Guest post By Ben Herman and Roger A. Pielke Sr.
During the past several months there have been various, unpublished studies circulating around the blogosphere and elsewhere claiming that the “greenhouse effect” cannot warm the Earth’s atmosphere. We would like to briefly explain the arguments that have been put forth and why they are incorrect. Two of the primary arguments that have been used are
- By virtue of the second law of Thermodynamics, heat cannot be transferred from a colder to a warmer body, and
- Since solar energy is the basic source of all energy on Earth, if we do not change the amount of solar energy absorbed, we cannot change the effective radiating temperature of the Earth.
Both of the above statements are certainly true, but as we will show, the so-called “greenhouse theory” does not violate either of these two statements. (we use quotation marks around the words “greenhouse theory” to indicate that while this terminology has been generally adopted to explain the predicted warming with the addition of absorbing gases into the atmosphere, the actual process is quite a bit different from how a greenhouse heats).
With regards to the violation of the second law, what actually happens when absorbing gases are added to the atmosphere is that the cooling is slowed down. Equilibrium with the incoming absorbed sunlight is maintained by the emission of infrared radiation to space. When absorbing gases are added to the atmosphere, more of emitted radiation from the ground is absorbed by the atmosphere. This results in increased downward radiation toward the surface, so that the rate of escape of IR radiation to space is decreased, i.e., the rate of infrared cooling is decreased. This results in warming of the lower atmosphere and thus the second law is not violated. Thus, the warming is a result of decreased cooling rates.
Going to the second statement above, it is true that in equilibrium, if the amount of solar energy absorbed is not changed, then the amount of IR energy escaping out of the top of the atmosphere also cannot change. Therefore the effective radiating temperature of the atmosphere cannot change. But, the effective radiating temperature of the atmosphere is different from the vertical profile of temperature in the atmosphere. The effective radiating temperature is that T that will give the proper value of upward IR radiation at the top of the atmosphere such that it equals the solar radiation absorbed by the Earth-atmosphere system.
In other words, it is the temperature such that 4 pi x Sigma T4 equals pi Re2 Fso, where Re is the Earth’s radius, and Fso is the solar constant. Now, when we add more CO2, the absorption per unit distance increases, and this warms the atmosphere. But the increased absorption also means that less radiation from lower, warmer levels of the atmosphere can escape to space. Thus, more of the escaping IR radiation originates from higher, cooler levels of the atmosphere. Thus, the same effective radiating temperature can exist, but the atmospheric column has warmed.
These arguments, of course, do not take into account feedbacks which will kick in as soon as a warming (or cooling) begins.
The bottom line here is that when you add IR absorbing gases to the atmosphere, you slow down the loss of energy from the ground and the ground must warm up. The rest of the processes, including convection, conduction, feedbacks, etc. are too complicated to discuss here and are not completely understood anyway. But the radiational forcing due to the addition of greenhouse gases must result in a warming contribution to the atmosphere. By itself, this will not result in a change of the effective radiation temperature of the atmosphere, but it will result in changes in the vertical profile of temperature.
The so-called “greenhouse effect” is real. The question is how much will this effect be, and this is not a simple question. There are also questions being raised as to the very sign of some of the larger feedbacks to add to the confusion. Our purpose here was to merely point out that the addition of absorbing gases into the atmosphere must result in warming, contrary to some research currently circulating that says to the contrary.
For those that might still question this conclusion, consider taking away the atmosphere from the Earth, but change nothing else, i.e., keep the solar albedo the same (the lack of clouds would of course change this), and calculate the equilibrium temperature of the Earth’s surface. If you’ve done your arithmetic correctly, you should have come up with something like 255 K. But with the atmosphere, it is about 288 K, 33 degrees warmer. This is the greenhouse effect of the atmosphere.
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tallbloke says: July 24, 2010 at 2:01 pm
———————–
A brief look at the flow chart http://www.realclimate.org/images/Minnett_1.gif
if I understood it correctly it lacks ‘ocean currents’ variability factor (in the certain critical areas by factor of 2). Efficiency of ocean currents heat transfer is crucial to the temperature oscillations in the polar regions, consequently to the ice coverage and albedo; resulting in a feedback.
Faster currents more heath to the poles, less ice, less reflection, more energy absorption, even warmer poles.
