“You Asked” is a series where Earth Institute experts tackle reader questions on science and sustainability. Over the past few years, we’ve received a lot of questions about carbon dioxide — how it traps heat, how it can have such a big effect if it only makes up a tiny percentage of the atmosphere, and more. With the help of Jason Smerdon, a climate scientist at Columbia University’s Lamont-Doherty Earth Observatory, we answer several of those questions here.
How does carbon dioxide trap heat?
You’ve probably already read that carbon dioxide and other greenhouse gases act like a blanket or a cap, trapping some of the heat that Earth might have otherwise radiated out into space. That’s the simple answer. But how exactly do certain molecules trap heat? The answer there requires diving into physics and chemistry.
When sunlight reaches Earth, the surface absorbs some of the light’s energy and reradiates it as infrared waves, which we feel as heat. (Hold your hand over a dark rock on a warm sunny day and you can feel this phenomenon for yourself.) These infrared waves travel up into the atmosphere and will escape back into space if unimpeded.
Oxygen and nitrogen don’t interfere with infrared waves in the atmosphere. That’s because molecules are picky about the range of wavelengths that they interact with, Smerdon explained. For example, oxygen and nitrogen absorb energy that has tightly packed wavelengths of around 200 nanometers or less, whereas infrared energy travels at wider and lazier wavelengths of 700 to 1,000,000 nanometers. Those ranges don’t overlap, so to oxygen and nitrogen, it’s as if the infrared waves don’t even exist; they let the waves (and heat) pass freely through the atmosphere.
With CO2 and other greenhouse gases, it’s different. Carbon dioxide, for example, absorbs energy at a variety of wavelengths between 2,000 and 15,000 nanometers — a range that overlaps with that of infrared energy. As CO2 soaks up this infrared energy, it vibrates and re-emits the infrared energy back in all directions. About half of that energy goes out into space, and about half of it returns to Earth as heat, contributing to the ‘greenhouse effect.’
Smerdon says that the reason why some molecules absorb infrared waves and some don’t “depends on their geometry and their composition.” He explained that oxygen and nitrogen molecules are simple — they’re each made up of only two atoms of the same element — which narrows their movements and the variety of wavelengths they can interact with. But greenhouse gases like CO2 and methane are made up of three or more atoms, which gives them a larger variety of ways to stretch and bend and twist. That means they can absorb a wider range of wavelengths — including infrared waves.
How can I see for myself that CO2 absorbs heat?
As an experiment that can be done in the home or the classroom, Smerdon recommends filling one soda bottle with CO2 (perhaps from a soda machine) and filling a second bottle with ambient air. “If you expose them both to a heat lamp, the CO2 bottle will warm up much more than the bottle with just ambient air,” he says. He recommends checking the bottle temperatures with a no-touch infrared thermometer. You’ll also want to make sure that you use the same style of bottle for each, and that both bottles receive the same amount of light from the lamp. Here’s a video of a similar experiment:
A more logistically challenging experiment that Smerdon recommends involves putting an infrared camera and a candle at opposite ends of a closed tube. When the tube is filled with ambient air, the camera picks up the infrared heat from the candle clearly. But once the tube is filled with carbon dioxide, the infrared image of the flame disappears, because the CO2 in the tube absorbs and scatters the heat from the candle in all directions, and therefore blurs out the image of the candle. There are several videos of the experiment online, including this one:
Why does carbon dioxide let heat in, but not out?
Energy enters our atmosphere as visible light, whereas it tries to leave as infrared energy. In other words, “energy coming into our planet from the Sun arrives as one currency, and it leaves in another,” said Smerdon.
CO2 molecules don’t really interact with sunlight’s wavelengths. Only after the Earth absorbs sunlight and reemits the energy as infrared waves can the CO2 and other greenhouse gases absorb the energy.
How can CO2 trap so much heat if it only makes up 0.04% of the atmosphere? Aren’t the molecules spaced too far apart?
Before humans began burning fossil fuels, naturally occurring greenhouse gases helped to make Earth’s climate habitable. Without them, the planet’s average temperature would be below freezing. So we know that even very low, natural levels of carbon dioxide and other greenhouse gases can make a huge difference in Earth’s climate.
Today, CO2 levels are higher than they have been in at least 3 million years. And although they still account for only 0.04% of the atmosphere, that still adds up to billions upon billions of tons of heat-trapping gas. For example, in 2019 alone, humans dumped 36.44 billion tonnes of CO2 into the atmosphere, where it will linger for hundreds of years. So there are plenty of CO2 molecules to provide a heat-trapping blanket across the entire atmosphere.
In addition, “trace amounts of a substance can have a large impact on a system,” explains Smerdon. Borrowing an analogy from Penn State meteorology professor David Titley, Smerdon said that “If someone my size drinks two beers, my blood alcohol content will be about 0.04 percent. That is right when the human body starts to feel the effects of alcohol.” Commercial drivers with a blood alcohol content of 0.04% can be convicted for driving under the influence.
“Similarly, it doesn’t take that much cyanide to poison a person,” adds Smerdon. “It has to do with how that specific substance interacts with the larger system and what it does to influence that system.”
In the case of greenhouse gases, the planet’s temperature is a balance between how much energy comes in versus how much energy goes out. Ultimately, any increase in the amount of heat-trapping means that the Earth’s surface gets hotter. (For a more advanced discussion of the thermodynamics involved, check out this NASA page.)
If there’s more water than CO2 in the atmosphere, how do we know that water isn’t to blame for climate change?
Water is indeed a greenhouse gas. It absorbs and re-emits infrared radiation, and thus makes the planet warmer. However, Smerdon says the amount of water vapor in the atmosphere is a consequence of warming rather than a driving force, because warmer air holds more water.
“We know this on a seasonal level,” he explains. “It’s generally drier in the winter when our local atmosphere is colder, and it’s more humid in the summer when it’s warmer.”
As carbon dioxide and other greenhouse gases heat up the planet, more water evaporates into the atmosphere, which in turn raises the temperature further. However, a hypothetical villain would not be able to exacerbate climate change by trying to pump more water vapor into the atmosphere, says Smerdon. “It would all rain out because temperature determines how much moisture can actually be held by the atmosphere.”
Similarly, it makes no sense to try to remove water vapor from the atmosphere, because natural, temperature-driven evaporation from plants and bodies of water would immediately replace it. To reduce water vapor in the atmosphere, we must lower global temperatures by reducing other greenhouse gases.
If Venus has an atmosphere that’s 95% CO2, shouldn’t it be a lot hotter than Earth?
The concentration of CO2 in Venus’ atmosphere is about 2,400 times higher than that of Earth. Yet the average temperature of Venus is only about 15 times higher. What gives?
Interestingly enough, part of the answer has to do with water vapor. According to Smerdon, scientists think that long ago, Venus experienced a runaway greenhouse effect that boiled away almost all of the planet’s water — and water vapor, remember, is also a heat-trapping gas.
“It doesn’t have water vapor in its atmosphere, which is an important factor,” says Smerdon. “And then the other important factor is Venus has all these crazy sulfuric acid clouds.”
High up in Venus’ atmosphere, he explained, clouds of sulfuric acid block about 75% of incoming sunlight. That means the vast majority of sunlight never gets a chance to reach the planet’s surface, return to the atmosphere as infrared energy, and get trapped by all that CO2 in the atmosphere.
Won’t the plants, ocean, and soil just absorb all the excess CO2?
Eventually … in several thousand years or so.
Plants, the oceans, and soil are natural carbon sinks — they remove some carbon dioxide from the atmosphere and store it underground, underwater, or in roots and tree trunks. Without human activity, the vast amounts of carbon in coal, oil, and natural gas deposits would have remained stored underground and mostly separate from the rest of the carbon cycle. But by burning these fossil fuels, humans are adding a lot more carbon into the atmosphere and ocean, and the carbon sinks don’t work fast enough to clean up our mess.
It’s like watering your garden with a firehose. Even though plants absorb water, they can only do so at a set rate, and if you keep running the firehose, your yard is going to flood. Currently our atmosphere and ocean are flooded with CO2, and we can see that the carbon sinks can’t keep up because the concentrations of CO2 in the atmosphere and oceans are rising quickly.
Unfortunately, we don’t have thousands of years to wait for nature to absorb the flood of CO2. By then, billions of people would have suffered and died from the impacts of climate change; there would be mass extinctions, and our beautiful planet would become unrecognizable. We can avoid much of that damage and suffering through a combination of decarbonizing our energy supply, pulling CO2 out the atmosphere, and developing more sustainable ways of thriving.
Editor’s note (March 17, 2021): This post was updated with additional links to Youtube videos with experiments showing the effects of carbon dioxide. Enjoy!
I’m writing a paper for my environmental class How does the cooler atmosphere transport heat Q to the warmer surface?
Q = sigma•(Ts^4 -Ta^4)
If the air’s cooler than the surface, it wouldn’t.
GREAT question Joe!
The short answer:
It doesn’t. Heat always flows from higher temperature to lower temperature.
If it didn’t, the 2nd Law of Thermodynamics would be violated, and entropy would decrease (as enthalpy increased).
The longer answer:
The “greenhouse gas” mechanism does not exist. The atmosphere (including CO2) provides convection cooling to the Earth’s surface. Cloud cover does *temporarily* prevent radiational cooling by reflecting radiation back to the surface. This is distinctly different than the fictitious greenhouse gas model of absorption-and-reemission. The atmosphere also distributes heat more evenly around the planet through convection heat transfer in general; this is why the planet surface doesn’t have wild temperature differences from day to night like the moon. There is NO net warming effect due to so-called greenhouse gases.
That being said, here’s what I’m NOT saying:
-I’m not saying global warming isn’t real. We are experiencing a warming trend.
-I’m not saying human activity doesn’t add to this warming trend; it does.
-I’m not saying trying to minimize environmental impact isn’t worthwhile. It is not only worthwhile, it is critical.
-I’m not saying plants and trees do not have a net cooling effect. They do, but it is because they are endothermic from a heat balance point of view. Plants are great because they absorb energy, NOT because they happen to use CO2 to do this.
All I’m saying is that if anyone is concerned about reducing anthropogenic global warming effects, the best approach is to try to minimize waste heat.
7.5 billion humans generate a LOT of waste heat. Birth control and insulation will help. Sequestering plant food (CO2) will make the problem worse.
Less CO2=less plant life=less radiant energy from the sun being used during photosynthesis.
