Guest Post by Willis Eschenbach
Of late there has been a lot written about the effect of “black carbon”, a.k.a. “soot”, and also “brown carbon”, a.k.a. wood and dung smoke, on the climate. Me, I think it’s worthwhile controlling black and brown carbon solely because of the health effects. Inhaled soot and wood smoke kill a lot of people every year. So reducing atmospheric black and brown carbon is an example of the “no-regrets” actions I have been advising that we should take. It is of value whether or not black carbon affects global climate.
And city dwellers are familiar with the phenomenon that when soot falls on snow, it absorbs sunlight, warms, and speeds the melting of the snow. In the country, people spread firewood ashes on frozen walkways to melt the ice. So black carbon tends to melt snow and ice, and thus reduce snow and ice albedo, and thus warms the climate. How much? Unknown, but estimates say black carbon is a definite factor in the Arctic warming.
However, there is one major misconception out there about the effect of black carbon on climate. It shows up in a recent editorial by Richard Kerr in Science magazine.
A Quick (Partial) Fix for an Ailing Atmosphere
Science 13 January 2012: , Vol. 335 no. 6065 p. 156 , DOI: 10.1126/science.335.6065.156
The world’s air could use a quick scrubbing. So a group of scientists has come up with 14 practicable approaches to doing just that. The researchers say the selected cleaning methods, described on page 183, would more than pay for themselves in lives saved and crop yields increased while cutting global warming to boot. “Technically, it can be done,” says atmospheric scientist Mark Jacobson of Stanford University in Palo Alto, California, who was not involved in the work. “It’s a question of will power.”
Scientists and policymakers alike have long known how, in principle, to get a quick start on cleaning up the atmosphere: Stop the gush of short-lived pollutants. Carbon dioxide will remain in the atmosphere for centuries, warming the world all the while, but pollutants like soot and methane remain airborne just a few weeks and a decade or so, respectively. Stop their emissions and their concentrations would promptly start dropping, sharply.
And that would be a good thing. Inhaled soot, also called black carbon, kills or debilitates millions of people each year, while soot in the atmosphere tends to warm climate, mainly by absorbing more sunlight.
It is the last statement, “soot in the atmosphere tends to warm climate, mainly by absorbing more sunlight”, that is in error. I can show this by means of a curious thought experiment, by taking black carbon to extremes.
The logic of their claim goes like this. The earth receives a global 24/7 average of 342 W/m2 at the top of the atmosphere. Of this, about 107 W/m2 is reflected back into space. Black carbon is very much like an ideal blackbody, it absorbs just about all of the light that hits it. The claim is that black carbon in the atmosphere absorbs the incoming solar radiation, so it cannot be reflected back to space. In addition, it also absorbs sunlight reflected from the ground and prevents it from escaping to space. So it intercepts and absorbs sunlight in both directions.
As a result, the system has to end up warmer than it is at present.
And to be fair, that all sounds eminently logical. We end up with more energy in the system, the atmosphere ends up warmer, because the black carbon is absorbing both more sunlight and more reflected sunlight. “Simple physics”, as the AGW folks are fond of saying.
So, here is the thought experiment. Suppose we have a planet just like the Earth, that receives a global 24/7 average of 342 W/m2 at the top of the atmosphere and reflects about 107 W/m2 back into space
We start adding black carbon to the atmosphere. We note that as Richard Kerr says, the black carbon absorbs more and more of both incoming (solar) and outgoing (reflected solar) radiation. Just as their logic says, there’s less and less energy reflected back into space.
We add more and more black carbon, slowly absorbing more and more sunlight and reflecting less and less sunlight. Finally we have added so much black carbon that it forms a shell of solid black carbon entirely surrounding the planet, say 20 kilometres above the surface. This shell is not reflecting anything at all, it is absorbing all the sunlight.
What happens to the temperature of the planet? This is the extreme case of black carbon in the atmosphere, and so it will tell us what the net effect is of adding black carbon to the atmosphere.
Well, we know that the shell has to radiate the same amount of energy that it receives, both inwards and outwards. Since the shell is the only thing heating the planet, that means the planet must be at the same temperature as the shell.
