Guest Post by Willis Eschenbach
Once again, the crazy idea that downwelling longwave radiation (DLR, also called infra-red or IR, or “greenhouse radiation”) can’t heat the ocean has raised its ugly head on one of my threads.
Figure 1. The question in question.
There are lots of good arguments against the AGW consensus, but this one is just silly. Here are four entirely separate and distinct lines of reasoning showing that DLR does in fact heat the oceans.
Argument 1. People claim that because the DLR is absorbed in the first mm of water, it can’t heat the mass of the ocean. But the same is true of the land. DLR is absorbed in the first mm of rock or soil. Yet the same people who claim that DLR can’t heat the ocean (because it’s absorbed in the first mm) still believe that DLR can heat the land (despite the fact that it’s absorbed in the first mm).
And this is in spite of the fact that the ocean can circulate the heat downwards through turbulence, while there is no such circulation in the land … but still people claim the ocean can’t heat from DLR but the land can. Logical contradiction, no cookies.
Argument 2. If the DLR isn’t heating the water, where is it going? It can’t be heating the air, because the atmosphere has far too little thermal mass. If DLR were heating the air we’d all be on fire.
Nor can it be going to evaporation as many claim, because the numbers are way too large. Evaporation is known to be on the order of 70 w/m2, while average downwelling longwave radiation is more than four times that amount … and some of the evaporation is surely coming from the heating from the visible light.
So if the DLR is not heating the ocean, and we know that a maximum of less than a quarter of the energy of the DLR might be going into evaporation, and the DLR is not heating the air … then where is it going?
Rumor has it that energy can’t be created or destroyed, so where is the energy from the DLR going after it is absorbed by the ocean, and what is it heating?
Argument 3. The claim is often made that warming the top millimetre can’t affect the heat of the bulk ocean. But in addition to the wind-driven turbulence of the topmost layer mixing the DLR energy downwards into lower layers, heating the surface affects the entire upper bulk temperature of the ocean every night when the ocean is overturning. At night the top layer of the ocean naturally overturns, driven by the temperature differences between surface and deeper waters (see the diagrams here). DLR heating of the top mm of the ocean reduces those differences and thus delays the onset of that oceanic overturning by slowing the night-time cooling of the topmost layer, and it also slows the speed of the overturning once it is established. This reduces the heat flow from the body of the upper ocean, and leaves the entire mass warmer than it would have been had the DLR not slowed the overturning.
Argument 4. Without the heating from the DLR, there’s not enough heating to explain the current liquid state of the ocean. The DLR is about two-thirds of the total downwelling radiation (solar plus DLR). Given the known heat losses of the ocean, it would be an ice-cube if it weren’t being warmed by the DLR. We know the radiative losses of the ocean, which depend only on its temperature, and are about 390 w/m2. In addition there are losses of sensible heat (~ 30 w/m2) and evaporative losses (~ 70 w/m2). That’s a total loss of 390 + 30 + 70 = 490 w/m2.
But the average solar input to the surface is only about 170 watts/square metre.
So if the DLR isn’t heating the ocean, with heat gains of only the solar 170 w/m2 and losses of 390 w/m2 … then why isn’t the ocean an ice-cube?
Note that each of these arguments against the idea that DLR can’t warm the ocean stands on its own. None of them depends on any of the others to be valid. So if you still think DLR can’t warm the ocean, you have to refute not one, but all four of those arguments.
Look, folks, there’s lot’s of good, valid scientific objections against the AGW claims, but the idea that DLR can’t heat the ocean is nonsense. Go buy an infrared lamp, put it over a pan of water, and see what happens. It only hurts the general skeptical arguments when people believe and espouse impossible things …
w.
Willis writes “You’re looking at this backwards. In a system in which the surface is maintained at a slightly lower temperature than the bulk … what happens if you forcibly warm the surface? Think it through all the way, Roger. The very surface warms … until it’s slightly warmer than the bulk … which then heats up slightly, until the surface is slightly cooler than the bulk, and the previous condition (cooler surface) is restored.”
No, you’re still missing it or at the very least describing it poorly. The “very surface” is always cooling, not warming. Adding GHGs doesn’t forcibly do anything with DLR warming the surface. The same relationship always exists with DLR < ULR
It is the 1mm depth and below, the "hook", that warms and it does so because the bulk is warming, not because the "very surface" is warming with the bulk following. When the 1mm depth warms from below by convection, it is the SST that has to come along for the ride.
