It looks like you're new here. If you want to get involved, click one of these buttons!
Azimuth wrote on Google plus:
The authors of the Wall Street Journal letter "No Need to Panic about Global Warming" have replied to a rebuttal of that letter, here:
http://online.wsj.com/article/SB10001424052970203646004577213244084429540.html
Scientifically the most interesting thing here is a graph that claims to compare predictions of global warming to the actual data. For a criticism of that graph, see below.
The WSJ rebuttal's reply ends with:
The computer-model predictions of alarming global warming have seriously exaggerated the warming by CO2 and have underestimated other causes. Since CO2 is not a pollutant but a substantial benefit to agriculture, and since its warming potential has been greatly exaggerated, it is time for the world to rethink its frenzied pursuit of decarbonization at any cost.
The way I personally perceive their final point is: "let's continue burning carbon (because that is what made us wealthy and happy) until it becomes too expensive to burn. Only the price of fossil fuels is the right measure to tell us when it's exactly the right moment for switching to other energy sources (or having to use less energy)."
Since CO2 is not a pollutant but a substantial benefit to agriculture
Does anyone know of a study where it is exactly the lack of CO2 that prevents plants from achieving optimal growth? (instead of lack of soil water, nitrogen conversion, solar light, trace minerals...)
I'm posting here because this is a more civilized place than Google plus.
Comments
Frederik wrote:
The Azimuth Wiki has a page on this topic:
So-called 'skeptics' like to hope that more CO2 will help plant growth, which in turn will keep the atmospheric CO2 concentration from rising as much as the IPCC predicts. Some of them seem to forget that the IPCC takes this effect into account. From our page:
There are a lot more details on the page, but if you think you might lose that neutrino bet you could consider improving its organization and making the overall state of the art a bit clearer.
Frederik wrote: > Does anyone know of a study where it is exactly the lack of CO2 that prevents plants from achieving optimal growth? (instead of lack of soil water, nitrogen conversion, solar light, trace minerals...) The Azimuth Wiki has a page on this topic: * [[Carbon dioxide fertilization]] So-called 'skeptics' like to hope that more CO<sub>2</sub> will help plant growth, which in turn will keep the atmospheric CO<sub>2</sub> concentration from rising as much as the IPCC predicts. Some of them seem to forget that the IPCC takes this effect into account. From our page: > In the third IPCC report, models predicted that by 2050, plants will be drawing down 6 gigatonnes more carbon per year than they do now! The fourth IPCC report was similar. > This a huge effect: remember that right now we emit about 8 gigatonnes pf carbon per year. Indeed, this effect could be the difference between the land being a big carbon _sink_ and a big carbon _source_. Why a carbon source? For one thing, without the plants sucking up CO<sub>2</sub>, temperatures will rise faster, and the Amazon rainforest may start to die, and permafrost in the Arctic may release more greenhouse gases (especially methane) as it melts. > In a simulation run by [[Stephen Pacala]], where he deliberately assumed that plants _fail_ to suck up more carbon dioxide, these effects happened and the biosphere dumped a huge amount of extra CO<sub>2</sub> into the atmosphere: the equivalent of 26 [[stabilization wedges]]: > * Stephen Pacala, [Equitable climate solutions](http://www.youtube.com/watch?v=2X2u7-R3Wrc), talk at the Energy Seminar, Woods Institute, Stanford University, 5 November 2008. > So, he points out **plans based on the IPCC models are essentially counting on plants to save us from ourselves**. There are a lot more details on the page, but if you think you might lose that neutrino bet you could consider improving its organization and making the overall state of the art a bit clearer.yes, thanks, I remembered the page after I posed the question and I have already read it (without rediscovering which part I added to the page, which is good).
But I think the question of "are there plants for which CO_2 is the primary factor limiting growth" is still open.
Actually, with respect to the WSJ reply, I now tend to suppose that they were only making a handwaving argument without having a study in mind.
I'll keep it in mind. Unfortunately it would take some time before I would be knowledgeable about this subject, so it's good the bet won't be settled before at least next year.