Of course, the reverse also holds true: slow current, less heath to the poles, more ice, more reflection, even colder poles.
What regulates ocean currents? I am sure you are (and many regulars) well aware of my ideas on that subject.
R. Gates says:
July 24, 2010 at 12:29 pm
But here’s some research:
http://adsabs.harvard.edu/abs/2006AGUSM.A44A..02M
My real point is that the effects of what happens at skin layer of the ocean from increases in downward LW radiation from GHG’s is far more complex than ‘the oceans don’t absorb LW” beyond the skin layer. The warming of that skin layer from increased LW from GHG’s does indeed play a role in heat flux from the deeper ocean layers to the atmosphere.
Ah yes, the Minnet presentation at the American Geophysical Union, Fall Meeting 2007.
This never did get published as a paper in a journal did it?
The methodology sounds very reminiscent of …. oh yes, the realclimate ‘experiment’ linked by Bob Tisdale above.
Lol.
‘Scuse me laughing, but, really, is this the best that millions of dollars poured down the atmospheric science climate hole can do? Are you really convinced by this? Is it not the case that Stephen Wilde has achieved more by the simple application of logic than Minnet and RealClimate did with their ship and superduper thermometers?
Mind you, what they did achieve was to show the proposed effect was so miniscule that no-one else has bothered wasting money on it since, so maybe they did a good job.
Take it from me R Gates, heating the ocean is what the Sun does. The ocean then heats the atmosphere, and the atmosphere then heats space. And the solid ground, a tiny bit. From an engineers perspective, the lack of comprehension of the relative strength of effects in the ocean-atmosphere interactions shown by climate ‘scientists’ is truly boggling.
Rob says:
July 24, 2010 at 10:38 am
I think this is an interesting point actually – everone talks about the warming of back radiation to the earths surface, but what about the effect it may have as it hits the oceans (71 % of the planets surface) and causes evaporation – that may have a net cooling effect. Has this ever been studied ?
———————–
I don’t think the people who should be studying it – the climatologists – are do so. That’s probably because either they haven’t the expertise or that it might negatively affect their funding. LWIR isnt’ going to penetrate the ocean to any depth compared to visible. What I’ve seen is some hocum about a skin layer that supposedly blocks thermal flow because it’s cooler and hence there’s less power transferring. What is actually happening is that this cooler skin layer is disposing of more power or energy per unit time than can be supplied to it if it were at a higher temperature. The other facet they ‘study’ is that more evaporation means more h2o vapor – but not more cloud cover which will reduce the amount of deep penetrating visible light energy as well as the total power reaching the surface.
What many climate scientists do not understand that 1 qcm of water has more than 3000 times heath capacity of a 1 qcm of air, maybe some of them have never experienced a full solar eclipse (personally 2), you can feel a nearly instant large temperature drop. Perhaps a night in a cloudless Sahara desert would be money well spent.
I don’t see where a figure of 288K for the equilibrium temperature of the earth comes from. That has to be if you ignore the huge pool of deep ocean water at around 278K or 5C. I would like to hear of a quantification of the process by which the deep ocean is cooled.
As I said earlier (July 24, 2010 at 7:08 am) I get the impression that it is not the “SCIENCE” that is in question. Not really! (Despite the difference of opinion expressed by some in the past 410 comments). It is the ‘interpretation’ of the science and the ‘identification’ of the problems which follow from these interpretations and the various ‘proposed solutions’ to the various problems from these same interpretations that are at issue.
Now, when “reasonable”, “mature”, “intelligent”, people assess the matter of AGW and attempt to Quantify the Greenhouse Effect they……….
Hummmmmmmmmmm…
Well, maybe —upon careful reflection— we ought to forget the science AND all the rest of the other stuff too.
Quantifying the Greenhouse Effect and coming to a consensus is still a little over our heads.
HankHenry says:
July 24, 2010 at 3:31 pm
I don’t see where a figure of 288K for the equilibrium temperature of the earth comes from. That has to be if you ignore the huge pool of deep ocean water at around 278K or 5C. I would like to hear of a quantification of the process by which the deep ocean is cooled.
the figure comes from the averaged surface temperature. forget about the deep ocean pool being part of the average surface temperature. The entire core of the Earth is vastly hotter than the surface with temperatures at its core in the vicinity of the surface of the sun, around 6000k. If you include this in some sort of average, you’ll have a temperature close to 6000k.
tallbloke wrote, “I’ll gladly host it, but I’d have thought E.M. Smith would be better qualified to deconstruct the ‘experiment’ than me. Should I ask him, or do you want to?”
