on this blog before, but never looked into it. According to Wikipedia, C4 plants evolved more recently than C3 (25 to 32 million years ago), have an advantage over C3 plants in arid, hot, and low nitrogen/CO2 conditions, and are common among grasses, e.g. food crops such as maize, sugar cane, millet, and sorghum.
http://en.wikipedia.org/wiki/C4_carbon_fixation#The_evolution_and_advantages_of_the_C4_pathway
Wiki predictably links C4 plants to climate change:
“Increasing the proportion of C4 plants on earth could assist biosequestration of CO2 and represent an important climate change avoidance strategy.”
Unless the “increased proportion” of C4 plants are long-lived species like trees, however, I don’t see the potential for much more “biosequestration”. Certainly maize and sugar cane grown for fuel ethanol don’t count.

Bruce Cunningham

I would like to repeat Alvin’s comment. Is Dr. Brown aware of any plants that are negatively affected by increased CO2? I’m not questioning that there might be some, but I can’t help but think that if there were any, the doomsayer chorus would have let us know about it long ago.

son of mulder

The more CO2, the faster the grass grows, the more CO2 produced by lawnmowers cutting the grass and by humans guiding them. I see nought but doom (;>)

Steve C

That 800ppm rice looks like a very happy plant indeed! Does anyone know of a study investigating whether such bigger plants also have the same nutritional value per kg? After all, if the ‘twice the size’ plant only has half the nutritional value, the actual ‘gain’ to humanity could be zero. Anyone wanting to throw money at me to do the research can get my email address from WUWT … though it’s only fair to mention that my ‘tender loving care’ has killed chlorophytum (= ‘spider plant’, = grass!)

davidmhoffer

Robert Brown;
The Idso brothers have been studying this for quite some time and have a remarkable database on the matter. There is the odd plant species that is negatively correlated with CO2 increases, but the vast bulk of them are positively correlated.
http://www.co2science.org/data/plant_growth/plantgrowth.php

MrX

I have a question. If plants can take that much advantage of higher levels of CO2 (look at 800ppm), is there any implication that there must have been a time in the past where these plants evolved to the point where they could make use of those higher levels of CO2? Or is it that at lower levels, they’d need to be more efficient and the higher levels is just the plant’s reaction to having evolved in lower CO2 environments? Can any assertions be made one way or the other? It seems like some plants take definite advantage of CO2 and that this is the way they evolved. I would think that if they were more efficient at lower CO2 levels, that they would “suffocate” at higher levels (or not the excess at all), but they don’t work that way. At least, not at 800ppm or even 1200ppm. For many plants, 1200ppm seems to be optimal growth. From what I understand, it is common to find 2000ppm inside buildings, though it should be kept below 1000ppm when possible.
Are there any indications that higher levels were required for plants to evolve to the point where they can take advantage of those levels as seen in the experiment in this article? (And not cause adverse effects to the plants).

farguard

The empirical data histogram, if put in the correct order and extended to 1000ppm, might actually look like a hockey stick! That’s my model.
Why would they not model c3 from the evidence, or use the evidence to challenge their model references? Of course I, Willis and other cynics on WUWT know the answer.

Greg House

omnologos says:
June 30, 2012 at 12:49 pm
the Mark of the Alarmist is the obsession in deleting from history (=”denying”) everything that was known before, even the most uncontroversial stuff like CO2 being “plant food”.
==============================================================
They have also managed to delete from history the experiment performed by an American physicist professor R.W.Wood (1909) demonstrating that no (or no significant) warming is possible by means of “trapped radiation”.

Scarface

@MrX The only sensible explanation I can come up with is, has to do with the fact that, with higer CO2-concentrations, plants are able to reduce the size of the openings on their leaves, that take in CO2 (at daytime at least) and so lower the loss of H2O. Therefore plants that need the most H2O, or are vulnerable to H2O-loss, might profit more from higher CO2. But i’m not a biologist.

Surely the experiment was done using good, natural CO2. It’s the bad, man-made CO2, no doubt filtered out of the growing chambers built by big oil and coal money, which is destroying the planet.

kadaka (KD Knoebel)

From davidmhoffer on June 30, 2012 at 1:22 pm:

The Idso brothers have been studying this for quite some time and have a remarkable database on the matter.

