Look at Gilbert's explanation. Then pick one of the following.
a) I don't understand what he is saying. I think it has calculus in it.
b) It makes perfect sense. It handily disproves all that IPCC hooey. I think it should be spread far and wide.
c) Neither a nor b.
I have some advice for you.
If (a) your problem is not one of logic but one of trust. You cannot figure this out for yourself and you need to figure out based on social reasoning who is telling you the truth and who is lying. This applies to many other technical matters besides climate change. You should read the book "What's the Worst That Could Happen?" by Greg Craven which is a very sane piece of advice for people in this position. After all, most people in democratic societies are in this position, and it's crucial to make the right decision even though you don;t really understand the arguments.
If (b) you overestimate your competence. Your confidence in conclusions matching your political beliefs is dominating your reason. You should be in group (a) but you overestimate your own abilities so you should try being irresponsible for a few years. You should take up less intellectually demanding hobbies and work on improving your personality.
If (c) stick around.
Debunking Gilbert's little undergraduate ploy is left as an exercise for the reader.
That people hold themselves in such esteem and the earth sciences in such contempt that they think things are so stupidly off-base is not remarkable. There are a lot of people in the world.
What is amazing is that someone whose full time job is to discuss these matters would see fit to promote it. It's another example of the extreme cynicism and contempt for reason that is so common nowadays. Morano probably has no idea that there is anything wrong with propagating this nonsense.
15 comments:
It's been a while since I've had to use calculus more advanced than first-year material, and I've never taken an atmospheric physics class, but I'm reasonably certain his foundational differential is dead wrong. He's differentiating twice in one step and combining their results, pretending it's only one differential. Even assuming the rest is entirely right, violating the fundamental theorem of calculus is a big fat red flag for shoddy math.
Of course, I could be dead wrong too - I never was very confident about my calculus even back when I was using it daily. Still, for folk in option A, am I the only one who thinks his final paragraph looks like a form letter, to wit:
"It is remarkable that this very simple [crank's work] is totally ignored in the field of [crank's target field] simply because it [violates the laws of physics/is based on shoddy math/fails basic logic/etc]. Hence, that community is relying on [the consensus] in order to [conspiracy theory]. If this is what “science” has become today, I, as a scientist [or other claim to authority], am ashamed."
Pretty sure I've seen that format used on everything from creationist screeds to free energy fools. It does seem oddly generic.
Huh, I haven;t really looked in a long time. I was assuming that this was a reasonable derivation of the dry adiabatic lapse rate. It is sort of amusing to conclude that one is done at that point.
Here's a link to a page full of (on average) paragraph long debunkings of similarly moronic pseudo-scientific posturing by, apparently, pseudo-scientists quoted on some of the denial sites. It's by (as readers of my little blog and as I've mentioned here on occasion) Professor Steven Dutch at the University of Wisconsin Green Bay Earth Sciences Department.
As a point of information, Dr. Dutch is politically conservative and thus provides evidence that such people are capable of rational thought and of applying logic to problems.
To clarify my point:
1) The analysis includes an atmosphere "at equilibrium". What does equilibrium mean in this circumstance? Does the real atmosphere qualify?
2) The analysis does not actually discuss the difference in temperature between a planet with an atmosphere and one without, or indeed what sets the surface temperature.
It just shows that in certain circumstances it will decline with height. But that has nothing to do with the 33 C in question, which is not the difference in temperature across the atmosphere but rather is the difference at the surface between the real-atmosphere and the no-atmosphere case.
Gilbert's argument (not a new one) is bogus on two fronts: (1) there's nothing that intrinsically forces atmospheres to decline in temperatures with altitude at the adiabatic lapse rate - the adiabatic lapse rate is a *limit*, and tells us only that for higher temperature gradients the atmosphere becomes unstable (leading to vertical convection etc.)
And (2) contrary to the final claim, every climate science textbook almost invariably *starts* by discussing the lapse rate - and explains how it affects surface temperatures relative to the tropopause. Gilbert obviously never even bothered to crack open a standard atmospheric science textbook.
I think my rather long-winded introductory comments here are also apropos:
-----
Almost everywhere, as you go up from the surface, the temperature of the air decreases. Rare occasions when this is not true constitute temperature inversions. However, this familiar situation is actually an artifact of the way things work here on Earth's surface - there is nothing intrinsic in atmospheres that forces temperature to increase or decrease with altitude. Temperature starts to increase again once you go above around 10 miles altitude. The lower portion of the atmosphere, where the temperature declines with altitude, is called the troposphere. The altitude where temperature decline switches to increase roughly defines the tropopause, and the upper region where temperature increases again is the stratosphere.
