Rising CO2 is causing plants to release less water to the atmosphere, researchers say

Mar 03, 2011
Researchers extract stomata-bearing leaves from a peat formation in Florida. At some sites, the peat was estimated to be as much as 150 years old. Credit: Emmy Lammertsma

As carbon dioxide levels have risen during the last 150 years, the density of pores that allow plants to breathe has dwindled by 34 percent, restricting the amount of water vapor the plants release to the atmosphere, report scientists from Indiana University Bloomington and Utrecht University in the Netherlands in an upcoming issue of the Proceedings of the National Academy of Sciences (now online).

In a separate paper, also to be published by PNAS, many of the same scientists describe a model they devised that predicts doubling today's carbon dioxide levels will dramatically reduce the amount of water released by .

The scientists gathered their data from a diversity of plant species in Florida, including living individuals as well as samples extracted from herbarium collections and peat formations 100 to 150 years old.

"The increase in carbon dioxide by about 100 parts per million has had a profound effect on the number of stomata and, to a lesser extent, the size of the stomata," said Research Scientist in Biology and Professor Emeritus in Geology David Dilcher, the two papers' sole American coauthor. "Our analysis of that structural change shows there's been a huge reduction in the release of water to the atmosphere."

Most plants use a pore-like structure called stomata (singular: stoma) on the undersides of leaves to absorb carbon dioxide from the air. The carbon dioxide is used to build sugars, which can be used by the plant as energy or for incorporation into the plants' fibrous cell walls. Stomata also allow plants to "transpire" water, or release water to the atmosphere. Transpiration helps drive the absorption of water at the roots, and also cools the plants in the same way sweating cools mammals.

If there are fewer stomata, or the stomata are closed more of the day, gas exchange will be limited -- transpiration included.

Stomata are structures that allow plants to exchange gases with the air. Contemporary plants in Florida have fewer stomata than their ancestors did a few decades ago. Credit: Emmy Lammertsma

"The carbon cycle is important, but so is the ," Dilcher said. "If transpiration decreases, there may be more moisture in the ground at first, but if there's less rainfall that may mean there's less moisture in ground eventually. This is part of the hyrdrogeologic cycle. Land plants are a crucially important part of it."

Dilcher also said less transpiration may mean the shade of an old oak tree may not be as cool of a respite as it used to be.

"When plants transpire they cool," he said. "So the air around the plants that are transpirating less could be a bit warmer than they have been. But the hydrogeologic cycle is complex. It's hard to predict how changing one thing will affect other aspects. We would have to see how these things play out."

While it is well known that long-lived plants can adjust their number of stomata each season depending on growing conditions, little is known about the long-term structural changes in stomata number or size over periods of decades or centuries.

"Our first paper shows connection between temperature, transpiration, and stomata density," Dilcher said. "The second paper really is about applying what we know to the future."

That model suggests that a doubling of today's carbon dioxide levels -- from 390 parts per million to 800 ppm -- will halve the amount of water lost to the air, concluding in the second paper that "plant adaptation to rising CO2 is currently altering the hydrological cycle and climate and will continue to do so throughout this century."

Dilcher and his Dutch colleagues say that a drier atmosphere could mean less rainfall and therefore less movement of water through Florida's watersheds.

The Florida Everglades depend heavily on the slow, steady flow of groundwater from upstate. The siphoning of that water to development has raised questions about the future of the Everglades as a national resource.

Explore further: Thousands of intense earthquakes rock Iceland

More information: "Global CO2 rise leads to reduced maximum stomatal conductance in Florida vegetation" Proceedings of the National Academy of Sciences (online)

"Climate forcing due to optimization of maximal leaf conductance in subtropical vegetation under rising CO2" Proceedings of the National Academy of Sciences (online)

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jmcanoy1860
2.8 / 5 (13) Mar 03, 2011
Decreased number of stomata indicates decreased CO2 uptake and decreased O2 release. So much for the hope by the anti-global warming crowd that the plants will somehow save our butts by increasing their uptake.
Quantum_Conundrum
3.1 / 5 (11) Mar 03, 2011
Decreased number of stomata indicates decreased CO2 uptake and decreased O2 release. So much for the hope by the anti-global warming crowd that the plants will somehow save our butts by increasing their uptake.