> The Azimuth Wiki has a page on this topic yes, thanks, I remembered the page after I posed the question and I have already read it (without rediscovering which part I added to the page, which is good). But I think the question of "are there plants for which CO_2 is the primary factor limiting growth" is still open. Actually, with respect to the WSJ reply, I now tend to suppose that they were only making a handwaving argument without having a study in mind. > There are a lot more details on the page, but if you think you might lose that neutrino bet you could consider improving its organization and making the overall state of the art a bit clearer. I'll keep it in mind. Unfortunately it would take some time before I would be knowledgeable about this subject, so it's good the bet won't be settled before at least next year.I've never heard of reputable claims that there are plants for which CO2 is "the primary factor limiting growth". The experiments are all trying to determine whether and how much boosting CO2 increases plant growth. It's an incredibly important issue!
I've never heard of reputable claims that there are plants for which CO<sub>2</sub> is "the primary factor limiting growth". The experiments are all trying to determine whether and how much boosting CO<sub>2</sub> increases plant growth. It's an incredibly important issue!@John: maybe it's a naive thought but how can increased $CO_2$ increase plant growth if it's not the limiting factor? (compared to, say, for the sake of the argument, water, sunshine or trace minerals)
@John: maybe it's a naive thought but how can increased $CO_2$ increase plant growth if it's not the limiting factor? (compared to, say, for the sake of the argument, water, sunshine or trace minerals)When plants started the CO2 levels were much higher (25%?). Compared to then we're in a CO2 desert. If you only look at the plants in the desert and see if they'd like more water, the answer is yes. But of course if it starts to rain more in a particular desert then the plants there don't do better, they get out-competed by invaders that need it wetter. Of course our CO2 desert is world-wide so there aren't any invaders around. Still we have this biosphere that survives on insanely low levels of CO2 so I'll be amazed if it isn't a limiting resource.
When plants started the CO2 levels were much higher (25%?). Compared to then we're in a CO2 desert. If you only look at the plants in the desert and see if they'd like more water, the answer is yes. But of course if it starts to rain more in a particular desert then the plants there don't do better, they get out-competed by invaders that need it wetter. Of course our CO2 desert is world-wide so there aren't any invaders around. Still we have this biosphere that survives on insanely low levels of CO2 so I'll be amazed if it isn't a limiting resource.@John you wrote on Google Plus: "Someone must have noticed that a perfectly transparent substance can't generate electricity from light"
What about eg the UV spectrum?
@Frederik wrote: "how can increased CO 2 increase plant growth if it's not the limiting factor?"
I guess John meant here with "limiting factor" eventually not the general meaning of a factor, which influences (and thus may limit) growth, but that there may for example be some kind of threshold (limit) for which a certain (like a too high) dosis of Co2 could eventually limit plant growth for certain plants. But I am not sure.
@John you wrote on Google Plus: "Someone must have noticed that a perfectly transparent substance can't generate electricity from light" What about eg the UV spectrum? @Frederik wrote: "how can increased CO 2 increase plant growth if it's not the limiting factor?" I guess John meant here with "limiting factor" eventually not the general meaning of a factor, which influences (and thus may limit) growth, but that there may for example be some kind of threshold (limit) for which a certain (like a too high) dosis of Co2 could eventually limit plant growth for certain plants. But I am not sure.Thanks for the comments! In this context: Liebig's law
When time permits I'll start reading this: Plant responses to envirmental factors. It's old but it's the first I found.
@Robert: maybe all plants have in time managed to cope with the low carbon dioxide levels, such that's it's not the limiting factor anymore. Then, a next question could be if natural evolution (or genetic modification) would easily allow a plant, in an environment of abundant carbon dioxide, to develop mechanisms that can more easily cope with the limiting factor once it doesn't have to concentrate so much anymore on the low carbon dioxide levels (sorry to speak so handwavingly)
I suppose it would be difficult because all plants are optimized for the present conditions. The main change with higher carbon dioxide levels would be the higher temperature near the poles, which (temperature being the limiting factor there) would allow additional plant growth on previously bare areas.