It is the "hook" which moves around from moment to moment trying to set the SST for equilibrium. Its driven by the incoming DSR. In the case of increased GHGs the equilibrium is still set by the incoming DSR and the "hook" except that the SST needs to be a little higher to account for the additional DLR that is (for want of a better term) re-radiated accounting for more of the Steffan-Boltzmann requirment for the ocean to radiate.
So where does any ocean warming ultimately come from? Increased GHGs have caused the SST to be a little higher and if you think of the ocean as having a top temperature of say 15C and a bottom temperature of say 3C then the GHGs will change the top temperature to say 15.5C and given time, the temperatures all the way down to the bottom will change to match. Not by adding 0.5C all the way down but there will be some related increase.
Wow there is a bunch of assumptions in that last statement isn't there. What if the ocean wasn't in equilibrium to start with?
Dave Springer at August 19 2011 5:16am
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Dave
Very much my take on things.
I have seen you before making your point on model runs without the oceans. I envisage that your predicted result is right. Since a model run in that condition would reveal a lot, it is surprising that such a run has never been made, or is it the case that ‘the Team’ have made such a run but have not published the result.
Richard, trace gas point taken. I actually had the prevalence of water vapour in mind when I wrote it, but you are right to pick up on it. Discussions like the one we’ve had are very valuable to help me hone my arguments.
I think we’ve covered some ground here, and hopefully sorted out some of the misunderstandings which lead people to think that the back radiation heating the oceans argument is ‘part of the basic physics’ that sceptics should accept. I’ve been resisting it for years, but it’s amazing how strong this mistaken meme is.
tallbloke says:
August 19, 2011 at 9:28 am
…which lead people to think that the back radiation heating the oceans argument is ‘part of the basic physics’ that sceptics should accept.”
If in fact back radiation could heat something or even slow down the rate of cooling then we should exchange the vacuum in thermos bottles for a mixture of CO2 and H2O. Using IPCC’s 5.35(ln C/Co) going from 1 ppm to 1 million yields almost 74 watts/m^2.
But sadly conduction would win out over a phenomena great enough to heat oceans.
Richard,
You are still missing at leas one key idea as to how the GH effect works. Let me use your slab analogy and give a few variations. I’ll assume the slab & walls have emissivity = 1 for thermal IR photons. I’ll assume that when warm, they emit 400 W/m^2 of thermal IR (T = ~ 33 C). Let’s also assume that any gas in between is separated from the slab and walls by a thin region of vacuum, so there is no conduction or convection.
CASE 1: Warm Slab; warm walls; vacuum in between.
It should be obvious that the slab will stay the same temperature, receiving and emitting 400 W/m^2, since it is in thermal equilibrium with the walls
NET RADIATION = 0 W/m^2
CASE 2: Warm slab; 0 K walls; vacuum in between.
The slab will cool quickly, since it is radiating 400 W/m and receiving none back.
NET RADIATION = – 400 W/m^2
CASE 3: Warm slab; warm walls; warm CO2 in between. (This is STILL not “the green house effect”)
The CO2 has no net effect. Some of the IR photons leaving the slab get absorbed by the CO2 and some of them will return to the slab. At first glance this might seem to warm the slab, since we have added IR photons to the slab. BUT! we have also blocked some of the IR photons heading from the walls toward the slab. A few photons that should have escaped get returned. A few photons that should have arrived get diverted. The slab will still emit 400 W/m^2. It will still receive 400 W/m^2. The only difference is that the slab receives x W/m^2 from the CO2 (the value of “x” depending on the geometry of the objects involved and the IR spectrum of CO2), and (400-x) W/m^2 from the walls.
NET RADIATION: 0 W/m^2
CASE 4: Warm slab; cold walls; warm CO2 in between. (THIS is “the green house effect”)
The slab loses 400 W/m^2. The CO2 radiates x W/m^2 to the slab (as above). But the walls radiate 0 W/m^2 to the slab because they are at 0 K. So the natural loss from the slab is moderated by the CO2. The slab only looses (400-x) W/m^2, but it gets nothing from the walls. It cools slower than CASE 2.