No it doesn't.

It could just indicate that since the CO2 content per unit atmosphere is larger the plant simply doesn't need as many Stomata to absorb as much CO2 as it needs.

So the plants are simply self-regulating their "diet" of CO2 in the same way your stomache tells your brain that you don't need more food.

If the amount of CO2 in the atmosphere has increased by a certain percentage, then the plants would need only a proportionate value of as many stomata to maintain the same CO2 intake.

Quantum_Conundrum
3.7 / 5 (11) Mar 03, 2011
As carbon dioxide levels have risen during the last 150 years, the density of pores that allow plants to breathe has dwindled by 34 percent.


The amount of CO2 has gone up about 25% to 30% in that time, which is consistent with what you would expect if the plants are self-regulating.

If you have 25% more CO2, i.e. 125% previous total, then intuitively you might need the reciprocal of as many stomata to maintain the same CO2 input, which would be 100/125 or 80%.

But then, because the plants need fewer stomata, they are actually more efficient, because they spent less energy to operate fewer stomata, yet transport the same amount of CO2, therefore, they can get away with using even FEWER stomata than the intuitive proportionate change.
Quantum_Conundrum
2.3 / 5 (7) Mar 03, 2011
In general, the more CO2 in the atmosphere, the less energy the plant "wastes" sorting and transporting gases, because there are more CO2 molecules total, and more percentage of molecules among all atmospheric molecules are likely to be CO2. This makes the plant's metabolism more efficient, in this case the total after all feedbacks ends up being around 34% more efficient.
Quantum_Conundrum
2.3 / 5 (7) Mar 03, 2011
It's sort of like if you were breathing air with a higher percent of oxygen, you wouldn't need to take breaths quite as often because you would be getting more than enough per respiration cycle.
3432682
2.7 / 5 (12) Mar 03, 2011
Plants open their pores to take up CO2. The increased CO2 makes it less necessary to open the pores, and thus they also lose less water. That makes plants much more tolerant to lack of water. This is a perfect example of how a very good thing - plants benefitting from increased CO2 - is turned on its head and presented as a bad thing by greenie alarmists.

The implication that plants have evolved 34% fewer pores in 150 years is hilarious. Plants have evolved in hundreds of millions of years to adapt to hugely variable levels of CO2. The plants are very happy right now, they are about 34% more lush than 150 years ago.
stealthc
2.8 / 5 (9) Mar 03, 2011
this is hilarious, scientists arguing over the water that plants release versus plants growing more efficiently, bigger, better and healthier. You are right about the efficiency argument, and the plant would actually need more water because water is a key to the transport mechanism for minerals in the soil. The soil has to get wet in order to allow acidity to influence the minerals into becoming actively soluble (at the right ph and soil chemistry) to be transported through the plant's structure to feed the development of the plant.

What is absurd is they draw this conclusion in the article claiming that these plants transpire less because they have fewer stomata. This is not the case. These plants grow faster and therefore need more raw material, and thus will need watering more frequently in order to facilitate the increased growth potential in order to transport nutrients to where they are needed, therefore this article is drawing a false conclusion.
Quantum_Conundrum
3 / 5 (6) Mar 03, 2011
stealthc:

I agree over all.

Because the plants are more efficient, they also make less waste heat, this means they need less water for cooling. However, as you pointed out, because they are more efficient they will also accelerate their growth (when conditions are favourable,) which means that, yes, over all, they will use more water than before, but only because they are making new cells fasters due to more energy available.

So a higher percentage of the energy and materials they absorb goes into building bio-mass, rather than wasteful things like cooling, etc.

Water transports energy and nutrients in life forms through electron transport, which is usually associated with the movement of ions. Therefore, if the plant is more efficient, then it uses less energy to do the same job, and therefore needs less water to do the same job, BUT because it will now do it's job so well, it will grow much faster, which means it will consume more water and CO2 total (more leaves, etc.)
stealthc
2.1 / 5 (7) Mar 03, 2011
Double the co2, would produce a 44% increase in growth in 95% of all species, and 22% increase in growth in another 1%, nothing from the remaining 4%.