Please do so. I haven’t had much interaction with E.M.Smith.
I don’t understand the logic that people are using to suggest the oceanic absorption of back IR radiation can be ignored or minimised, back radiation hits the ocean rather than land, what happens to it? It is absorbed, then what? It either goes into warming the water or it causes evaporation. If the latter the, energy doesn’t disappear, it’s still trapped in the troposphere.
Thanks to all who are trying to “demistefy” the GHG hypothesis and the warming that we all receive due to GHGs. Now, would someone please present some actual empirical data that demonstrates these “backradiation concepts.” It should be quite easy to do, if it is so simple, eh?
jae says:
July 24, 2010 at 6:02 pm
“Thanks to all who are trying to “demistefy” the GHG hypothesis and the warming that we all receive due to GHGs. Now, would someone please present some actual empirical data that demonstrates these “backradiation concepts.” It should be quite easy to do, if it is so simple, eh?”
Miskolczi has some:
http://met.hu/idojaras/IDOJARAS_vol108_No4_01.pdf
The backradiation (ED in his naming scheme) varies a lot depending on water vapor content.
Phil. says:
July 23, 2010 at 10:05 pm
kwik says:
July 23, 2010 at 2:40 pm
Phil. says:
July 23, 2010 at 12:42 pm
“Suppose you have an isolated black ball which you heat so that it eventually equilibrates at a certain temperature, introduce another ball nearby at a lower temperature, the hotter one will get hotter (as will the cooler).”
Are you sure about this, Phil? That the hottest will be hotter? I allways believed that this is exactly what was impossible, according to the 2′nd law….because if it got hotter…then heat has gone from colder to hotter…..
That’s exactly right, the version of the 2nd Law you quote is not applicable to radiation as George, I and others have pointed out above.
Interestingly Spencer has an entry on his blog today with exactly the same model experiment as I used (heaters instead of balls) and graphics etc. not just text.
http://www.drroyspencer.com/2010/07/yes-virginia-cooler-objects-can-make-warmer-objects-even-warmer-still/
Roy Spencer has chimed in with an explanation of cooler objects heating warmer, via radiation, and he has some cool diagrams, though the AGW one is poorly articulated.
http://www.climatechangefraud.com/behind-the-science/7393-yes-virginia-cooler-objects-can-make-warmer-objects-even-warmer-still
What’s going on with climate scientists? Why is everyone defending back radiation all of a sudden?
it goes into evaporation absorbing the latent heat of evaporation
h2o rich air is lighter, it rises
it goes up
eventually, it forms clouds or reaches the point where it gives up the latent heat – high above much of the ghgs and away from the surface.
Theo Goodwin says:
July 24, 2010 at 7:14 pm
“What’s going on with climate scientists? Why is everyone defending back radiation all of a sudden?”
Backradiation does exist and can be measured with IR cameras, for instance, but as a warmer object has higher frequency blackbody radiation plus all the lower frequencies, and the cooler object has only the lower frequencies, the net energy transfer goes from the warmer to the cooler object.
That’s why physicists like G&T usually insist on doing a vector subtraction first and can omit the backradiation from all further considerations. At least that’s how i understand it.
Andrew W says:
Bingo!!! I think the logic is just desperation for people who very badly went the greenhouse effect heating to magically disappear…or not exist in the first place.
stevengoddard says:
July 24, 2010 at 11:25 am
anna v
There is a big difference between “very few” greenhouse gases and “no” greenhouse gases. The first few ppm cause most of the greenhouse effect.
I think your statement violates physics laws. When there are gases and gravity and a heat source radiating on a planet there will be convection: gases get hot from ground conductivity to air if nothing else, and there exist plenty of else, since finally everything thermalizes to very low frequency modes. Hot gases rise, cool gases from the night side move to replace the vacuum they leave, there is the rotation of the planet and the coriollis effect so I see no way that your statement can be correct even on a planet without water.
