Frequently Made Errors in Climate Science – The Greenhouse Effect
Table of Contents
1.What is meant by “The Greenhouse Effect”?
Many gases, such as H2O, CO2, CH4, are transparent to visible light but absorb and emit parts of the infrared spectrum. Most of the visible light reaching the Earth’s surface gets re-emitted, eventually, as infrared. Media that pass visible light through but block infrared can act as heat traps.
2. Real Greenhouses
X “The Greenhouse Effect does not exist; Prof R.W.Wood proved it in 1909.”
Most glass also blocks parts of the infrared band. It was widely believed that this was primarily responsible for the effectiveness of greenhouses.
Prof. Wood suspected that blocking convection was the primary mechanism, so set up a simple experiment to test this. There are a number of weaknesses in the experiment, but the essential conclusion is correct: real greenhouses work primarily by blocking convection.
✓ “Whether or not the Greenhouse Effect exists, it is not the main way real greenhouses work”
However, this just means that the term ‘greenhouse effect’ may be misleading. Wood’s result says nothing about how the atmosphere works.
3. Black Body Earth
If we treat the Earth as emitting and absorbing radiation as a “black body”, ignoring the atmosphere, and treating incoming light as spread evenly over the whole Earth’s surface all the time, we can calculate the equilibrium temperature as -18C. At that temperature, black body radiation would balance insolation.
Adding a non-greenhouse atmosphere, e.g. pure nitrogen doesn’t change this. The atmosphere would take no part in the energy balance. By conduction, it would come to match the surface temperature of the Earth, throughout its depth.
Note:
- With a non-greenhouse atmosphere but now allowing the realities of a rotating sphere, convection would boost the upper atmosphere to something approaching the temperature of the hottest spot on the surface. The surface layer of the atmosphere would be a little cooler by virtue of conduction back to the cooler surface regions.)
- The non-greenhouse atmosphere may also result in some attenuation through Rayleigh scattering. The nitrogen in Earth’s atmosphere may scatter about 4% of light power back into space, taking the temperature down by maybe 3K.
4. The Troposphere
The atmosphere has many layers, featuring quite different processes and temperature profiles.
The atmospheric convection with which we’re familiar only operates up to the tropopause, the top of the troposphere – the band where weather happens. Beyond that, temperature inversions inhibit convection.
X “The ‘greenhouse gases’ are a net coolant since convection carries the heat through the troposphere, past 80% of them. They then block reradiation back to the surface.”
It’s the 20% above the tropopause that matters. This makes the tropopause warmer and/or higher. Since convection is limited by the lapse rate, a higher or warmer tropopause leads to a correspondingly warmer surface.
The existence of this “tropospheric hotspot” is considered a fingerprint of Global Warming.
5. Temperature and Pressure
X “It’s hotter at lower altitudes because it’s at a higher pressure, and compressing a gas heats it”
Compressing a gas heats it, but won’t keep it hot. If the atmosphere were just a static layer of gases, only heated or cooled by conduction, it would all come to the same temperature.
6. The Lapse Rate
X “It’s hotter at lower altitudes because if air rises it expands and cools”
This only explains why convection cannot bring the troposphere to a uniform temperature. It does not explain why there should be a temperature difference in the first place.
Since conduction is not limited by the pressure gradient, there must be an active process producing the temperature gradient. This process is the heating of the Earth’s surface by the sun.
The full story of energy transfers is quite complex. See Trenberth and Kiehl, 1997, Fig 7. Omitting all the absorptions and reradiations:
- The Sun warms the Earth’s surface
- The heat energy is transferred back to the air in the troposphere by a mix of conduction, convection and radiation. Overall, 60% makes it up through the troposphere at least partly by convection, 40% by radiation only.
- Convection’s ability to carry up the heat is limited because of the pressure gradient: rising air expands and cools. The resulting temperature gradient is known as the Lapse Rate
- The troposphere is the layer in which convection can operate. At the top (the tropopause), the temperature gradient is insufficient.
X “We can calculate the surface temperature from the height of the tropopause, the temperature there and the lapse rate. This fixes the surface temperature.”
That has causality backward.
✓ If the mean surface temperature changes, the height of the tropopause will change.
7. Greenhouse Gases
X “There’s nothing special about CO2. All gases can absorb heat”
All gases can conduct heat, but the ability of a molecular species to absorb and emit radiation depends on the intervals in its internal energy states and the polarity of its structure.
If vibration of the atoms in a molecule does not involve a net oscillation of electric field then that vibration cannot absorb or emit electromagnetic radiation. Diatomic gases like N2 and O2 are non-polar (or”homo-polar”). A vibration in the bond between the atoms does not result in any net movement of charge. Other energy levels of those molecules do not have the right intervals to interact with light in either the visible or infrared bands, so are completely transparent to both. Only much higher energies, sufficient to ionize the gases, would be strongly absorbed.
Both water and CO2 are hetero-polar, so can act as dipoles. Some vibrations involve a negatively charged atom group moving one way while a positively charged group moves the other. This net oscillation of charge allows them to interact with radiation at certain frequencies.
X “CO2 is insignificant compared with H2O as a greenhouse gas”
H2O, CO2, CH4 and many others can absorb/emit in parts of the infrared. None of them do so in the entire infrared band. Increasing the level of relatively rare greenhouse gas has more effect than increasing the level of a more common species.
8. Forcings and feedbacks
Climate scientists distinguish factors affecting global temperature as either forcings or feedbacks.
X “Atmospheric H2O is a forcing that overwhelms CO2”
A feedback is a variable which both affects temperature and is affected by temperature. Pure feedback would be a variable entirely controlled by temperature.
These can be further divided into negative and positive feedbacks. This list is by no means exhaustive.
- A few positive feedbacks
- Atmospheric H2O: the warmer the atmosphere, the more water vapor it will hold.
- Polar albedo: as ice caps melt, less incoming light is reflected straight back through the atmosphere.
- The warming of soils and oceans can lead to the release of CO2.
- A negative feedback
- The hotter the Earth’s surface, the more infrared it emits
Note: If something is a negative feedback it acts to dampen change; it cannot make the change go in reverse. That said, delayed feedback can lead to cyclic and chaotic behaviours.
A pure forcing is a variable which affects temperature but is not affected by it. Radiative output from the Sun clearly fits that description.
More loosely, a variable tends to be called a feedback if it is primarily controlled by temperature, and forcing if primarily controlled by other factors. On that basis, anthropogenic CO2 is forcing, but H2O is a feedback.
✓ Anthropogenic CO2 is a significant force because its effect is amplified by positive feedbacks, such as water vapor.
9. The Greenhouse Effect is Logarithmic, roughly
“The light passing through a filter should fall as the negative exponential of the optical thickness, so why is the effect logarithmic?”
“Solar Spectrum”. Licensed under CC BY-SA 3.0 via Wikimedia Commons – http://commons.wikimedia.org/wiki/File:Solar_Spectrum.png#/media/File:Solar_Spectrum.png; but note the 5250C is incorrect, it is closer to 5777K.
The diagram shows the absorption bands (yellow) for incoming radiation, and the same applies to outgoing. It shows that for most of the width of an H2O or CO2 band, absorption is already substantial.
The quantum basis for specific bands suggests, at first sight, that the wavelengths should be quite precise. However, some subtler processes spread the bands. In particular, the Doppler effect means that molecules moving towards the radiation absorb at a shorter wavelength, while those moving away absorb at a longer.
The primary consequence of adding more of an already abundant gas is to increase the number of molecules at the most extreme speeds relative to the radiation. This increases absorption at the edges of the band, broadening the band slightly. It is this that grows logarithmically with the prevalence of the gas.
“How can it be logarithmic? That would mean adding the first little bit of a new gas would have an infinite effect.”
The logarithmic relationship would not apply for a rarer gas that is still well short of full absorption in the center of its bands. Likewise, it breaks down when bands broaden so much that they overlap.
