By André Bijkerk
We start with the weather, but that helps us to understand how the real greenhouse effect works.
I took this photo many years ago on a cold morning at the end of September, the beginning of autumn, the trees were still green. When asked if there is something strange going on here, I am still waiting for the right answer. No idea? Meteorologically speaking, this is not possible – at least at first sight. But what is not possible? and obviously, why is it possible anyway?
We see a thin layer of fog over the farmlands. This indicates a very cold layer of air at the Earth surface that has cooled down at night by contact with the radiating soil, but also by radiation to the ground (indeed, it’s that greenhouse effect). This causes condensation and fog to form. This is called a ground inversion. The cold and therefore relatively heavy air on the surface apparently cannot mix with the warmer and therefore lighter air above it. So this is a stable situation that can be very persistent until it finally disappears due to the heat of the solar radiation
Behind it we see cumulus clouds light up in the sunrise. These clouds are created by heating the air on the ground, making it relatively lighter in relation to the environment and causing it to rise. As it ascends, it cools adiabatically, also causing condensation with shapes reminiscent of cauliflower or clouds of smoke, as it is subject to similar turbulence movements. We call this convection, except glider pilots, they call it thermals.
But how can the earth’s surface be simultaneously very cold and cause an inversion, but also so warm that it causes thermals and cumulus clouds? The answer to that contradiction is the still warm North Sea; which is behind it, pun intended. It does not cool down that quickly after a warm summer with such a first frost and therefore the air above it is also warmer.
And in these observations is the most important part of how the atmosphere works, cooling inversion and warming convection. How does that relate to the third element, the greenhouse effect?
Greenhouse effect has something to do with (electromagnetic) radiation. Heat and radiation are actually different forms of energy, which alternate, heat causes radiation and radiation causes heat. How much? This is regulated in Stefan Boltzmann’s law for the quantity and Planck’s law for the frequency band, in other words, the wavelength of the radiation. This can be infrared (longer waves), or visible light (shorter waves) at extreme temperatures on the sun or in the light bulb. Greenhouse gases such as water vapor and carbon dioxide have the ability to do that exchange of heat and radiation at the usual temperatures on Earth. The oxygen and nitrogen in the air can of course also radiate, but that is in the wrong frequency range that does not correspond to the temperatures on earth.
Now to see what that greenhouse effect does in the atmosphere, we should actually take that away. What happens to an imaginary earth with all the trimmings, except for those greenhouse gases and therefore also without water vapor, ergo also without water? It would then be more like the moon, but with a 24-hour day-night cycle and an atmosphere of mainly nitrogen and oxygen.
Now we bring in the sun, which irradiates the earth with the energy “flux” of about 1360 watts per square meter, mainly in the visible light area of the electromagnetic radiation. According to Stefan Boltzmann’s law, this implies temperatures above the boiling point of water. However, part of that radiation is absorbed by the atmosphere, and part is reflected by the earth’s surface. But what remains, the radiation absorbed by the ground surface, is still good for about eighty-ninety degrees Celcius, directly below the zenith, where the sun is perpendicular to the earth. Not too unlikely when you recall the Sahara’s desert heat, or the maximum temperature of the moon (127 degrees Celsius).
And then there is that atmosphere, which is heated by contact with the surface. As a result of which it expands, becomes lighter and takes off, convection, just like that first picture above the warm North Sea. There will only be no cumulus clouds because we had removed all the water. But that does not alter the fact that some of the radiant energy from the sun eventually finds its way as heat energy in the higher parts of the atmosphere.
What happens in places where the sun doesn’t shine? The dark side of the Earth, the night? The earth out radiates the energy, which cools it down, much like in the first picture; and also significantly so, because there are no greenhouse gases that absorb the radiation and partly reradiate back to slow down the cooling. The lower molecules of the atmosphere in contact with the earth, the boundary layer, also cool down, making this air layer heavier, creating the inversion. And not unlike in that picture, that cool air remains close to the earth and will not mix with the layers above it. How then should the higher atmosphere cool down, losing its heat energy? By out radiating? Normally yes, but only with the help of those greenhouse gases, which are not there at the moment. After all, had we had taken that away. There are no other ways to lose heat energy. The universe simply has no molecules to transfer heat to with conduction. To our utter amazement, we must conclude that the atmosphere at night cannot release its heat energy and therefore cannot cool down without greenhouse gases.
And so the days and nights alternate. During the day the atmosphere warms up by convection and at night that heat energy remains largely in the atmosphere until eventually convection subdues and an equilibrium is reached. But in order to achieve that, the atmosphere must eventually be as warm as it is at the zenith point directly under the sun.
But our atmosphere with greenhouse gases included is not nearly as hot as the zenith point. Obviously, the cooling of the atmosphere is a more important function of greenhouse gases than possible warming of the surface. Mind you, this is about the atmosphere, not the surface of the Earth itself. But that makes little sense because what we call surface temperature is in reality the temperature of the atmosphere in the Stevenson screen at about a meter and a half.