George E. Smith mocked me saying, “So Chad, when was the last time that you were in the shadow zone of a cloud that passed between you and the sun; and it got hotter; meaning that the clouds were retaining heat near the ground. Clouds (on a climate time scale) ALWAYS produce cooling; NEVER heating.”
I never said or suggested or implied that clouds produce heating. I said that they can keep heat near the ground from escaping more quickly into the upper atmosphere. And that is something that takes place especially at NIGHT. A world of difference! The next time you choose to mock someone, do yourself a favor and actually pay attention to what the person says.
anna v
It is difficult to believe that direct conduction from ground to air contributes much heat to the atmosphere. The vast majority of the heat is transmitted radiatively.
NASA has flown some interesting instruments that may help with understanding the radiation. These pictures were taken in the central US in 1996.
http://mas.arc.nasa.gov/gallery/comparison.html
The photos are from the visible (0.55 um) to far infrared (14.21 um). They appear to be calibrated but the details are not given. One easily notes the slight increase in land brightness as you go into the near infrared (0.7 to 1.75 um) as should be expected by anyone who has used IR photo film. Plants get very bright in this range. The clouds are white and reflecting in the range from 0.55 to 2.40 um. The land gets dark around 1.8 to 1.95 um and then brightens up again (perhaps ground vapor in the H2O band near 1.8). At 2.89 um the band goes gray, perhaps a large absorption band. And surprise above 3.21 um, the clouds start to absorb and the land starts to become very bright. I would say we are starting to see the “blackbody” radiation from the land here.
Interesting how the clouds reflect the visible and near IR but start to absorb in the far IR. They would tend to reflect most the incoming solar radiation but would absorb and re-emit the ground radiation.
The question I have is: why don’t we clearly see the CO2 absorption if it is such a problem? Perhaps the gray-out is CO2 at 2.89 um. We sure don’t see it obstructing the bands further out in the IR where the land is very bright but the clouds sure do. In fact, they appear to be absorbing both the incoming solar and outgoing blackbody IR, although it is possible that the solar radiation is much smaller here and we are mostly seeing the outgoing land radiation and the clouds are simply dark because the sun doesn’t reflect much far IR off them.
Phil. says:
July 24, 2010 at 7:00 pm
Phil. says:
July 23, 2010 at 10:05 pm
kwik says:
July 23, 2010 at 2:40 pm
Phil. says:
July 23, 2010 at 12:42 pm
“Suppose you have an isolated black ball which you heat so that it eventually equilibrates at a certain temperature, introduce another ball nearby at a lower temperature, the hotter one will get hotter (as will the cooler).”
Are you sure about this, Phil? That the hottest will be hotter? I allways believed that this is exactly what was impossible, according to the 2′nd law….because if it got hotter…then heat has gone from colder to hotter…..
That’s exactly right, the version of the 2nd Law you quote is not applicable to radiation as George, I and others have pointed out above.
Interestingly Spencer has an entry on his blog today with exactly the same model experiment as I used (heaters instead of balls) and graphics etc. not just text.
I infer from the statement “Suppose you have an isolated black ball which you heat so that it eventually equilibrates at a certain temperature, …” that energy in the form of heat is being supplied to the black ball at a constant rate. The black ball will then reach a temperature at which the energy per unit time radiated to space will equal the energy per unit time being supplied to the ball, and the temperature will remain constant. If a cooler black body is added to the mix and the same time rate of heat is supplied to the original black ball, I too believe the temperature of the original black ball will increase, but the temperature of the “added black ball” may or may not increase. For example, if a planet at 5,000 Kelvin degrees is placed in an Earth-like orbit about the sun, the temperature of that Earth-like object won’t increase, but rather will decrease to the approximate temperature of the Earth.
However, the reason the original black ball’s temperature increases is because we are continuing to supply it with energy at a constant rate. This doesn’t violate the 2nd law of thermodynamics, which in the Clausius formulation is:
“It is impossible to construct a perfect refrigerator”–i.e., it is impossible to move energy from a reservoir at lower temperature to a reservoir at higher temperature without affecting the environment in any other way.
In Phil’s example, I believe the envronment “is beng affected in some other way” in that a source of energy other than the “added black ball” is adding energy to the original black ball at a constant rate. If at the time the “second black ball is added to the system” the source of input energy to the original black ball is terminated, then the temperature of the original black ball will not increase. At least that’s the way I see it.