NET RADIATION – (400-x)
Suppose that x = 100 W/m^2. Then a 300 W/m^2 heater would keep the slab warm with CO2 present (CASE 4), but a 400 W/m^2 heater would be required for CASE 2. The CO2 help “warm” the slab. (For warm walls in CASES 1 & 3, the gas has no effect at all. That is why cold walls are a critical part of the experiment.)
If DLWR increases evaporation, then would it not also increase cloud cover? If cloud cover (and or humitity) increases, would it not decrease SWR from the Sun? Would this not reduce a more effective per watt source of energy warming the oceans, (SWR) thus cooling the deeper waters, and increasing the gradient between those waters and the surface?
Tim Folkerts says:
August 19, 2011 at 9:57 am
CASE 4: Warm slab; cold walls; warm CO2 in between. (THIS is “the green house effect”)
The slab loses 400 W/m^2. The CO2 radiates x W/m^2 to the slab (as above). But the walls radiate 0 W/m^2 to the slab because they are at 0 K. So the natural loss from the slab is moderated by the CO2. The slab only looses (400-x) W/m^2, but it gets nothing from the walls. It cools slower than CASE 2.
NET RADIATION – (400-x)
Suppose that x = 100 W/m^2. Then a 300 W/m^2 heater would keep the slab warm with CO2 present (CASE 4), but a 400 W/m^2 heater would be required for CASE 2. The CO2 help “warm” the slab. (For warm walls in CASES 1 & 3, the gas has no effect at all. That is why cold walls are a critical part of the experiment.)
How can a 300 W/m^2 heater get the slab to produce 400 W/m^2? Besides you cannot do heat transfer this way. You fail to show a temperature gradient which is required for heat transfer. The only actors in your play that are assigned a T are the slab T=33C and the cold wall of 0 K. So please don’t mix temperature scales and assign a T to the CO2 and so the proper transfer equations. Tell us what will be the emissivity of your CO2 and under what pressure?
Dave Springer says:
This is seems like a pretty sure statement from the man who had been bemoaning the lack of empirical evidence related to theories about the ocean. Without experimental backing, I would never endorse one hypothesis over another this adamantly.
You have an interesting and plausible hypothesis (energy absorbed from IR photons goes directly to evaporating the molecules, not to heating the surface). So do I (energy absorbed by IR photons heats the surface layer, which then fuels an increase in upward IR and evaporation). The truth is most likely somewhere in the middle.
But let me give one more argument as to why I am pretty sure that your description is not 100% correct (or even close to 100 % correct). I think we agree that “DLR” is absorbed in the first few μm. But note that this distance is NOT “the first few nm”. If an IR photon is typically absorbed 1 μm = 1000 nm down, and the typical size of a molecule is 1 nm, then the molecule with the extra energy has several hundred or several thousand molecules above it. It cannot “get knocked loose” directly because it will have to hit 100’s of other molecules “shielding” that energetic molecule from escaping. Long before that particular energetic molecule will “evaporate”, it must collide with 100’s (with 100’s be a very conservative estimate) of other molecules, sharing energy during every collision.
“Colliding with 100’s of molecules and sharing the excess energy among them” is pretty much exactly the definition of “raising the temperature”.
Tim,
Willis is talking about why the oceans don’t freeze. Other than the fact that they won’t radiate at 390w/m2 for very long as they cool and evaporation loss will also decrease, it is the bulk and not just a thin surface layer in question. How does this energy make it down against the gradient to warm the bulk. As we do not have measurements of high enough accuracy to know we are left to speculate.
I would suggest that the highly complex surface area we are talking about has not been defined in its entirety and probably won’t be in the near future (disregarding quantum levels even)
http://www.nytimes.com/2009/07/28/science/28ocea.html
It would seem that these findings would impact the energy flux a bit and the purely mechanical effects also. Would seem to be another reason the surface is distinct from a millimeter down.
Tim says:
“Colliding with 100′s of molecules and sharing the excess energy among them” is pretty much exactly the definition of “raising the temperature”.
And yet the skin surface is cooler and the lower 0.9mm warmer, whereas all the DLR is absorbed in the first 0.05mm. So something other than the radiation is controlling temperature at the skin. Since radiative action only represents 25% of ocean heat loss, I would presume that something else is the latent heat of evaporation, which sucks energy from the surrounding molecules as evaporation occurs.