Another demonstration that there's nothing intrinsically fundamental about temperatures declining with altitude in an atmosphere-like fluid is the behavior of Earth's oceans. Thanks to the thermohaline circulation, the deep ocean is much colder than the surface almost everywhere (effectively the deep oceans are most closely coupled to the polar surface waters, rather than to the equatorial ones), so for the oceans unlike the atmosphere, temperature rises as you go up. On the other hand, under solid ground temperature goes up as you go deeper thanks to Earth's radioactively heated interior, i.e. temperature declines with height. So we have a quite a mix of temperature gradients with altitude in our near vicinity - under ground (negative), under water (positive), in the troposphere (negative), and the stratosphere (positive). The explanation for each particular value depends on the details of heat flow in each case.
The decline in temperature with altitude in the troposphere is known as the "lapse rate". The heat flows responsible for Earth's tropospheric lapse rate come from the heating of Earth's surface by the sun (to which the atmosphere is largely transparent), the flow of this heat into the atmosphere, and then the subsequent radiation from the atmosphere into deep space. The stratosphere is above most of these heat flows, and is heated more directly by what it absorbs from the sun, allowing it to be warmer.
-----
In other words, the existence of the lapse rate is a consequence of the energy flows associated with radiation that constitute the greenhouse effect in the atmosphere. Without a greenhouse effect, the lapse rate would be zero (the average tropopause would be roughly at the surface).
Uhh, I didn't check if the calculation assumptions are valid ie dU/dh=0.
But of course the atmosphere of a real planet is not in isolation, there's radiation from the sun, the surface and other layers of the atmosphere.
At least. You can probably leave out convection in a first approximation.
The earlier explanations in the text are really really weird btw.
-
I always failed to get the classic greenhouse effect explanation: radiation goes in, radiation tries to go out but it is reflected. How does the atmosphere know how to block the upgoing radiation but not the downgoing?
Of course, this explanation sucked (BUT IT'S STILL IN USE) and it was impossible to understand it logically only from this explanation, because it lacked the KEY idea of visible vs infrared and the transparency of CO2 to visible light but opaqueness to (certain) infrared.
I think this is the same thing Barton Paul Levinson was asking about in RC. A tricky one if you see it for the first time, but it's really very simple: the 9.8K/km gradient only applies to the adiabatic situation. That is not the situation where the Earth surface directly cools itself radiatively to space, and the atmosphere is isothermal at 255K, being embedded in a radiation field of the same temperature. Absorbing from the lower celestial hemisphere, emitting to the upper one, for thermal equilibrium at precisely 255K, and Kirchhoff and Bunsen signing the bill.
Dunning, meet Kruger. Dr Gilbert should be asked to explain the various "snowball Earth" episodes illustrating precisely what he claims cannot happen.
Ah, yes, this argument. The critical flaw in the argument is assuming that the effective radiating level of the atmosphere is not dependent on the composition of the atmosphere. The logic of this paper is that if the effective radiating level of the atmosphere is at 5 km, then one can use the 6.5K lapse rate to calculate a total atmosphere effect of 33K.
Which is fine, except that the radiating level of the atmosphere is only at 5 km _because of_ greenhouse gases. A thought experiment: if the atmosphere were totally transparent to all wavelengths of light, then the only loss of heat from the earth-atmosphere system would be direct radiation from the surface (since vacuum is a perfect insulator). Therefore, the effective radiating level wouldbe at the surface, which would have to be at the blackbody temperature of 255K. The lapse rate would still function because it is dependent on PV=nRT, and so at 5 km the temperature would be 222K (well, actually, it would be 205K because without water vapor the lapse rate would be 10K, not 6.5. I think any effect of other GHGs on the lapse rate would be small).
Another related discussion to this topic can be found here:
http://chriscolose.wordpress.com/2008/03/09/physics-of-the-greenhouse-effect-pt-1/
Marcus:
The lapse rate would still function because it is dependent on PV=nRT, and so at 5 km the temperature would be 222K
Marcus, I question that... see my earlier post. In the absence of convection, packets of air would not be adiabatic; they would exchange thermal radiation with the ground and with space faster than any other heat exchange mechanism can move energy vertically. Even a non-greenhouse gas has some absorbtivity/emissivity in parts of the IR spectrum, and at the black-body temperature, courtesy of Kirchhoff-Bunsen, a pocket of gas would emit to the top half of their local celestial sphere precisely what it absorbs from the bottom half (i.e., from the planetary surface). The atmosphere would be stably isothermal.
