Guest Post by Willis Eschenbach
There’s a recent paper paywalled here, called Arctic winter warming amplified by the thermal inversion and consequent low infrared cooling to space. Fortunately, the Supplementary Online Information is available here, and it contains much valuable information. The paper claims that during the arctic winter, the atmospheric radiation doesn’t go out to space … instead it is directed downwards, increasing the surface warming.
Now I haven’t figured out yet how that works, radiation being “directed downwards”. But that’s what they say. From their Abstract:
We find that the surface inversion in fact intensifies Arctic amplification, because the ability of the Arctic wintertime clear-sky atmosphere to cool to space decreases with inversion strength. Specifically, we find that the cold layers close to the surface in Arctic winter, where most of the warming takes place, hardly contribute to the infrared radiation that goes out to space. Instead, the additional radiation that is generated by the warming of these layers is directed downwards, and thus amplifies the warming. We conclude that the predominant Arctic wintertime temperature inversion damps infrared cooling of the system, and thus constitutes a positive warming feedback.
Hmmm … so their basic claim is that the (poorly named) “greenhouse effect” is strengthened by the temperature inversion in the winter, that this slows the surface cooling, and that as a result the surface ends up warmer than it would otherwise be. A second claim is that the cause of additional Arctic winter downwelling radiation at the surface is a temperature inversion. The third claim is that this Arctic inversion is not unusual, but that there is a “predominate” winter temperature inversion in the Arctic.
Now, all of these claims can be investigated using the CERES satellite radiation dataset. To look at their first claim, I thought I’d follow the lead of the estimable Ramanathan and consider how much of the upwelling radiation from the surface is absorbed during the Arctic summer versus the Arctic winter. Ramanathan proposed the use of this atmospheric absorption of surface radiation as a measure of the strength of the greenhouse effect. Obviously, the more upwelling longwave that is absorbed by the atmosphere, the warmer the surface ends up. Figure 1 shows the strength of the greenhouse effect using Ramanathan’s measurement (absorbed radiation as a percentage of surface radiation) in June and in December.
Figure 1. Strength of the poorly-named “greenhouse effect”, as measured by the percentage of the surface upwelling longwave radiation (thermal infrared radiation) that is absorbed by the atmosphere. The situation is shown for the month of June (upper panel) and December (lower panel). Following Ramanathan, the absorbed radiation is calculated as the upwelling surface radiation minus the upwelling TOA radiation.
As you might imagine, and can see in Figure 1, the greenhouse effect is strongest where there is water. As a result, the effect is strongest in the tropics, and is stronger over the ocean than over the land. For the same reason, the greenhouse effect is weaker over the deserts and at the poles.
Now, their claim is that there is additional greenhouse warming in the Arctic in the wintertime compared to the summertime, slowing the radiative cooling of the surface. However, the CERES data disagrees, and indeed it shows the opposite. The CERES data says that at both poles, the greenhouse effect is stronger in the summertime, not weaker. This makes sense, because there is more water vapor in the air in the summer.
Note also that while there are areas of temperature inversions (shown in blue), and they do occur in a few areas in the Arctic winter(lower panel), they are not a general feature of the Arctic. On the other hand, large areas of the Antarctic do have a temperature inversion in winter (upper panel, blue).
So the CERES data doesn’t agree with the study regarding the slowed cooling in winter. The CERES data says the opposite, that cooling is easier in winter because less upwelling surface longwave is absorbed by the atmosphere. Nor does the Arctic temperature inversion seem to be as widespread or pervasive as the authors state.
Next, they claim increased downwelling longwave at the surface in the Arctic winter. To investigate this claim, Figure 2 shows the June and December downwelling longwave surface radiation, once again as a percentage of the upwelling longwave surface radiation.
Figure 2. Downwelling surface longwave radiation as a percentage of the upwelling longwave surface radiation, June (upper panel) and December (lower panel).