Masters in Mathematics. Interests: climate change & renewable energy; travel; cycling, bushwalking; mathematical puzzles and paradoxes, Azed crosswords, bridge
[QUOTE="haruspex, post: 5516530, member: 334404"]The net effect of the greenhouse gas is therefore to slow the transfer of heat into space. That is all that is meant by trapping in this context.[/QUOTE]Once air reaches tropopause it's above most of the greenhouse gas so radiation has a shorter hop to makeHurricanes can move something like 10^22 joules a year up therehttp://www.aoml.noaa.gov/hrd/tcfaq/D7.htmlten twenty day storms in a season ? lately we're having more…Is that a significant number ?
[QUOTE="Reality Is Fake, post: 5516452, member: 598755"]convection by rising air. Which is the dominant way of heat transfer from the surface of earth.[/QUOTE]Only up to the tropopause. Going any further depends almost entirely on radiation.[QUOTE="Reality Is Fake, post: 5516452, member: 598755"]The concept of stopping heat or thermic radiation towards space, or "trapping" it as often is said, is a nonexistant phenomenon in calculated heat transfer and thermic radiation.[/QUOTE]It depends what you mean by "trapping". Infrared Radiation is absorbed from either direction (up or down) and reradiated equally in both directions. Since the Earth reradiates absorbed visible and IR as IR, there is more IR coming from below than from above. The net effect of the greenhouse gas is therefore to slow the transfer of heat into space. That is all that is meant by trapping in this context.
[QUOTE="mheslep, post: 5332308, member: 70823"]Heat capacity of the molecule is no more relevant to radiative forcing than is the heat capacty of glass in a greenhouse. The ability of CO2 to scatter certain infrared wavelengths is the issue, that is, to stop some infrared from escaping to space.[/QUOTE]The greenhouse glass is a conductive boundary, preventing heat transfer in other ways than conduction. Primarily by preventing convection by rising air. Which is the dominant way of heat transfer from the surface of earth.Co2 absorbs thermal radiation and acts as a body in heat transfer with the surface. S-B law can be used for that and is very clear about the rate of heat transfer as the difference in temperature as the only regulator of the rate. Two bodys at same temperature does not exchange heat and the rate increases with difference in temperature. There is no "stopping" infrared from escaping to space that is at 3K in vacuum. We know from applied thermodynamics in constructions using S-B law for heat transfer, that the radiation from a surface is dependant only of temperature, and the rate of heat transfer is defined by the difference in temperature only. The concept of stopping heat or thermic radiation towards space, or "trapping" it as often is said, is a nonexistant phenomenon in calculated heat transfer and thermic radiation.
[QUOTE="Bandersnatch, post: 5515065, member: 399360"]Hi [USER=598755]@Reality Is Fake[/USER] :welcome:I'm having a little trouble parsing your post, so correct me if I misunderstood your main point.Space, despite being close to 0K in temperature, when treated as a heat sink, doesn't have an arbitrarily high capacity to remove heat. Since the only mode of heat transport is radiative, you're limited by the black body radiation (i.e., Stefan-Boltzman law). All the effects you mentioned – blowing air over a hot surface or evaporative cooling of water – are internal to the Earth-atmosphere system. They only serve to redistribute heat across the planet, but they can't remove any heat from the system. In the end, everything must leave via radiation.[/QUOTE]I´m sorry if it´s hard to understand my writing, english is not my native language.Of course all energy leaves as radiation and it leaves from the top of atmosphere. As far as I can see it doesn´t matter that the gas is distributing the heat by cooling the surface at any location to all the volume of the atmosphere. That is a process that maximize the atmospheres capacity to radiate to space.Black body radiation is a beutiful concept and S-B law is the reason that we can use space as a heat sink. Because it defines the energy leaving the boundary of a system that transfers heat to the surroundings as an effect only depending on temperature. It is true for the transfer of heat no matter if it is in the state of radiation or heat as kinetic energy. It is used for heat transfer and thermic radiation.Are you saying that if we consider an imaginary furnace transferring heat from a heat source to a gasmix like the atmosphere that surrounds the source, then we would need no isolating walls if it was surrounded by zero-degree vacuum?Wouldn´t that make gravity the force preventing cooling?As I see it, earth doesn´t have any internal system above the surface that can be treated as an enclosure. The thing that defines an enclosure is that it has a boundary that is a surface or has surface-like properties that transfer heat by conduction. A boundary must be heated and then emit energy according to it´s temperature, and the transferred heat is dependant on temperature only. According to S-B law = P/A=σT1^4 and for graybodys the temperature for all parts is lowered by emissivity.So, yes, all energy leaves by radiation. And, yes, according to S-B law that is valid for both thermic radiation and heat transfer in gasses, we can calculate the transfer from earth to space as an optimal heat sink. That makes the atmosphere an added value of heat transfer to the surface, since there is no barrier that transfer by conduction at the boundary. And heat transfer is defined by S-B law only as a product of temperature, which makes it clear that the lower temperature of the atmosphere, only acts as a receiver of the energy from the surface. The temperature of the source is constant even if it transfers heat to a colder body, when in an open system without boundary. If we study the internal structure of earth we see the difference to a closed system. Very little heat is transfered at the boundary, the earth surface.According to theory of heat transfer, the rate of transfer is defined by the difference in temperature, and it shrinks as the difference gets smaller. So that makes a transfer of energy from atmosphere to surface a violation of the concept black body and even more for grey body. It only happens in closed systems with boundarys that reflects a large fraction and conducts a small fraction to the surrounding outside. The gas transfers heat back to the source when the gas has reached an even temperature in the system. That is the opposite of the earth surface and it´s atmosphere.[QUOTE]If you then put something in the way of the outgoing radiation, so that part of it gets reflected back to the surface, you end up raising the surface to a higher equilibrium temperature..[/QUOTE]Only if the reflected radiation is hotter than the surface, hot as in higher energy radiation. And there is no reflection, the gasses absorb and emit, and that is a product of temperature only. Applying S-B for heat and radiation for absorbing gas gives a rate of heat transfer that adds up to much below 0 for the low atmosphere temperature and earth surface. But we only need to apply it for heat gain in the gas, the earth surface will not gain anything from the low temp.[QUOTE]In you example with the rock by a fire place – if you could modify the experiment to use close-circulation air supply, and ensure that the only way heat can leave the system is via radiation (and keep the radiative surface area the same etc.), then as soon as the system reaches thermal equilibrium you won't get any cooling from the air circulating inside.[/QUOTE]And that would be a system that had an totally even temperature in the gas surrounding the heat source, which is thermal equilibrium. The opposite of what we observe in the atmosphere that has a very steep gradient from the surface and the average temperature of the whole volume is a lot less than the surface. According to S-B law there is no doubt that the transfer of heat goes in one direction only and that is towards a bottomless heat sink. The atmosphere is just a big lossy extension of surface area from 2 to 3 dimensions, even 4 dimensions as it spreads heat transfer in time, and it is a large addition to the capacity of transfer in relation to the energy absorbed from insolation by only half the surface of the earth.As I wrote before, I´ve been thinking and reading a lot about this and it really is a problem in the way earth temperature is approached in the greenhouse theory. There is a few things we can be sure of, that the sun can be treated as an almost perfect blackbody, the earth is definatly a grey body, and that makes it clear that the laws for radiation, heat, effect and temperature is the only way that we can define the interaction. Those laws, that is applied in many ways in technology and very functional, says that the emitted energy from a planet like earth heated by the sun, is a product of temperature only. The atmosphere heated by the earth is a product of temperature only. Transfer of heat in the system has a rate that is equal to the difference in temperature and it is lower for a small difference. When temperature is equal in two bodys in contact, there is no transfer of heat between the bodys. Heat is never transferred from cold to hot and that is proven by S-B law that gives the rate of transfer.Another interesting thing is that I always had a hard time visualizing Einsteins theory of relativity, E=mc^2, but the greenhouse theory solved that for me.Since mass * speed of light is equal to energy, and speed of light is the definition of a photon, and earth´s energy that is equal to temperature which is a product of photons radiated from the sun, we can be absolutely sure of that added co2 cannot heat the earth when all other things is constant.If E/m=c^2 and E=Temperature of the earth, then an increased mass in the atmosphere by added co2 without solar insolation increasing, would result in an increased speed of light in the photon if Energy that is divided by mass is increased. Which we know is an absolute limit for speed, as calculated for macroscopic relations in space. This is because the source of energy is external and fixed in addition to c that is an upper limit. The only thing that changes is the mass, and that actually would result in a decrease in energy measured as lower temperature of earth. A very small decrease but still, it seems like the whole theory of an atmosphere heating anything as an added volume of low density mass with a low emissivity above the surface, is a direct violation of E=mc^2. And even more so, added co2 to any calculation cannot change temperature without adding more energy from the source, that is our sun.I have searched intensivly for a complete calculation with S-B law that shows heating from the icecold atmosphere, and have found none. It has to include all bodys, the sun, earth and it´s atmosphere. And a calculation of radiation balance at any point has to relate to the source, the sun. I f co2 heats the surface as the last passive body in the chain, then it has to heat the sun as well if it is true. But it is not necessary to go that far, we only need to apply S-B law for heat transfer that is valid for both kinetic energy and radiation, dependant on temperature only, and there is no question that it is a violation of the relationship between matter and energy.That is also confirmed by observation of energy as temperature in the atmosphere, steep gradients an very low temperatures that is averaged much below surface, is the tell-tale sign of something acting cooling on the surface. I was quite happy when I realized that I finally can visualize Einsteins theory in matter with radiation of photons and energy as temperature of mass.I don´t want to come across as a sceptic of AGW, I´m just really trying to figure out how added mass of co2, without added energy from the source, can raise temperature by heat transfer from hot to cold? And basically, how can an atmosphere that is an added low density volume to the surface, warm the earth?When the numbers add up wihout an atmosphere? And why do we treat water and air as warming in the atmosphere when we never use it in that way in daily life?