Theo Goodwin says:
July 24, 2010 at 11:11 am
Tallbloke and 899,
Here’s my point in a practical way. The CO2 concentration is approximately 387 ppm. So, let’s say that 1/10 will send an emission of radiation to Earth daily, and round the figure to 39. I want to say that Earth receives whatever comes from the sun plus the 39 from CO2 per unit. I want to say that CO2 warms the Earth. You say that Earth receives whatever comes from the sun and nothing more but CO2 slows Earth’s cooling. The advantage of my approach is that it quantifies the effects of CO2 and it describes the force of emitted radiation from CO2.
Theo,
You talk about numbers of molecules of CO2, but you entirely neglect to consider what those do in the way of passing energy from one place to another.
CO2 behaves in an entirely reciprocal fashion, regardless from whence any impinging energy arrives.
CO2 resonates to a certain spectra (IR), and largely acts as an insulator otherwise, just as with most other atmospheric gasses.
The more gas in an atmosphere, the more insulation. If the Earth had twice the atmospheric pressure —with the same ratio of constituent gasses— it would retain far more heat, because of the insulative character of the gasses.
The Sun’s energy passes through the atmosphere, heats the surface, and the gasses keep the surface from losing the heat energy too quickly.
CO2 is beneficial for a number of reasons, not the least of which is that it helps ‘conduct’ surface IR back into space by dint of its reciprocal character.
Ergo, if we have MORE CO2 in the atmosphere, we’d lose heat faster than we do at present.
Now, some might be inclined to say that with MORE CO2, the Earth will be warmer, but that’s simply not true for the reason of reciprocity: The heat will leave just as fast as it is generated, and the more CO2, the faster the heat will be conducted away from the surface.
In the present sense, the level of CO2 needed to make a ‘snowball Earth’ would have be far, far greater than now, and even the Vostok Ice Cores show that that level was never reached.
I dare say, that it was the CO2 which continued to conduct heat away from the Earth as the Sun’s energy decreased in those instances revealed in the aforementioned ice cores, and as a result that caused the cooling which took place as the Sun diminished its output.
However, the CO2 was absorbed by the oceans in large quantities when the temperatures dropped, and as a result the cooling was greatly moderated.
In finality then, CO2 is both a moderator and an indicator gas for the amount of the Sun’s energy impinging upon the Earth.
We find ourself to be in a very luck happenstance: The plants and other things which employ CO2 as a function of life benefit from the CO2, and we who generate it are able to sustain our existence by that production.
The authors in the 4th paragraph state:- “This results in increased downward radiation toward the surface…”
This downward radiation is often called back-radiation and is essentially radiation from a cold body to a warmer body. The case for the existence of this ‘back radiation’ is weak. There is no evidence that ‘back-radiation’ has ever been detected or measured. OK, some claim they have measured back radiation and claim values of around 300 W/m2. The instrument used to obtain this figure is called a Pyrgeometer.
To calculate the incoming LW irradiance or back radiation at the detector, the temperature of the pyrgeometer body must be known. The downward longwave radiation EL is then calculated using the following formula :-
EL = Uemf/S + ( 5.67*10-8 * Tb^4 )
where
Uemf is the output voltage from the thermopile,
S is the calibration constant of the instrument, and
Tb is the pyrgeometer body temperature in Kelvin.
Note that for an upward facing pyrgeometer, the thermopile output voltage will be negative. This is because the upward radiation from the pyrgeometer is greater then the incoming irradiance from the sky.
Measurement of back-radiation has not been achieved, or more accurately, radiation from a cold surface to a warm surface has never been observed or measured. The pyrgeometer measures upward radiation and subtract this value from a hypothetical value relative to absolute zero. The difference is the so-called back-radiation. Surely the values quoted, typically around 300W/m2, would seem implausible as they are comparable in magnitude to the radiance from the Sun!
I think the belief in the existence of back-radiation comes from a misunderstanding of the Stefan-Boltzmann model which is often quoted as E = s*T^4 for a “black body where:-
E is the emissive power or irradiance,
s (sigma) is the Stefan–Boltzmann constant
T is the absolute temperature of the emitting surface
This model describes the emissive power of a surface relative to a surface at absolute zero. The model is a relative construct. The Emissive power of a hot body relative to a cold body is a positive value and that of a cold body relative to a hot body is a negative value, meaning that there is no net emission from the cold body. It absorbs radiation from the hotter body.