"watkins co2 plants" on google produced the article that tells me this.

So 34% fewer stomata, 44% increase in growth=more stomata than equivalent plant. This is a poorly written "climate change" alarmist article.
Eikka
2.6 / 5 (5) Mar 03, 2011
How about the notion that the climate is driven 80% by water vapor, and water vapor is being driven by CO2?

Seems like evidence to the opposite. Plants releasing less water would mean less of a greenhouse effect, and with increasing CO2 levels decreasing evaporation by plants, the drive should be towards cancelling the greenhouse effect.
stealthc
1 / 5 (7) Mar 03, 2011
Decreased number of stomata indicates decreased CO2 uptake and decreased O2 release. So much for the hope by the anti-global warming crowd that the plants will somehow save our butts by increasing their uptake.

wow, dude, seriously... you need to take a Zoloft or something.
plants like more co2 in the atmosphere because they process more of it. You should slap yourself, you've been indoctrinated into a following of borg drone people reciting crap made up by a bunch of rich people to make you happy to part with your labors and benefits.
stealthc
2.8 / 5 (9) Mar 03, 2011
How about the notion that the climate is driven 80% by water vapor, and water vapor is being driven by CO2?

Seems like evidence to the opposite. Plants releasing less water would mean less of a greenhouse effect, and with increasing CO2 levels decreasing evaporation by plants, the drive should be towards cancelling the greenhouse effect.


Shoot I knew that I'd forgotten something. Exactly -- if there is less water then the planet begins to cool, given the 80% figure you just mentioned.

As I said clearly this is a biased, spin-MSM, crap article and we need to start seriously considering that loons run our society and it's due time us awake folk start to put 'em in their place.

NO FREAKING WAY I'LL LET THESE DUMMIES COAX ME INTO EVEN MORE SLAVERY.
Shootist
1 / 5 (8) Mar 03, 2011
Rising CO2 is causing plants to release less water to the atmosphere, researchers say


Oh, the humanity!

"The polar bears will be fine". -Freeman Dyson
Djincss
3.1 / 5 (9) Mar 03, 2011
"So the air around the plants that are transpirating less could be a bit warmer than they have been."
They are manipulating here, every man with basic understanding on thermodynamic knows it.
Second why everybody try to make things look worse and that all the effects this GW will have are negative?
Why is that, they deliberately try to make things look bad, and they are not objective, how can scientist be like that, what kind of scientist is that?
Plants in greenhouses with more CO2 are more productive, so in places where the CO2 is the limiting factor for the growing of a plant-more product, in places where water is scares I think plants will grow with the same rate, and the effect of CO2 wont be significant.
From plants perspective increasing the CO2 cant be something bad, but still some people will make the craziest theory to make it look this law.
Quantum_Conundrum
3.5 / 5 (6) Mar 03, 2011
Plants in greenhouses with more CO2 are more productive.


This is true, and I think it's hilarious.

I've even seen demonstrations on television and internet for greenhouses where they pump the exaust CO2 from a generator directly into a greenhouse for tomatoes and other grocery plants, because it accelerates the plant growth.

Oh yeah, gave the article a 5, not because it's a good article, but because the discussion is so relevant and hilarious, and the findings actually verify everything I've said for years on the subjects of plants and CO2 increases.
Parsec
3 / 5 (2) Mar 03, 2011
"So the air around the plants that are transpirating less could be a bit warmer than they have been."
They are manipulating here, every man with basic understanding on thermodynamic knows it.
Second why everybody try to make things look worse and that all the effects this GW will have are negative?
Why is that, they deliberately try to make things look bad, and they are not objective, how can scientist be like that, what kind of scientist is that?
Plants in greenhouses with more CO2 are more productive, so in places where the CO2 is the limiting factor for the growing of a plant-more product, in places where water is scares I think plants will grow with the same rate, and the effect of CO2 wont be significant.
From plants perspective increasing the CO2 cant be something bad, but still some people will make the craziest theory to make it look this law.

better to keep ones mouth closed and have everyone think you a fool than open it and confirm it.
GSwift7
2.9 / 5 (7) Mar 03, 2011
These plants grow faster and therefore need more raw material, and thus will need watering more frequently in order to facilitate the increased growth