[QUOTE="haruspex, post: 5327846, member: 334404"]Thanks D H, I was not aware that was wrong. But I like the image, much clearer than most, so I've just added a note. (Is the curve wrong, or just the number? The peak seems to be in about the same place as in other images I found.)[/QUOTE]I think the curve is useful and accurate enough. So I would suggest changing the number on the image, and changing the note to indicate what you did.I see no reason to leave that uncorrected error.
Hi [USER=598755]@Reality Is Fake[/USER] :welcome:I'm having a little trouble parsing your post, so correct me if I misunderstood your main point.Space, despite being close to 0K in temperature, when treated as a heat sink, doesn't have an arbitrarily high capacity to remove heat. Since the only mode of heat transport is radiative, you're limited by the black body radiation (i.e., Stefan-Boltzman law). All the effects you mentioned – blowing air over a hot surface or evaporative cooling of water – are internal to the Earth-atmosphere system. They only serve to redistribute heat across the planet, but they can't remove any heat from the system. In the end, everything must leave via radiation.If you then put something in the way of the outgoing radiation, so that part of it gets reflected back to the surface, you end up raising the surface to a higher equilibrium temperature.In you example with the rock by a fire place – if you could modify the experiment to use close-circulation air supply, and ensure that the only way heat can leave the system is via radiation (and keep the radiative surface area the same etc.), then as soon as the system reaches thermal equilibrium you won't get any cooling from the air circulating inside.
[QUOTE="Bandersnatch, post: 5347132, member: 399360"]Intuition from other, physically similar setups can help you here. Consider what it means to be a good heat insulator.For example, you're an Arctic explorer and it's -70 degrees centigrade outside. Yet, thanks to the many layers of good insulation, your internal body temperature is kept at the healthy 36.6 degrees. That's over a 100 K difference. The indication that the clothes you're wearing are a good insulator, is that it lets very little heat escape, and there's a large gradient of temperature as you get deeper inside.This is the same for Earth's lithosphere, made largely of poorly-conducting silicates – if it were a good heat conductor, you wouldn't get an increase in temperature as you get down the mine – the surface temperature would be instead almost the same as that of the deeper layers. Which would incidentally cause the whole planet to cool very rapidly as that hot surface would radiate heat profusely.Again, this is the same as with warm clothing – if you can feel your body temperature when you're touching the outer layers, then it ain't a good thing to wear in the winter.[/QUOTE]Hi, new member here. That sounds as just the right metaphore for earth`s intestines. Similar ways of illustrating the relationship between temperature and surroundings is used for atmosphere by many.I think it is a bit misguiding that analogies for the atmosphere is used so often in explaining the effect on surface temperature. It consists of air and we don´t need metaphores for air.The correct version of the Arctics explorer would then be for the atmosphere: how does his temperature of 300K change when it is immersed in air at about 200K?And as I have done a lot of reading about this lately, the right approach to surface temperature in contact with atmospheric gasses is basicly the same way we think about all warm surfaces in contact with cold air. And of course in the long run evaluate all different mechanisms in air that is involved in the observed distribution of temperature.The most important aspect is that air does not insulate very well when it`s not surrounded by a structure that keeps it in place like we observe in insulation within walls or carefully designed surfaces in walls of furnaces that operate at high temps. The best experience is in engineering that have to use the right methods, because the result has to be a design based on a correct understanding of heat and radiation combined with a somewhat complete knowledge of all included transfers of the energy produced by a hot source.Their approach to heat transfer and air which mostly is an intention to contain or shield from heat/radiation, is that air must be kept in/outside an enclosure with walls that keeps transfer to a minimum. Because atmospheric gases that is allowed to come in contact with a heat source and ireact to heat freely like air in contact with earth surface, will transfer very large amounts of energy away from the heat source as heat transfers to all possible points with a lower temperature.Considering this experience in applied theory of heat transfer and thermal radiation that has been succesfully used in constructing devices with increasing performance, the right "analogy" of surface temperature and atmosphere is a hot external source of intense thermal radiation that heat the surface(mainly) of half the absorbing body wich radiates a fraction of that heat to air that surrounds it, reduced by emitting same amount from twice the area that absorbed it, and the gasses that is much lower in temperature at all distances from the surface is immersed in 0K vacuum with no enclosure or insulating barriers that prevent heat transfer from both the surface an the gas by a wide selection of transfer in the molecules absorption wavelenghts. The transfer can happen in almost all wavelengths in the total spectrum for both bodys that is included, and even a bit more. The many diffrent ways of absorbing provides many ways of transfer that I think can be seen as several "lanes" that prevent traffic jams efficiently. With overlaps that enhaces exchange between molecules and also change of wavelenght.The difference to engineering furnaces or other ways to control temperature that is aimed at making the insulating enclosure as effective as possible when it comes to keep the gasses heat capacity under control to do work. We can instead imagine something quite the opposite, that air or other gasses can, without any restrictions, transfer the maximal amount of heat in all possible ways, to an optimal heat sink that has no resistance. A way to increase heat transfer in a furnace is to add a second surface that absorbs heat and reach the same temperature, this increase surfacecontact with the gas that transfer the heat. Adding an atmosphere with high absorbing capacity to earth surface would be very much like adding more surface that is involved in the transfer of energy to the heat sink in space. And also extending the twodimensional surface into three dimensions. I have turned the atmosphere inside out when trying to find the insulating effect, which would be easy to spot in the gradient. There is not any way to interpret observed temperature and behaviour of the gasmix and water, than a clear display of very efficient heat transfer through the whole spectrum into an optimal heat sink. On top of that, consider the absorbed energy/m^2 that is emitted from double the surface area as only one side is irradiated, and that the atmosphere is reducing the effect at the surface before absorbtion. As icing on the cake the atmosphere transport heat away from irradiated surface and volume to the side that is constant cooling. It´s like a ridicoulus excess of cooling functions and then the biggest is not mentioned yet. The oceans acts very much like an AC with compression and expansion in circulation to the icecaps. The top carries heat with high speed to cooling icy waters and sinks to a compressed slow stream at the bottom back to places that warms.My first thought that made me investigate this was: What happens if i put a stone beside a fire and observe the temperature when,*I pour water over it*I place it in a waterbath that covers a part of the surface* I add some really large pieces of ice both on the dry parts and in the waterbath*Blows compressed air across the surface with a rate that is about the same rate as convection works on earth*Adding absorbing gases Which one is raising temperature/limiting loss?I can´t see that there is such a mechansim present. Not around the stone and not anywhere in the atmosphere. All these influences are the foundation in the greenhouse theory that claims the opposite effect on surface temperature than we observe in all other circumstances when heat is transfered from a source with higher temperature towards all colder surroundings. If we think about how these ways of heat transfer in gasses and water from hot surfaces and spaces in normal situations daily, we never treat air or water as a heat transfer from cold temperature fluid or gas to the hot volume or surface of matter.And in relation to threadtopic, what would the internal distribution look like if there was no sun?Our core is even hotter than the suns surface, rightThe difference in about 1000W/m^2 hitting half of surface, ignoring atmosphere, to a heat sink of 0K without any heat source…. that must be more like Pluto or something?Even with an atmosphere there has to be a difference, am I right?