Hi Daniel,
The obvious retort here is that many actions essential if mainstream theories are correct make sense regardless of the nature, extent, cause and direction if climate change. They would help cope with a volcanic winter (e.g. that in 1816 after the Tambora eruption) and also the collapse of a major food crop. Examples include less waste, combining conservation with careful use, restoring fish stocks, growing fewer cash crops, regenerative agriculture, silviculture and reducing the impact per head and probably numbers of conventional livestock.. Instead of shovelling grain and soya down cattle they can be fed on crop residues, natural vegetation and spent brewery grain while methane-reducing feed additives like Asparogopsis taxiformis in livestock feed could give a huge cut in emissions and some boost growth.
These are all win-win options which make sense regardless. Instead of adopting them, humanity has wasted decades bickering about who is right. I despair at times!
I posted something on food security on the climate coalition website last year if you’re interested.
Send me the link
The greenhouse gas mechanism definitely does exist. Colder objects still radiate, unless they are at absolute zero. The atmosphere is well above that at 255 K or so on average, and it radiates plenty of infrared light. When that infrared light strikes the ground, what do you think happens?
. . . it doesn’t reflect to the ground at all. Virtually all of the terrestrial IR is captured by CO2. For the same reason, virtually all of the terrestrial IR that can be absorbed by CO2 is absorbed within 15m of the ground.
Not true, the atmospheric window allows IR in the 8-14 micron wavelengths to pass to outer space. What you are saying only holds true in the 4.3 and 15 micron absorption bands.
Sir, if I understand you correctly…some of the CO2 driven IR energy safely dissipates through an atmospheric window in the 8-14 micron range?
With respect to cumulative greenhouse gases, why are holes in the earths ozone no longer mentioned as threat? How did those holes repair? How did the Great Barrier reef make a recovery?
What common sense you bring to the table Daniel. ISA temperature of our world is 15C, the aim of the low carbon believers is to keep Global Warming to + 1.5 degrees ie. an
increase of 10% in ISA to 17.5C. If CO2 were to cause this increase it would need to form 10% of the atmosphere, assuming it was totally opaque to heat transfer. Being heavier than air, the warming would not bother us at all, all air breathing life would be extinct from suffocation.
Sorry, can’ do arithmetic for 17.5 read 16.5…
It gets worse. 1.5C is not a 10% rise in temperature! To write about temperature in percent one must use Kelvin so 1.5C rise is only 1.5/288 = 0.5%. Can we stick with real science?
Hi Daniel,
Your argument conflates infrared radiation with heat, but they are not the same thing. The phenomenon of “heat” is due to kinetic energy at the molecular level, i.e., the motion of molecules and atoms. Infrared radiation is a form of electromagnetic radiation and, although it can cause heat by causing molecules to vibrate (kinetic energy), it is not, itself, a form of heat energy.
In the specific case of heat energy, yes, the 2nd law of thermodynamics says that “heat” always “flows” from regions of higher temperature to regions of lower temperature. That is because heat energy is transmitted by molecules “bumping into” other molecules causing some of their kinetic energy to be transferred. Since the motion of the molecules is random, the energy spreads out and thus heat tends to “flow” from hotter to cooler molecules.
Electromagnetic energy is transmitted in totally different way that DOES NOT violate the 2nd law of thermodynamics. It is the ability of CO2 to “trap” infrared radiation and reflect it back to earth (not convection) that is the cause of the so-called “greenhouse effect” and therefore it does not violate the 2nd law.
Molecules bumping into one another is conduction, not radiation. It does not explain to the layman how heat supposedly radiates back to warmer surface from the cooler CO2 in the atmosphere. Just saying.
The Greenhouse warming effect of CO2 is real. But so are the cooling effects of CO2: the Co-aerosol effect and the Green effect. This is a layman explanation.
The Greenhouse effect is visible using official biospheric records over deserts with little flora. A change in CO2 leads to (precedes) a proportional change in temperature. CO2 “receives” the electromagnetic wave (at quantum frequencies) to move the orbit of electrons to an unstable and higher energy state (EM energy is converted to potential energy). At more than a billion times a second, that CO2 molecule “bumps” into another molecule at near the speed of sound. The electron returns to a more stable orbit, and the potential energy is converted to a photon that randomly emits in a direction that has a near 50% chance of going “down” vs. “up”. This delay, ever so slightly, lowers the emissivity of air (how quickly the atmosphere gives up radiative heat). The radiation that no longer shoots directly to space now lingers … maybe affecting the temperature of your skin or thermometer. If isolating this property of CO2, more CO2 begets higher temperatures.
The Co-aerosol effect is visible on an hourly scale at climate observatories (e.g., Mauna Loa). Co-aerosols are produced when natural organic sources are used to create energy. These co-aerosols, mostly invisible and odorless, reflect incoming shortwave solar radiation back to space before it is absorbed by our biosphere. If isolating this property of CO2, more CO2 begets lower temperatures.
The Green effect is visible on a monthly scale over farming areas and jungles (think Amazon). As stated in other posts, this is primarily due to the absorption of photons in the endothermic (cooling) photosynthesis process. Just like the greenhouse effect, the absorption is not totally permanent. Think exothermic (warm) decay of plant matter. But that delay change the emissivity of our atmosphere just like the greenhouse effect, but in the opposite direction. This cooling effect is so strong that temperatures have actually dropped in central Amazon. If isolating this property of CO2, more CO2 begets lower temperatures.
People that understand that anthropogenic CO2 has three effects on climate change, one that warms and two that cool, then ask a key question. Globally, which climate changing property is strongest?
That answer is fascinating. When Earth is really cold, there is little flora and few humans. So the primary effect of CO2 is to warm. When Earth is gets warm (on its way to too warm), flora and humans flourish. Our biosphere greens and cools (Google NASA Green Earth). And for those that also know that CO2 is at about a third to a half of where it needs to be and that the glacial maximum was only about 20,000 years ago, we crossed the Greenhouse vs Green effect line in approximately the 1970s. Our biosphere had finally gotten green enough to overpower the greenhouse effect and cool–partially mitigating the natural sun/sea caused 200+ year rise in global temperatures since the mini-Ice Age.
You are correct re ‘convectional cooling’, and as such means that ‘convectional heating’ is also applicable.
Seeing as CO2 have been known and proven since early 1800’s to absorb and radiate heat, your statement that greenhouse gases have no affect creates a conflict in your statement.
That is unless you can prove CO2 doesn’t do any such thing? Any kid with a couple empty bottles and a temp gauge can prove CO2 does indeed do.
But that’s the problem. The earth is not a couple of empty bottles. The earth’s atmosphere is much much more complex!
Trapped heat is not the same as the earths convection system. Anyone thinking that must have been emptying those bottles wholesale!
I strongly believe that waste heat from human activities dominates the warming, just like air conditioning a house by spending energy. About 80% of globally consumed energy enters the environment as waste heat, which cannot be ignored, from daily life (boiling water, cooking foods, air conditioning), transportation to industries.
From this point one can reasonably understand how the global warming can be linked to our activities that release waste heat. Actually it can easily simulate the temperature changes in air, land and oceans according to the waste heat allocated to them based on simple thermodynamic calculations.
Waste heat: the dominating root cause of current global warming | Environmental Systems Research | Full Text (springeropen.com)
I have never given much thought to waste heat from human activity. In fact, scientist have never really mentione it and only focused on co2,methane and deforestation.
The main focus is co2. If it were lower the waste heat would escape and no warming.
I spent time on Lake Keowee in South Carolina last month. This lake is a part of a set of reservoirs owned by Georgia Power. On Lake Keowee is a nuclear reactor, which utilizes the reservoir for cooling. Going swimming I was shocked at the warmth of the water temperature. This really made me think about heat from human activities This is not a small body of water. I can only imagine what compounding this around the world could do.
Whether nuclear, coal, gas, solar or wind the amount of energy produced ends up being expelled as some form of energy that eventually turns to heat. I’m not a CO2 control believer. However, it became very apparent to me reducing usage can’t be all that bad.
Reduce, reuse, recycle
The Earths historical temperature over billions of years shows very strong links between CO2 levels and ambient temperature. There is no other cause, no one had cars 350 million years ago when CO2 levels were similar and a mass extinction resulted.
Geothermal heating from 1000 centigrade magma is a major contender by conduction!
Nobody seems to discuss the small influence a relatively large increase in CO2 has on plant growth. I used to represent commercial marijuana growers. Most of them grew indoors and augmented their controlled atmosphere with CO2. Now cannabis is called weed for a reason. It grows pretty easily and is not finicky. Yet to double the plant’s yield with CO2, you need at least 3.5x increase in CO2 from ambient and, in fact, it’s more like 5x. So there’s no way this extra CO2 we are producing is just going to be gobbled up by plants.
Are you saying that the plant won’t absorb the CO2 at all unless it is increased by 3.5x or more like 5x?
Wild temperatures happen daily on the moon? Where can I get info
Magnificent! CO2 is a fake?
What about endless geothermal heating and it’s energy supply, since constant motion (energy) is illegal physics
Good answer!
The best, most complete and correct answer below is from Lisa Goddard. I will simplify it even further by saying there are only two forms of heat transfer – conduction and radiation. Convection is a special case of conduction in which fluid flow (air in this case) is taken into account as a heat distribution mechanism, and influencer of heat transfer coefficients (I got an A- in my first semester of heat transfer), but ultimately it is still conduction.
Conduction occurs with the molecules or atoms of a substance come into contact and transfer energy to one another. So it is fair to say there will not be a net transfer of thermal energy (heat) from cooler air to a warmer surface through conduction.
The other mechanism of heat flow is radiation. This is the radiation of electromagnetic radiation from objects, ie the molecules and atoms in bodies. This form of energy can travel through a vacuum, such as the various forms of electromagnetic radiation that travel through the vacuum of space to our Earth. After absorbing this radiation from the sun, the earth’s surface radiates some of it back into space in the form of infrared radiation which has a little bit longer wave length than the various visible light wavelengths we see. Oxygen and Nitrogen in the air mostly ignore it, but Carbon Dioxide molecules have the geometry and composition that allows them to absorb the radiation of this wavelength. They get “excited” and re-radiate the energy, again as infrared, back out. Some goes up, and some goes back down to the surface.
So if there was only O2 and N2 in the atmosphere the infrared energy would mostly radiate back into the black body of space. But each CO2 molecule catches some and sends a portion back to earth. The more CO2 molecules there are, the more infrared radiation gets interrupted and sent back to earth, instead of out to space. That is how CO2 in the atmosphere can transfer energy to the surface, by blocking infrared energy heading to space and sending some of it back to the surface.
Overall, increasing CO2 and other greenhouse gasses reduces the earth’s ability to “cool itself off” by radiating energy into space. In other words the greenhouse gas molecules “catch” the infrared energy trying to escape earth, and “throw” some of it back to earth. Increasing greenhouse molecules, increases the amount of energy that gets caught and sent back.