Thanks for the comments! In this context: [Liebig's law](http://en.wikipedia.org/wiki/Liebig%27s_Law) When time permits I'll start reading this: [Plant responses to envirmental factors](http://courses.missouristate.edu/tomtomasi/tom/bio%20567/Plant%20responses%20to%20environ%20factors%20%28Bioscience%2037,49-57%29.pdf). It's old but it's the first I found. @Robert: maybe all plants have in time managed to cope with the low carbon dioxide levels, such that's it's not the limiting factor anymore. Then, a next question could be if natural evolution (or genetic modification) would easily allow a plant, in an environment of abundant carbon dioxide, to develop mechanisms that can more easily cope with the limiting factor once it doesn't have to concentrate so much anymore on the low carbon dioxide levels (sorry to speak so handwavingly) I suppose it would be difficult because all plants are optimized for the present conditions. The main change with higher carbon dioxide levels would be the higher temperature near the poles, which (temperature being the limiting factor there) would allow additional plant growth on previously bare areas.Martin Gisser once referred to an article about Eucalyptys leaves here and at least one conclusion seems in agreement with the paper I referred to in my previous comment in this thread: if plants can get carbon more easily than nitrogen, this will result in carbon-rich leaves which are less palatable. ("plant" is an extrapolation for the sake of controversy, there are only limited studies, I'll write it more carefully before putting it on the wiki)
Martin Gisser once referred to an article about Eucalyptys leaves [here](http://www.math.ntnu.no/~stacey/Mathforge/Azimuth/comments.php?DiscussionID=637&Focus=4144#Comment_4144) and at least one conclusion seems in agreement with the paper I referred to in my previous comment in this thread: *if plants can get carbon more easily than nitrogen, this will result in carbon-rich leaves which are less palatable.* ("plant" is an extrapolation for the sake of controversy, there are only limited studies, I'll write it more carefully before putting it on the wiki)I mentioned this already in a comment on Azimuth, but I want to mention this again - in the context of the CO2 levels I would like to know more about the issue of O2, this is explained a bit more in the randform post: O2 or not O2
I mentioned this already in a comment on Azimuth, but I want to mention this again - in the context of the CO2 levels I would like to know more about the issue of O2, this is explained a bit more in the randform post: <a href="http://www.randform.org/blog/?p=4195">O2 or not O2</a>@nad: I guess one could roughly expect that for each $CO_2$ into the atmosphere there will be one $\mathrm{O}_2$ leaving. Does anyone expect that $CO_2$ levels may soon rise to 5%? (and $O_2$ dropping to 15% as in the Biosphere2 that you mention?) If so, it would be worrisome too, but I haven't heard yet claims for such a large rise in $CO_2$ levels.
@nad: I guess one could roughly expect that for each $CO_2$ into the atmosphere there will be one $\mathrm{O}_2$ leaving. Does anyone expect that $CO_2$ levels may soon rise to 5%? (and $O_2$ dropping to 15% as in the Biosphere2 that you mention?) If so, it would be worrisome too, but I haven't heard yet claims for such a large rise in $CO_2$ levels.@Frederick I don't know like it seems there is also methane released.
@Frederick I don't know like it seems there is also methane released.Nadja wrote:
Good point, I'd completely forgotten that!
There's not much power in the ultraviolet:
There's more in the infrared, but it looks 40% or so is in the visible.
Can anyone build materials transparent in visible light that efficiently convert infrared light to electric power? I'll ask on Google+ and/or Azimuth. In Southern California, where it's hot, it would be very nice to have windows that blocked infrared light as well as producing power. I think people sell windows that do the former... but not also the latter!