However, this only accounts for about 80W/m^2. Stephen Wilde has some ideas on this I seem to remember.
Tallbloke,
I think we are not so far apart. I am not arguing that the skin should be warmer that the layers below. When things are in equilibrium, then the skin is indeed cooler by ~ 0.2 – 0.3 K compared with the layers below. This is a consequence of the entire energy balance, especially the loss of energy from the top via evaporation, convection AND IR. As long as things are quasi-stable, this gradient exists. In this situation, ~ 170 W/m^2 can be conducted upward thru the top layer from the layer below. Thus the bulk of the ocean would not be warming or cooling.
What I am saying is that IF there is some extra energy to the skin (for example from extra downward thermal IR, then the balance will get upset. The temperature gradient will decrease (and not merely increase in evaporation rate as Dave Springer is arguing). Less of a gradient –> less conduction of energy from below –> the temperature of the bulk of the ocean must increase.
This simply illustrates one possible mechanism by which extra downward thermal IR will result in higher temperature of the bulk of the ocean without those IR photons ever actually reaching the bulk of the ocean.
@Myrhh
Visible light can travel thousands of meters through very clear water. Ultimately there is no such thing as absolutely pure water because it’s a universal solvent. Obtaining absolutely pure water is like trying to obtain a complete vacuum or a temperature of absolute zero. They can be approached but never obtained in nature. It is the impurities in seawater which limit how far visible light can penetrate. If it were pure unadulterated H2O you could read a newspaper during the day at the bottom of the Marianas Trench.
tallbloke says:
August 19, 2011 at 12:51 pm
Where do you get that 80W/m^2 number for latent heat loss? Actual measurements show 200Wm incoming from solar shortwave, 10Wm outgoing via conduction, 50Wm outgoing via radiation, and 140Wm outgoing in latent heat of vaporization. You’re reducing a measured value for latent heat by almost half with the 80Mw figure.
Tim Folkerts says:
August 19, 2011 at 3:28 pm
“What I am saying is that IF there is some extra energy to the skin (for example from extra downward thermal IR, then the balance will get upset. The temperature gradient will decrease (and not merely increase in evaporation rate as Dave Springer is arguing). Less of a gradient –> less conduction of energy from below –> the temperature of the bulk of the ocean must increase.”
Tim if there is extra energy to the skin does it not increase the water vapor in the air just above the skin? Would this increase in water vapor not reduce the SWR entering the oceans below the skin, thus possibly maintaining or increasing the gradient over time? Would it not also increase the absorbtion of LWIR just before it reaches the skin? Also, due to the residence time of SWR being far longer in the oceans, a 2W/m^2 reduction in SWR would have a greater cooling effect, again over time, then a 2 W/m^2 reduction in LWIR. Yet nobody has quantifed these numbers.
“Stephen Wilde has some ideas on this I seem to remember.”
Yes indeed.
I’ve already set out my propositions in this thread and elsewhere but no one seems to have read them because you are all talking around the very same issues without any reference to what I said.
Stephen Wilde says:
August 19, 2011 at 4:55 pm
If you gave me a link to what you said that was important, I’d have gone there and read it already.
But I’m not going to go looking for some un-named something you think is important, heck, how would I know it if I saw it?
Link to or quote what you think is important, otherwise I for one am not chasing it. Copy the link contained in the date/time line under your name above your important words, and paste it into your message.
w.
Tim Folkerts says:
August 19, 2011 at 3:28 pm
Tim, I think a small change in the relatively small energy flux at the interface of 66W/m^2 wouldn’t change things because it would be overwhelmed by the other factors maintaining the differential. Not the least being the air temperature itself, which follows the ocean SST fairly closely, about 3 months later on the global average. It is interesting that there seems to be a cycle over ~110 years though.