The main oddity in Figure 2 is that most places, most of the time, the downwelling radiation is about 86-88%, with not much difference summer to winter or place to place, particularly in the ocean. I wouldn’t have guessed that. Note that Figure 2 also reveals the widespread winter temperature inversion in the Antarctic winter (upper panel, red) indicated by downwelling longwave radiation exceeding upwelling surface radiation, and the lack of such a widespread inversion in the Arctic winter (lower panel, red).
More to the current point, we have a curiosity related to the authors’ claims about the Arctic. Note that in Antarctica in the wintertime (upper panel) there is a marked increase in the downwelling radiation as a percentage of the surface radiation compared to their summer (lower panel). The difference is large, 98% versus 64%. Presumably, this is the increased downwelling that they describe in their paper (although as expected the upwelling also increases).
But in the Arctic, where the paper claims this phenomenon of increased downwelling radiation is occurring, there is no difference between the downwelling surface longwave in the summer and the winter (88% in both cases).
So we do in fact find the phenomenon they point to of increasing downwelling radiation … but we don’t find it in the Arctic as they claim, we find it at the opposite pole.
Summary
1. Their claim, that there is “reduced cooling” in the arctic in wintertime that affects the surface temperature, is not supported by the CERES data. To the contrary, the CERES data shows the Arctic radiative cooling is much more rapid in the winter than the summer, because the atmosphere is absorbing much less radiation. Note that this is what we’d expect, due to the reduced amount of water vapor in winter.
2. Their claim, that the Arctic temperature inversion is widespread, is not supported by the CERES data. It shows general wintertime temperature inversion in the Antarctic, but not in the Arctic.
3. Their claim, that the Arctic downwelling longwave radiation increases in the winter, is not supported by the CERES data. Curiously, it is true in the Antarctic. In the Arctic, however, there is almost no difference between summer and winter.
Now, how did they get this so wrong? From their methods section (emphasis mine):
An often used method to increase the signal-to-noise (i.e. climate change- to-variability) ratio is to study multi-model output, such as those obtained in the CMIP3 initiative for ‘realistic’ forcing scenarios. The general idea then is to apply statistics on the multitude of independent members (individual models) to reduce the noise, and also to use intermodel differences to relate climate processes to feedbacks2.
Another method, the one employed here, is to use one climate model and apply a sufficiently large forcing (e.g. 2xCO2) to obtain a climate change signal that is much larger than the noise. The advantage of this approach is that dedicated experiments can be carried out, including changing certain model processes in order to link these to feedbacks (as is done in this study).
So … as usual, rather than mess with ugly observational data, it’s models all the way down. Actually it’s worse, it’s the output of one single solitary model all the way down. Or as a typical adulatory media report of the story says:
Pithan and co-author Thorsten Mauritsen tested air layering and many other Arctic climate feedback effects using sophisticated climate computer models.
Hey, as long they used a sophisticated climate model, and it is reportedly “based on true physics” in the best Hollywood tradition, what’s not to like?
Best to everyone,
w.
The Usual Request: If you disagree with something I say, please quote my exact words so we know what you are referring to. I can defend my own words. I cannot defend some vague claim like “Willis, your logic is wrong”. It may well be … but we’ll never find out unless you quote exactly the logical claims I made that you don’t like.
Data and Code: CERES calculated surface data (in R “save()” format) is here, 110Mbytes. and the CERES measured TOA data is here, 230 Mbytes. CERES Setup.R and CERES Functions.R are needed for the analysis. Finally, the code for this post is Arctic Amplification.R
Also, it’s worth noting that while the CERES top-of-atmosphere data is from measurements, the surface data is calculated from the TOA data using energy balance considerations. Obviously, a global set of observational surface radiation data would be wonderful … but since we haven’t got that, the CERES data is the best we have.
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“Hmmm … so their basic claim is that the (poorly named) “greenhouse effect” is strengthened by the temperature inversion in the winter,”
Since a temperature inversion suppresses convection it would keep the surface warmer via the same mechanism that a greenhouse actually does instead of the mechanism most using the term are referring to.