In your final sentence you say that radiation increases greenhouse molecules. Energy converts to matter. That sounds faintly ridiculous. It would be useful to read an explanation of how that works.
David Watson is not saying that radiation increases greenhouse molecules. He is saying that as CO2 concentrations increase in the atmosphere due to other means (e.g., by combustion of molecules that include carbon such as petroleum, coal and wood), that more infrared radiation that would otherwise radiate out into space is being reflected back to earth. The reason is that physics of CO2 molecules allow them to be excited by radiation in infrared wavelengths where as other molecules present in our atmosphere, such as O2 and N2 do not. The energy absorbed by the CO2 when it is excited by infrared radiation causes them to vibrate and thus emit infrared radiation themselves, some of which is radiated into space, but some of which are radiated back to earth, causing the molecules of earth to vibrate (because most molecules are capable of absorbing infrared) and thus create heat. Ergo, there is a net gain of heat on earth.
It would seem that if N2 and O2 are transparent to incoming radiation that the introduction of CO2 would also act to ‘insulate’ the incoming radiation and reflect some of it back into space as well as reflect some of the exiting radiation (from the earth) back to the earth. Why don’t these effects offset?
As mentioned above, visible light coming from the sun passes the CO2 molecules without interaction. Upon reaching the ground some of the visible light is re-radiated from the ground as infra-red radiation, which does interact with CO2.
They do!
That’s one of the reasons why a Greenhouse period has a more stable temperature around the planet.
They leave out the global greening caused by c02 fertilization which = more oxygen = thicker atmosphere because of an over simplistic empty bottle experiment done over a hundred years ago.
A rather severe misunderstanding.
When a CO2 molecule absorbs a photon of IR, it become energized. I will lose this energy by collision with another air molecule, in which case the energy shows up a kinetis energy or heat. This occurrs some billion times per second.
It also can spontaneously emit a photon, returning to the ground state. In a vacuum, the life is about one second.
So heat release is effectively 100%, and photon emission is a vanishingly small portion
Effectively, CO2 affects the global heat balance only in the 14-16micron wavelength range. NASA data shows that ZERO energy goes to space in this wavelength band. All else is just talk. The NASA data is at NASA Technical Memorandum 103957, Appendix E.
So why is the whole earth at a nice pleasant 80F during a Greenhouse period with co2 10 times higher then today?
What you’re saying is correct but there are obviously other things going on in the atmosphere you are not aware of.
No matter what else is causing the planet to warm, CO-w, methane, and greenhouse gases are making it worse – far worse.
If I can interject into this, the other thing we are warned about is acidification of seas by co2 and that it causes north & south pole ice to melt ..
dumb question from a science dummy….
at what concentration of CO2 will ALL IR energy be trapped on earths surface and NONE be radiated into space??
at that point, will further increases in CO2 be irrelevant because there will be no more heat to trap??
At the end of the day equilibrium is between the release into our atmosphere and us consuming. THIS IS THE BEST THANK U
Read about the Second Law of Thermodynamics that heat always flows to cooler areas not hotter ones.
There are 3 ways that energy can be transferred: conduction, convection, and radiation. What John LK and Daniel H have described are 2 of those, and both are certainly at play in distributing the sun’s energy that the surface (and some atmospheric constituents) absorb. What they both have not addressed is radiation. This is how greenhouse gasses work in our atmosphere, and incidentally, how the sun’s energy reaches Earth. If there were no greenhouse gasses in the atmosphere, heat energy radiated from the surface would almost entirely radiate back to space, leaving the surface at a very very cold -18C (or about 0F, and that is averaged over the whole planet surface!). Greenhouse gasses (like CO2 and water vapor) can effectively absorb the wavelengths associated with what we call “heat”, or infrared radiation, coming from the surface or other parts of the atmosphere. They will re-radiate that energy in all directions, sending energy back to the surface, as well as out to space. This is how the surface is effectively receiving additional energy (and thus can warm). Those greenhouse gas molecules will radiate at the temperature of their immediate environment. So, CO2 or H2O near the surface radiate at a higher temperature than those same molecules higher up in the atmosphere. The altitude, above which there are no more appreciable greenhouse gasses will appear to be the radiating temperature at that point (often called outgoing long wave radiation).
@Joe — in your equation below, this would be an expression for the energy balance at the surface, used to determine either the temperature of the surface or of the atmosphere, in a very idealized context, where the atmosphere is one big slab of stuff. What you are missing there though, is an ‘epsilon’ that represents the opacity of the atmosphere, basically the ability to absorb/emit radiation. The Q in that equation would be the net energy received from the sun, which is known and become approximate in the specific value for the Earth’s albedo (how much sun is reflected back to space). If you add one more equation – say the energy balance within the atmosphere, or at the top of the atmosphere, you would have enough information to solve for one, say T_surface, and find the other (T_atmosphere — though again, this would be an idealized representative temperature for the entire atmospheric column over the planet, but that is a similar situation for the surface temperature in this case too).
Hi Lisa,
The intelligent and accurate retort as opposed to my less intellectual bypassing the whole argument – see previous post.
Regards,.
Iain
Thanks,
I’m after the physics describing the greenhouse effect/mechanism of heat transfer.
The equation is a radiative heat transfer equation the units are expressed in power per unit area, not energy. To get energy integrate power per unit area over time then multiply by area
The equation is for heat transfer between two surfaces, earth and the atmosphere.
Suppose the sun is delivering power to the surface over time transferring energy
generating surface temperature Ts.
Q=sigma(Ts^4-Ta^4)
When is Q negative? K
Thanks,
In my paper I’m after the physics describing the greenhouse effect/mechanism of heat transfer.
The equation used is a radiative heat transfer equation applied between two surfaces, earth and the atmosphere. The equation has units of power not energy. For simplicity epsilon is 1.
Applying the equation to a single layer atmospheric model we know heat from the sun (Qs), and can find atmosphere temperature (Ta), earth surface temperature (Ts)……
The term “back radiation” is used to describe the heat transfer mechanism. Using the radiative heat transfer equation and applying it to a single layer model with the known values for Ts & Ta;
Q=sigma(Ts^4-Ta^4)
When is Q negative for atmosphere to surface heat transfer?
Joe,
Your equation is set up to always give the answer that the atmosphere can’t warm the surface, which is wrong. You need to compare the situation with a warm atmosphere to one with no atmosphere at all.
For the present situation, Ts = 288, Ta = 255, so Q = 5.670373e-8 (288^4 – 255^4) = 150 W m^-2.
Now try Ts = 288, Ta = 2.7 K (the temperature of interstellar space). You get Q = 390 W m^-2.
In other words, with the warm atmosphere there, net radiation leaving the surface is 150 W m^-2, but without the atmosphere in the way, it would be 390 W m^-2. Input and output would no longer balance and the Earth would cool off until it was radiating as much as comes in. (This whole discussion ignores sunlight, convection, and evapotranspiration, which are necessary to give a proper balance.)
Many, many universities and others will have attempted to prove the Greenhouse Effect in a lab. However, nobody has published a single paper demonstrating heating from such a mechanism. The rewards for demonstrating the GHE are multiple Nobel Prizes for everyone involved – probably even including the president of the country.
Worse still, not one publication has been seen covering failed experiments or null results. That is just dishonest surely. Null results are extremely important in science – otherwise it just becomes Groupthink.
Because it has been demonstrated so much that it is not paper worthy any more.
For instance this very article says how someone can do an experiment to show the effect themselves.
Plus you can measure the IR radiation leaving the earth with satellites.
I have done that experiment. The temperature increase was the same.
Thank you for reason and sanity
If 97 to 98% of the co2 in the atmosphere comes from natural sources how much impact can industrial sources have based on the small % of co2 in air. Isn’t it true that during the jurrasic period co2 levels were 10 times what they are today. Seems to me like a futile effort, nature rules in this case.
The atmosphere is not 2-3% artificial CO2 but 33% artificial CO2. You are confusing the fraction of emissions with the fraction of build-up. All the natural sources are matched by natural SINKS. The artificial production is not, so that’s where the increase comes from.
what are the natural Co2 ? I assume the other types are a product of burning or combustion, how do those trace gases sty up in the clouds ?-for years
It is true that CO2 concentrations in some prehistoric eras were much higher than their current levels. We believe this because of the preponderance of evidence found in the the fossil record the tells us so. (by “fossil record”, I don’t mean just actual fossils, but also other geological evidence of past climate conditions such as glacial ice cores, etc.) What the fossil record also tells us is that higher atmospheric CO2 concentrations are always associated with higher world-wide average temperatures. More importantly, it also tells us that the rate of increase of atmospheric CO2 in the current era has no precedent, i.e. it is increasing MUCH more rapidly. In the past, climate significant changes in the world wide climate occurred over extend periods of time that allowed evolutionary adaptation to occur in time to avoid catastrophic die-offs. The climate is changing far more rapidly this time around such evolutionary adaptation will not save us. What keeps me up at night is the loss of large swaths of arable land and ocean fish stock depletion.
And yet global greening grows to 7% and beyond from co2 fertilization.
We need to concentrate on the 95% of the batteries filling our land fills, leaching acid into the water chain and killing the coral reefs.
As this interglacial continues to warm the oceans and eventually melt the northern hemisphere like every other interglacial in the past, will release even more co2 before the next glacial period starts.
Every greenhouse growers will tell you that 420 ppm co2 is a fraction for what these co2 starved plants need today.
More plant growth is healthy for the planet no matter how you look at it!
What should be keeping you awake at night is how close to end of life we came at a 180 ppm in 1850!
150 ppm is a threshold. 400 ppm is no scientific threshold that I know of.
In a recent study baby coral was attached to dead coral ( caused by acidity) the baby coral thrived. Explain that, but look up the experiment first.
As of 2023, the CO2 level in the atmosphere is 46% higher than the level in 1800. I’ve seen this calculated as just over 1 trillion additional tonnes of CO2 now, versus in 1800.
The “small” percentage measurement is over 2 trillion tonnes. One is a small number and the other is large. But they describe the same thing. Don’t be misled by intuition regarding the size of numbers and percentages.
yes, remove all the CO2, and all the plants die, and the human race is not far behind. you can kiss your ass goodbye if all the plants die.
No one is saying we should remove all the CO2. It’s about returning CO2 to reasonable levels.
CO2 is at the Optimal level right now
Yeah I guess if you like extra droughts and wildfires and deadlier hurricanes? Not my idea of optimal.