Brothers?
The Many Benefits of Atmospheric CO2 Enrichment
Press Release: 2 Feb 2011

Snippet: “The book is The Many Benefits of Atmospheric CO2 Enrichment, written by the son/father team of Craig D. and Sherwood B. Idso.”
We’ll let it slide this time, but if you ever similarly call the Pielke’s “brothers” we’ll be forced to promptly kick you out of the Skeptic’s Clubhouse and tear up your membership card.

John Silver

Me and my green friends demand 1200 ppm.

Can anybody here hand-deliver a copy of this report to the head of the EPA (Lisa Jackson)?
.

Most plant species evolved during times of much higher CO2 concentration. At the historical level of 280 ppm, they were near starvation. ( At about 100 ppm some species die).
C4 type metabolism is a relatively recent invention and lets plants survive in lowering CO2 levels.
As a result, C3 plants respond more to increases in CO2 than do C4 plants.
In general, the increase in yields and growth continues to about 1000 ppm / 2000 ppm range (which is about where it was when the c3 plants were dominant).
The planet has been sequestering CO2 to excess as carbonates for so long that the plants were on the verge of dying. Their breathing a sigh of relief and getting back to normal (higher) growth rates as CO2 rises is clear evidence of that.
A forest or a bamboo plot will clear 100% of the CO2 above it in short order if allowed to grow.
http://chiefio.wordpress.com/2010/10/10/got-wood/
So world plant growth “limits” on CO2 as the limiting nutrient unless someone puts a lot more into the air or forest fires burn…

rgbatduke

I would like to repeat Alvin’s comment. Is Dr. Brown aware of any plants that are negatively affected by increased CO2? I’m not questioning that there might be some, but I can’t help but think that if there were any, the doomsayer chorus would have let us know about it long ago.
As I said “I’m not an expert…” — I’m a physicist. However, I remember at least one CAGW-believing individual who asserted that there are plants for which excess CO_2 is not beneficial. Then there are secondary problems — the CO_2 might be good, but a side effect of the CO_2 might be worse. That’s the argument concerning CO_2 uptake in the ocean and acidification — the idea that it might push the pH of the ocean out of acceptable bounds. I’m properly skeptical of the argument, but I repeat — one doesn’t need an experiment to show that 800 ppm CO_2 is good for at least some crops. It’s standard practice in many greenhouses to bump it to 1000-1500 ppm (and amusingly, pot growers all seem to take advantage of that to grow their valuable crops faster:-).
But just as excess water kill cactus, it is by no means implausible that some plants object to excess CO_2. And a single experiment does not prove that the result is generalizable in any venue, let alone one with millions of species in a staggering array of ecologies. I’m a general purpose skeptic, not just skeptical about CAGW…;-)
Overall, it is probably better to keep our CO_2 level close to “normal” quite aside from what one thinks about CAGW simply because our ignorance can kill us in this as in many things. It isn’t probable, I agree. But wow, sometimes improbable things happen (and sometimes we have the estimates of probability wrong!)
rgb

Greg House says:
June 30, 2012 at 1:36 pm

They have also managed to delete from history the experiment performed by an American physicist professor R.W.Wood (1909) demonstrating that no (or no significant) warming is possible by means of “trapped radiation”.

Greg, that statement would look just on the surface to go against common sense.
Of course, you are aware of, and do not deny, the GHG effect by water vapor, a much more plentiful constituent of the atmosphere than CO2 …
.

Chas

Steve C – humans dont often eat the plant itself, we eat the seeds.
If the increased photosynthesis results just in an increased seed starch content then, if other things were equal, one would expect a proportional dilution of the other consituents ; protein and some minerals.
However if the increase energy surplus enabled greater root exploration then this might offset a small proportion of this dilution, but overall there will be dilution.
However ‘starch’ is energy and whilst most of the western world’s problem is overconsumption of such stuff, to those short of food energy is a primary nutrient.
The increased photosynthesis (or reduced plant respiration) might be expected to increase the nitrogen fixing of legumes – who trade energy for protein with the organisms in their nodules. So increasing the general supply of protein – very important to those short of food.
So the gain to humanity is very much more than zero, but as you say the increase in supply of some other nutrients might be zero or small.