We have seen that heat energy enters the atmosphere from the earth’s surface by convection and comes out again by radiation through the greenhouse effect. Hence the conclusion is inevitable that the atmosphere of the earth will warm up strongly without greenhouse gases. The main function of these gasses is to limit the warming of the atmosphere. Hence it is also clear that that widespread conception of 33-degree Celcius greenhouse effect is false and misleading, based on incorrect assumptions and incorrect simplifications.
Without greenhouse gases it gets hot and that is the real greenhouse effect: cooling of the atmosphere.
On scientific websites, I read that the atmosphere without greenhouse gases would be -18°C. Look for example at https://www.giss.nasa.gov/research/briefs/ma_01/: “Without naturally occurring greenhouse gases, Earth’s average temperature would be near 0°F (or -18°C) instead of the much warmer 59°F (15°C).”
Nowhere in your article do you write anything about what, in your opinion, the average temperature without greenhouse gases would be. You only claim “the ground surface … about eighty-ninety degrees Celcius [sic, directly below the zenith, where the sun is perpendicular to the earth”. But you do not back that claim up with a reference. You only describe a local temperature of the ground, and not a global average temperature of the atmosphere, so this isn’t relevant anyway.
Then you come with lots of vague claims, but at no stage with verifiable formulas, values of radiations or temperatures. But still, you conclude that the “widespread conception of 33-degree Celcius [sic] greenhouse effect is false and misleading, based on incorrect assumptions and incorrect simplifications”. But since you present no proper argument on how you reach this conclusion, that you do not present a proper scientific argument. As far as I can judge, you yourself came with “incorrect assumptions and incorrect simplifications”, because nowhere do you present any proper science to support all the vague claims you make.
That’s a DH3 reply. http://www.paulgraham.com/disagree.html
You can do better than that.
There is nothing vague here. And all the processes mentioned here have been substantiated. Maybe quote exactly which of the elements you are challenging and then demonstrate why it is wrong. That can’t be hard, can it?
The point with the -18 /33 degrees greenhouse myth; is that it would be the temperature of an ideal gray (black) body that would be emitting at 1/4th of the solar constant, minus albedo.
The main errors are:
1. A theoretical black body is a perfect conductor, dividing the heat over the complete surface instantaneously. The earth is a near-perfect insolator and nearly all heat is retained at the area that is exposed to the sun.
2 The factor 4 to account for the difference of the surface of the earth disc and the total earth surface. That is not valid in a nonlinear relationship. Where the temperature is proportional to the fourth root of the energy.
3 It disregards the diurnal effects and the effects of an inert non-radiating atmosphere.
The temperature on the zenith point on a barren earth would be close to what it is on the moon. (127C), with the difference that the atmosphere absorbs some incoming radiation. Therefore it is slightly less. Consider that 90% of 1360 W/m2 makes it to the surface (h ttps://www.fondriest.com/environmental-measurements/parameters/weather/photosynthetically-active-radiation/) and that some 12% (moon albedo) is reflected then we have T=383.57K or 110,5 Celcius. At 70% of the solar energy that would be 87,2 degrees Celsius.
André, you have not addressed the point I made: “
1/ You rely on the “maximum temperature of the moon”, while this temperature varies from -173°C to +127°C (.space.com/18175-moon-temperature.html)
2/ Your assumption of “Consider that 90% of 1360 W/m2 makes it to the surface” is not correct. On the weblink you give, I read “Only 56% of the solar radiation that reaches the atmosphere makes it through to earths surface.”
3/ You do not explain where the factor of “At 70% of the solar energy” comes from.
4/ You do not give any explanation how this local maximum temperature of the ground that you claim to have calculated this way, relates to a global average temperature of the atmosphere.
I repeat my conclusion from a few days ago: “As far as I can judge, you yourself came with “incorrect assumptions and incorrect simplifications”, because nowhere do you present any proper science to support all the vague claims you make.”
I forgot to add:
The temperature on the moon varies from -173°C to +127°C. That averaged out to -23°C. That may be too simple a calculation, but that is quite close to the -18°C and a long way from the +89°C you claim.
Any meteorologist can tell you that I merely reproduced textbook knowledge, backed by references. If you just clicked links. The only thing is that I showed the consequences of this textbook knowledge, which is omitted by the 33C greenhouse myth.
1/4. Yes, only the maximum temperature is a parameter of this system. For instance in a metaphor: Only the maximum pressure that an air pump can deliver, controls the maximum pressure of the tyre. It doesn’t matter that the momentary pressure of the pump is lower because the check valve prevents the pressure of the tyre to be released.*
The non-radiation property of an inert atmosphere without greenhouse gasses, act as a check valve. The heat energy can enter the atmosphere via convection but then it’s trapped and it cannot exit the atmosphere. (with the exception of the lowest boundary layer). So, that process continues as long as the maximum temperature of the surface at zenith is still higher than the temperature of the lower atmosphere, and the higher levels according to the dry adiabatic lapse rate. Only when those become equal, then the convection stops. Which would imply that the temperature range of the whole atmosphere is at that maximum temperature, minus the leaking of the boundary layer. But what that temperature would be’exactly with so many decimals, isn’t relevant to demonstrate that the main function of greenhouse gasses is cooling the atmosphere.