Martin - actually, if the atmosphere radiates at all, it would tend to be colder than the surface. But you're right, the situation marcus describes would have an isothermal atmosphere - if the only thermal interactions of the atmosphere are with the surface (it can't radiate out to space, so the surface is it) then it cannot be colder than the surface over the long term; the surface will warm it up or cool it down to be the same temperature, and it has no other heat exchange avenue to alter that.
Things are a little more complicated when you have a surface of varying temperature (the atmosphere can help transport heat from hot spots to colder ones) but again the averages of atmospheric and surface temperature, when there's no radiation to space, have to be very close.
The lapse rate is only there when the effective radiating surface is way up in the atmosphere, i.e. it requires a radiating atmosphere.
The Exxon Emeriti work to keep their grey matter intact, rather than waste it on trivial matters like perpetuating civilization.
Society for American Baseball Research
(poster #4 , see bio)
http://www.sabr.org/sabr.cfm?a=cms,c,826
Arthur, Martin: I'm still unconvinced. I think that in the absence of other forcings, the atmosphere will tend towards the adiabatic lapse rate as driven by the ideal gas law: ie, a parcel of air in contact with the ground will be at the same temperature of the ground, but as it rises it will cool down, so the equilibrium temperature at altitude will be lower than the ground.
While an isothermal atmosphere would technically be stable (in the sense that vertical movement of air is suppressed), I would believe that over the long term it would shift toward the adiabat: if a perturbation of the atmosphere causes a switch between a surface parcel and a parcel above it, the formerly surface parcel will cool, the new surface parcel will warmer, and the new surface parcel will transmit that extra heat to the surface which will radiate it away, and this process will continue until it reaches the neutral stability case.
The exceptions that Arthur lists all have other forcings: eg, the stratosphere has solar heat input at high altitude.
Perhaps the take-away here is that I need to dig up my copy of Goody & Yung and remind myself how all this stuff works...
ps. Martin: why would there be an absence of convection? I guess I'm assuming that in the absence of GHGs, energy transfer in my hypothetical scenario occurs _only_ through convection and conduction.
Elevator speech needed: This is a crock. It assumes a surface temperature which only exists because of the greenhouse effect, and a radiating level of 5 km which only exists because of the greenhouse effect. Then it claims there is no greenhouse effect.
Marcus - it's the flow of energy from sun to surface to atmosphere to space that drives (vertical) convection. When that flow becomes just sun to surface back to space, there's nothing to drive convection (but then one has to account for day/night and latitudinal temperature differences which would lead to some convective flow again).
When motion is slow, adiabatic change switches to isothermal change - a parcel of air moved upward from the surface, if moved slowly, would continually exchange energy with its surrounding atmosphere and stay at that same temperature as the surrounding atmosphere. Adiabatic change assumes no heat flow, and is valid for rapid motion. That wouldn't be the case unless artificially forced in an atmosphere above a truly uniform-temperature surface - the atmosphere would reach the same temperature and be unchanging from that point forward.
First: I think all of us in this discussion would agree with Eli Rabett's elevator speech about the idiocy of the paper that started this, we're just busy doing "how many angels on the head of a pin" discussions about the details.
So, back to the angels: "a parcel of air moved upward from the surface, if moved slowly, would continually exchange energy with its surrounding atmosphere and stay at that same temperature as the surrounding atmosphere." My argument would be that if the parcel is moved so slowly that it remains fully equilibrated with the nearby atmosphere, that there would have to be a slight cooling of the surrounding atmosphere as you did so. (and a slight warming of the level that the parcel has left, as a new parcel moves down to take its place) Therefore, even if convection is near-zero, even if you started at an isothermal gradient you would end up at an adiabatic one.
In contrast, can you come up with an argument for how an atmosphere that starts at the adiabatic equilibrium would shift to an isothermal one? There still would be hardly any convection, but even small micro-movements won't change anything, unlike in my example.
(Also: in the case where we did have day/night and lat differences: would that be sufficient convection to move from isothermal to adiabat in your opinion? In my world, I would think... hmm. If we assume an infinite plane with a heat source that turns on and off, the day cycle would lead to an adiabatic atmosphere equilibrated to the heated surface temperature. The night cycle would cool the surface and the lowest layer of atmosphere, but it would stop there because of stability. So with the exception of a tiny skin of cooler atmosphere during the cool cycle, the whole atmosphere would permanently be close to the high noon adiabatic equilibrium. Make it a sphere with latitudes, and... I don't know. You might get Hadley cells and coriolis effects and all that, and I was more an atmospheric chemist than a dynamicist, so I can't even come up with a half-way reasonable answer)
Post a Comment