The emissive power of Body 1 relative to Body 2 should be written as :-
E = s (T1 – T2)^4.
Take a simpler example where T1 = T2. Between the surfaces there is no emission or absorption. I anticipate that some will say that one body will emit sT1^4 toward the other body and absorb sT2^4 from the other body… but what does that mean? Will a body absorb a photon and emit one of the same energy simultaneously? Well, maybe, but you could never observe this. A photon may be reflected but how would you know the difference? Both the Stefan-Boltzmann Law and the Second Law of Thermodynamics are statistical models. They do not predict the path of a single photon.
It appears that a small misconception in the application of the Stefan-Boltzmann law has led to the invention of so-called back-radiation
To clarify consider two tanks of water both with water level H relative to the ground. The simplified flow rate from a pipe at the base of the tanks is given by:-
F = k.H
Where:
k is a constant which allows for radius and length of the pipe, viscosity etc.
H is the Head or water level above our reference point (the ground).
What would happen if we joined these tanks together by attaching the pipes to the other tank? According to the concept of back-radiation , F would flow from Tank1 into Tank2 and F would flow in the reverse direction from Tank2 into Tank1 simultaneously.
If we put a flow meter in a pipe we could measure the flow between the tanks. The flow would be zero. The value F could not be observed in any direction. F is a measure of ‘backflow’, analogous to back radiation. But does this backflow really exist?
Back radiation has not been detected, why continue with this mis-construed concept?
The top line is that the solar radiation has not only a visible spectra, but also an infrared spectra. It is a poor mathematical sand box game to take the solar radiation energy at soil level as a constant and only do sophisticated calculations about the outgoing radiation. CO_2 also reduces the incoming radiation as well, and therefore the difference of in- and outgoing radiation has to be shown in a energy balance at soil level.
Another point is the averaging of radiation:
In the model the earth is irradiated as disc, cooling as a sphere. Albeit Stefan-Boltzman includes temperatures in T^4, daytime heating at different latitudes and nighttime cooling is neglected. In the measurement temperatures were averaged, not energy.
The presented temperature of 288K is a measured result depending on a lot of parameters, canceling each other to a small residue.
Especially water vapor and cloud cover is included in this number of 33K .
This difference is a total of all effects, not only shielding of radiation by CO_2 and the proof of a “CO_2 Greenhouse”.
Anything may be calculated, but nature does not care about it. This modeling is no contribution to a better understanding of weather and resulting climate.
“Joel Shore says:
July 24, 2010 at 7:47 pm
Andrew W says:
I don’t understand the logic that people are using to suggest the oceanic absorption of back IR radiation can be ignored or minimised, back radiation hits the ocean rather than land, what happens to it? It is absorbed, then what? It either goes into warming the water or it causes evaporation. If the latter the, energy doesn’t disappear, it’s still trapped in the troposphere.
Bingo!!! I think the logic is just desperation for people who very badly went the greenhouse effect heating to magically disappear…or not exist in the first place.”
Not so.
To all intents and purposes latent heat does disappear because it does not register on sensors so as to affect temperatures. Hence the term ‘latent’.
Thus net cooling of the surrounding environment wherever evaporation occurs and the more evaporation the greater the cooling.
The energy does however remain in the troposphere but does not warm it. Instead the energy in the water vapour makes the vapour lighter than the surrounding Oxygen and Nitrogen so it rises towards the tropopause and at some higher level is released again when condensation occurs. However at that point the energy is much higher and is simply accelerated away to space by radiative processes.
So it’s not trapped, it has no warming effect on the lower troposphere and the energy hungry process of evaporation cools the sea surface and/or surface air rather than allowing either to warm.
So where is the calculation that there is a residue of surplus sensible (not latent) energy left over to effect warming once an IR photon has caused a molecule of water to evaporate ?
There can be no such calculation because it is established fact that evaporation is a net cooling process.
The so called ocean skin theory promulgated by RealClimate and others is a desperate ploy to avoid that problem and I think I have adequately deconstructed it already in another place as per the link I supplied previously.
http://climaterealists.com/index.php?id=4245
“Greenhouse Gases Can Cause Cooling !”
I have been waiting for a serious attempt at rebuttal for some time.