Absorptions bands in the Earth’s atmosphere created by
greenhouse gases and the resulting effects on transmitted radiation. (Photo
credit: Wikipedia)
Guest post by Reed Coray
The following example illustrates the issues I have with reasoning often used
to argue that increasing the amount of CO
2 in the Earth’s atmosphere
will increase both the Earth’s surface temperature and the Earth’s atmosphere
temperature. Immediately following is a direct quote from URL
“
The present situation is that there has been an increase in
infrared-absorbing gases in the atmosphere, such as carbon dioxide
(CO2) and methane (CH4).
Energy that would normally escape into space is absorbed by these molecules,
thus heating the atmosphere and spreading through convection currents. The
average temperature of the atmosphere has increased 0.25 °C since 1980, mainly
attributed to an increase in infrared-absorbing gases in the
atmosphere.”
Although the above statement makes no direct reference to Earth surface
temperature, I believe it carries the implication that greenhouse gases in the
Earth’s atmosphere increase the Earth’s surface temperature.
I make two comments: the first is relevant only if the above implication is
valid, the second is relevant independent of the validity of the implication.
First, placing matter adjacent to a warm surface such that the matter is capable
of absorbing/blocking radiation to space from the warm surface can lead to a
decrease in the warm surface’s temperature. Second, increasing the amount of the
absorbing/blocking matter can lower the temperature of the absorbing/blocking
material.
Take for example an internal
combustion engine whose metal surface is exposed to a vacuum. In addition to
doing useful work, the engine produces thermal energy (heat). That thermal
energy will produce a rise in the temperature of the engine’s surface such that
in energy-rate equilibrium the rate energy is radiated to space from the
engine’s surface is equal to the rate thermal energy is generated within the
engine. By attaching radiating plates to the engine’s surface, some of the
energy radiated to space from the engine’s original surface will be
absorbed/blocked by the plates;
not true only radiation leaving the surface at some acute angle will be re-absorbed
but because thermal energy can be transferred
from the engine to the plates via both radiation and conduction, the temperature
of the engine’s original surface will be lowered.
Wrong - if less radiation is leaving the engine gets hotter
This is the principle of an
air-cooled engine
[1]: provide a means other than radiation of transferring
heat from an engine to a large surface area from which heat can be removed via a
combination of conduction, convection and radiation, and the engine’s surface
temperature will be lowered.
If plates at a temperature lower than the original engine surface temperature
are attached to the engine, it’s true that the temperature of the plates will
increase to establish energy-rate equilibrium. Once energy-rate equilibrium is
established, however, increasing the plate radiating area (adding additional
matter that blocks more of the energy radiated from the original engine surface)
will likely lower the plate temperature.
Depends on conduction of fin and relative temperature of cooling air and fin
Thus, blocking the amount of surface radiation escaping to space does not
necessarily increase the surface temperature; and increasing the amount of
radiation blocking material does not necessarily increase the temperature of
that material. In both cases (the Earth/Earth-atmosphere and the internal
combustion engine in a vacuum), the heat eventually escapes to space–otherwise
the temperature of the Earth’s surface and the engine would continue to rise
indefinitely.
All that is just garbage. All solids radiate (accoding to its temperature and emissivity - not necessarily fitting a black body curve). Take away any GHGs and the surface of the earth radiates directly to space with no back radiation and no impeding of radiation to the background temp of space. O2 an N2 and H2 etc. do not stop significant radiated energy but they will be warmed by the earth - none of the O2 N2 will be able to radiate this heat to space. The temperature of the O2 and N2 will get NO HOTTER than the surface of the Earth, but they WILL NOT enable the earth to heat up further. Add GHGs and each molecule will "absorb" and "retransmit" radiation. The radiation retransmitted can be in any direction but nearly 50%- hits the earth and 50%+ goes to space. The 50% hitting the earth is 50% that would have escaped had there been no GHG. -The earth warmed by the sun cools slower because of GHG presence. The earth conducts to the rest of the atmosphere warming it.
The difference isn’t that the energy doesn’t eventually escape to
space (it does in both cases), the difference is in the path the energy takes to
reach space. The amount of generated thermal energy in conjunction with the path
the thermal energy takes to get to space determines temperatures along the path;
and adding more material may increase or decrease those temperatures. To say
that “
Energy that would normally escape into space is absorbed by these
molecules, thus heating the atmosphere…” by itself is unwarranted; because
an equivalent statement for the case of adding extra plate material to the
engine would be “
Energy that would normally escape to space from an engine
with small attached plates is absorbed by additional plate material, thus
heating the plates…” For air-cooled engines, this statement is not
true—otherwise the plate surface area of air-cooled engines would be as small as
possible.
WHAT!!!!