http://tallbloke.wordpress.com/2011/02/17/roger-andrews-the-solar-sst-relationship-part-ii/
Not surprisingly, there HAVE been studies done on the skin temperature
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 95, NO. C8, PP. 13,341-13,356, 1990
doi:10.1029/JC095iC08p13341
On the Bulk-Skin Temperature Difference and Its Impact on Satellite Remote Sensing of Sea Surface Temperature
Peter Schluessel, William J. Emery, Hartmut Grassl, Theodor Mammen
Satellite infrared sensors only observe the temperature of the skin of the ocean rather than the bulk sea surface temperature (SST) traditionally measured from ships and buoys. In order to examine the differences and similarities between skin and bulk temperatures, radiometric measurements of skin temperature were made in the North Atlantic Ocean from a research vessel along with coincident measurements of subsurface bulk temperatures, radiative fluxes, and meteorological variables. Over the entire 6-week data set the bulk-skin temperature differences (ΔT) range between −1.0 and 1.0 K with mean differences of 0.1 to 0.2 K depending on wind and surface heat flux conditions. The bulk-skin temperature difference varied between day and night (mean differences 0.11 and 0.30 K, respectively) as well as with different cloud conditions, which can mask the horizontal variability of SST in regions of weak horizontal temperature gradients. A coherency analysis reveals strong correlations between skin and bulk temperatures at longer length scales in regions with relatively weak horizontal temperature gradients. The skin-bulk temperature difference is parameterized in terms of heat and momentum fluxes (or their related variables) with a resulting accuracy of 0.11 K and 0.17 K for night and daytime. A recommendation is made to calibrate satellite derived SST’s during night with buoy measurements and the additional aid of meteorological variables to properly handle ΔT variations.
Measurement show the skin CAN be warmer than the layer below! Only on average is the skin cooler than the surface. If the skin gets extra energy, it apparently can and does decrease (or even reverse) the temperature gradient,
Stephen Wilde says:
August 15, 2011 at 2:52 pm
Stephen Wilde says:
August 15, 2011 at 4:18 pm
Stephen Wilde says:
August 18, 2011 at 12:16 pm
Stephen Wilde says:
August 18, 2011 at 12:27 pm
WTF, Willis?
I think I asked, twice, a very important question that goes to the heart of this (nonsense?) about the putative “atmospheric greenhouse effect.” I have asked this question for about 5 years and have never received a decent response. I had hope HERE, but, alas, I have been completely ignored, and frankly, it bugs me that YOU, of all people, would do that. I have asked the same questions at “science-of-doom” and Surreal-Climate and have received either snips or vague nonsense responses (at least I was not ignored!!!). But YOU are one of my heros, and I am now pissed off. I challenged you, and it appears to me that you have have slithered away into the grass on me?? Colorado cowboys don’t differ much from Montana cowboys, fella. Same sense of FAIRNESS.
THE BASIC QUESTION IS: WHY HAS THE “BACKRADIATION/ATMOSPHERIC GREENHOUSE EFFECT” NEVER BEEN DEMONSTRATED EMPIRICALLY? UNTIL IT IS, IT IS MERELY A THEORY/FIGMENT. CONSULT EINSTEIN AND OTHER SCIENTISTS ABOUT THIS, IF YOU DOUBT IT.
When one asks over and over for a response and is consistently ignored, I guess that one can draw only a few conclusions:
1) He/she is just considered irrelevant/stupid or off-topic and is not worth a response.
2) He/she has a point that the “expert” does not how to address.
3) His/her thought could embarrass the “expert,” so he/she must be ignored (extremely not likely here, considering the integrity of the “expert”).
4) He/she is a butt.
5) He/she has no clue
6) Other possibilities.
“Measurement show the skin CAN be warmer than the layer below! Only on average is the skin cooler than the surface. If the skin gets extra energy, it apparently can and does decrease (or even reverse) the temperature gradient,”
Indeed, but it is the global average that counts as regards the global energy budget.
I suspect that the energy budget between ocean and air is balanced by the average global depth of the interface between skin and bulk and the size of the temperature differential across that interface. That balance is affected by changes in the flow of energy up from the ocean bulk (solar shortwave driven) rather than changes in DLR.
Similarly the energy budget between air and space is balanced at the stratopause which is the point where the balance of ozone destruction/creation changes in response to varying levels of solar activity. The effect of solar variability on ozone quantities apparently reverses at about 45km which is approximately at the stratopause.
The climate zones are controlled by the interaction betwen those two ever shifting points of balance and the visible manifestation of the changing balances is latitudinal shifts in the surface air pressure distribution. Hence climate changes.
Tim Folkerts writes : “Measurement show the skin CAN be warmer than the layer below!”