Bandersnatch, thank you once more for an enlightening response! I’d never have guessed that the outer layer of our planet is such a good insulator (basalt and granite being pretty cool to the touch — but not -237 centrigades cool, for which we have to thank the Sun).
[QUOTE=”Danielvr, post: 5346889, member: 581571″]Intuitively, I still find it hard to understand[/QUOTE]
Intuition from other, physically similar setups can help you here. Consider what it means to be a good heat insulator.
For example, you’re an Arctic explorer and it’s -70 degrees centigrade outside. Yet, thanks to the many layers of good insulation, your internal body temperature is kept at the healthy 36.6 degrees. That’s over a 100 K difference. The indication that the clothes you’re wearing are a good insulator, is that it lets very little heat escape, and there’s a large gradient of temperature as you get deeper inside.
This is the same for Earth’s lithosphere, made largely of poorly-conducting silicates – if it were a good heat conductor, you wouldn’t get an increase in temperature as you get down the mine – the surface temperature would be instead almost the same as that of the deeper layers. Which would incidentally cause the whole planet to cool very rapidly as that hot surface would radiate heat profusely.
Again, this is the same as with warm clothing – if you can feel your body temperature when you’re touching the outer layers, then it ain’t a good thing to wear in the winter.
[QUOTE=”Danielvr, post: 5346889, member: 581571″]Do you happen to know how warm (cold) Earth would be if there were no Sun? If 0 Kelvin is the absolute minimum and 287 Kelvin is the current average temperature on Earth’s surface, I wonder how much that would be if we only had Earth’s core as an energy source.[/QUOTE]
Putting a precise number on that is beyond my paygrade. What I can do is provide an approximation of the upper bound.
Take the Stefan-Boltzman law:
##P=sigma T^4##
We know that for the current surface temperature of ##T_1=300 K## (the calculations are too simplified to worry about being imprecise), the power received from the sun and reradiated by the surface (approximated as a black body) is ##P_1=1.7*10^{17} W##
The energy estimated to be leaving the surface after being conducted from deeper layers (i.e., the internal energy heating up the surface) each second is ##P_2=4*10^{13}W##
By comparing ##P_1/P_2## we can get the temperature of a black body radiating with power equal to only the internal energy loss (at its current magnitude):
##frac{P_1}{P_2}=frac{T_1^4}{T_2^4}##
##T_2= T_1 sqrt[4](frac{P_2}{P_1})##
You plug in the numbers given above, and get the approximate temperature ##T_2 = 36K## or -237 degrees centigrade.
This in an upper bound, because without the Sun, you’d end up with a planet that is not constantly heated up by it, so it’d cool faster over its life, so by today it’d be losing even less heat that it does now. It’s about right an answer if you were looking for a scenario where the Sun magically disappears today.
The atmosphere would probably not affect that temperature by much – at 36K most of the gasses would liquify or solidify, and the peak radiation would be shifted much farther into the infrared, so any greenhouse effects would be negligible.
Point 5 states that
“Compressing a gas heats it, but won’t keep it hot. If the atmosphere were just a static layer of gases, only heated or cooled by conduction, it would all come to the same temperature.”
Would pure heat conduction really result in the same adiabatic temperature gradient?
Just a thought on clouds and the effect of water vapor
the effect of water vapor on convection is tremendous
with Molecular Weight of just 18 vs air’s ~29 , water vapor makes moist air less dense so it rises,
and its enormous heat of vaporization affects lapse rate causing an awful lot moisture laden air to rise above most of the atmosphere’s CO2
[IMG]https://gregklein.files.wordpress.com/2011/01/pressure_vs_altitude.png[/IMG]
at 5km, around 16,000 ft, it’s already above nearly half the atmosphere
and any decent thunderstorm has tops above 20,000 ft
hurricanes more like 50,000
Given that a hurricane removes something like 5 X 10^19 joules per day from the ocean ([URL]http://www.aoml.noaa.gov/hrd/tcfaq/D7.html[/URL]),
[QUOTE]
[B]Subject: D7) How much energy does a hurricane release?[/B]
[I]Contributed by Chris Landsea (NHC)[/I]
Hurricanes can be thought of, to a first approximation, as a heat engine; obtaining its heat input from the warm, humid air over the tropical ocean, and releasing this heat through the condensation of water vapor into water droplets in deep thunderstorms of the eyewall and rainbands, then giving off a cold exhaust in the upper levels of the troposphere (~12 km/8 mi up)…..
[B]….
Method 1) – Total energy released through cloud/rain formation:[/B]
An average hurricane produces 1.5 cm/day (0.6 inches/day) of rain inside a circle of radius 665 km (360 n.mi) (Gray 1981). (More rain falls in the inner portion of hurricane around the eyewall, less in the outer rainbands.) Converting this to a volume of rain gives 2.1 x 1016 cm3/day. A cubic cm of rain weighs 1 gm. Using the latent heat of condensation, this amount of rain produced gives
5.2 x 10[SUP]19[/SUP] Joules/day or
6.0 x 10[SUP]14[/SUP] Watts.
[/QUOTE]
If we just USWAG 70 hurricane days a year , ten storms at a week apiece,
that’s 3.64 X 10 [SUP]21[/SUP] joules
comparable to the heat content of earth’s whole inventory of air.
[ATTACH=full]93970[/ATTACH]
[URL]https://www.quora.com/What-is-the-total-heat-content-of-the-Earths-atmosphere-partitioned-between-its-various-layers[/URL]
if this guy is in the ball park
[URL]http://www.ecd.bnl.gov/steve/pubs/HeatCapacity.pdf[/URL]
[ATTACH=full]93971[/ATTACH]
16.7 watt years per square meter per degree
how many joules in that many watt-years ?
16.7 watts = 16.7 Joules/sec, X 60sec/min X 1440min/day X365.25 day/year = 5.27 X 10[SUP]8[/SUP] joules /year X 1 year
multiplied by earth’s area of pi X 12,742000^[SUP]2[/SUP], 5.1 X 10 [SUP]14[/SUP]m[SUP]2[/SUP] = 2.69 X 10[SUP]23[/SUP] joules
our 3.64 X 10[SUP]21[/SUP] joules lifted by hurricanes is only 1.35 % of that number
aha
Sooo can i suggest
hurricanes don’t cool the whole climate system very much
they just help convey heat from the tropics to the upper atmosphere
where it migrates to the poles and radiates away ?
While that amount of heat isn’t very significant to the oceans
it’s darn significant to the air, amounting to 73% of its heat capacity number
and that air is responsible for most of the thermal radiation
[QUOTE=http://earthobservatory.nasa.gov/Features/EnergyBalance/page4.php] The atmosphere radiates heat equivalent to 59 percent of incoming sunlight; the surface radiates only 12 percent. In other words, most solar heating happens at the surface, while most radiative cooling happens in the atmosphere. How does this reshuffling of energy between the surface and atmosphere happen? [/QUOTE]
I wish i were smart enough to work this in my head and ascribe numbers.