And what temperature would that be? Well, it would be the blackbody temperature sufficient to radiate 342 W/m2, which is … wait for it …
5.5°C or 42°F
This is well below the current temperature of the planet, which is usually taken to be about 14-15°C, or 58°F.
And this means that black carbon in the atmosphere cools the planet.
So where did the logic go wrong?
Their logic went wrong by not considering the effect of atmospheric black carbon on the poorly named planetary “greenhouse effect”. The greenhouse effect works because sunlight strikes the surface. When that energy is radiated back out towards space, some of the energy is absorbed by the atmosphere.
About half of that energy is radiated from the atmosphere back to earth, while the rest is radiated back to space. As a result, the earth ends up warmer than it would be without “greenhouse” gases in the atmosphere.
But when atmospheric black carbon absorbs the solar energy, only about half of the absorbed energy is radiated down to the surface, with the rest radiating upwards towards space.
And as a result, the surface only receives half the radiant energy from the sun that it would have gotten if the black carbon were not there.
In other words, atmospheric absorption of solar energy by any aerosols or molecules, including black carbon, reduces the efficiency of the greenhouse effect. Instead of the surface receiving energy from both the sun and the atmosphere, when black carbon intercepts the sunlight, the surface receives energy solely from the atmosphere.
For the greenhouse effect to work, the sun has to strike the surface. Any solar absorption in the atmosphere reduces the greenhouse effect, and in the extreme, total solar absorption in the atmosphere reduces the greenhouse effect to zero.
And as a result, as the thought experiment shows, adding black carbon (or anything that absorbs sunlight) to the atmosphere cools the planetary surface.
I cannot let this go by without expressing my displeasure at the use of bad science in pushing public policy. As Richard Kerr has just amply demonstrated, the understanding of climate even among scientists is still far too poor to serve as a base for any kind of policy decisions.
w.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Paint a rock in space white, it will cool; paint it black, it will warm.
But what about convection?
If black carbon warms the atmosphere, it decreases the lapse rate and convection reduces, that causes heat to accumulate close to the ground until the surface layer reaches a sufficiently high temperature for convection to occur again.
Titan 28 says:
February 7, 2012 at 7:04 pm
What is Mr Feht talking about? Did I miss something?
In Mr. Eschenbach’s answer to my footnote above you can see exactly, what I am talking about.
Mr. Eschenbach allows himself to use vilest insults if he doesn’t like somebody’s comments (and I am not the exclusive target of these attacks). Since his answers are posted in non-moderated format, these puerile escapades are first and only examples of such behavior, unabated, on WUWT pages.
I already wrote to Mr. Watts about it but, as it seems, Mr. Eschenbach is regarded as too valuable an asset here to be limited by the same rules that apply to everybody else. A pity, since civility has been — until now — a distinctive feature of this blog that made it radically different from the style habitual on alarmist sites.
Willis, as I sit here in my apartment with my windows open with an outside temperature of -10C in Sweden utilizing communal heat which is fueled by the burning of household garbage I also have concerns regarding soot.
The mathematics and data mining are all useful and entertaining exercises(mental masturbation would be the term used by some).
The Kepler discoveries show earth like planets. Sci-Fi incessantly pushes the concept of man’s ability to terraform a planet. If an advanced species discovered Earth what would they determine would be the average phone number or the average global temperature? (Pielke Sr. is the most rational scientist in my book on Climate).
In a fictional world where Mike Mann and his hockey team could control the earth’s temperature with their mythical CO2 thermostat, what temperature would they set it?
Instead of ankle biting around the issue with truly eloquent mathematics and computer modeling I think there first has to be established that there is a problem.
Once a problem has been identified there must be a cost effective solution presented.
As far back as I can remember the once fertile arctic in my school boy days was referred as the “arctic wasteland”.
Wastelands have dubious meanings today. In the USA the desert wasteland must be maintained at all costs because or some rodent unless huge patches can be bulldozed so that useless solar panels or wind mills can be implemented to destroy all local wild life.