Nadja wrote: > @John you wrote on Google Plus: "Someone must have noticed that a perfectly transparent substance can't generate electricity from light" > What about e.g. the UV spectrum? Good point, I'd completely forgotten that! <img src = "http://math.ucr.edu/home/baez/emoticons/doh20.gif" alt =""/> There's not much power in the ultraviolet: <img width = "400" src = "http://upload.wikimedia.org/wikipedia/commons/4/4c/Solar_Spectrum.png" alt = ""/> There's more in the infrared, but it looks 40% or so is in the visible. Can anyone build materials transparent in visible light that efficiently convert infrared light to electric power? I'll ask on Google+ and/or Azimuth. In Southern California, where it's hot, it would be very nice to have windows that blocked infrared light as well as producing power. I think people sell windows that do the former... but not also the latter!(a) $E = h c / \lambda $ and $ h c \approx 1.240 eV \mu m$ so a semiconductor would need a bandgap smaller than 1.8 eV.
(b) I think it will be difficult to have a material transparent enough if you also want to catch a fair amount of energy. (but I guess it should be possible, my glasses block UV - not the goal, but a consequence of the breaking index- and they are certainly transparent)
(a) $E = h c / \lambda $ and $ h c \approx 1.240 eV \mu m$ so a semiconductor would need a bandgap smaller than 1.8 eV. (b) I think it will be difficult to have a material transparent enough if you also want to catch a fair amount of energy. (but I guess it should be possible, my glasses block UV - not the goal, but a consequence of the breaking index- and they are certainly transparent)Something funny is going on. I saw error messages in the first line of Frederik's last post, and I tried to edit them - somehow he'd typed the Greek letter mu instead of \mu, but changing that didn't fix the problem. Indeed it seems even worse now! I can't see the equations in the first line of his post. Does anyone else? It's this line, in iTeX:
$E = h c / \lambda $ and $ h c \approx 1.240 eV \mu m$ so a semiconductor would need a bandgap smaller than 1.8 eV.Something funny is going on. I saw error messages in the first line of Frederik's last post, and I tried to edit them - somehow he'd typed the Greek letter mu instead of \mu, but changing that didn't fix the problem. Indeed it seems even worse now! I can't see the equations in the first line of his post. Does anyone else? It's this line, in iTeX: `$E = h c / \lambda $ and $ h c \approx 1.240 eV \mu m$ so a semiconductor would need a bandgap smaller than 1.8 eV.`Frederik wrote:
Worst-case projections for this century are roughly 1000 ppm, which is 1%. In his AMOC paper Nathan Urban used a model where we burnt all the carbon we could find, so he should have an idea of what that could cause - but I forget. 5% would be pretty terrible!
Frederik wrote: > Does anyone expect that CO<sub>2</sub> levels may soon rise to 5%? Worst-case projections for this century are roughly 1000 ppm, which is 1%. In his [[AMOC]] paper Nathan Urban used a model where we burnt all the carbon we could find, so he should have an idea of what that could cause - but I forget. 5% would be pretty terrible!(Re 15: At the moment, iTeX is converted to MathML by sending it to a conversion program which resides on the same server as the nLab and Azimuth wiki. For some unknown reason, the VPS hosting those is down at the moment - I've emailed the company and am waiting for a reply - so no iTeX conversions can happen for the time being. Sorry.)
(Re 15: At the moment, iTeX is converted to MathML by sending it to a conversion program which resides on the same server as the nLab and Azimuth wiki. For some unknown reason, the VPS hosting those is down at the moment - I've emailed the company and am waiting for a reply - so no iTeX conversions can happen for the time being. Sorry.)Okay, thanks for the explanation Andrew! It was very mysterious because the system broke down in the middle of me editing Frederik's post - first it half-worked, then it didn't work at all.
Okay, thanks for the explanation Andrew! It was very mysterious because the system broke down in the middle of me editing Frederik's post - first it half-worked, then it didn't work at all.I think the "burn all hypothesized carbon" scenario gets up to 2500 ppm CO2 or so in a few centuries after this one.
I think the "burn all hypothesized carbon" scenario gets up to 2500 ppm CO2 or so in a few centuries after this one.John wrote:
Really ? I actually forgot or never calculated the ratio of UV power versus IR power in the spectrum.