Thanks for reading ,
old jim
[QUOTE=”BillyT, post: 5333788, member: 536963″]Now hundreds or years of accumuated soot are being exposed – that drops the albedo from about 0.9 to 0.1 so a nine fold increase in the solar heating occurs – your will be hard pressed to find any more strong positive feed back than that….[/QUOTE]
I don’t think soot (black carbon) is properly described as a feedback of any kind. Rather, soot acts independently of CO2 radiative effects, i.e. a direct driver, like methane or aerosols. That is, if more soot were sprayed on the Greenland ice sheet from, say, a volcanic eruption, the albedo would further decrease even if CO2 concentration suddenly reverted to preindustrial levels.
Forcings graphic from AR4:
[IMG]https://www.ipcc.ch/publications_and_data/ar4/syr/en/fig/figure-2-4-l.png[/IMG]
[QUOTE=”Jeff Rosenbury, post: 5333742, member: 476307″]The polar regions still have a low “average angle of incidence of insolation” (which is what I thought I said)….[/QUOTE]
Yes, but ranging up to 24 hours a day in season.
[QUOTE=”Jeff Rosenbury, post: 5334022, member: 476307″]Brewster’s angle (53º) is the angle where about half of light is reflected off the surface of water. [/QUOTE]
That is not what Brewster’s angle is. Brewster’s angle is the angle at which none of the [I]p[/I]-polarized light is reflected. All of that light enters the water. Most of the [I]s[/I]-polarized light also enters the water at this angle. At Brewster’s angle, over 95% of the incident light on a flat air/water surface enters the water. Water is darker than fresh asphalt at this angle. Water is darker than fresh asphalt at most angles. It’s not until the light rays become very close to parallel to the surface (84 degree angle of incidence) that more light is reflected than transmitted.
[QUOTE=”BillyT, post: 5333788, member: 536963″]Beause it is. The greater heat absorbed by lower albedo melts more ice and snow. lowering the albedo even more as bare (darker) spots develope.
Also often there develope pools of water in low spots and the albedo there is lowered too, compared to the ice under the bottom of the pool. Again, I challenge you to find any Postive Feedback as strong as the one happening NOW in Greenland’s ice sheet.[/QUOTE]
While this is likely true for Greenland, it’s not at all clear it’s true for sea ice.
Brewster’s angle (53º) is the angle where about half of light is reflected off the surface of water. This means that above 53º latitude, naively, the albedo of water is over 0.5. (It is far more complicated than that of course — which is my point.) Since ice and snow’s albedo ranges from 0.9 to 0.3, it is not clear water’s albedo is lower than ice in the arctic — even in the summer. (In the winter the albedo is irrelevant because there is effectively no incident sunlight.)
Meanwhile, the arctic area can still “see” the night sky at a 90º angle. Its emissivity remains and the area continues to emit longwave infrared radiation. The limitting factor on this is likely the ∆T[SUP]4[/SUP]between the ground/sea and the night sky. Raising the temperature in the region raises the ∆T and gets that 4[SUP]th[/SUP] power emission bonus.
I want to make it clear I am not claiming this melting is a good thing. I’m just claiming it has been poorly studied. The arctic environment is probably the most fragile in the world. Given the large methane deposits in the tundra and oceans (clathrates) which even small temperature rises might release, there is cause for concern.
I can think of a number of things wrong with my model, the most obvious is that water (and arctic ice for that matter) is not flat. Waves will create a chop effect limiting the albedo gain due to the Brewster angle. The Brewster angle will change with the seasonal axial tilt. The atmosphere above the ice will have a large effect since waves incident at a low angle will travel through much more air. These conundrums are just off the top of my head. My point is that this is a complex subject and any positive feedback loop is at best not obvious.
But the idea that the albedo is of great concern in a region getting little sunlight seems oddly immune to logic. Global warming is a big enough problem without adherents practicing bad science and settling for confirming their bias.
[QUOTE=”Jeff Rosenbury, post: 5333742, member: 476307″]If the changing polar albedo effect is well understood, why do educated climatologists continually refer to a lowered polar albedo as absorbing more heat as a positive feedback? … [/QUOTE]Beause it is. The greater heat absorbed by lower albedo melts more ice and snow. lowering the albedo even more as bare (darker) spots develope.
Also often there develope pools of water in low spots and the albedo there is lowered too, compared to the ice under the bottom of the pool.
It is even more comlex as for hundreds of years (or more) soot from forest fires has been falling on the snow but is soon covered when the snow is not melting, as it is today. Now hundreds or years of accumuated soot are being exposed – that drops the albedo from about 0.9 to 0.1 so a nine fold increase in the solar heating occurs – your will be hard pressed to find any more strong positive feed back than that.
This video discusses the “lakes” forming on the ice increasing solar absorption: [URL]http://cdn.rollingstone.com/feature/greenland/video/lakes.webm[/URL]
If you watch this UCLA video / discusion below, not only will you better understand the positive feed back of melt water effects but also as their sensor moves over the ice, you will see it is quite dark in some areas with decades of accumulated soot are now exposed on the surface.
[MEDIA=youtube]-EMCxE1v22I[/MEDIA] Even without opening this video, you can see the ice/ snow surface is far from the white you expect for snow. Again, I challenge you to find any Postive Feedback as strong as the one happening NOW in Greenland’s ice sheet.
[QUOTE=”saturn9, post: 5332297, member: 580631″]Water has a 4 times higher heat capacity than CO[SIZE=3]2[/SIZE]. …[/QUOTE]I doubt that as H2O is not a linear molecule as 0-C-O is. Thus with an extra non-zero monent of inertia for storing energy in rotation H2O vapor should have slightly greater means of storing energy when heated say, 0.1 C degree.
Water has the two Hs on the same side of the O, with 105 degree angle between them and having partially lost their electron are with positive charged and the O is negatively charged. – Why water molecule has a permanet dipole and is such a powerful radiator and absorber IR compared to CO2 or more graphically, 0-C-O.
[QUOTE=”saturn9, post: 5332297, member: 580631″]Water has a 4 times higher heat capacity than CO[SIZE=3]2[/SIZE]. Also the heat capacity of air is higher than of CO[SIZE=3]2[/SIZE]. .[/QUOTE]Heat capacity of the molecule is no more relevant to radiative forcing than is the heat capacty of glass in a greenhouse. The ability of CO2 to scatter certain infrared wavelengths is the issue, that is, to stop some infrared from escaping to space.
Water has a 4 times higher heat capacity than CO[SIZE=3]2[/SIZE]. Also the heat capacity of air is higher than of CO[SIZE=3]2[/SIZE]. Similar is the course of the conductivity of heat with the lowest amount by CO[SIZE=3]2[/SIZE] (Datas of the Handbook of Chemistry and Physics 14 -24, 81. Ed., 2000/2001). There is a wide range of overlapping of the absorption of the infrared between water and CO[SIZE=3]2[/SIZE]. Mostly in the atmosphere is a higher concentration of water than of CO[SIZE=3]2[/SIZE]. Therefore water should have a higher radiation force than CO[SIZE=3]2[/SIZE]. By most processes, where humans produce CO[SIZE=3]2[/SIZE] and many others much water gets in the atmosphere. The contribution of water of the greenhouse effect is about 60%. Therefor is to avoid the production of steam and heat in first line and not 0,04 % of CO[SIZE=3]2[/SIZE].
Jeff Rosenbury (post 29) said:
“Meanwhile heat energy radiates more or less uniformly.” Not true, not even close. In order for this to be true, the two major radiators, the Earth’s surface and the greenhouse gases would have to be almost isothermal. They are far from that. In actuality, both the wavelengths and the intensities of global terrestrial radiation vary tremendously from place to place and from time to time.
“This causes the poles to be cooler than the equator.” Not true. The poles are cooler because the average angle of incidence of insolation is lower. This, in turn, is due to the fact that the Earth is a sphere.