Almost every comment above, including the original article, makes the assumption that CO2 concentration is the main limiting factor and therefore the largest influence on stoma density. What about all the other factors? 1)An increase in average wind speed would have the same effect as increasing the CO2. 2)An increase in the amount of average daily sunlight in the growing season would have an effect. 3)No matter how much CO2 you have in the air, or how much water you have, if you don't have enough nitrogen/phosphorus/iron/etc. then you aren't going to grow squat. The decrease in pores could mean that the plant is trying to limit CO2 intake to match the available level of some other factor. As for water: what about the longer growing season? Does that offset the decrease in stoma? Foolish crystal-ballery.
GSwift7
1 / 5 (4) Mar 03, 2011
@ Djincss:

Good point about the greenhouse. There have also been a few different studies in forests where they have been adding CO2 over long time periods and watching what it does to the natural plants there. Some of those experiments have been going on for decades. I wonder if samples from those experiments would confirm the claims from the above article or not?
Quantum_Conundrum
3 / 5 (2) Mar 03, 2011
Gswift7:

We aren't discounting other conditions on growth. See above where I said, "When conditions are favourable".

Of course other nutrients in the environment are limiting factors.
GSwift7
1.6 / 5 (7) Mar 03, 2011
Yes, as I said; "Almost every comment above"

Some people are actually using their brains today (like you and Djincss), rather than accepting the black and white options suggested by the article authors as the only two choices.

Here's a hint for all the non-thinking people: Any time you see something in natural science that suggests you are limited to only one of two options, you're probably being hood-winked by the author because they don't want you to think about the other options. It's like the Wizard of Oz telling you to ignore the man behind the curtain. lol.
Alphakronik
2.3 / 5 (3) Mar 03, 2011
So, plants are releasing less water, yet what are the polar ice caps doing?

Sounds to me that the earth is taking care of itself. The Gaia Hypothesis becomes reality more and more every day it seems.
stealthc
2.3 / 5 (6) Mar 03, 2011
I addressed the nutrient thing but wind is only good for strengthening the internal fiber structure of the plant, and minimally impacts stomata. Just because air moves faster doesn't mean the stomata are more efficient, they still have the same relative density of co2 in the air with which to work with and still work at the same rate regardless if you try to jam more gas in there or not.

I edited this to include that wind allows water and oxygen to transpire from the plant a little faster, and it is the water evaporation which drives this process (to draw water, and thus nutrients from the soil). Surely conditions will vary but clearly the science shows that such subtle influences don't really modify the outcome of this conclusion:

This article is AGW/climate change, scaremongering, brainwashing propaganda. It's conclusions are false and misleading. There is nothing scientific about this article it is purely a strawman theory.
GSwift7
1.3 / 5 (4) Mar 03, 2011
@ Stealthc:

Wind is important in areas with low average wind speed and thick concentrations of vegetation because plants actually consume the CO2 in the air relatively quickly if there's no air flow to stir the CO2 around. Keep in mind that CO2 a meter away from a plant is no good to the plant. Lots of plants jammed together in a small space with stagnant air flow can greatly reduce the CO2 in close proximity to the plants. Air flow is a major factor. I have seen studies about this effect, so I'm sure you could look it up if you want to. Granted, it's a small effect, but they are talking about small effects above, and in combination with the effects you mentioned it could become statistically signifigant to the results they are claiming. You have to explain any source of noise, ritht?
GSwift7
1 / 5 (3) Mar 03, 2011
This article is AGW/climate change, scaremongering, brainwashing propaganda.


I agree. Physorg has a rather large bias in that regard. That becomes clear if you go out and read very many other sources.
hush1
1 / 5 (1) Mar 03, 2011
Cool comments.
The handbook "Encyclopedia of all known adaptive changes to all known climactic variables for all known plant life forms" was really helpful.

Of course, the book was never published. The original manuscript perished in a fire with no backup writings at all.

I have the only copy.
No. I don't share. :)
Author: unknown
GSwift7
1 / 5 (3) Mar 03, 2011
The handbook "Encyclopedia of all known adaptive changes to all known climactic variables for all known plant life forms" was really helpful


If you don't want to read comments about science articles then don't read the comment section of a science article web site?