It’s fairly easy to visualize why (a) adding thermally radiating plates to an
air-cooled engine might decrease the engine’s surface temperature, and (b)
increasing the area of the radiating plates might decrease the plate
temperature. It’s not so easy to visualize, and
may not be true, why (a) adding
greenhouse gases to the Earth’s atmosphere decreases the Earth’s surface
temperature; and (b) increasing the amount of atmospheric greenhouse gases
lowers the temperature of the Earth’s atmosphere. I now present one possible
argument. I do not claim that the argument is valid for greenhouse gases in the
Earth’s atmosphere, but I do claim that the argument might be valid, and can
only be refuted by an analysis more detailed than simply claiming “
Energy
that would normally escape into space is absorbed by these molecules, thus
heating the atmosphere.”
I do not believe photons absorbed by GHGs heat the atmosphere The photons emitted from GHGs eventually(perhaps after many absorbtion/retransmittions eithe leave the system or hit the earth warming it. The warm earth heats the atmosphere
If we assume that (a) matter cannot leave the Earth/Earth-atmosphere system,
and (b) non-greenhouse gases radiate negligible energy to space, then for a
non-greenhouse gas atmosphere the only way thermal energy can leave the
Earth/Earth-atmosphere system to space is via radiation from the surface of the
Earth. The rate radiation leaves the surface is in part a function of both the
area and temperature of the surface. For a greenhouse gas atmosphere, energy can
leave the Earth/Earth-atmosphere system to space both via radiation from the
Earth’s surface and radiation from greenhouse gases in the atmosphere. Suppose
it is true that the density of greenhouse gases near the Earth’s surface is such
that radiation emitted from low-altitude greenhouse gases does not directly
escape to space, but is in part directed towards the Earth’s surface and in part
absorbed by other atmospheric greenhouse gases. As the atmospheric greenhouse
gas density decreases with increasing altitude, radiation emitted from
high-altitude greenhouse gases can directly escape to space.
Now it’s not impossible that since (a) in addition to radiation, heat is
transferred from the Earth’s surface to greenhouse gases via conduction, and (b)
convection currents (i) circulate the heated greenhouse gases to higher
altitudes where energy transfer to space can take place and (ii) return cooler
greenhouse gases to the Earth’s surface, that the process of heat transfer away
from the Earth’s surface via greenhouse gases is more efficient than simple
radiation from the Earth’s surface.
Heated molecules share heat by conduction. In space there is nothing to conduct to. No heat is transfered. What is transfered to space is radiation, From photons absorbed by GHGs and from photons emitted from earth that are not touched by GHGs (wrong wavelength)
Many engines are cooled using this concept.
Specifically, a coolant is brought into contact with a heated surface which
raises the coolant’s temperature via conduction and radiation, and the coolant
is moved to a location where thermal energy transfer away from the coolant to a
heat sink is more efficient than direct thermal energy transfer from the heated
surface to the heat sink.
One way to realize increased thermal transfer efficiency would be to use a
coolant, such as greenhouse gases, that efficiently radiates energy in the IR
band (i.e., radiates energy at temperatures around 500 K). Another way would be
to spread the heated coolant over a large surface area. Since surface area
increases with increasing altitude, thereby providing expanded “area” (in the
case of a gas, expanded volume) from which radiation to space can occur, it’s
not clear to me (one way or the other) that greenhouse gases won’t act as a
“coolant” reducing both the temperatures of the Earth’s atmosphere and the Earth
surface.
Ye Gods!, did Tony read this before publishing... or is this what he believes??!!!!!!
RGB loses his cool with a true sceptic (at last!)
LET US HEAR WHAT YOU HAVE GOT TO CONTRIBUTE!
I may admit I may not
always be right but sure as hell you lot do not even know the people you are
quoting.
You not only aren’t “always right” in regard to radiation theory, you are so
infinitely wrong that you are, quite seriously, almost stunning in any
conversation. Worse, you haven’t a clue that you are clueless, and make your
vastly incorrect statements to correct somebody that actually has a clue.
Here’s what I have to contribute. Light is electromagnetic radiation. Go on,
look it up. The entire electromagnetic spectrum is light. Radio waves are light.
Microwaves are light. Infrared radiation is light. Visible light is a narrow
band of light. Ultraviolet radiation is light. X-rays are light. Finally, gamma
rays are light. The only thing that differentiates a gamma ray from a radio wave
is its frequency and wavelength, and those aren’t even invariant properties —
one can in principle doppler shift a radio wave into an x-ray by moving through
it fast enough.
Second, the only thing the human eye can see is light. I mean good God, man,
why do you think they call it
turning on the lights when you enter a dark
room?
Third, radiation from the sun does not, for the most part “turn into light”
only when it reaches our atmosphere. Again, this is so wrong it is difficult
even know how to begin. Children understand this better than that.