Willis, What is the ideal temperature of our plane?. Why is that temperature different than what we have now? Why is my local commune burning my garbage and putting black soot in the air towards Finland and Russia?
Willis, I love your posts but I would really love for them to focus on the hard core of the issue. Is there a problem and if so do we have a solution.
Now that I have bastardized the English language I will continue my day in Sweden.
Poriwoggu says:
February 7, 2012 at 10:39 pm
You sound like a fairly intelligent person, so I won’t be fully mean but give you a taste of what community science can come up with.
There is a *difference between the illumination and received energies. Received includes albedo but the albedo is affected by the presence of CO2 which reflects 50% of the Sun’s irradiance back to space at its absorption frequencies. Increasing CO2 will therefore increase albedo. This would suggest that CO2 cools but in fact the effect is net neutral because it similarly reduces emissivity in those same bands.
Consider an addition of two molecules of CO2, one on the day side and one on the night side (for simplicity). Each would have an equal chance of passing a photon on or back (as CO2 re-radiates omni-directionally). The four possible outcomes are;
1. Sun >[~>( 0 )~>]> Space. = Sun radiated photon in. Earth radiated photon out.
2. Sun >[~>(+1)<~] Space. = Sun radiated photon in. Earth radiated photon in.
3. Sun ^[<~( 0 )<~] Space. = Sun radiated photon out. Earth radiated photon in.
4. Sun ^[]> Space.= Sun radiated photon out. Earth radiated photon out.
Key;
> Photon and direction.
~> Absorbing & radiating carbon dioxide molecule.
[Earth-atmosphere system]
(System energy change)
Where, over time, the average will be a zero addition to system energy. By the same logic reversing the process by removal of CO2 from the atmosphere, albedo will reduce and emissivity increase but again, system energy will remain static.
The conclusion is that ‘GHG’ concentrations in the atmosphere do not change system energy. Any energy level is therefore a function of the planet-atmosphere itself and supports the N&Z finding that annual average near surface temperature is independent of the level of atmospheric carbon dioxide.
* Illumination 343W, received 240W and radiated out 240W. 103W is albedo loss of illumination which includes CO2 reflection.
Shoot. I meant
Poriwoggu says:
February 7, 2012 at 10:39 pm
“markus says: …Given that the atmospheric density… ”
There has to be a paper on this, it has to have peaked someones interest.””
You sound like a……. blah blah blah
[FIXED. -w.]
Willis what the hell did you do? You have opened pandora’s box of AGW trolls. I have never seen so many on one thread.
Poriwoggu, it can also follow that additional atmospheric mass (black coal) gives a, if you will, extra brick to the atmosphere. Upper atmosphere turbulence can sheer off when entering or exiting timescales of planetary harmonics as described by Dr Scafetta. This, and other, e.g: solar isolation, multivariate data of a planet with atmosphere can predict near surface climate exponentially compared to the greenhouse paradigm.
Co2 back radiation principle is analogous to steel balls, in a pinball machine, bouncing against the posts on a plane. The models have been guessing the result. As a first principle the greenhouse effect was wrong. The “science” that followed was also wrong.
Can you see the logic of treating atmospheric gases in a climate machine using the mechanism of the pinball machine plunger (solar radiation), and the slope of the the climate (force of pressure), to predict climate.
Of course, as the science suggests, atmospheric gases are only on part of the puzzle, if the community keeps thinking individually, and combineing their predicates, they’ll progress well.
There is still plenty of science yet in macroclimatology, but by gosh it’s fascinating.
“Alexander Feht says:
February 8, 2012 at 12:21 am
Mr. Eschenbach allows himself to use vilest insults if he doesn’t like somebody’s comments (and I am not the exclusive target of these attacks).”
I know Alex, he can be just so mean sometimes. He is such a naughty man when he hurts your feelings. Just naughty.
It’s only Wednesday, we’ve got 3 more days of Gaiety this week.
Haaaaaa….
Stephen Richards says:
February 8, 2012 at 1:06 am Willis what the hell did you do?
KISS
Is there a problem?
If there is a problem what is the reasonable solution?