By the way, @ Stealthc: I did some research on my claims about local CO2 consumption and air mixing. I found the following paper at ScienceDirect: "CO2 concentration profiles, and carbon and oxygen isotopes in C3 and C4 crop canopies "

Here's a quote from the first paragraph of the abstract. They are talking about corn and alfalfa:

Daily fluctuations were observed within the canopy and extended into the canopy boundary layer (at heights 2 to 3 times higher than the maximum plant height). Photosynthetic demand for canopy CO2 exceeded soil respiration to such an extent that daytime [CO2] values were depleted 15 to 50 ppm below tropospheric values


That's a big drop.
hush1
3.7 / 5 (3) Mar 03, 2011
@GSwift

If you don't want to read comments about science articles then don't read the comment section of a science article web site?


Naw. Just a tad bit of wry humor. And wishful thinking - imagining such a encyclopedic consolidation and knowledge is what is needed.

Cool comments=I like the parsed thoughts given. :)
GSwift7
1 / 5 (2) Mar 03, 2011
Yeah, I like the random things I learn when people disagree with me too. That's why I like to post. I never know when I'm wrong until someone points it out. That's when I learn something cool.

I got your wry humor and raised you a dollar. :P
Djincss
3 / 5 (2) Mar 03, 2011
Yps my comment is a little bit messy, I was distracted with other things, never mind, I mean about the thermodynamic think I mentioned I wanted to say that vapor eventually comes to wather again and the heat absorbed is released again, and as someone have mentioned above vapor is greenhouse gas as well.
About what will be the spending(evaporating) of water with more CO2 in the air for the plants is really hard to be said, H2O take parts in the methabolism of the plants as well, to create glucose it takes carbon from CO2 and, hydrogen from the water, the oxygen is for us, I mean lots of factors should be considered, and the only way to know for sure is testing.
And about my first comment my last word should have been way not law...never mind.
Djincss
2.7 / 5 (3) Mar 03, 2011
But I stand behind my words 98% of the things I read about this GW is how bad it is, things are changing, they always are but we should be objective what is the bad and what is the good.If somebody say something good about it he wont be considered as criminal does he!
Djincss
2.3 / 5 (3) Mar 03, 2011
"better to keep ones mouth closed and have everyone think you a fool than open it and confirm it."

Yeh wise!
When you are so wise, why dont you share with me what exactly what I said is so stupid?
I mean I dont deserve your time and efforts for argument?(you have waste time and effort to reply to my comment, why dont you just made your point)
If you are so much smarter you will deal with me easily dont worry.
tpb
3.4 / 5 (5) Mar 03, 2011
Using "increased CO2" interchangeably with "Global Warming" and "Climate Change" is unscientific.
We don't know how much warming is from CO2.
We don't know how much CO2 is from warming.
We don't know the magnitude or number of feedback mechanisms that affect global temperature.
Plant metabolism is only one.
We don't even know if warming, on balance, is good or bad.

Anyone who says with any certainty that we know what is going to happen to global temperature or what effect doubling CO2 will have is a charlatan, not a scientist.

tpb
2.3 / 5 (6) Mar 03, 2011
I remember reading that the suns output has increased something like 30 percent in ??? millions of years, yet the earths temperature has been pretty constant except for periodic ice ages in earths recent history.(causes unknown)
A thirty percent increase in the suns output should have warmed up the earth by about 100C, 30% of 290K, but it didn't.
This pretty much says that the earth has some pretty powerful negative feedback mechanisms.
Yet for some reason all the GW models have positive feedback.

Doom1974
5 / 5 (3) Mar 03, 2011
Wow dudes...cool down with the scientific tidbids your read. Leave the science to the scientists please!! Btw...CO2 is not a limiting factor for growth, micronutrients in the soil and water are. Second, water cycle is extremely fast and therefore always at quasi-equilibrium compared to other gases in the atmosphere. The driving force for CO2 uptake has increased, therefore for a constant, regulated uptake less stomata are needed. Stomata are proportional to CO2 and not to water. Therefore less water evaporation from the plants and water transport from the roots to the plants. The rest is in the fantasy of the authors...
sstritt
2.3 / 5 (3) Mar 03, 2011
This pretty much says that the earth has some pretty powerful negative feedback mechanisms.
Yet for some reason all the GW models have positive feedback.