2/3. The amount of energy that reaches the earth surface is mostly dependent on the absorption by water vapor. If we remove the water, the amount of sunlight that reaches the surface will only be dependent on the rayleigh scattering. So in our atmosphere without greenhouse gasses, more solar energy will reach the surface. But if that’s 60% or 70% or 100% isn’t relevant to the principle.
* okay, waiting for a blown tyre joke.
André, in other places than under the zenith, the earth (and the lower atmosphere) will not reach the maximum temperature. Also, in your article you confirm that the lower atmosphere cools every night (gives heat back to the earth). Convection in the lower atmosphere (=wind) may transport some of the heat to cooler places, but that heat will not stay in the atmosphere, but returned to the cooler earth (which in turn radiates it out).
So the lower atmosphere simply cannot reach maximum temperature at a worldwide scale.
Therefore, my criticism remains:
Let’s go back to the tyre. The pressure within the tyre not less at a greater distance from the valve, It is equal everywhere and equal to the pressure that the pump delivered. It’s one-way traffic -mostly-.
And yes the lower boundary lower returns heat energy to earth, which is then radiated out, but look again at the picture, there it is only a few meters and that’s with the assistance of radiation from the greenhouse gasses. But the kilometers of atmosphere above that boundary layer retain their heat, because it cannot radiate energy out without greenhouse gasses.
So heat keeps accumulating and spreads all over the atmosphere like the pressure does in the tyre. and like the Hadley cell does on earth, with the difference that the high atmosphere in upper part of the atmosphere radiates the energy out again. https://en.wikipedia.org/wiki/Hadley_cell
André, you seem to believe that there is a stable “lower boundary “of “only a few meters” that exchanges heat with the ground, but has no interaction with the air above it? That is too simple an assumption to make.
You need wind to transport heat from the equator away to towards the poles. This wind will mix the air, making this stable boundary non-existent. Also, the Earth is not flat, so there will be turbulence around mountains etc that mix this non-existing boundary with the higher air.
Also, your article concludes with “the real greenhouse effect: cooling of the atmosphere“. Now, we all know that CO2 has increased from 280 to 420 ppm (50% increase). We also know that the global average temperature has increased. So where is this “cooling“? The facts contradict your idea!
No, that’s not my belief, that’s textbook wisdom https://en.wikipedia.org/wiki/Wind_gradient
Mind that without greenhouse gasses, lacking back radiation, the earth cools more strongly in the night, hence the lowest molecule layers cool also and get much denser as in the normal Earth situation, intensifying the wind shear.
Sure, sometimes it’s a bit warmer and sometimes it’s a bit cooler. Maybe there are other reasons for that. Yet, another article about that soon.
Let me elaborate further. Check this google image search:
(Pictures may be copyrighted therefore not posting one here)
Here you see direct evidence that winds at higher levels do not mix with the cold ground inversion layer. We know that there is quite some wind, due to the wake activity of the wind turbines, but unless forced by that wake, the cold fog layer does not show any sign of mixing with higher warmer layers.
I can ready Wikipedia too:
All this confirms what I wrote at 12:05 today: That boundary layer is much larger than what you describe as “only a few meters” and it mixes due to the structure of the surface.
Heat exchange with the surface means that the local air temperature will relate to the local ground temperature and not to the “the maximum temperature of the surface at zenith”.
We know that CO2 has increased from 280 to 420 ppm and that the global average temperature has increased. So are you going to ignore my question “So where is this “cooling“?”?
And what is in your world without greenhouse gases the global average temperature of the atmosphere, at 1.5 meter above the ground?
Here are some results of surface temperature calculations I made about an Earth without an atmosphere and with albedo 0.3.
1. Sunlight dispersed homogeneously over the globe: local temperature is equal to average temperature: -18°C.
2. Non-rotating Earth (with respect to the Sun): The temperature varies between 88°C (Sun in zenith) and -273°C (backside of Earth). Average: -129°C.
3. Quickly rotating Earth with obliquity= 0 (constant temperatures along latitudes). At the equator the temperature will be -2°C, at both Poles -273°C. Average: -21°C.
Conclusion: The rotation of the Earth can distribute the energy of the Sun very efficiently.
If the Earth has an atmosphere without greenhouse gases the averages of 2. and 3. will be raised slightly due to advection.The atmosphere cannot radiate so its temperature distribution is of no importance.
If greenhouse gases are added the atmosphere can now radiate but, due to the adiabatic cooling rate, at a lower temperature than the surface. This is not extra radiation but intercepted radiation from the surface. To restore equilibrium the temperature between the hypothetical emission height and the surface has to rise.
De gemiddelde temperatuur op de maan is halverwege het maximum en minimum. (-173 en 109C). Dat is dus ruim onder 0 (ongeveer -40C). De afstand van de aarde tot de zon is identiek, en de aarde heeft een gemiddelde temperatuur van +10. De combinatie van het broeikaseffect, aangevuld met natuurlijke radiatie uit de korst maakt het verschil. Arrhenius’ conclusie staat nog fier overeind.