” . . . actually increases the blackbody radiation . . .” The Earth emits no blackbody radiation. The Earth emits as a greybody. Many scholars put the coefficient of emissivity at about 0.95.
” . . .to get a poorly understood mix of feedback loops.” It is actually fairly well understood, and whole library shelves of books and tens of thousands of scholarly articles have been written on the subject. I refer you to almost any Climatology 101 course.
I, too, have been to the Arctic (Thule, Greenland)–although during the summer months. We enjoyed continuous daylight.
[QUOTE=”BillyT, post: 5331049, member: 536963″]O2, N2,NO2, & argon all supply “bound electrons” for the incident sunlight’s E-field to shake.[/QUOTE]
Hi [USER=536963]@BillyT[/USER]:
Thanks for your post answering my question. I apologize for misinterpreting your
[INDENT]”EM wave is passing thur a dense medium the E-field will oscillate the bound electrons, and an accelerated electron produces radiation which combines with the incident radiation to change the net phase of radiation field.”[/INDENT]
The technical aspects of E-field and change to the net phase of the radiation field are a bit over my head. In the context of the other quote, I was confused and thought you were saying the Einstein / Smoluchowski theory was a sufficient explanation.
Regards,
Buzz
[QUOTE=”Danielvr, post: 5331195, member: 581571″]I wonder how all this figures in climate models.[/QUOTE]
This is a negligible effect – while it gets very hot deep inside the planet, this heat is not well conducted towards the surface, and contributes only a minuscule part of the heat the surface receives from the sun.
See here:
[URL]https://en.wikipedia.org/wiki/Earth’s_internal_heat_budget[/URL]
[QUOTE=”Danielvr, post: 5331195, member: 581571″]I read the third section above, “Black Body Earth”, which speaks of an -18 degree equilibrium, but I don’t think I understand. Does that or does that not account for this heat from within the planet? I don’t think it does, or else there wouldn’t be places on Earth where it gets even colder in Winter. Or, maybe those colder places can be explained by regional differences in heat conductivity of the planet’s mantle and crust?[/QUOTE]
The equilibrium temperature is the uniform temperature the whole surface would need to have in order to reradiate the specified amount of energy. You can have places during winter, at high latitudes, or simply at night with lower temperatures, as long as there are places with higher temperatures elsewhere.
I.e., it has to be compared with the averaged global temperature, not with specific individual instances.
[QUOTE=”Buzz Bloom, post: 5331004, member: 547865″]Hi [USER=536963]@BillyT[/USER]:
Thanks very much for the reference. I am a bit confused by your quote relative to what I read in the reference.
The quote above seems to be saying that the Einstein / Smoluchowski theory about fluxuations explains the blue sky. The following is a quote from the reference.
[INDENT]Einstein stated that “it is remarkable that our theory does not make [I]direct[/I] use of the assumption of the discrete distribution of matter” . . .
There is no dispute, then, about what really causes the sky to be blue? Is it “really” scattering by molecules? Or, if you want to be more precise, scattering by electrons. Even more precise, scattering by [I]bound[/I] electrons: free electrons would not give us a blue sky. The preposition “by” indicates an agent, and molecular scattering is the agent responsible for the sky’s blueness.[/INDENT]
This seems to contradict your quote’s suggestion that molecules are [U]not[/U] responsible for the blue sky. Your quote seems to support the Einstein / Smoluchowski theory, and the references seems to say it’s wrong. Or have I misinterpreted what you said? Or what the article says?
ADDED
Now that I have read the whole article, I get that any molecule of sufficiently small size, e.g. argon, would also make the sky blue, provided such molecules have no specific energy levels in its spectrum that would absorb blue light. So the reason that NO2 makes the sky blue is that NO2 makes up most (~80%) of the atmosphere. Since O2 makes up most of the remainder, I am curious. Does O2 also scatter light with smaller wavelengths like blue and violet? Regards, Buzz[/QUOTE]Note I said:
“EM wave is passing thur a dense medium the E-field will oscillate the bound electrons, and an accelerated electron produces radiation which combines with the incident radiation to change the net phase of radiation field. (Why the refractive index exist.*) ”
So yes there must be some matter (especially bound electrons) to make a refractive index. O2, N2,NO2, & argon all supply “bound electrons” for the incident sunlight’s E-field to shake.
If the bound electronic density were exactly the same every where, so would be the index of refration and there would be only forward (and bckward) scattering. What Einstein / Smoluchowski theory does is to note that all you need is variation of the index of refraction on wave lenght scale. – you don’t really need to get into the facts relating to how the index of refraction is created, but that was the approach used to explain blue sky originally. Einstein / Smoluchowski skipped the real details about atoms having bound electrons, but they must be present to make the index of refracion, and if their density is varying on the wave length scale, then so will th index of refraction. – One is a high-level POV and the standard, older one is a more detailed POV, but they are essentially the same.
Sort of like the difference between: The IC motor makes torque that turns the wheels vs The vaporized gasoline volume and presure greatly increases as it oxidizes and they forces the pistons down …”
[QUOTE=”BillyT, post: 5330817, member: 536963″]That gives the Einstein / Smoluchowski theory which does not even require discrete molecules – only density fluxuation, that cause refractive index spatial variation.[/QUOTE]
Hi [USER=536963]@BillyT[/USER]:
Thanks very much for the reference. I am a bit confused by your quote relative to what I read in the reference.
The quote above seems to be saying that the Einstein / Smoluchowski theory about fluxuations explains the blue sky. The following is a quote from the reference.
[INDENT]Einstein stated that “it is remarkable that our theory does not make [I]direct[/I] use of the assumption of the discrete distribution of matter” . . .
There is no dispute, then, about what really causes the sky to be blue? Is it “really” scattering by molecules? Or, if you want to be more precise, scattering by electrons. Even more precise, scattering by [I]bound[/I] electrons: free electrons would not give us a blue sky. The preposition “by” indicates an agent, and molecular scattering is the agent responsible for the sky’s blueness.[/INDENT]
This seems to contradict your quote’s suggestion that molecules are [U]not[/U] responsible for the blue sky. Your quote seems to support the Einstein / Smoluchowski theory, and the references seems to say it’s wrong. Or have I misinterpreted what you said? Or what the article says?
ADDED
Now that I have read the whole article, I get that any molecule of sufficiently small size, e.g. argon, would also make the sky blue, provided such molecules have no specific energy levels in its spectrum that would absorb blue light. So the reason that NO2 makes the sky blue is that NO2 makes up most (~80%) of the atmosphere. Since O2 makes up most of the remainder, I am curious. Does O2 also scatter light with smaller wavelengths like blue and violet?
Regards,
Buzz
[QUOTE=”Buzz Bloom, post: 5330660, member: 547865″]Hi BillyT: Thanks for your post. I am always interested in learning something new. Can you recommend a reference that explains more about this phenomenon? Regards, Buzz[/QUOTE]Read the last paragraph of right column, page 269 here:
[URL]http://homepages.wmich.edu/~korista/colors_of_the_sky-Bohren_Fraser.pdf[/URL] That gives the Einstein / Smoluchowski theory which does not even require discrete molecules – only density fluxuation, that cause refractive index spatial variation.
Prior to that Einstein / Smoluchowski theory, the scatering of molecules was used (and still usually is) to explain why the sky is blue. Basically if a plane EM wave is passing thur a dense medium the E-field will oscillate the bound electrons, and an accelerated electron produces radiation which combines with the incident radiation to change the net phase of radiation field. (Why the refractive index exist.*) This electronic radiation goes in all direction in a plain normal to the oscillator motion, but that of many electrons all driven in phase (dense medium & plain wave) only constructively interfer in the forward (or backward, but 180 scatter is weak) direction. I.e. in dense medium of uniform density there is no scattering, but add dynamic density variation on the scale of the wave length you do get scattering.
These small scale density fluxuation are percentage wise much larger in a rarified gas. So most of the scattering of blue light takes place high up in the atmosphere, but not so high that there is little there. Lower in the armosphere, most of the scattering is by small particles (dust etc.).