Exactly! Very good point. Also, the statement that stromata have decreased 34% in 150 yrs means that Earth's plant life is well adapted to deal with changing levels of CO2. Another powerful negative feedback mechanism.
GSwift7
1 / 5 (3) Mar 04, 2011
Joke:

If we extrapolate this trend into the future, assuming a 34% drop, compounded every 150 years, then plants will have essentially no stomata in just under 2000 years. That would be cool. (I know the math doesn't work like that, but calculus hurts my brain on Fridays) :)
Skeptic_Heretic
5 / 5 (4) Mar 05, 2011
This pretty much says that the earth has some pretty powerful negative feedback mechanisms.
Yet for some reason all the GW models have positive feedback.

Exactly! Very good point. Also, the statement that stromata have decreased 34% in 150 yrs means that Earth's plant life is well adapted to deal with changing levels of CO2. Another powerful negative feedback mechanism.

Actually, a reduction in transevaporation is another positive feedback. This is very bad news as the plants will be functioning to cool the atmosphere less.
jmcanoy1860
1 / 5 (1) Mar 05, 2011


No it doesn't.

It could just indicate that since the CO2 content per unit atmosphere is larger the plant simply doesn't need as many Stomata to absorb as much CO2 as it needs.

So the plants are simply self-regulating their "diet" of CO2 in the same way your stomache tells your brain that you don't need more food.

If the amount of CO2 in the atmosphere has increased by a certain percentage, then the plants would need only a proportionate value of as many stomata to maintain the same CO2 intake.


And this differs from what I said how?

jmcanoy1860
1 / 5 (1) Mar 05, 2011
Decreased number of stomata indicates decreased CO2 uptake and decreased O2 release. So much for the hope by the anti-global warming crowd that the plants will somehow save our butts by increasing their uptake.

wow, dude, seriously... you need to take a Zoloft or something.
plants like more co2 in the atmosphere because they process more of it. You should slap yourself, you've been indoctrinated into a following of borg drone people reciting crap made up by a bunch of rich people to make you happy to part with your labors and benefits.


How does fewer stomata per leaf translate into less money for me? If you don't understand basic cause and effect then you shouldn't comment.
Skeptic_Heretic
5 / 5 (3) Mar 05, 2011
TBP,
I remember reading that the suns output has increased something like 30 percent in ??? millions of years, yet the earths temperature has been pretty constant except for periodic ice ages in earths recent history.(causes unknown)
A thirty percent increase in the suns output should have warmed up the earth by about 100C, 30% of 290K, but it didn't.
You're absolutely wrong on all fronts of this garbage you've posted.

The Solar irradiance hasn't been primarily a variation of the sun, it has been variation in the orbit of the Earth, the Earth sun interaction, the magentic periods of the sun, and the atmospheric content of the Earth. This has been used to measure all of the data that you say is in the category of (cause unknown).

The first aspect of climate examined was the sun. The sun has been intimately linked in all former periods of variation in climate with the exception of current phenomina. Second, learn the radiace equation properly.
Egleton
2 / 5 (4) Mar 06, 2011
There are a lot of people on this site who are mouth pieces for the fossil fuel industry.
There is no stopping them, they do it for the money.

The sun turns hydrogen into helium.
Helium is a greenhouse gas for the sun. It traps heat in the sun.
In the 4.5 billion years that the sun has been alight it has got 20% hotter.
The earth's atmosphere had a greater carbon dioxide content in the past.
As the sun heats up the earth responds by drawing down carbon dioxide to maintain thermostasis.
This negative feedback loop is not working any moreas we are down to the last dregs. Hence the C4 plants, grasses, that are super efficient at scrubbing CO2 out of the air.
The feedback loop fails leading to wild oscillations in the temperature, The Ice ages.
And then along comes Man. . . My oh my what a lot of lovely coal to burn.
GSwift7
1 / 5 (2) Mar 07, 2011
@ Skeptic Heretic:

You are acting far more certain about your assertions than any official source I can find. I could provide links, but I know you've been to the NOAA, NCDC and NASA web sites I'm talking about.