Frederick wrote:
And that is exactly a problem, because due to the small band gap inefficiences due to thermal fluctuations take place.
However I could imagine that with more refined methods then with tight binding approximations* (especially if you have material, which has more complicated geometric sturcture) one could get further. Like I never learned about these ab-initio methods. The testbooks in solid state physics are incredible expensive, like one book I really liked was 300 Euro.
*I actually once taught a course on photovoltaics, since as a Lehrbeauftragter I was not allowed to use the university's software I discussed with the students more theoretical issues. Like I let them glue together a little paper model of the Brioullin zone of silicon. But unfortunately a lot of the students where not really paying attention but just played soccyer with it.
John wrote: >There's not much power in the ultraviolet Really ? I actually forgot or never calculated the ratio of UV power versus IR power in the spectrum. Frederick wrote: >(a) E=hc/λ and hc≈1.240eVμm so a semiconductor would need a bandgap smaller than 1.8 eV. And that is exactly a problem, because due to the small band gap inefficiences due to thermal fluctuations take place. However I could imagine that with more refined methods then with tight binding approximations* (especially if you have material, which has more complicated geometric sturcture) one could get further. Like I never learned about these ab-initio methods. The testbooks in solid state physics are incredible expensive, like one book I really liked was 300 Euro. *I actually once taught a course on photovoltaics, since as a Lehrbeauftragter I was not allowed to use the university's software I discussed with the students more theoretical issues. Like I let them glue together a little paper model of the Brioullin zone of silicon. But unfortunately a lot of the students where not really paying attention but just played soccyer with it.nad wrote:
I should may be explain that for the photovoltaics course I got 23.50 Euro for the lecture hour cash without social security benefits. Course Preparation, exam preparation, exam correction and time for commuting were not payed, but required.
Since I was not overly familiar with the subject and there were no course notes I could use, I needed a lot of preparation time. Hence as you can imagine this was for me something -if at all- like a socalled 1 Euro job.
And since my husband was at that time (this lasted for about 10 years) also on semester-wise jobs (luckily he was better paid) and we had two small kids, a book of 300 Euro was completely out of reach. We were lucky enough that for the pain we could sustain ourselves. I actually found the book in a library, but the book was very sought after, so you could keep it only for 4 weeks and then you had to give it away again, which is less optimal for a continuous learning process.
nad wrote: >like one book I really liked was 300 Euro. I should may be explain that for the photovoltaics course I got 23.50 Euro for the lecture hour cash without social security benefits. Course Preparation, exam preparation, exam correction and time for commuting were not payed, but required. Since I was not overly familiar with the subject and there were no course notes I could use, I needed a lot of preparation time. Hence as you can imagine this was for me something -if at all- like a socalled <a href="http://en.wikipedia.org/wiki/Working_opportunities_with_additional_expenses_compensation">1 Euro job.</a> And since my husband was at that time (this lasted for about 10 years) also on semester-wise jobs (luckily he was better paid) and we had two small kids, a book of 300 Euro was completely out of reach. We were lucky enough that for the pain we could sustain ourselves. I actually found the book in a library, but the book was very sought after, so you could keep it only for 4 weeks and then you had to give it away again, which is less optimal for a continuous learning process.John wrote:
Nad wrote:
Well, if I'm not misinterpreting the graph I showed you and it's correct, the power in the ultraviolet is given by area of the red region to the left of the left-hand line here:
John wrote: > There's not much power in the ultraviolet: Nad wrote: > Really? Well, if I'm not misinterpreting the graph I showed you and it's correct, the power in the ultraviolet is given by area of the red region to the left of the left-hand line here: <img width = "400" src = "http://upload.wikimedia.org/wikipedia/commons/4/4c/Solar_Spectrum.png" alt = ""/>The interplay between plants and soil is an important factor in CO2 "fertilization". I've added a little to the wiki page Carbon dioxide fertilization.
The interplay between plants and soil is an important factor in CO2 "fertilization". I've added a little to the wiki page [[Carbon dioxide fertilization]].