So we need to stop emitting CO2 right now or it will go out of optimal levels very quickly?
What is a reasonable level in ppm.?
Climate scientist James Hansen has suggested that we should try to limit CO2 to 350ppm, although for thousands of years, natural cycles didn’t bring it above 300ppm: https://climate.nasa.gov/vital-signs/carbon-dioxide/
Why 350. Cause it’s a little lower then 400?
All human civilization and agriculture developed when the CO2 level was about 280 ppmv and the (mean global annual surface) temperature was 286-287 K. Serious deviations from that either way have the potential to badly disrupt our agriculture and our civilization.
That is ridiculous. Those levels would produce Plague. Famine and War, just as they did during the Little Ice Age. Why would you want to go back to a climate that was bad for 700 years ? This mystifies me.
Agriculture is up and will continue to go up with increased co2.
Decreasing co2 will lead to more starvation and more war.
…at least you see the true impetus. The entire GHE is predicated on the economic model of war mongers.
This is all nonsense. CO2 drives water vapor out of air per the Le Chateliaer Principle. H2O absorbs 7 time as
much IR energy as CO2 per molecule so the temperature
drops! It does not rise. This is easily demonstrated with
a large bottle, baking soda and Vinegar.
So, what is your opinion of what a “reasonable level” of CO₂ is? Do you think that during the Ordovician period when the CO₂ level was at 2,240 ppm and the Earth survived that was a “reasonable level”?
Yeah, the Earth has survived a lot of things. For millions of years, the surface of the planet was molten from being struck by so many asteroids and other space debris, and the Earth survived. So I guess it’s ok to return to those conditions, too? Just because the Earth has survived hell, doesn’t necessarily mean the human species can or will. Climate change is already causing a lot of human suffering, and it could get worse if we let it — does that just not matter to you? Do the profits of fossil fuel companies matter more than human lives?
Is CFC no more depleting the ozone? Is CO2 blanketing the atmosphere at the moment?
Have you ever though considered an alternative world to fossil fuels? In 1820 86% of the entire world lived in extreme poverty, of which only 12% of the world were literate. Planes have made us less xenophobic, & civilised in a really short period of time. How would we all get around today otherwise, certainly without assembly lines? ‘Horseback’, or steam-fueled modes powered by wood, ‘all’ things powered by wood. Wood we don’t have to spare. Streets caked in manure. Meat & milk reliance. Even if due to mortality, the population was just 3 billion today, it would be a planet of ruminants, undrinkable water, and deforestation. No satellites to help us know about the Earth. Sub out that 3% Co2 we’ve added for a ‘lot’ more methane. And for the fear CO2 lives a long time, it also becomes exponentially ineffective at warming beyond saturation, as the IPCCs formula demonstrates. Doubling all the CO2 in the atmosphere today (to 800ppm) would see 0.06 degrees C of warming by 2100, according to that formula. Isn’t this purely in the hands of cloud formation and weather systems? Positive & negative feedbacks? How can it not be? How would we know if we’ve
not spared the planet from global cooling if negative feedbacks had gathered momentum centuries ago? What if our CO2 prevented that from occuring? Whether water vapour is an effect or not, it’s still the major player. I find it odd in the 2000s NASA articles stated how the ozone hole had wreaked havoc with the climate & seen masses of water vapour end up in the sky. Aren’t we just trying to decide why more water is in the sky? I just don’t feel like an experiment with bottles cuts it. If the climate has never changed drastically in short periods of time before, how does adding 3% of something cause sudden extreme change? I’m aware feedback loops should exercise caution, but the Earth seems to have arrived at pretty impressive regulation systems. Maybe we just don’t understand them yet because we have about 60 years of semi-reliable data. A century ago to measure the ocean we’d pull up a bucket & pop a thermometer into it.
Survived??
180 ppm is just Surviving.
4000 ppm grew enough food to feed dinosaurs.
Dinosaurs would starve today!
John Kerry is:
Neither John Kerry or anyone else is suggesting that we eliminate all CO2 from the atmosphere (which is neither possible or desirable). If you read the quote above carefully you will note it says “net zero”, which means getting to the point where our CO2 emmissions are no longer increasing the CO2 concentration in the atmosphere. He is also warning that he thinks getting to “net zero” would insufficient to avoid the long term effects of climate change because current levels are already too high and we will therefore need to find ways to reduce the concentration to safer levels.
I thought net zero meant putting out no more than can be reabsorbed by the earth’s soils, rocks trees, oceans..with the number of people on the planet, the amount of activity, I think it will be a tall order to get to the point where there is no more Co2 being emitted..it would have to be a very basic, frugal existence. If you look at the ‘prospects’ for electric vehicles, as one example, doubts are already surfacing about how viable they are on a mass scale..
how?
But how can we remove it from from the atmosphere yet daily industries are evolving
And what scientific reasonable co2 level would that be?
150 ppm is plant death.
420 ppm is better but still in co2 starved condition.
1500 ppm is a good level for these starved co2 plants we have today.
4000 ppm is some of earth’s strongest/healthiest times when mammals were ten times the size.
However, at concentrations above 1%, CO2 may start to affect [4]:
(or 1000ppm)
https://labs.selfdecode.com/blog/carbon-dioxide-poisoning/
Plus buildings have issues with ventilation so a 1000ppm outdoor setting would have much more inside.
check your maths mate. 1% = 10 000ppm
The Earth didn’t have 9 billion people living on it when co2 was 4000 ppm. In India right now people are dying from the existing conditions because they can’t afford air conditioning or they have to work outside when the temperature is 114F with 60% humidity. For Mediterranean climates like California, Spain, Portugal, southern France, Italy and Greece a couple of degrees hotter could mean a desert. Just look across the sea. Billions of people will have to migrate to avoid death. Small countries can’t afford to have thousands of people even walking through their country. The US the richest country in the world is having trouble dealing with 3000 people a day. The war in Syria was the result of a drought causing people to lose their livelihoods and because they were a different sect than the people living within the Capital, the government decided it was cheaper and they thought easier to bomb them out of existence than to provide welfare for them. This situation caused hundreds of thousands of deaths and the largest migration in the world’s history.
Don’t just think of the plants, think of the people and other animals too.
Strive to improve, protect, serve, sufficient, prosperous, resilient, peaceful, Civil and Wild Life on Earth.
What is the rate of decay of CO2 to return to reasonable levels?
But the solution doesn’t seem reasonable at the present time.
It’s not only the plants, the Earth’s largest lungs are planctons who’ll extinct if the temp of the sea rises a bit…. That will kill the plants as well everything else, and all just because co2 rising levels
But the plants are being fed CO2 right
I am strugling to find a percentage, or range of percentages showing the proven human activity responsible for the global warming. This is a question I get stumped with by sceptics. Is there unquestionable data and science to support that, say, 70% to say 90% of the increase in temperature is proven to be a result of human activity? While CO2 modelling I appreciate is complex, does the science (at a molecular modelled level) show without question that the increase in CO2 in our atmosphere causes the associated increase in termperature we measure. While I can see the data graphs that imply this, is there detailed modelling that supports this? I am working with the IMechE to have a supportive presence at COP26 and, while I just want to clean up our planet regardless, I need good back up when I field questions from sceptics.
Hi John,
The obvious retort to sceptics is that many ideas essential if mainstream views are correct make sense even if climate change were a damp squib or temperatures fell e.g following a major volcanic eruption like Tambora in 1815. For that matter they work if a major food crop collapses. Typical actions include reducing waste, silviculture, regenerative agriculture, alternatives to fossil fuels (whose extraction can be polluting or destructive), fewer cash crops, combining conservation with careful use and cutting the impact per head and probably numbers of conventional livestock. These win-win options are effective no matter what. Instead the last few decades have seen huge debate on climate change rather than doing something effective to cover all bases.
All the recent warming can be attributed to human activity. If you add up all the natural forcings, the Earth should be slowly cooling. It’s only when you add the artificial ones that you get warming.
how is the temperature measured ? where do stick the thermometer ?
We can measure how much IR is coming off of the earth for starters.
There’s no good back up. Once, it was CFC depleting ozone layer. Nowadays, it’s CO2 blanketing the atmosphere. The good concept is that the entropy of the universe increases but never decreases. As the entropy increases the temperature rises. The randomness of occurances is called ENTROPY. This can be seen from the ice age glacier and interglacial zillions of years ago. The universe climate is irreversible. Therefore, heat death is a state where there’s no structure but constant temperature .
I have some question, When the sunlight hit the ground it transforms into infrared light, when the infrared light hit the CO2, shouldn’t the wavelength changed too?
My understanding is that when sunlight hits the ground, it heats the ground. Because the surface of the sun is so hot, the radiation is mainly in the visual, i.e. at relatively short wavelengths. The ground is radiating back, but because the ground is so much less hot, it radiates at longer wavelengths, i.e. in infrared. The sunlight is not transformed directly. It is the net result of absorption and emission by the ground. If CO2 is then heated by infrared radiation, and the temperature is not much different, it should re-emit the radiation in about the same wavelength.
So does Co2 absorb and emit radiation or does it block it ?
The article talks about radiating, but the experiment you show seems to show blocking. Shouldn’t we see the Co2 absorb the heat and re radiate it ? Of course the experiment is faked anyway. That is a laboratory FLIR. Camera. It can show temperatures in at least 4000 colors . But the only thing it shows at all is the candle flame. Therefore the sensitivity on the expensive FLIR camera is cranked down so low it only registers if something is on fire. Then he fills the chamber with gas from a cylinder. That comes out very cold. The carbon dioxide which is cold, would have to be on fire to register on the misadjusted FLIR cam, and so effectively blocks the flame like a cold smoke screen. Then he cuts it short. I’m sorry, that is fakery to fool children.
The CO2 scatters the infrared by absorbing it and reemitting in all directions — which is exactly what the video claims to show. Since some of the infrared is bounced back to the source, it is often characterized as “blocking.”
But it doesn’t show that at all. It only shows that the cold gas blocks infrared for few seconds, to a badly adjusted FLIR camera.
Unfortunately, neither you nor I know the exact conditions of the experiment and what temperature the CO2 gas was at. However, climate scientist Jason Smerdon says that even if the gas was cold, the IR from the candle would still transmit directly to the camera if the gas were not interacting with the IR radiation. So, the experiment shows that the CO2 is scattering the IR, regardless of the gas’s temperature.
It’s also worth noting that even if there were a problem with the experiment, scientists know from many other lines of evidence that CO2 absorbs and scatters infrared energy — that fact of nature does not hinge on this one Youtube video.