Actually, a reduction in transevaporation is another positive feedback. This is very bad news as the plants will be functioning to cool the atmosphere less.


As far as I know, you are correct in that what you said is one of several likely scenarios. Exactly which scenario is the correct one is still in question, and the latest results seem to indicate that the answer may depend on exactly where you are talking about. For example, the effect of increased/decreased evapo-trans on jungle is not the same as the effect in a savanah or tundra. As far as I know, the jury is still out on that question, right?

As for the solar question: same. The newest solar observatories are just starting to give good data. We will see.
GSwift7
1 / 5 (2) Mar 07, 2011
continuted:

As to whether the increase/decrease in evapo-trans will result in a + or - feedback kinda depends on more than just how much direct cooling the plants provide. The rate of evapo-trans also affects the amounts and types of plant aerosols produced, as well as the amount of secondary biological effects like insect productivity, gasses from decay, soil uptake, runoff patterns, erosion, wind-born dust, etc.

The question of land vegitation feedback effects is mountainously complicated.

Your solid claim that it will be a positive feedback is nothing more than a positively solid guess.
Skeptic_Heretic
not rated yet Mar 07, 2011
Going off this:
htp://www.annualreviews.org/doi/abs/10.1146/annurev.pp.22.060171.001255

As so far no one has produced results that shed any disparity on the findings of this paper, and it's been around since 71. If you have any updates, or better info, please share.
tpb
1 / 5 (1) Mar 07, 2011
SKEPTIC HERETIC
Do some research before you talk garbage.
The suns output has increased 40 percent in 4.6 billion years.
The suns output will double in another 4.6 billion years.
The earths temperature has stayed approximately constant for about the last 3.5 billion years, despite the increase in the suns output.
A change of +-10 degrees out of 290 degrees is pretty small.
http://math.ucr.e...#4600Myr

EGLETON
Helium is not a greenhouse gas for the sun.
The earth has been cooling off for about 65 million years.
If you think that is because most of the CO2 has been sequestered, then we better start burning it as fast as we can.
Water is the dominant greenhouse gas by several orders of magnitude.
There is no reason to believe that CO2 is any more likely to have anything to do with the periodic ice ages than any of a dozen other theories.
Skeptic_Heretic
5 / 5 (1) Mar 08, 2011
SKEPTIC HERETIC
Do some research before you talk garbage.
The suns output has increased 40 percent in 4.6 billion years.
Source it.
The suns output will double in another 4.6 billion years.
Actually it will probably have decreased by about 98% in 4.6 billion years after ramping up to be about double what it is now.
The earths temperature has stayed approximately constant for about the last 3.5 billion years, despite the increase in the suns output.
A change of +-10 degrees out of 290 degrees is pretty small.
This is nonsense. You are again confusing average temperature with periodic temperature.

Beyond that, you have another 5 issues with your summary that I pointed out. Feel free to continue so I can provide you with more information that you are lacking.
There is no reason to believe that CO2 is any more likely to have anything to do with the periodic ice ages than any of a dozen other theories.
Wrong, horridly wrong.
GSwift7
1 / 5 (3) Mar 08, 2011
To Skeptic_Heretic:

If you have any updates, or better info, please share


As always, you know that I'm happy to provide diverse and high quality sources. Try to google the following for a 2008 Nature paper about the response of the carbon cycle feedbacks to rising temperatures:

Terrestrial ecosystem carbon dynamics and climate feedbacks

The supplemental materials (the only part I can reach because of the paywall) cover a good deal of the meat of the paper. In the section immediately follwing figure 2 they discuss, in brief, how the various models differ in the way they handle the terrestrial feedbacks in response to rising temperature and CO2. They specifically state that a positive feedback is likely, as you said above and which I agreed was an accepted possible outcome. They do however, also point out the various factors, as I mentioned above which confound that prediction.

I found several other article along the same lines with a quick google.

Skeptic_Heretic
5 / 5 (1) Mar 08, 2011
They specifically state that a positive feedback is likely, as you said above and which I agreed was an accepted possible outcome. They do however, also point out the various factors, as I mentioned above which confound that prediction.
I wouldn't say confound is a proper word to use there. I think your intent is better suited utilizing the word obscures.