I question the claim that the Arctic inversion is not a widespread feature. Possibly it does not show up on this one CERES December plot. The arctic winter sometimes does not get fully going until January. I have been weather forecasting for the Canadian Arctic (north of 60N) for the better part of my lifetime now and I can assure that dealing with dramatic and persistent low level winter temperature inversions is a part of the forecasting situation. You can see these inversions using the upper air soundings available from sites such as the U of Wyoming. I just had a look through many of the soundings in the Arctic today and the vast majority show pronounced inversions as occur throughout the winter. Have a look at YBK, YCB, YVQ, etc. Those are typical winter time inversions. Certainly not something you see much of in the main U.S.
http://weather.uwyo.edu/upperair/sounding.html
Willis Eschenbach says:
Over land (including ice) a surface temperature inversion occurs every day an hour or so before sun set. The inversion lasts until a few hours after sun rise. The inversions occur because the surface radiates heat to space faster than the lower atmosphere. Since the surface becomes colder than the atmosphere, there is a net radiation flow from the atmosphere toward the surface – typically referred to as “back radiation”. From the radiosonde data, it is clear that by morning the atmosphere over land is still slightly warmer than the surface and that the atmospheric temperature increases with increasing height up to the very obvious point where the atmosphere becomes IR opaque based on the available greenhouse gases. In other words, heat is flowing from hot to cold.
The oceans are different. The surface of the ocean does not cool the same way a solid surface does because the water’s density increases as the temperature decreases. As a result, the surface temperature stays fairly stable during the diurnal cycle.
Why do you say it is not that strong? What do you think the winter (6 months, no sun) temperature would be if there was no downwelling radiation from the atmosphere? Based on measurements from the moon (dark for only 14 days at a time) and data from a satellite design manual, I think it would be about 45K. Assuming that that is a reasonable estimate, then a surface temperature of 203K to 220K without solar heating is a pretty big deal.
I guess that I should have said that the surface inversion is only “a part of” of the greenhouse effect. However, it appears to be the tropospheric part affected most by changes in CO2 concentration.
george e. smith says:
February 4, 2014 at 12:21 pm
“So “Black Bodies” don’t exist; so how come we have a theory of how they work ??”
George: You really must familiarize yourself with the mathematical and scientific concept of a “limiting case”. They are used in many fields, and to great effect in coming to an understanding of principles involved. Sometimes, they are even good enough approximations.
If you take an introductory Newtonian mechanics physics course, all of your early problems will involve frictionless systems. No such thing, so why is it taught that way? Well, first it makes the problems simple enough for starting students so they can solve them and understand how phenomena such as inertia operate. Second, zero friction is the limiting case – you can approach it, but never pass it, as there is no such thing as negative friction. Third, it is possible in many systems to make the friction negligible enough that it can be ignored for many purposes of analysis. I regularly deal with systems using air bearings or magnetic bearings where this is the case.
Similarly, the idealized blackbody is the limiting case of the “perfect” absorber/emitter. Real-world substances will absorb and emit less than the theoretical blackbody would, but never more (from thermal effects, that is). Also, we know that many, many substances behave in a manner very close to a blackbody, absorbing 95-99% of what a “mythical” blackbody would. For first-cut analysis at least, the small percentage difference can often be ignored.
Do they even talk about the heat of fusion of water? For every KM^3 of water converted to ice or 1,000 Km of 1 m thick ice, the water is going to give up 3.34E+17 J of heat. It has to go somewere and must supply some of the wintertime no sun temperature inversion.
Same goes for the summer as as the ice melts, it will pull the same 3.34E+17 j of heat to melt each Km^3 of ice.
Ever notice how 31 F in a soft snowfall will feel warmer that 33 F in the spring as the snow melts? It is the heat of fusion.
DD More:
Is that 3.34 E+17 J of energy usable to being with?
Meant to say Usable to begin with>>
Ren, would you mind recasting this sentence so that it is clearer? I realized as I read down that English is not your mother tongue, and I appreciate your effort to communicate in English. I am asking because I want to understand what you are talking about. Thx.