Hi James, here’s a slightly experiment where cold CO2 is definitely not an issue, and it shows the same results: https://youtu.be/Rt6gLt6G5Kc?t=107 Hope this helps
How come experiments that claim to prove CO2 is a key driver of AGW use CO2 concentrations at exaggerated levels instead of the .03% to .06% we are concerned about.
I think this paper reflects a more realistic experiment. The Influence of IR Absorption and Backscatter Radiation from CO2 on Air Temperature during Heating in a Simulated Earth/Atmosphere Experiment: uhttps://www.scirp.org/journal/paperinformation.aspx?paperid=99608
If Mars is 95%co2 how come it is not hotter. My last question is what happened to the sunspots. Did the industrial revolution cause that too?
Most of Earth’s greenhouse effect comes from water vapor and clouds, which together account for about 25 K of the Earth’s 33 K difference from the radiative equilibrium temperature (CO2 accounts for most of the rest). Mars has a very dry atmosphere. In addition, its atmospheric pressure is very low, so the absorption lines are not pressure-broadened the way they are on Earth, and the greenhouse effect is less effective. Lastly, Mars receives much less sunlight than Earth. Despite all this, Mars does wind up with a greenhouse effect of about 4 K (radiative equilibrium temperature is 210, emission temperature is 214).
Because Mars is further away from the sun and has less atmosphere to keep the temperature in.
If CO2 is not responsible for temperature increases why is Venus hotter then Mercury?
Indeed the climate is changing and CO2 certainly seems to be playing a role. However, I find the statement “Unfortunately, we don’t have thousands of years to wait for nature to absorb the flood of CO2. By then, billions of people would have suffered and died from the impacts of climate change; there would be mass extinctions, and our beautiful planet would become unrecognizable” to be coming out of thin air. The climate has changed in human history (medieval warm period, ice ages) and humans have always been able to adapt. Why would this climate change be different? “Billions dead” ? Why?
Droughts, wildfires, extreme heat, hurricanes, sea level rise, infectious disease — climate change makes all of these things worse, and the climate is changing faster and more dramatically than in all of human history. Surely we can and will adapt, and a big part of adapting means moving away from fossil fuels.
Recently, I became embroiled in an online debate on the subject of anthropogenic global warming (“Claim”) originated by a talk radio host, who was hostile to the claim of anthropogenic global warming. Some responders were outright abusive, but one at least posed the following counter-arguments to the Claim:
(1) “So one of you educated climate alarmists please the explanation of how CO2 in the atmosphere is capable of increasing its fingerprint absorption wavelengths of 2.7, 4.3, and 15 microns so that it can absorb more than 8% of the infrared spectrum that it already does” “Don’t give me the ‘broadens its wings’ explanation b/c that only accounts for about 1.7% increase when the CO2 is doubled” (explanation offered by the IPCC)
“Since the science is ‘settled’, you no doubt have that explanation handy and it will no doubt be in peer reviewed form”.
(2) “Explain while the dilution of the CO2 molecules by other molecules is ignored. Every CO@ molecule in the atmosphere is, at current concentration, surrounded by 2500 other molecules. In order for CO2 to heat the atmosphere to just one degree, the CO2 molecule would have to start at a temperature of 2500 degrees C.
(3) “Also, explain why the climate scientists use the Stefan-Boltzmann constant incorrectly to explain radiation from the air to the ground. (The) Stefan-Boltzmann constant is how much radiation is given off an OPAQUE surface at a given temperature.”
This was actually the least contentious response. I was just wondering how anyone at Columbia would answer these counter-arguments.
https://news.climate.columbia.edu/2021/02/25/carbon-dioxide-cause-global-warming/
Dr. Fecht:
I did read the article, which was very informative. I was informed by someone else that the Stefan-Boltzmann constant is not used in the more current, detailed models, which accounts for “Challenge” 3. Challenge 2 seems a bit absurd, and is a thermal transfer issue. The one that kind of confounded me was Challenge 1, an atmospheric chemistry issue. Would have something specific to say about this one, say if it was posed directly to you?
Thank You
1) A quick thought experiment.
Average moon temperature 133.15K (quick guess based on google searching)
Average earth temperature 293.15K (Another guess based on a guess of 20C average)
160K difference due the greenhouse effect.
1.7% of that works out at 3 degrees of warming
You forgot to mention the earth is bigger and has a liquid metal core.
I would like to know what is the way that carbon dioxide involves global warming
If you see the earth as a ball receiving energy (from the sun) and emitting energy (infrared due to the earth’s temp), you may understand that in the long run , incoming and outgoing energies must be equal.exept for storage changes. So all outgoing energy is infrared.
From infrared spectroscopy we know some gases absorb infrared energy in the infrared area. CO2 is one of them as is H2O vapour.
Gasses like CO2 do not only absorb infrared radiation, but they also re-emit the same radiation, , this time in whathever direction, partly back to the earth.
If you would measure the infrared output of the earth at sealevel and you would measure this outside the atmosphere, you would find a difference.
in certain bands, much less infrared energy leaves the earth. If this energy does not leave the earth, it can only heat it. Wenn the temperature of the earth rises a little bit, the earth starts emitting more infrared energy, so balancing again, at a sligtly higher temp.
Hi I was wondering how does carbon dioxide have a big impact on global warming. I was just wondering for a school project.
Be sure: You will not get an answer here.
I find many of these answers far too simplistic and not nearly quantitative enough to satisfy my curiosity.
I note that the insulation response involves elements of convective resistance, conductive resistance and radiative resistance. In all cases it is a logarithmic function and not linear. Why no mention of any of these factors when it comes to CO2? Doesnt each doubling of CO2 halve its already minuscule IR absorption factor? If so shouldn’t you point this out so your followers are not unduly alarmed
I also note that the hottest areas on Earth are found in dry, below-sea-level valleys located in temperate zones. This correlation appears to have nothing to do with CO2 concentrations. The hottest official temperature that ever occurred on Earth occurred at Greenland Ranch in Death Valley in 1913 long before the heavy use of fossil fuels were in effect. How can this be? Are we cherry picking only the factoids that support our preferred premise?
My own idea is that moist air carries far more thermal inertia than dry air and yet the two are treated identically by using simple average temperature. Aren’t joules/mass the appropriate metric for the effect of heat trapping gases?
Further, how far must IR radiation travel before encountering a CO2 molecule that absorbs its energy at .04% concentration at standard temperature and pressure? Once absorbed doesn’t this energy lead to convective forces carrying the molecule into lower pressure zones at higher altitude before losing its energy to other cooler molecules. There are endless complexities to these energy transfers that I have never heard explained satisfactorily, other than with the typical simple bromides.
Moreover, more CO2 can’t simply mean increased oceanic evaporation because if that were true there would be runaway evaporation causing more greenhouse gases until the oceans boiled away. Clearly there can be no positive feedback associated with increased evaporation. I might suggest that cloud cover of all types have a great deal of influence over regulating radiation flux impinging on the surface. No mention of any of this – why?
Lastly your spectrum of greenhouse radiation chart (above) makes no mention whatsoever of water vapor with its broad spectrum of IR radiation absorption making it the only significant greenhouse gas and often completely masking the effects of any additional CO2 interference
If I understand you correctly, you want to adress 3 points.
What is the quantative relation between absorbtion and concentration for CO2?
Such issues are very well known in standard Chemical analysis, Any good chemistry book on spectroscopy can help you further.
The relation between amount of water vapour in the air and temperature.
You state correctly that dry area’s have the highest temperatures. This is very well known in all desert area;s around the world. However, only at daytime, the nights are cold.
In general, very unevenly distributed water vapour levels, both by region as by height, makes understanding and calculating very difficult.
CO2 levels, which are, contrarely to water, evenly distributed around the world, have virtually no influence on local temp. differences.
Your third point:,”” more CO2 can’t simply mean increased oceanic evaporation”” is incorrect. CO2 has an independent (its own) contribution to earths temperature and thus to oceanic evaporation.An associated positive feedback can be a moderate one, it does not automatically mean an explosive one.
Thanks for affirming my point that measuring the actual heat retaining characteristics of our complex atmosphere is difficult. I have always suspected as much.
Can you address another question I have regarding the IR heat trapping capabilities of atmospheric CO2. I have a very image oriented mind and here is the image I conjure up regarding the phenomenon.
Sol generated photons of some arbitrary wavelength eventually pierce the atmosphere to strike (interact) with atoms/molecules of the Earth’s surface thereby raising their energy level. These atoms/molecules in turn transfer their excess energy by conduction/radiation to adjacent particles who which selectively lose energy by emitting photons of a wavelength that CO2 molecules can catch. Since the solid angle of these emitted photons will occur in any random x,y,z coordinate, only 50% should be “sky bound” Correct?
At some point CO2 does its job of catching a sky traveling photon only to re-emit it at another random solid angle. Presumably half of all these photons will emerge in the hemisphere headed back towards the solid Earth, the other half will continue in some random skybound direction. To my simple way of thinking the net effect of these interactions is zero
Where have I gone wrong in my thinking ?
The planet Mars has an atmosphere of 96% CO2 but a surface temperature of -62°C (-80°F) shouldn’t the planet be a bit warmer than this if CO2 traps heat even allowing for the thinner atmosphere and a further distance from the Sun that the Earth?
I just want the temperature to be 70 degrees F constantly, worldwide, how would I go about accomplishing that?
Impossible.
Suppose, it was 70 degrees worldwide, so emitting roughly equal amounts of IR radiation per square meter everywhere, where would that energy come from ?, the sun?, no way.
Impossible.
Why are most, if not all, of the UN’s IPCC temperature models over the past 20 years showing temperature increases much, much higher than what has actually happened? And that’s even with RSS temperature models cooling the past and warming the present more and more with every new model version? If the IPCC’s models can’t have at least an average error over and under actual temperatures, measured by a obviously biased-to-warmth RSS model set, then how can we ever believe the CO2 alarmist’s calls to action on climate change?
All the models fail because only parameterizations instead of established meteorological equations. Plus, since none of them can replicate past climates — they can’t predict the future. However, I have found some proof of human-caused climate change … https://www.youtube.com/watch?v=2BPsloM04R0
How Exactly Does Carbon Dioxide Cause Global Warming?
BY SARAH FECHT |FEBRUARY 25, 2021
The article notes that ‘Water is indeed a greenhouse gas (and) it absorbs and re-emits infrared radiation, and thus makes the planet warmer.’ The article also notes that ‘warmer air holds more water’
This appears to suggest an uncontrolled feedback loop where warmer air holds more water in turn making the planet warmer.
The article also notes that ‘temperature determines how much moisture can actually be held by the atmosphere.’ Again suggesting the possibility of an uncontrolled feedback loop.