rgbatduke

Most plant species evolved during times of much higher CO2 concentration. At the historical level of 280 ppm, they were near starvation. ( At about 100 ppm some species die).
One of the many risks of ice age — the low concentration of CO_2 in the last glaciation period was around 180 ppm. That really is getting too close for comfort, because before they die they fail to thrive… it is probably why we evolved plants that are more tolerant of low CO_2.
rgb

Amr marzouk

Too obvious for some

Steve C

@Chas – (blush) Yeah, actually I’d sussed it was the seeds we actually eat (from every bag of rice I ever bought!) … the important thing here is finding somebody with a stack of spare cash … 😀

jdgalt

No, no. CO2 is what plants breathe in. Articles that continue to express belief in AGW are plant food.

gofer

“The U.S. Department of Agriculture (USDA) has determined that a one percent increase in CO2 boosts crop yields by eight percent, translating into a 33-pound-per-acre yield per 1-ppm rise in CO2. The USDA also found that a field of corn in full sunlight consumes all of the CO2 within three feet of the ground. The corn will stop growing unless the surrounding air is stirred constantly by wind currents. In fact, the plants are harmed at CO2 concentrations of 240 ppm, and they die at 160 ppm.” Source: Climate Realists -Kirk Myers

Frank Kotler

Quite some time ago, Anthony made us aware of a (volcanic) site – “Mammoth Mountain” or “Mammoth Lake” ? – where the CO2 content was killing trees. So there is a limit!

Gary Hladik

Greg House says (June 30, 2012 at 1:36 pm): ‘They have also managed to delete from history the experiment performed by an American physicist professor R.W.Wood (1909) demonstrating that no (or no significant) warming is possible by means of “trapped radiation”.’
Er, no. Wood’s experiment only show’s that the so-called “greenhouse effect” is misnamed, which isn’t news. As Wood showed, a common greenhouse raises the interior temperature by preventing convective heat loss. The blocking of IR radiation apparently makes a minimal contribution to heat retention in an actual glass greenhouse. The earth’s atmosphere, with its constant convection, is in a sense the exact opposite of a greenhouse, but we’re stuck with the terminology.
_Jim says (June 30, 2012 at 2:14 pm): “Greg, that statement would look just on the surface to go against common sense.
Of course, you are aware of, and do not deny, the GHG effect by water vapor, a much more plentiful constituent of the atmosphere than CO2 …”
Incoming! [Dons helmet, ducks into foxhole.]

Greg House

rgbatduke says:
June 30, 2012 at 2:13 pm
Overall, it is probably better to keep our CO_2 level close to “normal” quite aside from what one thinks about CAGW simply because our ignorance can kill us in this as in many things.
==========================================================
Beyond the unscientific AGW concept, there is no scientific notion of “normal CO2 level”.
From the health standpoint the current OSHA PEL (permissible level at the work place) is 5,000 ppm (http://www.cdc.gov/niosh/idlh/124389.html).
Our ignorance, no, ignorance of our policy makers and machinations of climate scaremongers may cost us our money and our freedom.

Greg House

_Jim says:
June 30, 2012 at 2:14 pm
Of course, you are aware of, and do not deny, the GHG effect by water vapor, a much more plentiful constituent of the atmosphere than CO2 …
========================================================
When you say “GHG effect”, you need to specify which one of at least 3 conflicting narratives you mean.

gofer

I did a google search for “CO2 concentration and plant nutrition” and got a slew of negative articles about declining nutrition, for instance, potato protein declined by 14%. Potatoes have 2.1g protein per 100g. Studies show there are small changes in some nutritional content, however, legumes aren’t affected. They never state the CO2 concentration used in the study, only what it was supposed to be at the end of the century. There seems to be a lack of consideration for tradeoffs and they seem to have cherry-picked those plants that could shown to be negatively affected.