* As the earlier theory which does consider the individual atomic / molecular scattering gives almost the correct results, few of the papers found by Google have much to say about Einstein / Smoluchowski theory, but it clearly does not depend upon the existance of atoms or molecules – Certainly not what they are. Why I could say that an argon amosphere would also make the sky blue.
[QUOTE=”BillyT, post: 5328816, member: 536963″]I think that is miss leading. Even if the atmosphere were argon, the sky would still be blue.[/QUOTE]
Hi BillyT:
Thanks for your post. I am always interested in learning something new. Can you recommend a reference that explains more about this phenomenon?
Regards,
Buzz
Haruspex,
Like you, I much admire the 1997 paper by Kiehl and Trenberth. I think it should be in every atmospheric scholar’s sourcebook. I believe it to be the standard to which all subsequent global heat budget studies should be compared. Which brings me to another quibble:
In your point 7, you object to the statement, “CO2 is insignificant compared with H2O as a greenhouse gas”. I would object right along with you, but I don’t know any serious scholars of the atmosphere who would make such an unsupported statement. On the other hand, a good many atmospheric scholars would strongly agree that it is a [B]less significant[/B] greenhouse gas. Kiehl and Trenberth [1997] are among them. They call the role of water vapor “dominant”.
1. Water vapor accounts for more than 40 Wm[SUP]-2[/SUP] of absorption of short-wave (solar) radiation. Carbon-dioxide accounts for less than 1 Wm[SUP]-2[/SUP] (none, under cloudy skies).
2. The vast majority of photons emitted by terrestrial IR sources are emitted by water molecules. Atmospheric water molecules can absorb all of these photons, atmospheric carbon-dioxide can absorb only a small fraction (the “overlap” wavelengths). Carbon-dioxide plays no significant role in the emission of terrestrial IR.
3. At 4,000 ppm compared to 400 ppm, water vapor is ten times more abundant in our atmosphere than is carbon-dioxide. In your argument you state, “Increasing the level of a relatively rare greenhouse gas has more effect than increasing the level of a more common species.” This statement is true only if the more common gas is approaching its optical saturation density. This is not true for water vapor. This fact is attested to by the common observation that ground fogs and mists are rapidly dissipated by direct sunlight.
[QUOTE=”klimatos, post: 5329206, member: 225464″]2) More than 90% of the heat transmitted from the surface to the atmosphere comes in the form of terrestrial infrared radiation. Again, mostly radiation from water molecules. Conduction and enthalpic cycling (condensation, not evaporation) play only very minor roles.[/QUOTE]
You’re right, I missed a chunk. But I believe the fraction reradiated is more like 80% (Kiehl and Trenberth, 1997). Most of that is radiated back down again, so convection is (just) the major escape route through the troposphere.
Derek,
Excellent post–although I have a few quibbles. You probably would have addressed them if you were given more space, but here goes:
In your point 6, you state:
1) The Sun warms the Earth’s surface.
2) Conduction and evaporation carry this heat energy to the air at the Earth’s surface.
3) Some conduction, but mostly convection, carries the heat energy higher.
All of these statements are misleading in some respect:
1) Some two-thirds of the radiant energy reaching the surface of the Earth comes from atmospheric molecules—mostly water molecules, the remaining third comes from the Sun. These atmospheric water molecules, of course, got their energy from the Sun in the first place. If you had simply said that, “The Sun warms the Earth”, your statement would be correct.
2) More than 90% of the heat transmitted from the surface to the atmosphere comes in the form of terrestrial infrared radiation. Again, mostly radiation from water molecules. Conduction and enthalpic cycling (condensation, not evaporation) play only very minor roles.
3) Once again, radiation plays the dominant role. Air is simply an extremely poor conductor of heat. An air mass has less thermal energy and a much lower temperature after it has been forced up than it had at its lower elevation. How does this “carry the heat energy higher”?
[QUOTE=”Buzz Bloom, post: 5326117, member: 547865″]… I understood that N2 scatters blue light, and this is what makes the sky look blue. … Buzz[/QUOTE]I think that is miss leading. Even if the atmosphere were argon, the sky would still be blue. On the scale of longer wave lengths, say red light wave length, there is nearly a constant number of atoms (or molecules) in a cube with edge of length equal to red wave lengths. But in a cube with half that edge length (1/8 as many molecules inside) the statistical fluctuation as a percentage in number of molecules inside the cube are more significant. The scattering is due to the greater varying index of refraction that small volumes have. Nothing to due with air being mostly N2.
[QUOTE=”haruspex, post: 5328606, member: 334404″]To address your earlier comment I already added a clause on time delayed feedbacks. If you feel it is necessary to mention instability specifically I’m happy to add that.
Thanks.[/QUOTE]
No. I like your insight post. Thanks for the addition. I think what you have is as good as it can reasonable be. Negative feedback such a can of worms that it’s not realistically possible to do much better.
[QUOTE=”FactChecker, post: 5328600, member: 500115″]Negative feedback is more complicated than you imply. It can cause dynamic instability. It depends on the dynamics of the system, which is very complicated in this case.[/QUOTE]
To address your earlier comment I already added a clause on time delayed feedbacks. If you feel it is necessary to mention instability specifically I’m happy to add that.
Thanks.
[QUOTE=”haruspex, post: 5328379, member: 334404″]I included some examples. I made no claim it was exhaustive. There are several more I could have listed (positive and negative). My purpose was to illustrate what is meant by a feedback.
The Insights post concerns aspects of climate science that are well settled and uncontentious yet often misunderstood or misrepresented. I have no plan to get into the more debatable areas. That would be beyond my expertise.
Last I checked, the general view was that whether clouds act mainly as negative or positive feedbacks depended on altitude, but I don’t recall which way it worked or whether there was consensus on which dominates.[/QUOTE]Negative feedback is more complicated than you imply. It can cause dynamic instability. It depends on the dynamics of the system, which is very complicated in this case.
[QUOTE=”mheslep, post: 5328383, member: 70823″]Sure, then perhaps say so? “divided into negative and positive feedbacks, [I]such as …[/I]”. Or, “[I]…for example[/I]”[/QUOTE]
Done.
[QUOTE=”haruspex, post: 5328379, member: 334404″]I included some examples. I made no claim it was exhaustive. …[/QUOTE]Sure, then perhaps say so? “divided into negative and positive feedbacks, [I]such as …[/I]”. Or, “[I]…for example[/I]”
[QUOTE=”mheslep, post: 5328373, member: 70823″]Regardless of the current uncertainty on the subject, why no inclusion of the possibility of clouds in Negative Feedbacks? The CFMIP modeled feedback is “approximately zero”, but this is not the same as saying there is none.
IPCC AR5 7.2.5.4: “The key physics is in any case not adequately represented in climate models. Thus this particular feedback mechanism is highly uncertain”[/QUOTE]
I included some examples. I made no claim it was exhaustive. There are several more I could have listed (positive and negative). My purpose was to illustrate what is meant by a feedback.
The Insights post concerns aspects of climate science that are well settled and uncontentious yet often misunderstood or misrepresented. I have no plan to get into the more debatable areas. That would be beyond my expertise.
Last I checked, the general view was that whether clouds act mainly as negative or positive feedbacks depended on altitude, but I don’t recall which way it worked or whether there was consensus on which dominates.
[QUOTE=”D H, post: 5327586, member: 42688″]Minor comment: Please replace that image that depicts a 5250 °C blackbody curve with something else. The Sun’s effective blackbody temperature is not 5250 °C, or 5523 kelvins. It is 5777 or 5778 kelvins, depending on who you read. Siting that image has become a “frequently made error in climate science.” This is a good example of why wikipedia is not a good source.
Otherwise, this is a very nice insight article.[/QUOTE]
Thanks D H, I was not aware that was wrong. But I like the image, much clearer than most, so I’ve just added a note. (Is the curve wrong, or just the number? The peak seems to be in about the same place as in other images I found.)
