You can pump a whole lot of the gas into a greenhouse but not all of it will be absorbed, a fair bit of it will stay in the air to warm the actual structure.

For the majority of greenhouse crops, net photosynthesis increases as CO2 levels increase from 340–1,000 ppm (parts per million). Most crops show that for any given level of photosynthetically active radiation (PAR), increasing the CO2 level to 1,000 ppm will increase the photosynthesis by about 50% over ambient CO2 levels.

First paragraph above: False. It will all be absorbed down to roughly 200 ppm, when the plants die! (assuming a sealed, airtight greenhouse) The [CO2] will only stay constant through additional imputs to replace what is removed by (improved) plant growth.

Second paragraph above: Copied from your supplied link. Plant growth continues to increase up to 1000ppm. When we get to 1000ppm [CO2] in the atsmosphere, give me a call.

Yes too much CO2 will harm the plants

And so will too little, and the level of CO2 that is optimum for plants in greenhouses is uncomfortable for humans … (much higher than current levels in the atmosphere).

Methane reflects the sun’s light back to the earth? Then it should also reflect incoming light back into space. Unless we have a one-way mirror. Now that would be worthy of several Nobel prizes.

Fascinating concept, a gas that reflects light. Must be that new silver plated methane. Absorb, yes. Reflect? Hmmm. ”

It’s not quite like that Retired Engineer, gases don’t exactly do a lot of reflecting. Clouds reflect due to the fact that they consist of water droplets, and ice crystals. When you have true reflection (from optical materials, the reflected radiation has pretty much the same spectrum as the incident radiation such as sunlight for example. To the extent that reflected spectra may differ from incident, some of the incident radiation may be absorbed by the materials so it is subtracted from the incident.

The action of “Greenhouse gases” is quite different. They work their wonders, by ABSORBING a portion of the total spectrum that falls on them.
The portion that is absorbed depends on the atom or molecule doing the absorbing. For example in the case of CO2, the molecule looks (vaguely) like this; O=C-O
Now why did I draw it like that? The O is actually linked to the C by two electron bonds as shown with the first O on the left. There are also two electron bonds to the O on the right, but you can’t see them both, because the pair are at right angles to the pair on the left; so there really are two on the right (trust me). At the central carbon, the four bonds actually form the corners of a tetrahedron; which a little playing with your fingers will show it is like two pairs at right angles.
Now the bonds are somewhat like connecting springs; they are stretchy and bendy.
So the CO2 molecule is capable of oscillating, with the two oxygens moving back and forth along the horizontal line in opposite directions so the carbon stays stationary,a dn the two oxygens always move opposite each other. That is called the “symmetrical stretch” mode, and becasue it is symmetrical, the center of the electric charge stays put in the middle of the carbon. So it doesn’t generate much of an external electric field.
Alternatively, the oxygens can move in the same direction, and they would tend to push/pull the carbon with them, but they will move to the center of mass stays stationary. This is the assymmetrical stretch mode, and its frequency corresponds to a wavelength of about 4 microns.
The really interesting mode is when the molecule bends about the carbon atom. Those two springs on the left can bend back and forth in and out of the page toward you; or the pair on the right can bend the same way, but only up and dowen in the plane of the paper. It is pretty obvious that those two bending situations are really exactly the same thing, just at right angles tyo each other. We call that a degenerate mode because there are really two modes that are identical in frequency. This one has a frequency corresponding to a 15 micron wavelength (roughly).

Now if you thought of a child’s swing, you can make it oscillate if you push it at the right rate, depending on how long the chains are.

Same thing with molecules; if you hit them with photons that correspond to the same frequency of the molecular oscillation, then they absorb those photons very efficiently and start oscillating, so at 15 microns CO2 absorbs infrared radiation, and goes into this degenerate bending mode of vibration.
So those IR photons emitted from the surface of the earth get captured by the CO2 molecule and set it ringing like a bell. The molecules are also moving about due to collisions with other air molecules, so the exact frequency that gets absorbed depends on a doppler shift mechanism as well so it really becomes a band of wavelength due to “temperature broadening” ie the doppler effect. Also depending on the gas density, the molecules coillide now and then, and when the CO2 molecule bangs into a nitrogen or Oxygen molecule or once in a while one of those snooty loner Argon chaps; it’s like spilling your coffee when somebody nudges your elbow, and the CO2 molecule will spit out the exciting photon, and stop bending or stretching. When it does so, once again you get a doppler effect, so the wavelength of the emitted photon might be slightly different from the one that was absorbed, and the final energy of the CO2 molecule will alter a little bit.

Now the molecule doesn’t know up from down, so when it spits the photon, it could go in any direction, so the photons that are “re-radiatted” (not reflected) by the molecules of CO2 will go up down left roight etc, and about half go back down towards the ground, and the other half head upwards towards oouter space. They may get absorbed and re-emitted many times before they escape, and it is that delay in escaping that creates a warming effect, because druring that delay, solar photons are still arriving at the same rate as before, so more are getting absorbed, than ir ones are escaping.
So the ir radiation is not really “blocked” from escape; we don’t know how to block radiation from ultimately escaping; that would make one hell of a thermal insulation.