Chas

MrX
A large part of the response to increased CO2 is down to a ‘cock up’ in the design of of one a plants main enzymes, which is called ‘Rubisco’ – this enzyme captures CO2 and joins it to make sugars – it has a big defect; it cannot properly distinguish CO2 from O2. This means that a proportion of the time it grabs oxygen and adds it to partly built sugars – effectively ‘burning’ them (which is very pointless) . However the more CO2 there is in the air, the less often this wastefull reaction occurs leading to an improvement in the overall photosynthetic efficiency and output.
Evolution has worked hard on this problem, but there are trade offs: some Rubisco variants are more CO2 selective but they are slower enzymes ( a smaller, more selective active site doesnt let the CO2 ‘in’ as easily) -There are suggestions that an algal Rubisco exists that is both selective and fast.
An alternative approach is to capture CO2 chemically by another reaction (sadly this requires energy) and then release it again very close to the Rubisco – this is called the ‘C4’ or ‘CAM’ pathway. Because C4 plants are already ‘pumping’ the CO2 they do not respond as much to increases in outside CO2 levels.
The adavantage of a C4 system really shows up in dry conditions as you dont need your stomata open so long to take in a given amount of CO2. Or even more cleverly CAM plants like pineapples open their stomata at night – suck in the CO2 and then release it internally during the day 🙂
http://en.wikipedia.org/wiki/RuBisCO
http://en.wikipedia.org/wiki/Crassulacean_acid_metabolism

Gary Hladik

Steve C says (June 30, 2012 at 2:30 pm): “@Chas – (blush) Yeah, actually I’d sussed it was the seeds we actually eat”
Well, when we eat meat (e.g. beef), we’re indirectly eating the whole plant. I did a quick search on alfalfa and found this paper:
http://www.springerlink.com/content/r042040x33296x85/
Apparently additional CO2 enhances alfalfa growth, but the effect depends on the “rhizobial strain” associated with the plants. Life is never simple. 🙂

Jack

Long time since I studied biology, so correct me please. All plants have C4 and C3 cycles. When you see the red leaves of autumn, the C3 cycle is dominant. So it is not unusual. The red pigment takes over as the processing centre for plant energy. Just another adaption under differing circumstances that makes up our world of variation.

Greg House

Gary Hladik says:
June 30, 2012 at 2:45 pm
Er, no. Wood’s experiment only show’s that the so-called “greenhouse effect” is misnamed, which isn’t news. As Wood showed, a common greenhouse raises the interior temperature by preventing convective heat loss. The blocking of IR radiation apparently makes a minimal contribution to heat retention in an actual glass greenhouse. The earth’s atmosphere, with its constant convection, is in a sense the exact opposite of a greenhouse, but we’re stuck with the terminology.
===========================================================
No, it was not just a misnomer, it was a misconception of the “grounding fathers” of the AGW concept. And Wood did not need to show that in an enclosed space convective heat loss is prevented, I guess everyone new that.
He demonstrated that AGW concept won’t work, because “trapped radiation” produced nothing or next to nothing. Conduction and convection work, of course, but not “trapped radiation”.

SidViscous

Plants are carbon, can’t imagine any plant that is made of carbon that would be harmed by C02.
Nice place to put Feynman

The relevant point starts about 2:14

SidViscous

Even funnier that he calls Oxygen “Some sort of horrible by-product”

Jimbo

There is no doubt that Co2 is a plant food. How much is too much for which plants? Even here we may have to go past 1,000 ppm or more for most plants and we are currently not even half way there. Tip: the Earth has had 10x more co2 in the pas than today.

graphicconception

Let’s look at this the other way.
Are there any plants that can survive without C02?

AndyG55

gofer:
IIRC that study also limited the amount of nutrients actually available. DOH !!
If a plant is growing faster because it is making better use of the available water, then it also needs more trace nuitrients.
The way I understand it is that below about 280ppm, the stomate are packed tight, and every time they are opened to breath in CO2, they also let water vapour out. (try breathing at the top of a high mountain. poor plants have been really struggling for a long time)
As the atmospheric CO2 increases, the plants need less stomate density (its actually been measured, iirc) and so they loose less water through transpiration, and become more efficient.
There are many things that limit plant grow, lack of CO2 and H2O are primary ones since they are the building blocks, but other nutrients also play a big role, for example, you need nitrogen to make protein and many plants need to get it from the soil.
If you study predator prey relationships, you can see that the Earth’s CO2 content has been very low for a long time. This indicates that it was a limiting factor on plant growth, We are now , fortunately releasing some of the long buried carbon.. and JUST AT THE RIGHT TIME TO SUSTAIN THE FOOD SUPPLY (so long as we don’t waste it on bio-fuels) Isn’t it VERY FORTUITOUS that we find coal and the released CO2 gives the plants a growth spurt just as the human population expands…… maybe someone planned it that way.(there you go, religious and creationists, think about that one ;-). so maybe we better get out of the way and let it happen.