Although most water drops out of the atmosphere as rain there is still significant volumes of water in air across the globe where the temperature is above the dew point.
These natural volumes of water in air appear to be significantly in excess of the volumes of CO2.
Indeed the volumes of water being injected into the upper atmosphere by aviation contrails have had the effect of increasing the level of atmospheric water through a mechanism that has not existed in the past.
Given that both CO2 and H2O are greenhouse gases the article does not seem to address how we can measure the relative influence of the two gasses.
The article addresses this issue. We can lower the amount of water in the atmosphere by lowering the temperature. We can lower the temperature by reducing carbon emissions.
Thank you for the prompt response and appreciate your feedback that we can lower the temperature by reducing carbon emissions. Given the clear evidence of global warming what is the scientific explanation for the way in which carbon emissions absorb more sunlight than water vapour.
I Think water vapour absorbs more, but 2 aspects might be considered.
Sorry but I keep hearing this..H20 or water is a gas ?? it’s water !
The author seems to have forgotten that plants take up CO2. There will be better plant growth with more CO2. Insufficient CO2 will make a block to plant growth. There are more people on the planet, surely we need more plants to grow more food?
The author of this comment seems to have not read through to the end of the piece.
I want to propose a different perspective on the way we should looking.
Look only to energy in and energy out at the very outside of the worlds atmosfere.
Use minds experiment.
Use a world with a normal airshield, but without CO2.
We use long term stable temp., incoming energy (sun) and outgoing, let’s say at a 50 miles border outside the world( IR radiation), must be equal.
Now we add CO2.
From spectroscopic data we read that outgoing energy is far less in the CO2 absorbtion window.
see eg.:
https://www.physi.uni-heidelberg.de/~eisele/schuelerlabor/SpektroskopieUmweltphysikExperimente.pdf
We started with incoming and outgoiing energies are equal in stable temp. conditions. As the sun is still the same and less energy is emitted in the greenhouse absorbtion bands, the temp starts raising untill the emitted IR once again , aquals thes sun’s
The earth can be considered what in physics is a black radiator. Its behavior can easily be calculated using a formula.
The rising temp. of the earth leads to more IR radiation, outside the greenhouse windows, leaving us forever.
Now we have a stable and equal situation again,
The energy not leaving the earth in the greenhouse windows equals the energy difference between the 2 black radiators is thus easily calculable.
A simplified way of calculating is:
1/ the energy blocked in the greenhouse gas window is expressed as a percentage of total IR radiation. example 5%
2/ the extra IR energy emitted by the black radiator (the earth) per degree temp raise is expressed in percentage of total IR emitted, example 2%.
Now the earths temp. raise is 2.5 %
sorry, 2.5 degrees of course
In the climate discussion the fate of excited CO2 molecules in the earth’s atmosphere has been ignored. The amount of CO2 in the atmosphere is widely believed to be responsible for global warming due to human activity. The IPCC explains the greenhouse effect in the atmosphere in their frequently asked questions as follows: “Much of the thermal radiation emitted by the land and ocean is absorbed by the atmosphere, including clouds, and re-radiated back to Earth. This is called the greenhouse effect.”
The mentioned greenhouse effect of CO2 is not in accordance with the molecular properties of CO2. These have to be treated quantum mechanically. The interaction with radiation as well as intermolecular interactions are described by quantum mechanics.
There are selection rules for possible energy transtions in molecules. Vibrational transitions are limited to molecules whose electric dipole varies during the vibration. This exclude homonuclear diatomic molecules such as O2 and N2 . For rotational transitions, the molecule must have a permanent electric dipole. This excludes homonuclear diatomics, with the exception of O2 which has a triplet electronic ground state allowing magnetic dipole rotational transitions. Therefore O2 is important in cooling the earth by emitting radiation from rotational states.
The radiative lifetime and collisional deactivation of vibrationally excited CO2 have important consequences for its ability to emit infrared radiation under atmospheric conditions. CO2 in its vibrational ground state may be excited to its vibrational excited state
CO2 (0110) by radiation with wavenumber 667.4 cm-1.This is the strongest infrared absorption of CO2 and therefore the main process for excitation of CO2 by infrared radiation from the earth’s surface. The vibrationally excited state CO2 (0110) emits radiation with a rate constant kr = 2.98 s -1 This state may be deactivated in bimolecular collisions with CO2 and N2 in their vibrational ground state. The deactivation rate may be calculated using data from J. A. Blauer and G.R. Nickerson, A survey of vibrational relaxation rate data for processes important to C02-N2-H20 infrared plume radiation. Prepared for Air Force Rocket Propulsion Laboratory, October 1973, Distributed by National Technical Information Service, US Department of Commerce, 5285 Port Royal Road, Springfield VA. 22151.
The rate constant for bimolecular deactivation by ground state CO2 or N2 depends on temperature T. For instance in the case 200 ppmv of CO2 in the air the rate of deactivation by collission with N2 amounts to 6.8 x 1014 s-1 at 288 K at ground level and to 5.5 x 1010 s-1 at 198.5 K and 80 km and above sea level. This means that as soon as a CO2 molecule gets excited by absorption of surface IR radiation to the state CO2 (0110) it has a negligible chance of emitting a photon. Therefore the entire observed 667.4 cm-1 radiation from the atmosphere must arise from the Boltzmann population of the state CO2 (0110). This holds even if the CO2 concentration is doubled. Therefore the statement of the IPCC concerning back radiation is untenable. Any observed 667 cm-1 radiation in the atmosphere originates from the sun, directly or through Raleigh scattering by CO2 in the upper atmosphere.
Oef, quite a bit, if I understand you correctly, You think CO2 molecules remain in their excited state for a longer time, making them inactive for further action.
Not from theory, but from real measurements, we know that in the CO2 window, the IR emitted at sealevel is far larger than outside the atmosphere, proving there is constant absorbtion.
How do you explain this.?
Dear harrie geenen,
Note that one day after I posted my comment, I saw that there were serious typographical errors in the representation. I submitted a revised version with a different notation of powers of ten. Please adhere to the new version.
The particular excited vibrational state of CO2 has a radiative lifetime of 1/kr = 336 ms. That would be the lifetime under collision free conditions. However under atmospheric conditions the excited molecule suffers many collisions during that period which convert the excitation energy into translational and rotational energy of the collision partners.
Denote the rate constants for quenching the 667.4 cm-1 emission by collisions with CO2 or N2 respectively by k1(T) and k2(T). The concentrations of CO2 is denoted as Ω(CO2). It is given by Ω(CO2) = FC * (DA / MA) [mol / m^3] where the molar mass of air MA = 0,289644 kg / mol. DA is the local density of air, FC is the fraction of CO2 in air.
The quantum yield Φ(T) for emission of radiation by CO2 (0110) at temperature T is given by Φ(T) = kr / { kr + k1(T) + k2(T) }.
Denote the number density in the Boltzmann population of the excited state CO2(01^10).for the given temperature and fraction of CO2 by N(BEC,T). It is given by
N(BEC,T) = A x Ω(CO2) x exp{-667.4 / (kB x T)}
where A is Avogadro’s constant, kB is Boltzmann’s constant. Their values are A = 6,022 x 10^23 and kB = 0.6952 cm^-1 / K.
The number of photons NP emitted per second by CO2(01^1 0) is given by
NP(T) = Φ(T) x N(BEC,T) x kr / s
With the energy EP of a photon at 667.4 cm^-1 = 1325.4 x 10^-23 J, the amount of energy E(667 cm-1 ) radiated per second from 1 m3 air is given by
E(667 cm-1 ) = NP(T) * EP [J /s]
The values of E(667 cm-1 ) obtained in this manner in the case of 200 ppmv are:
1.56 x 10^-11 J /(s m^3) at 288 K and 0 km above ground and 6.51 x 10^-12 J /(s m^3) at
198.5 K and 80 km above ground.
Clearly more energy is radiated at ground level. The basic reasons are that both the thermal energy kB x T and the density of air larger.
With regard to the satellite measurements, I wonder what the technical details are. Such as the exact radiation frequency and bandwidth selected for detection and how an intensity profile as a function of height above ground is extracted from the total energy measured.
Although CO2 does not reemit radiation, its effect on radiative transfer is evident above 60 km height. There it contributes to absorption and scattering of direct solar radiation on its path to the earth’s surface. At heights above 40 km interaction of high energy solar particles can lead to destruction of CO2. Capture of electrons emitted from the sun may produce the anion CO2−.Reaction of CO2 with solvated electrons in water droplets will also produce the anion CO2−. Photoionization of CO2 yields the cation CO2+. Excitation by 150 -210 nm radiation leads to photodissociation of CO2. These photo products of CO2 can react further with other intact components of air or their photo products. For instance the anion CO2− reacts with H2O yielding hydrocarbonate and formate anions. At 50 km height with 400 ppm CO2 and 25000 ppm H2O, the collision rate between CO2 and H2O molecules is calculated to be 6.14 x 10^33 / (s m^3) . Prior to electron autodetachment the anion CO2− has a lifetime of 30-60 μs. During its lifetime there are many collisions with H2O to cause reaction. The processes mentioned above initiated by solar radiation decrease the concentration CO2 at heights above say 40 km, resulting in both more 667 cm-1 solar radiation reaching ground level and less Raleigh scattering of it into space.
Finally, I want to stress the importance of radiation from rotational states of O2 in cooling the planet. A result of burning materials is the consumption of O2. Photosynthesis in plants, bacteria and algae repair the damage by producing O2 from CO2. This may not fully refill the loss of O2 as forests are destroyed. It would be helpful to find if the concentration O2 in the atmosphere is affected by human actions.
Unfortunately superscripts and subscripts were ignored in the representation of my comment 2053342. Therefore I modified the text to indicate superscripts with the symbol ^. Powers of 10 are now represented as 10^.
6.8 x 1014 s-1 had to be 6.8 x 10^14 / s and 5.5 x 1010 s-1 had to be 5.5 x 10^10 / s. The revised version of the comment appears below.
In the climate discussion the fate of excited CO2 molecules in the earth’s atmosphere has been ignored. The amount of CO2 in the atmosphere is widely believed to be responsible for global warming due to human activity. The IPCC explains the greenhouse effect in the atmosphere in their frequently asked questions as follows: “Much of the thermal radiation emitted by the land and ocean is absorbed by the atmosphere, including clouds, and re-radiated back to Earth. This is called the greenhouse effect.”
The mentioned greenhouse effect of CO2 is not in accordance with the molecular properties of CO2. These have to be treated quantum mechanically. The interaction with radiation as well as intermolecular interactions are described by quantum mechanics.