So that is the basic mechanism by which all GHGs work including water vapor, and each of them have their own modes of molecular vibrations oscillations, rotations to capture different wavelength photons.

Of course there are lots of other things that can happen next to alter the outcome of the GHG absorbing and re-emitting photons, and figuring out exactly what that is is where all the disagreements come in.

Now aren’t you glad you are a Retired Engineer ?

George

Yes, but the figures they quote are around 1000 – 1300ppm, which is more than three times current atmospheric levels.

Because it was a “what if” scenario. If you would take a look at the primer, it warns against putting more than about 1,000 ppm of CO2 because it will disrupt the very natural processes you say will gobble it up. You don’t see the point because you need to go back in the discussion.

The question was: “how do you know that plants will only absorb so much CO2 if greenhouses pump in more of the gas than normal to make plants grow faster?” This was the answer. We know because guidelines for greenhouses state that over 1,000 ppm, and the plants you’re trying to grow with a flood of CO2 are damaged.

The references to sunlight and heat and so on are red herrings here.

REPLY: Red Herrings? This thread is about METHANE and you’ve gone OT and turned it into an argument about CO2 in greenhouses. Go find another website to waste time on. I’d never said this to a commenter before, but you sir (whomever you are) are are making an idiotic and disingenuous argument. – Anthony

The galactic rotation does nothing for the Earth. The only reason the seasons change is because of the Earth’s tilt on its axis.

According to this primer on the use of carbon dioxide in greenhouses from the Canadian government, you can’t put too much of the gas in the air because the plants will be damaged by the excess gas. So if you pump too much carbon dioxide into a greenhouse, it will just stay in the air.

Most greenhouses are very precisely controlled which is why that doesn’t happen in the vast majority of them. I admit my explanation was a little confusing, but the point remains valid. Plants only need so much carbon dioxide.

REPLY: Why not simply admit that your explanation about CO2 causing warming in greenhouses was wrong rather than confusing? Whether the CO2 stays in the air or not makes no impact on the heat balance in the greenhouse. The effect is too small and is swamped by other physical processes. Yes too much CO2 will harm the plants, too much sunlight will do that, too much heat, too much cold, too much fertilizer…so I don’t see any point there. – Anthony

Whatever made you think I do?

I’m talking rubbish, but the sources I get to supposedly refute what I say don’t actually say anything of the sort the posters claim they do. That is, if I actually get any sources. Most of the time I’m being bombarded by those who just lay out indignant red herrings that have nothing to do with what I said or question “how do you know that?” when I linked to a source right in my post. If you won’t actually read what is being said or don’t want to read it, I can’t help you.

And yes, every living things only needs so much carbon dioxide. You can pump a whole lot of the gas into a greenhouse but not all of it will be absorbed, a fair bit of it will stay in the air to warm the actual structure. Why do you think the gases are called “greenhouse gases.” It’s not because they’re green. It’s because they do the same job as they do in the greenhouse.

All of this tell me one thing. Many of you have no interest in the science. None. Zero. Never had. All you care about is opposing the idea of global warming because… why? What do you have to gain? Some sense of moral satisfaction of “sticking it to the liberal do-gooder enviros?” Feeling smarter than everybody else? Numerous scientists all over the world investigating what’s going on with the climate and you all know better because you took a look at a few obscure graphs and ignore all data to the contrary?

Like I said, this is a political discussion. As science and religion don’t mix, neither do science and politics.

REPLY:You wrote: “You can pump a whole lot of the gas into a greenhouse but not all of it will be absorbed, a fair bit of it will stay in the air to warm the actual structure. Why do you think the gases are called “greenhouse gases.”

I’m sorry but that is patently false. CO2 does nothing in a greenhouse related to warming. Glass and lack of convective heat transfer is the real reason for retained heat. CO2 in a greenhouse does nothing except help the plants with their chemical processes. – Anthony

Duh! You think?

This is reminiscent of the startling revelation by a Time magazine cover story, Men and Women are Different.

More study required which, of course, requires more funding to discover a repetition of Nature’s cycles which are a part of a historical record available at your local library and certainly available on the internet.

Is Dr. Pachauri involved? Will New Zealand’s bovine flatulence patrol go global?

Computer models are not reality. Nature is reality.

Retired Engineer (16:26:49) :

“Fascinating concept, a gas that reflects light. Must be that new silver plated methane. Absorb, yes. Reflect? Hmmm.”

Methane is to the Earth as a thin-film coating is to a camera lens. /sarc off

All based on the arrogant presumption that these computer models are programmed correctly!

We know these models cannot be infallible because they all make different assumptions of how certain variables work, particularly water vapour & clouds, which they are only just embarking on studying so that they can get the models to work better.

It’s also interesting reading in the article that they set out to find evidence of man’s signal in the Antarctic, & they keep saying the old IPCC SPM statement of “a lack of warming” which hides that fact that temperatures are not stagnating down there, but are cooling. Again clever use of wording to imply one thing has occurred when in fact another actually happened. If you look hard enough for something you can find it. None of the models predicted or even projected the cooling this century, yet they constantly claim “great accuracy” of the models.