The paper is behind a paywall. But “bulk” doesn’t mean 1mm below, it means deeper.
You can see that the SST is both warmer and colder than the bulk where the bulk is measured at some number of cm depth (Minnett used 5cm depth in his experiment)
http://en.wikipedia.org/wiki/File:MODIS_and_AIRS_SST_comp_fig2.i.jpg
Having said that there are always exceptions and DSR could be greater than ULR around coastlines for example where warm air comes from the land and onto the water. I’m sure there are other examples. In these cases depending on the rate of evaporation there may be no cool skin.
“depending on the rate of evaporation there may be no cool skin.”
Exactly. Evaporation mops up whatever DLR is left over after upward radiation, convection and conduction have taken their slices.
When evaporation is constrained the coolness and depth of the skin may decline but they will be local variations only. What matters is the global average.
Martin Lewitt says:
August 16, 2011 at 1:35 pm
Martin, you say DLW can warm the ocean. However, tallbloke and a host of others have repeatedly made the claim that the DLW cannot heat the ocean. Which is why I wrote what I wrote. So your claim about what “the point” is misses the point—there are a lot of people out there claiming that DLR can’t heat the ocean, and so that’s what I wrote about.
Do I know what I’m talking about? Do you specialize in unpleasant questions? Heck, that’s what this whole process is designed to find out, isn’t it? I make scientific claims, and people try to overthrow them or show that there’s problems with my logic or my numbers or anything else. Sometimes I’m found wrong, and I admit it … but most of the time, people can’t poke holes in my claims.
So in answer to your question, do I know what I’m talking about, I’d have to say “Yeah, most of the time.”
I doubt that “models generally couple them both to the mixing layer as if they were equivalent”. I’d have to see a citation for that. Possible, but modelers aren’t fools. They’re foolish, to be sure, but not fools, if that makes sense …
Dang, another internet mind reader who wants to tell me what my argument is. QUOTE MY WORDS if you disagree with me, don’t bother me with your fantasy of what my argument “amounts to”. I didn’t say anything about how the models handle the two types of energy. I didn’t discuss which was more likely to be re-radiated. I didn’t say which one penetrates further than the other, or discuss what the difference in their effect is. I didn’t say a watt is a watt, or imply it.
In fact, since the radiation at the surface slows the cooling of the ocean, it affects the entire mixed layer. So distinguishing the effects of the two types of radiation is not as simple as it might be, because both affect the entire mixed layer.
And that’s all interesting stuff … but it doesn’t have anything to do with my argument or what you think it “amounts to”. Here’s my argument, listen up so if you object to anything you can quote it:
My argument is that the ocean is warmer, both at the surface and in the bulk of the mixed layer, than it would be if it were not absorbing DLR.
I think that you agree with me. Now go convince tallbloke that the ocean absorbs DLR, and stop faffing around trying to explain to me what my argument “amounts to”.
w.
jae says:
August 19, 2011 at 7:00 pm
jae, your question doesn’t get answered because it is based on a false assumption. The fallacy is that downwelling longwave radiation can’t be demonstrated empirically.
Not sure how you missed the following items. There’s an entire industry out there making instruments that are specifically designed to measure the DLR. There are scientists who make a living measuring the DLR. There are a host of papers about the measurements of DLR.
So the idea that DLR “can’t be demonstrated empirically” doesn’t even pass the laugh test, much less the smell test. It is a fantasy without a scrap of observational support. Not only that, but you don’t need instruments to know DLR is real. I can feel DLR, it’s warmer when a cloud passes over during a winter night. When the cloud goes away, the clear sky just sucks the warmth out, but when the cloud is over me, I can feel the warmth from the cloud. So I know from my experience that there is DLR, regardless of what EINSTEIN AND OTHER SCIENTISTS might say about it.
And questions that don’t even pass the laugh test generally don’t get answered by me. It just spins off into strangeness, I’ve got no time for that.
w.
PS – Here’s a protip. Entire paragraphs of capitalized text, especially if they mention God, Gandhi, or Einstein, are the hallmarks of the SIF, the “single-issue fanatic”. Basically, putting in a paragraph of that kind is like waving a big sign saying “I AM A NUTTER! IGNORE ME!”
As a result, when I see paragraphs like that, I just skip to the next posting.
Just sayin’ how it looks from this side of the screen …