Sun
light is emitted
as light by our
very hot sun. It
travels
as light — both visible and invisible, an entire spectrum of
light — through the near-vacuum in between the Sun and the Earth. When it
reaches the Earth, in very crude terms some of it is reflected at some point or
another by the atmosphere without losing (much) energy, some of it is
transmitted, and some of it is absorbed. How much of each depends on a host of
things — clouds reflect more energy back to space than clear dry air, but clouds
and water vapor also absorb more on the way to the ground than clear dry air. Of
the radiation that reaches the ground, some is reflected and
again passes
more or less completely out of the atmosphere without significant loss, and the
rest is absorbed. Of the radiation that reaches the ocean, some is reflected at
or near the upper surface, and virtually all the rest is absorbed.
Fourth, if you want to understand the way electromagnetic radiation is
created, transmitted, absorbed, scattered, you have to
begin by learning
Maxwell’s Equations. Maxwell’s equations are the classical partial differential
equations that describe the electromagnetic field. They aren’t complete — they
are classical and atoms and molecules are really quantum mechanical — but to
even think of understanding quantum electrodynamics it helps to start with
classical electrodynamics. To understand classical electrodynamics, it would
really help you to take a class in introductory physics one day, assuming that
your calculus background is up to the task. Even in a first year intro physics
course in E&M, like the one I am teaching right now, you would learn all of
the things I listed above and more besides — I generally try to teach my
students that transmitted electromagnetic power is the flux of the Poynting
vector through the specified surface, for example, which is entirely apropos of
the current conversation.
If you cannot afford a physics textbook, feel free to use the ones I’ve
written — they are available for free online here:
and if you want to try to tackle
real graduate level electrodynamics,
you can try:
but be warned, it isn’t for the faint of heart and you’ll need a reasonable
proficiency with partial differential equations and non-Abelian algebras and Lie
groups to get through the book. A knowledge of tensors would also be very
useful, but sadly few students (even physics graduate students) have much of one
so the book tries to be self-contained in this regard. It is also intended to be
the
second semester of a two semester series, so it presumes you’ve
already mastered the Poisson equation and spherical decompositions and
magnetostatics and are ready to get on with Maxwell’s equations and true
Electrodynamics.
Now “we lot” — by which I assume you means “warmists” used as a pejorative
term — sometimes do know very, very well precisely of what we speak. I, for
example, do. And I’m not a “warmist”, for that matter. That smacks of religion,
and I can and do justify my opinions about almost anything all the way down to
the microscopic level — or admit ignorance.
So it is from a state of very much non-ignorance that I repeat — your
previous statement, criticizing the entirely correct statement of Mr. Hoffer who
is
also no warmist, merely a rational skeptic who doubts the alleged
magnitude or
importance of the GHE, not its very existence — was
something that left anyone who read it very slightly dumber. I could feel my own
brain cells reeling in shock from it. Radiation turning into light only when it
hits the atmosphere? Eyes unable to see light? It made me feel that my entire
professional career, spent teaching people far better than that, has been
wasted.
How is it even possible for a
high school education to
turn you out into the world that ignorant? I knew better in grade school.
So your statement was not only not a rebuttal of David Hoffer — it was an
open insult to the entire US educational system. It was
unamerican! Do
you want the entire world to laugh at us?
Hence my unaccustomed vigor in striking down your contribution, which, you
will note, I am continuing. I’m quite serious. You owe it to yourself, you owe
it to
simple honesty to crack a physics book and at least
try to
understand
what electromagnetic radiation is before again entering a
public debate on the subject and attempting to correct people that have actually
studied it, or teach it.
But of course you won’t, will you? Neither will Greg House, or any of the
others that make absurd statements about radiation being unable to be reflected
back to a warm surface and thereby slow its cooling. It’s so startlingly
ignorant a statement that it makes one want to simply throw one’s hands up in
despair. Not even my suggestion to
go buy a space blanket and wrap yourself
in it to gain firsthand experience of “warming” by trapping your own body’s
radiation — an “experiment” you can actually perform at home — will actually get
you to do it. Or taking an ordinary light bulb and placing it in front of a
sheet of plastic wrap, then in front of a sheet of aluminum foil, to see which
one reflects more heat (and note well —
reflects heat from something
much cooler than the light bulb filament). I could probably think up a
half dozen other table top experiments to demonstrate radiative heating and
cooling — they are elementary school science fair stuff — but of course to you
they can’t exist because you know radiation only turns into light when
air molecules experience friction or some other long line of complete, utter,
absurdities.
I do declare, with people like you “helping” the skeptical “cause”, it
doesn’t
need to be opposed — the real warmists of the world can just
point at you and wait for people to stop laughing themselves to death. Which is
a logical fallacy, of course — you can disbelieve in CAGW because a pink unicorn
came to you in a dream and told you to and still be right, just as they can be
supported by not entirely implausible arguments and still be wrong, and wise
people look at the arguments themselves and not individuals — but it does make
it all to easy for
sensible skeptical arguments to be dismissed when
there exist “skeptics” whose arguments are only a hair better than pink
unicorns.
rgb
On the other hand, you may wish to consider steps in your own jurisdiction.
REPLY: I’ve made some changes to the text which will likely yield better results – Anthony