There are selection rules for possible energy transtions in molecules. Vibrational transitions are limited to molecules whose electric dipole varies during the vibration. This exclude homonuclear diatomic molecules such as O2 and N2 . For rotational transitions, the molecule must have a permanent electric dipole. This excludes homonuclear diatomics, with the exception of O2 which has a triplet electronic ground state allowing magnetic dipole rotational transitions. Therefore O2 is important in cooling the earth by emitting radiation from rotational states.
The radiative lifetime and collisional deactivation of vibrationally excited CO2 have important consequences for its ability to emit infrared radiation under atmospheric conditions. CO2 in its vibrational ground state may be excited to its vibrational excited state
CO2 (01^10) by radiation with wavenumber 667.4 cm-1.This is the strongest infrared absorption of CO2 and therefore the main process for excitation of CO2 by infrared radiation from the earth’s surface. The vibrationally excited state CO2 (01^10) emits radiation with a rate constant kr = 2.98 / s. This state may be deactivated in bimolecular collisions with CO2 and N2 in their vibrational ground state. The deactivation rate may be calculated using data from J. A. Blauer and G.R. Nickerson, A survey of vibrational relaxation rate data for processes important to C02-N2-H20 infrared plume radiation. Prepared for Air Force Rocket Propulsion Laboratory, October 1973, Distributed by National Technical Information Service, US Department of Commerce, 5285 Port Royal Road, Springfield VA. 22151.
The rate constant for bimolecular deactivation by ground state CO2 or N2 depends on temperature T. For instance in the case 200 ppmv of CO2 in the air the rate of deactivation by collission with N2 amounts to 6.8 x 10^14 / s at 288 K at ground level and to 5.5 x 10^10 / s at 198.5 K and 80 km and above sea level. This means that as soon as a CO2 molecule gets excited by absorption of surface IR radiation to the state CO2 (0110) it has a negligible chance of emitting a photon. Therefore the entire observed 667.4 cm-1 radiation from the atmosphere must arise from the Boltzmann population of the state CO2 (0110). This holds even if the CO2 concentration is doubled. Therefore the statement of the IPCC concerning back radiation is untenable. Any observed 667 cm-1 radiation in the atmosphere originates from the sun, directly or through Raleigh scattering by CO2 in the upper atmosphere.
I hope we can agree on the fact that in the CO2 window, there is a constant strong absorbtion of the infrared radiation originating from the earth.
There are 2 possibilities to release this energy again,
1, by emitting IR radiation, what the IPCC sees as dominant, in any direction, partly into space, partly back to earth. In reality, not a single action, but many absorbtions and re-emittings.
2, what I think you are meaning, by colliding to other molecules.
In this case the greenhouse effect would be larger.
In the radiation option, a part is kept here and a part goes in space and is lost.
In loosing energy through collisions, all energy remains here and the greenhouse effect would be a lot stronger.
In principle both effects could be working but there would be a difference in the thermal gradient from the earth to the outside off our air layer.
By measuring this gradient, one can calculate the relative contributions.
If there would be no other greenhouse gasses, outher CO2, and all absorbed IR radiation would be transferred into heat (collisions), we would have an inverse thermal gradient, so hottest high in air and cooler closer to earth.
harrie,
I do not agree with your statement that in the CO2 window, there is a constant strong absorbtion of the infrared radiation originating from the earth.
The earth is not a black body. The materials of which the earth surface consists are not homogeneously distributed. Different constituents have different emission spectra. Therefore you have to distinguish were the observations are made. Above sea or above forests or above desserts? With regard to CO2 we may restrict the discussion to vibrational and rotational transitions. Vibrational transitions are in the infrared and rotational transitions in the microwave region of the electromagnetic spectrum. Energies within molecules are quantized. That means that only radiation with specific frequencies are absorbed or emitted. The probability for absorption or spontaneous emission at such frequencies depends on the magnitude of the corresponding transition moments. The important question is which constituents of the earth surface emit radiation at the specific frequencies required for these transitions in CO2 at the actual surface temperature. I did not came across the relevant data. One thing is certain, transfer of energy from the earth surface to molecules is possible without involvement of radiation, namely when they collide with the surface.
The thermal gradient in the atmosphere is a consequence of the gradual reduction in pressure as the height increases, arising from the action of gravity. At constant volume the temperature drops according to the ideal gas law:
P V = n R T with n the amount of substance and R the gas constant.
The temperature gradient has nothing to do with global warming due to human activity.
increased emissions of CO suppress the oxidative capacity or power of the atmosphere which leads to more CO2 and stronger greenhouse effect. Many blame Co2 as the main cause of global warming while the CO is actual problem and prevents CO2 from functioning naturaly. Am I correct?
So if CO2 reflects infrared radiation coming from earth, wouldn’t it also reflect radiation from the sun back into space?
Yes, but it reflects back far more infrared than it does visible light. So the visible light can reach the earth and turn to heat. Part of the heat which would previously escape as infrared is now trapped.
what is the average distance an infrared photon travels before encountering a CO2 molecule at 400 ppm and STP?
As water vapor concentration is roughly 100 times bigger than CO2 and it also traps infrared light .Why it is ignored ?
Isn’t “ambient air only 0.004 % CO2? Then how can a “hollow tube filled with CO2” be valld test? Why don’t they use ambient air and try the same experiment?
You stated “Before humans began burning fossil fuels, naturally occurring greenhouse gases helped to make Earth’s climate habitable. Without them, the planet’s average temperature would be below freezing. So we know that even very low, natural levels of carbon dioxide and other greenhouse gases can make a huge difference in Earth’s climate.” Haven’t you ignored the large effect of water vapor when you conclude that “even very low” CO2 and “other greenhouse gases can make a huge difference” Didn’t you just incorrectly imply that water vapor percentage is “very low” by not mentioning it or its effect is minimal? Neither is true are they?
The runaway Greenhouse effect on Venus is not real. It goes as follows: During the cosmic bombardment; when the planets were molten rock, Venus and Earth received water through millions of meteorites that were constantly crashing into the planets. On Venus, being much closer to the sun, water never got the chance to condensate to water. So all the water received, built up as vapor from the start. The pressure kept increasing while it received more water until the level we see today. It never got a chance to form oceans and rivers. The energy that Earth receives from the sun is less so oceans could form. With the energy that Earth receives from the sun it is a physical impossibility to trigger a runaway greenhouse effect like on Venus. Whatever we do, even if we burn every last grain of coal and drop of oil, we will never completely destroy earths life sustaining climate. All fossil fuels come from a vibrant earth full of life, if we recycle all that dead carbon back into the atmosphere and into new life, the total biomass on earth will be similar than that of the time all fossil fuels formed; millions of years ago.
i didn’t read the whole paper, but the response was unresponsive
re: co2. the response referred to many or all greenhouse gases,
and didn’t address CO2 contribution solely.
Ha! I wonder who came here solely because of online school.
A better experiment would be to have 3 large containers – one containing earth’s atmosphere with no CO2, one with atmosphere of 0.025% CO2 and one with atmosphere of 0.04% CO2 (present level). Apply exactly equal heat to all 3 containers in a controlled environment for the same length of time. Then see how much more or less heat each container retains over a period of time.
im new to this global warming and climate change and i was looking for how much the earth temperature increases for the past 150 years (from 1850-2000). i have no idea about this 0.177±0.052°c. what does the temperature in the left and right is for? thank you so much.
I’m not sure where you found that. Every climate center in the world has different growth rates since 1850. They all hover around 1.7 degrees C for the time period in questions. You can easily download their data by searching for Global Temperature History … followed by the site: NOAA, NASA, Berkeley Earth, UK Met Center, Cowtan-Way, Japan Meteorological Organization.
Excellent science. But the title is misleading. The title makes the assumption that CO2 only has one climate-change property–Greenhouse. Let’s be specific.
CO2 has three climate change properties that are well documented. Co-Aerosol that cools the planet from aerosols associated with anthropogenic CO2. And Green, the huge effect that CO2 is having on type C3 flora that cools Earth. So one warming property and two cooling properties.
The way to discover the “full” effect of CO2 is to look at the past 60+ years of real-time CO2 cause-effects on global temperature and the results are quite clear. The highest annual increases seen in CO2 precede global cooling. The lowest increases seen in CO2 annual increase precede explosive global warming. Please do this simple analysis with any of the full set of records from: NASA, NOAA, MLO, Berkeley Earth, Met Center, Cowtan-Way, Japan Meteorological Organization, RSS, or UAH.
Looking at any long-term lag (more than three months, the time it takes CO2’s Green property to create life that cools) proves this point. All of the above highest authorities in climate science concur. There is no higher authority than actual climate data.
Good science. Great explanation of the greenhouse property. But misleading because of factual omissions.
The title should be, “How Exactly Does Carbon Dioxide’s Greenhouse Property Warm the Atmosphere”. And then at the end, note that anthropogenic CO2 has two properties that cool. And that the full effect of CO2 is to cool Earth. The co-aerosol effect is currently neutralizing the Greenhouse effect in the short-term. The Green effect overpowers the Greenhouse effect after three months and is lasting.
one thing that bothers me after reading the scientific facts on the warming effects of CO2 is that the heat absorbed by the greenhouse gas seems to be radiated from the earths surface, and following this trend I would say that the action seems to be secondary, after the suns light is absorbed at the surface. Would it not be more accurate to say that the denuding of millions of hectares with deforestation, would be the initial cause of the source of the heat, especially as trees absorb CO2, and many studies claim the shade caused by the canopy is between 10 and 20C cooler, this cool air blanket being removed would be as much if not more of a cause of g;global warming than the CO2 by itself?
Photosynthesis is endotermic reaction and good adsorber of extra energy. If energy is not going in to the plants, it
s heating up land and atmosphere.
What you write in the end is basically Urban Heat Island effect.
willl we eventually run out of air to breathe?
No, earth is getting greener due higher CO2 and temperature. Earth is still below optimal CO2 consentration for plant growth. In Photosynthesis basically each CO2 molecule will produce equal amount of O2. “Today’s concentration of oxygen could be produced by photosynthetic organisms in 2,000 years” says Dole, M. (1965). “The Natural History of Oxygen”. The Journal of General Physiology
Firstly, Co2 is heavier than air. how does it stay in the upper atmosphere ? Since it’s a trace gas, where do these images we see, come from? there is the train of thought that increases in Co2 do not lead to corresponding increases in temperature. how is the Earth’s tempereature measured ?