It is not productive to spend this many hours, days and weeks doing mathematical gymnastics on a problem that might not exist for a century if the problem exists at all especially being there currently are no cost effected solution if the problem does exist.
The carriage has been brought before the horse.
Non-workable and detrimental solutions have been implemented prior to an actual problem being identified.
Puzzles and math games are fun. Wake up, public funds are being stolen for something that may or may not be a problem a century from now and the solutions that are being implemented haven’t a snow ball’s chance in hell if the problem actually exists.
Get off the high horse and look at the task at hand.
Come on Willis, get back to reality.
If you want to continue to violate the laws of thermodynamics then go ahead but for me the GHG theory and the re-radiated heat is bunkum.
As my lecturer at Imperial used to say, Hot>cold yes Cold>Hot never.
Willis says: “the planet must be at the same temperature as the shell.”
This is wrong, very wong
You forget that the atmosphere is not a solid thing, it’s moving gases. This movement creates the lapse rate effect with decreasing temperatures at higher elevations.
Jesse says:
February 7, 2012 at 7:47 pm
Layman’s question: What goes up must come down. Is that true? If we intentionally put a lot of black carbon (or anything else) into the atmosphere, wouldn’t it eventually come back to earth? Would my white car turn black?
Mine always does, I have to keep cleaning it!
I wonder if this is all correct because the system is not homogenius and that means there must be an entropy problem. At lower lattitudes there is an energy surplus(Watts emitted to space will be less than received) dissipating to the higher lattitudes(Watts emitted to space will be higher than received).
So it seems to me that carbon in the atmosphere at the equatorial region cools but in the polar region warms.
Given the fact that the emission and distribution of all carbon is by average higher in the high lattitudes the overall effect is an increase of the temperature.
Adding more explanation to my previous info it is of course correct when the distribution of the carbon would be homogenius. The low lattitude temperatures would drop and the high lattitude temperatures would raise and converge more and more. In the end at increasing carbon the 5,5 oC will be reached
I’m still shocked/amazed that in places like China, coal is still used as fuel for cooking at home.
willis, Do a second thought experiment. Put your carbon black shell one meter above the surface of the earth. In that case we’ve replaced the earth’s surface with a perfect black body, but we still have greenhouse gasses reabsorbing and emitting infared radiation, so the net effect has to be warming. Now gradually move the shell further and further from the earth’s surface. If you are correct that at a distance of 20 kilometers from the eatth’s surface the shell results in cooling, then somewhere between one meter and 20 kilometers the effect has to change from warming to cooling. The implication is that the effect of black carbon depends on the height of the carbon in the atmosphere. My guess is that the average height is closer to one meter than to 20 kilometers, so the net effect is warming.
Willis Eschenbach says:
I explained the mechanism: The surface temperature is determined by the top-of-the-atmosphere radiative balance as long as there is sufficient warming of the surface and cooling of the upper layers of the troposphere to peg the lapse rate at the appropriate adiabatic lapse rate.
Well, you seem to go with Occam only in certain contexts. In the context of climate sensitivity, you believe that approximating it as being linear over a fairly small range of forcings is totally unjustified. However, in this case, you believe that you can go from one extreme to a dramaticaly different extreme and that the behavior of the surface temperature will be nice and monotonic.
No…The surface forcing due to radiative effects ONLY is negative from BC. However, the surface temperature is not determined by the surface radiative forcing. It is determined more by the TOA forcing. As Ramanathan himself explains: “The TOA BC forcing implies that BC has a surface warming effect of about 0.5 to 1 °C, where we have assumed a climate sensitivity of 2 to 4 ºC for a doubling of CO2.”
One of the ironies of the climate debate is that AGW skeptics often claim that the consensus scientists are too hung up on radiation and ignore convective effects when the truth is exactly the opposite: It is often AGW skeptics who look at the surface radiative balance, thus ignoring convection. The consensus scientists understand the correct way to look at things: You consider the top-of-the-atmosphere balance that is in fact determined by radiative effects because that is the only game in town between the Earth and space. Then, you know that the surface temperature will be determined by that balance plus the fact that convection’s role is to keep the troposphere near the (appropriate) adiabatic lapse rate.