Henry Clark

Good article.
To add a bit more, take the example of what are perhaps the top half-dozen agricultural crops:
Wheat, rice, soybeans, and potatoes are C3. Corn and sugarcane are C4. Each benefits at higher CO2, as can be seen at http://www.co2science.org/data/plant_growth/dry/dry_subject.php
As an illustration, let’s compare wheat (C3) with corn (C4):
Wheat has much extra growth, around a 49.6% increase in biomass, for a 600 ppm increase of CO2.
Meanwhile, corn for the same CO2 increase has a 33% increase.
The C3 plant (wheat) had a bit more benefit than the C4 plant but both greatly benefited.
There is also a major water usage efficiency benefit, due to plants adjusting their stomatal conductance when they don’t need as much air flow (more CO2 per unit of air) and thus can reduce water losses. Here’s a graph for corn and soybeans, where again both greatly benefited even though the C3 plant had a still greater percentage rise:
http://buythetruth.files.wordpress.com/2009/06/wateruseefficiency1.jpg?w=500
This is unsurprising, as CO2 earlier in geological history was thousands of ppm, a nutrient for lush abundant vegetation (that which became today’s fossil fuels, aside from the abiotic hypothesis which is a mostly unrelated topic).
Combine this with how global warming is more arctic warming than elsewhere. Primary productivity has risen as observed by satellites:
Global terrestrial net primary production increased by 6% from 1982 to 1999 ( http://dx.doi.org/10.1126%2Fscience.1082750 ), then was reportedly stagnant (fluctuating down by 1%) from 2000 to 2009. The 2000 to 2009 period was actually a time of slight global cooling, after the high point at the end of the 1990s, as can be seen from the following, so the preceding is not surprising:
http://www.woodfortrees.org/plot/rss/from:2000/to:2009/plot/rss/from:2000/to:2009/trend
Over a lengthier time period, an ORNL study estimated that carbon in global terrestrial vegetation increased from approximately 740 billion tons in 1910 to 780 billion tons in 1990.
http://cdiac.esd.ornl.gov/pns/doers/doer34/doer34.htm
Nitrogen in soil is remarked upon at http://www.co2science.org/articles/V15/N26/EDIT.php although, besides, we use artificial fertilizer in modern agriculture to keep it not a limiting nutrient.
For a large amount of discussion, there is http://nipccreport.org/reports/2009/pdf/Chapter%207.pdf which is chapter 7 of the NIPCC report at http://nipccreport.org/reports/2009/2009report.html
Plus, one can copy and paste part of the title of any of countless papers referenced there, to google such and find the corresponding paper online.

Henry Clark

gofer says:
June 30, 2012 at 3:00 pm
I did a google search for “CO2 concentration and plant nutrition” and got a slew of negative articles about declining nutrition, for instance, potato protein declined by 14%. Potatoes have 2.1g protein per 100g. Studies show there are small changes in some nutritional content, however, legumes aren’t affected. They never state the CO2 concentration used in the study, only what it was supposed to be at the end of the century. There seems to be a lack of consideration for tradeoffs and they seem to have cherry-picked those plants that could shown to be negatively affected.
They do a dishonest presentation. You only get that result if you don’t apply enough additional nitrogen fertilizer per unit area to properly fit the increased biomass. For propaganda purposes, making the crop nitrogen deficient is the goal, but it is avoidable. You use a comparable amount of nitrogen fertilizer to now per unit mass of potatoes produced. You just apply more per unit area; for a particular level of production, your total farm area needed goes down. In transparent bias, they are careful not to mention, for example, the 30% yield increase of potatoes at a 300 ppm CO2 increase, like having 130g of potatoes instead of 100g ( http://www.co2science.org/data/plant_growth/dry/s/solanumt.php ).

dp

Frank Kotler says:
June 30, 2012 at 2:44 pm

“The high CO2 concentrations in the soil on Mammoth Mountain are killing trees by denying their roots O2 and by interfering with nutrient uptake.”
http://pubs.usgs.gov/fs/fs172-96/

It isn’t CO2 in the atmosphere that is killing trees. It is in the soil and affecting the roots. Same thing that happens when a residential gas line springs a pinhole leak.

Henry Clark

Regarding my prior post, I forgot to mention more than nitrogen alone fertilizer, but anything from phosphorus to sulfur is the same idea, just adding if needed and not deliberately failing to adjust for greater yields.