Minor comment: Please replace that image that depicts a 5250 °C blackbody curve with something else. The Sun’s effective blackbody temperature is not 5250 °C, or 5523 kelvins. It is 5777 or 5778 kelvins, depending on who you read. Siting that image has become a “frequently made error in climate science.” This is a good example of why wikipedia is not a good source.
Otherwise, this is a very nice insight article.
The Insight article is excellent. But I can’t help making a small correction to this statement:
“[I]Note[/I]: If something is a negative feedback it acts to dampen change; it cannot make the change go in reverse.”
In systems with time delays, accumulated effects, and limiting functions, negative feedback can cause cyclic behavior that includes periodic reverse effects.
The dynamics of the system we are talking about is very complicated and includes all those features.
That being said, if the negative feedback causes a reverse effect at one time, there will probably be a contributing effect later. So it might fool us now and cause a catastrophe later.
[QUOTE=”alw34, post: 5326639, member: 580161″]Oh, the horror!! Yet, one must secure government grants or perish.
In most scientific models, a single false prediction invalidates the model.
Climate models seem immune from such scrutiny.[/QUOTE]
You are wandering off the topic of what errors are commonly made and what the correct versions are. If you wish to engage in a discussion on the politicisation of science; on the relationship between scepticism, consensus, scientific progress and public policy; or on the use of models of complex systems, let’s do that as a private dialogue.
[QUOTE=”haruspex, post: 5326631, member: 334404″]some people making climate science errors do so disingenuously.[/QUOTE]
Oh, the horror!! Yet, one must secure government grants or perish.
In most scientific models, a single false prediction invalidates the model.
Climate models seem immune from such scrutiny.
[QUOTE=”alw34, post: 5326504, member: 580161″]What conclusions can be drawn from such ‘frequent errors”. Who do you think is making such errors and what are the effects? Thanks.[/QUOTE]
They are errors I have come across in posts (not just in these forums), and, just occasionally, errors I have made myself.
This particular FME post is a bit different from my others (Friction, Moments, etc.) in that there is reason to suspect that some people making climate science errors do so disingenuously.
What conclusions can be drawn from such ‘frequent errors”. Who do you think is making such errors and what are the effects? Thanks.
[QUOTE=”Buzz Bloom, post: 5326117, member: 547865″]Hi haruspex:
I very much like your Insight article. I have a question though.
The article says:
[INDENT]If we treat the Earth as emitting and absorbing radiation as a “black body”, ignoring the atmosphere, and treating incoming light as spread evenly over the whole Earth’s surface all the time, we can calculate the equilibrium temperature as -18C. At that temperature, black body radiation would balance insolation.
Adding a non-greenhouse atmosphere, e.g. pure nitrogen, doesn’t change this.[/INDENT]
I understood that N2 scatters blue light, and this is what makes the sky look blue. Wouldn’t the scattering of blue photons by N2 then reduce the number of blue photons that hit the earth, since about half the scattered photons return to space? Wouldn’t this [U]reduce[/U] the equilibrium average temperature of the surface compared with no atmosphere?
Regards,
Buzz[/QUOTE]
Yes, that’s true too. From what I read, the scattering of green light in air at 1atm. is 10[SUP]-5[/SUP]m[SUP]-1[/SUP], and blue light about double that. From that I calculate that about 4% of green light and 8% of blue light would never make it through. Taking the mean power loss as 6%, that would knock 1.5% off the surface temperature, or 4[SUP]o[/SUP] K.
Edit: I forgot to allow for IR, barely scattered at all. So I would think the power lost would be no more than 4% in total.
Hi haruspex:
I very much like your Insight article. I have a question though.
The article says:
[INDENT]If we treat the Earth as emitting and absorbing radiation as a “black body”, ignoring the atmosphere, and treating incoming light as spread evenly over the whole Earth’s surface all the time, we can calculate the equilibrium temperature as -18C. At that temperature, black body radiation would balance insolation.
Adding a non-greenhouse atmosphere, e.g. pure nitrogen, doesn’t change this.[/INDENT]
I understood that N2 scatters blue light, and this is what makes the sky look blue. Wouldn’t the scattering of blue photons by N2 then reduce the number of blue photons that hit the earth, since about half the scattered photons return to space? Wouldn’t this [U]reduce[/U] the equilibrium average temperature of the surface compared with no atmosphere?
Regards,
Buzz
Bandersnatch, thanks kindly for answering my question!Intuitively, I still find it hard to understand that we, living on the thin crust of the planet, get so little heat from within the endlessly more voluminous and blazingly hot mantle. Particularly because when you descend into a mine, it gets so much hotter so quickly (1 degree F per 70 feet of depth). You'd think that a lot of that energy would find its way to the surface and be dissipated through the oceans and the athmosphere.Do you happen to know how warm (cold) Earth would be if there were no Sun? If 0 Kelvin is the absolute minimum and 287 Kelvin is the current average temperature on Earth's surface, I wonder how much that would be if we only had Earth's core as an energy source.
If the changing polar albedo effect is well understood, why do educated climatologists continually refer to a lowered polar albedo as absorbing more heat as a positive feedback? The polar regions still have a low "average angle of incidence of insolation" (which is what I thought I said). That means little light coming in. On the greybody thing, I did equate mistakenly albedo with thermal emissivity which is only a weak approximation. Albedo refers to the incoming light (visible and short wave infarred) and emissivity the outgoing light (long wave infarred). The two aren't the same, particularly for liquid water which is very complex (varying with surface conditions like wind/wave conditions). But the reciprocity principal means darker surfaces which absorb more also emit more greybody radiation (though that changes with wavelength). Still, a look at outgoing longwave maps makes it clear that ice is a poorer emitter than water. None of your comments change the point that polar regions emit more heat than they absorb, and polar albedo is not a clear positive feedback.
Light does not strike the earth evenly. Light at the equator (on average) hits at a 90º angle and has full effect. But toward the poles this drops off. Meanwhile heat energy radiates more or less uniformly. This causes the poles to be cooler than the equator. It also means melting icecaps decrease the albedo actually increases the blackbody radiation all other things being equal (which they are not of course). This is complex because of the earths tilt on its axis affects the radiation patterns which interacts with the seasonal changes in albedo. Add clouds, water vapor, and seasonal temperature variations to get a poorly understood mix of feedback loops. I know it's poorly understood since few people seem able to remember the sun doesn't shine in the arctic in the winter. I've been there. It's dark for months at a time.
Hi, a noob here, so please bear with me as I show my ignorance :) Anyone who has ever spent some time in the depths of a coalmine knows that it can get pretty hot down in Earth's crust. (much) Deeper still, the core of our planet has even been calculated to be 10,800 degrees hot (as hot as the Sun's surface!). Some 90% of the energy required to maintain this temperature comes from the decay of radioactive elements, and if I understand correctly, it is eventually dissipated through (infrared?) radiation at Earth's surface. I read that the amount of heat caused by this radiation is almost the same as the total heat measured emanating from the planet (http://phys.org/news/2006-03-probing-earth-core.html).I wonder how all this figures in climate models. Climate scientists always seem to talk about light (energy) coming into our athmosphere from the Sun and then being converted into infrared light, which may or may not be trapped as heat in the athmosphere. But how about the (apparently) much more significant amount of infrared radiation coming from within – do today's models account for that at all?I read the third section above, "Black Body Earth", which speaks of an -18 degree equilibrium, but I don't think I understand. Does that or does that not account for this heat from within the planet? I don't think it does, or else there wouldn't be places on Earth where it gets even colder in Winter. Or, maybe those colder places can be explained by regional differences in heat conductivity of the planet's mantle and crust?Thanks in advance for any enlightening comments!
Regardless of the current uncertainty on the subject, why no inclusion of the possibility of clouds in Negative Feedbacks? The CFMIP modeled feedback is "approximately zero", but this is not the same as saying there is none. IPCC AR5 7.2.5.4: "The key physics is in any case not adequately represented in climate models. Thus this particular feedback mechanism is highly uncertain"