Willis,
The result would depend on the lapse rate of the atmosphere below the carbon layer. If there were enough atmosphere mixing (due to day to night and latitude local variation causing atmosphere circulation), the lapse rate would be non-zero, and might even approach adiabatic. In that case, the ground level temperature would be above the carbon level temperature. In any realistic case, with less than total obscuration, some solar energy reaching the ground would assure buoyancy assisted mixing, and would drive the lapse rate toward the adiabatic level. This is the condition on Venus, where the clouds block most, but not all solar energy from reaching the ground, but the temperature profile is almost exactly the adiabatic lapse rate, and results in the very got ground.
If a simplified model of uniformly illumination on a totally opaque layer occurs, with no planet rotation, you might be correct, but all real cases are not that way.
“Matthew W. says:
February 8, 2012 at 4:57 am
I’m still shocked/amazed that in places like China, coal is still used as fuel for cooking at home”.
Oh come on Mathew W., how much walkabout have you done in China. I remember more cold than warm, even through the mist, morning coal stoves most corners, most towns, municipal coal powered electrical distribution along inefficient infrastructure. Street cluttered with antiqued taxis and buses. They’ve been doing it for years too.
You’ll end up with phobias, like the next bloke, if you really believe co2 adds heat to the Earth from a cooler upper atmosphere.
jjm gommers says:
February 8, 2012 at 4:46 am
Adding more is of course correct when the distribution of the carbon would be homogenius (sic). In the end at increasing carbon the 5,5 oC will be reached
Oh come on jjm gommers , co2 doesn’t take on some mystical homogenous proprieties, turning it into some sort of transsexual devil. Ah! that gives me a psychological insight, jjm gommers. Scary.
But..if you exchange black carbon to infra red carbon dioxide? It absorbs incoming infra red light, whereby it is heated and thus emits energy, half of it back into space and half of it down to the earth’s surface. Does that also mean that CO2 cools the surface? It acts as a shield against infra red light from the sun?
Joel Shore says:
February 8, 2012 at 5:11 am
“”It is often AGW skeptics who look at the surface radiative balance, thus ignoring convection.”
“You consider the top-of-the-atmosphere balance that is in fact determined by radiative effects because that is the only game in town between the Earth and space.Then, you know that the surface temperature will be determined by that balance plus the fact that convection’s role is to keep the troposphere near the (appropriate) adiabatic lapse rate.”
Oh come on Joel Shore, If the consensus scientists think that is the correct way to look at things, well, no wonder you blokes have been in trouble for so long. What latent force does convection have that maintains a theoretically corrected BB Illumination described as, 343W: received 240W and radiated out 240W.and the 103W albedo loss of illumination which includes CO2 reflection.
Maybe you don’t want to ping your IP over at tallblokes’, so you’ll miss out on the discussion Bob Fernley-Jones’, AKA Bob_FJ, is having on the effects of convection in the radiative illumination budget of a theoretical BB with an atmosphere.
Leonard Weinstein” but all real cases are not that way “‘
I agree with your statement, see my previous comments.
Only in case of homogenius distribution of the carbon in the atmosphere it works. In that case the temperature difference between equator and polar regions start to converge with increasing carbon concentration and drops to the 5.5 oC.
Willis, if I interpret your argument correctly, are you saying that there is a linear relationship between black carbon concentrations in the atmosphere and cooling on the surface?
Is there a way to determine whether this would hold true at the tiny amounts of black carbon currently in the atmosphere (in contrast to the asymptotic argument that if the atmosphere were completely covered with black carbon, the earth would be frigid, which is obviously correct)?
The other issue I wonder about is that if black carbon concentrations in the atmosphere are mainly in a few places (over India, China, parts of Europe (where there are various combinations of diesels; residential burning of wood, coal, and dung; “backyard” steel mills burning coal without emission controls), there wouldn’t be a “shell” of black carbon around the earth. Sunlight would penetrate to the surface in most places. Would your conclusions change if black carbon concentrations in the atmosphere were “patchy”?
Just asking, not being contentious. The subject is pretty complicated!