Ray C

I know plants utilise co2 during photosynthesis. This results in the production of carbohydrates and proteins which the plant uses in various ways to complete its’ growth cycle. Any enrichment needs to be balanced against the plants other nutritional requirements, but I’m pretty sure ecosystems will thrive and Net Primary Production will increase. There will be winners and losers as always but green stuff will flourish.
One thing that will also result from enrichment is the production of more aerosol, the IPCCs’ biggest area of uncertainty = aerosols and their forcing in the settled science!
If arid areas are stabilised, to some extent, there will be less dust aerosol production , and on the other side there will be more biological aerosol particles produced from more vibrant plant growth.
http://pielkeclimatesci.wordpress.com/2012/02/29/biological-aersol-particles-are-a-larger-climate-forcing-than-considered-by-the-ipcc/
Biological Aerosol Particles Are A Larger Climate Forcing Than Considered By The IPCC – A New Paper “Primary Biological Aerosol Particles In The Atmosphere: A Review” By Després Et al 2012
The thing is I don’t think they have the dust forcing sign correct because they estimate too much clay aerosol=cooling and not enough dark silt aerosol=warming.
http://sitemaker.umich.edu/jasperkok/files/kok2011_pnas_scalingtheorydustpsd.pdf
“On a global scale, the dust cycle in most GCMs is tuned to match radiative measurements, such that the overestimation of the radiative cooling of a given quantity of emitted dust has likely caused GCMs to underestimate the global dust emission rate. This implies that the deposition flux of dust and its fertilizing effects on ecosystems may be substantially larger than thought.”
So you have dust that may be warming more and fertilising more and plants producing rain forming aerosols from BVOCs which all assist stabilisation and enhance ecosystem productivity. Maybe its’ all a bit Gaia! One thing’s for sure Aerosols have a big say in how the climate changes.
And then you have the atmosphere cleaning itself! Good old Hydroxyl radicals!
Atmosphere cleans itself more efficiently than previously thought
http://www.mpg.de/990456/Pressrelease20110113?filter_order=TL&research_topic=UK-CH
These findings refute the view held by other scientists who believed that the atmosphere is very sensitive to air pollutants (Science, January 7, 2011).

Ian H

I have heard people talk about negative effects. But they seem to be only able to manage it by adopting bizarre viewpoints.
One approach is to argue that while all plants seem to respond positively to increased CO2 levels there might be some that respond more positively than others. If you can find a “weed” that responds more positively than an associated “crop” you can try to argue that increasing CO2 levels will cause greater problems with weed control.
Another approach is to look at the make up of the plant. A plant which is growing very vigorously is likely to have a higher sugar and starch content. You can flip this around and claim instead that the concentrations of other things – vitamins – minerals – are less. This may be true in some cases primarily because the dilution effect of having more sugar and starch.
These kinds of arguments are so bizarrely contrived that you can’t help but wonder at the motivations of those who make them.

Operators of commercial greenhouses growing all sorts of vegetables and fruits regularly run CO2 atmospheres with much higher concentrations than the outside air has. They do not do this as an experiment but because they know it makes the plants grow faster and bigger. The upper limit of concentration is encountered when workers entering the greenhouse suffer loss of consciousness and death. This is known to be a very bad look for the Company.

Bill Illis

C3 plants – wheat, rice, barley, potatoes, most broad-leafed plants.
C4 plants – corn, sugar cane, ordinary grasses, bamboo.
The C4 plants don’t need high CO2 levels to grow well and can survive low CO2 levels when there is less precipitation.
C3 plants grow much better as CO2 levels go higher and higher but when CO2 levels are low, they need to have significant precipitation in order to survive – hence the ice ages were mainly a C4 world with C3 plants primarily relegated to very high rainfall areas, which would currently be tropical rainforest areas today.

F. Ross


_Jim says:
June 30, 2012 at 2:06 pm
Can anybody here hand-deliver a copy of this report to the head of the EPA (Lisa Jackson)?

Nice idea but do you really think it would do any good? After all you can bring water to a jenny [a female ass] but you can’t make her drink.

The negative effects some commentators mention works like this: example, you have twice as much food but only 1.92 times as much nutrition. I really don’t see this as a problem, or a real negative.