It obscures the total impact without changing the net result. It will cause a positive feedback, but to what degree is uncertain.
GSwift7
1 / 5 (2) Mar 08, 2011
Here's another one, but I bet you won't like this one. The article is called:

Interactions between the atmosphere and terrestrial ecosystems: influence on weather and climate

It was in Global Change Biology, 2003, but one of the authors is Roger Pielke Sr, so I'm guessing you will discard that one.

You'll like this one much better:

Terrestrial carbon-cycle feedback to climate warming

available on your annual review site from 2007. They site the popular view you expressed in the abstract and then go on to explain the generally more complicated nature of the question.
Skeptic_Heretic
5 / 5 (2) Mar 08, 2011
It was in Global Change Biology, 2003, but one of the authors is Roger Pielke Sr, so I'm guessing you will discard that one.
No, I often cite Pielke's work on radiative balance of aerosols. I don't 'like' or dislike a paper based on the author. I like or dislike a paper based on the accuracy of the content. From Peilke
Vegetation physiology and the SEB exert strong short-term influences through Ts(T sub s). This feedback acts positively on Ts at temperatures high enough for an increase in Ts to cause stomatal conductance.


So yes, as we both agree, it is a complicated question, but as to whether this is a positive or negative feedback, all parties agree, this is a positive feedback.
GSwift7
1 / 5 (2) Mar 09, 2011
Yes, if the plant transpires less water, it will cool the air less. However, you may not be seeing the whole picture when you only count the stomata. There has been an overall increase in summer precipitation globally. Plants use up all the available water in the soil relatively quickly, meaning that there are a lot of days when they do very little transpiration, regardless of the number of stoma. If you increase the number of days when transpiration is occurring, you could more than make up for the decreased daily rate. Maybe there are less stoma because the plants are able to productively transpire on a larger percent of summer days and therefore don't need to be as productive on each day. It may not only be related to co2 uptake rates. The overall cause/effect web is not very well constrained yet.
Skeptic_Heretic
not rated yet Mar 09, 2011
If you increase the number of days when transpiration is occurring, you could more than make up for the decreased daily rate.
But if you permanently decrease the transpiration element of trans evaporation, you end up with soil degradation which further reduces transpiration in addition to reducing the uptake of atmospheric carbon.
GSwift7
1 / 5 (3) Mar 09, 2011
That may be true but my point is that although the plants are showing fewer stomata, the net change in evapo-trans may not be negative, after accounting for longer growing seasons and increased growth days in each season. Controlled experiments where co2 levels are increased result in more growth in almost every case. That's pretty conclusive.

The above story is far from conclusive. There are too many noise factors to justify the conclusions. Did they examine, for example, any possible trend in sunny vrs cloudy days over the time span in question? How about rainfall trends? Laying the blame solely on carbon seems dicy to me.
Skeptic_Heretic
5 / 5 (2) Mar 09, 2011
That may be true but my point is that although the plants are showing fewer stomata, the net change in evapo-trans may not be negative, after accounting for longer growing seasons and increased growth days in each season. Controlled experiments where co2 levels are increased result in more growth in almost every case. That's pretty conclusive.
Yes but more growth means greater water uptake creating more water stress, yielding lower evapotranspiration.
GSwift7
1 / 5 (3) Mar 09, 2011
not if there's more water in the growing season.
Skeptic_Heretic
5 / 5 (2) Mar 09, 2011
not if there's more water in the growing season.

And that is the piece that cannot be quantified. The rainfall patterns cannot currently be quatified, as per the statement within the research paper you noted. SEB is uncertain.
GSwift7
1 / 5 (3) Mar 10, 2011
lol, sombody created a dummy account and looked up all my comments to rate them 1/5. I wonder who I pissed off this time. The new account is called something like johnboy or something, created at 3 am last night. Probably some european anti-american zealot. On second thought, it's probably just another dummy account from one of the usual suspects like marjon or howhot. I think it would be interresting if physorg consolidated all the same-IP accounts one day. It would be cool to see how many people have conversations with themselves on here.