Can we agree Co2 has helped green the planet ? more crops more trees, more grass. healthier soil
Yes. Nasa tells “The Earth has become five percent greener in 20 years. In total, the increase in leaf area over the past two decades corresponds to an area as large as the Amazon rainforests”.
That’s interesting..so if most of the world moves to Net Zero…that could be less good for all plants, crops. that would require more fertiliser, chemicals etc. Funny how this was not mentioned at Cop26 nor the effect of world population increase
It is said that without greenhouse gasses average temperature of earth would be abouf 32K colder. It is also said that DOUBLING of CO2 will cause 1,5 to 4,5 K warming. This should also apply for slitting the amount of GHC in atmosphere.
We can calculate that from single CO2 atom we have doubled CO2 about 137 times. Justsplit molecular weight of CO2 by Avogardo number to get weight of CO2 and then start to double it. After 137 doubling you will get about then amount of CO2 in atmosphere.
So if CO2 would be ONLY GHC shoudn’t each doubling increase temperature by 32K/137? And because water has effect too, GHC effect is much smaller?
The sun shines light upon the earth, both visible and infrared. The earth radiates almost all energy back into space as infrared. Some of the infrared is absorbed by CO2 and other gases. These gases absorb certain wavelengths while allowing others to be transmitted. What is the relationship between the density of these gases and transmission through the atmosphere? It seems to me that transmission through miles of atmosphere would be completely blocked once any level of gas was present and the addition of more gas would make no difference.
Part of the problem is the 24/7 society we live in..at any time someone is driving, flying, using electricity, buying a product, making meals…being born ! so Net Zero targets are harder to acheive now than in the pre industrial age..even with new technology
I chose this link because of a comment made regarding the use of carbon dioxide as a refrigerant, alleging that this fact makes climate change due to gasses like CO2 highly unlikely.
A couple of websites explain how CO2 works as a refrigerant, which I only read enough to grasp imperfectly and came looking for more.
Since the person who made the assertion that drove me here has, in the past, expressed ideas that, while couched in seemingly articulate terms, strike me occasionally as patent conservative gobbledegook.
Being too polite to immediately call him out on his altered state, wishing to afford him the benefit of the doubt, I re*trained myself.
It seems to me that what he proposes might do well being included in discussions like this to insure greater understanding of this horrendously significant natural phenomenon.
CO2 is used as a refrigerant because the CFC / HCFC / HFC refrigerants are problematic for the ozone layer. CO2 is not.
You’ll note that they don’t use, for an example, monoatomics as a refrigerant. Why? Because the amount of energy an atom or molecule can transit from one place to another (its specific heat capacity and latent heat capacity) is dependent upon the DOF (Degrees of Freedom) of that atom or molecule.
No, they use complex CFC, HCFC or HFC molecules with many DOF.
By the same token, they don’t use complex high-DOF molecules as a filler gas in dual-pane windows… they use low-DOF monoatomics. Why? Because the low Degrees of Freedom transit less energy from one window pane to the other. If CO2 was such a terrific ‘heat trapping’ gas, it’d be used as a filler gas in dual pane windows. It’s not.
CO2 is similar, it is a high-DOF molecule which can transit quite a bit of energy, especially if compressed to the point that it undergoes phase change. It requires higher pressure than the CFC, HCFC or HFC molecules, but that’s a tradeoff that’s apparently acceptable.
It is the monoatomics (Ar) and homonuclear diatomics (N2, O2) which are the actual ‘greenhouse’ gases. Remember that an actual greenhouse works by hindering convection.
In an atmosphere consisting of solely monoatomics and homonuclear diatomics, the atoms / molecules could pick up energy via conduction by contacting the surface, just as the polyatomics do; they could convect just as the polyatomics do… but once in the upper atmosphere, they could not as effectively radiatively emit that energy, the upper atmosphere would warm, lending less buoyancy to convecting air, thus hindering convection… and that’s how an actual greenhouse works, by hindering convection.
We can see this in the dry and humid adiabatic lapse rate. Remember that the lapse rate is ‘anchored’ at TOA (Top of Atmosphere… that altitude where air density reduces sufficient that the atmosphere is no longer opaque to any given wavelength of radiation).
Water vapor reduces the lapse rate (~9.81 K km-1 dry ALR; ~3.5 – ~6.5 humid ALR) by transiting more energy from surface to upper atmosphere, which has the effect of attempting to reduce temperature differential with altitude (ie: the lapse rate reduces), while at the same time it radiatively cools the upper troposphere faster than it can convectively warm it. This cools the surface.
Thus water vapor, by dint of its higher molar heat capacity and latent heat capacity, is actually a net atmospheric radiative coolant… it increases thermodynamic coupling between heat source (the surface) and heat sink (space).
By the same token, the higher molar heat capacity of CO2 convectively transits more energy than bulk air. A parcel of air with higher CO2 concentration will convectively transit more energy from surface to upper atmosphere than will a lower CO2 concentration parcel, which has the effect (just as it does with water vapor) of reducing temperature differential with altitude, while at the same time radiatively cooling the upper atmosphere faster than it can convectively warm it. IOW, CO2 is also a net atmospheric radiative coolant.
In point of fact, water vapor is the prevalent atmospheric radiative coolant below the tropopause, and CO2 is the prevalent atmospheric radiative coolant above the tropopause.
The image above is from a presentation given by atmospheric research scientist Maria Z. Hakuba at NASA JPL.
That’s adapted from the Clough and Iacono study, Journal Of Geophysical Research, Vol. 100, No. D8, Pages 16,519-16,535, August 20, 1995.
Note that the Clough & Iacono study is for the atmospheric radiative cooling effect, so positive numbers at right are cooling, negative numbers are warming.
In the Clough & Iacono study, cooling rate refers to the divergence of total flux. It is essentially a measure of the difference between upward and downward flux, or how much power is locally lost to radiation. This is a real cooling, but it must be compared to the situation with no greenhouse gases — in which case the cooling rate would be an enormous delta function at the surface.
Greenhouse gases push the radiative energy loss from the surface up to higher in the atmosphere. At these altitudes the temperature is lower, and so the cooling is less than it would otherwise be at the surface.
How does the LWIR absorption properties affect both the lapse rate and the Effective Radiating Level? Hence what must be the climate sensitivity of CO2?
William,
AFAIK,
the the absorption properties of CO2 have had little affect on the lapse rate. This implies that the warmer surface has resulted in a higher ERL, and visa versa.
I realize that as derived from first principals the dry lapse rate in the troposphere is equal to -g/cp where g is the acceleration of gravity and cp is the heat capacity of the atmosphere at constant pressure. Hence the LWIR absorption properties of component gases have no effect on the thermal insulating properties of the atmosphere. Exact;y how does CO2 affect the ERL and what does that say about the climate sensitivity of CO2?
The GHE can also be understood in terms of residence time – how long does the sun’s heat stick around in a given area, in this case Earth’s atmosphere, before exiting into space? Longer means more will accumulate, shorter, less will accumulate.
You could look at all sorts of heat flow problems in a similar way, including home insulation, the clothes we wear to stay warm, or an actual greenhouse.
In all cases the heat is not actually trapped, it is made to linger longer while leaving.
As a certified infrared thermographer, I have always had significant misgivings regarding the proposition of CO2 as a greenhouse gas on the basis of it absorbing and scattering emitted infrared from the earth, thus retaining this energy within the atmosphere. The infrared wavelengths emitted by a body are temperature dependant, and, given a surface temperature range somewhere between -40 and +50 at the extremes, then for CO2 to be a problem it would need to absorb and scatter the upgoing infrared wavelengths between around 8 and 12 microns. Quite simply, it does not. The absorption range for CO2 is around 11 to 18 microns. There is a small overlap between these ranges; but there is more. Also hugely important is that the total absorption and scattering even in the wavelength range that is affected by CO2 is total (much of it by water vapour b.t.w.), i.e. 100%, none of it escapes and this has been the case for centuries. If the absorption and scattering of upgoing infrared in the ranges affected by CO2 was already at saturation before the industrial revolution, how can more CO2 possibly have an adverse effect? I do have good references for the above assertions and I have voiced my doubts in many forums, but have never been provided a satisfactory resolution – I just keep getting the same polemic responses. I am very receptive to a genuine scientific and logic based argument (oh please not the ice core records) but have yet to encounter one. But I live in hope. Incidentally, the article is not quite correct in saying that atmospheric nitrogen and oxygen do not absorb and scatter IR energy – they do, in the range 5 – 8 microns (which is why LW infrared cameras operate in the region below and SW cameras above). But this is only relevant to temperatures above those of the Earth’s surface so the article perhaps skipped this detail for simplicity.
Chris,
You’re coming at this from a false premise,
“none of it escapes and this has been the case for centuries.”
Every pulse of solar energy that gets absorbed by the surface, clouds or atmosphere will eventually make its way to space. All of it escapes.
Perhaps this will give you the answer you are seeking: https://principia-scientific.com/the-absorption-of-thermal-emitted-infrared-radiation-by-co2/
The article discusses why water in the atmosphere is not responsible for global warming. I am interested in your thoughts on the opposite question: could increasing the amount of water in the atmosphere cool the planet?
I have read that high (stratospheric) clouds act as a greenhouse gas much like CO2 but weaker in effect. I have read that low (tropospheric) clouds do not act this way but actually cool the surface.
I also read that the net effect of low and high clouds is currently net slightly cooling. I also read that it is uncertain whether global warming will lead to more low clouds or more high clouds or less of either. I also read that vegetation plays a major role in low cloud formation. Could we increase vegetation to increase the low clouds to cool the Earth?
The idea about co2 and its heating effect is actually only a theory and no matter how many experiments and cool (pun) things we come up with we really don’t no what is actually occurring out in space. Seems like a lot of conjecturing. We can make little greenhouses and try to project are ideas, but I don’t think we really know. Try not to make this a political issue.
Have there been any laboratory experiments showing how much 400 ppm CO2 scatters infrared wavelengths? I’m thinking of a 100 foot large diameter pipe with a tunable laser at one end pointed to a laser detector at the other end and the CO2 concentration varied from about 300 to 500 ppm. As the CO2 ppm is varied, the laser detector output current should also vary by some amount. But, by how much.
I wonder whether the real intensity of the sun is increased more than the weather bureau air temperature quoted, and how much is it increased? I think it highly likely the sun’s heat is much more intense now, December 2021, than it has been within the last ten years or so. ie The air temperature is quoted according to scientific instruments, but the actual radiation intensity is much higher.
Something missing in the colour diagram.. A colour coded arrow should show radiated heat leaving Earth surface and going BEYOND atmosphere into space – 1, low atmospheric ghg content and high atmospheric ghg content.
Allan Shiff, Toronto.