Wrong data to detect inversions.
Our model is different than other models. Most models only go up to 10. THIS model goes up to 11. (H/T Spinal Tap)
When considering the effect of DWLWIR, it is necessary to know the absorption charactericis of water and ice to low grazing angle LWIR. Given that the re-radiation of LW is unidirectional, it is important to bear in mind that approximately 10% of all DWLWIR must be interacting with the surface at an angle of less than 10 deg.
Water is a very good absorber of LWIR, when interceptimng at the perpendicular, but how does it behave when LWIR is grazing at say 5deg? Ditto ice. I have not seen the experimetal data, but it must be out there.
The K&T energy budget diagram shows sunlight being reflected, but shows no DWLWIR whatsoever being reflected. Is this reasonable? Does anyone know?
@Steven Mosher-The authors of the study purport that the Arctic Winter Inversion has a particular set of effects on the local radiation budget. Logically one would in fact use these data to see if, in fact, the radiation budget is effected in the stated way.
However, for the existence of the Arctic Inversion itself, is there good data covering the area to various altitudes?
And it does need to cover the area, the Rossby Radius of Deformation is inversely proportional to the sine of the latitude, so sampling large distances apart won’t work well in the Arctic.
I do know there are *reanalyses* that show an Arctic Winter Inversion. But that’s models, not data.
JBJ says:
February 4, 2014 at 1:11 am
The data here tends to suggest that there is reduced cooling in winter: http://ocean.dmi.dk/arctic/meant80n.uk.php
—————————-
The years 1963, 1964, 1966, 1969, 1971,1988, 1992, 1995, 1998, 1999, 2001, and 2008 were all below the median line for Arctic temps. The years 1958, 1959, 1972, 1973, 1974, 1976, 1977, 1980, 1981, 1984, 1990, 2000, 2002, 2005, 2006, 2007, 2009, 2010, 2011, 2012, and 2013 were all above average temps. Other years saw swings that crossed the median trend line multiple times. Some of the above years also had slight shift reversals during the season, but the predominant direction was below or above.
timetochooseagain says:
However, for the existence of the Arctic Inversion itself, is there good data covering the area to various altitudes?
If you are looking for the upper air sounding data there are a number of sites you can get that from. One of the more popular ones is the U of Wyoming:
http://weather.uwyo.edu/upperair/sounding.html
If you want all the historical sounding data you can get that from the NOAA/ESRL Radiosonde Database:
http://www.esrl.noaa.gov/raobs/
Robert Clemenzi wrote –
“Over land (including ice) a surface temperature inversion occurs every day an hour or so before sun set. The inversion lasts until a few hours after sun rise. The inversions occur because the surface radiates heat to space faster than the lower atmosphere.”
None of you appear to be capable of translating the observations into dynamical form and there is a very good reason for that. It is quite profound for all the wrong reasons given that normally the appearance and disappearance of the Sun each 24 hours is due to a rotating Earth and there is absolutely no reason to believe that they will ever fall out of step despite the current belief that they do –
“The Earth spins on its axis about 366 and 1/4 times each year, but there are only 365 and 1/4 days per year. This is because we define a day not based on the Earth’s period of rotation, but based on the average time from noon one day to noon the next. Gradually over the course of a year the Sun appears to go ‘backwards’ (West to East) around the Earth compared to the far away stars (this is because we are really going around the Sun). Subtracting this 1 time backwards from the 366 and 1/4 times forward, we get the typical 365 and 1/4 days per year.”
http://imagine.gsfc.nasa.gov/docs/ask_astro/answers/970714.html
I have seen dozens of variants of this comical theme but the result is always the same – when you lose the ability to read the rotation of the Earth out of massive daily temperature fluctuations you are entering the realm of the diseased mind . Of course the unfortunate RA/Dec assertion is important to the ‘predictions’ crowd as they drew a conclusion based on timekeeping averages and stellar circumpolar motion a few centuries ago and rigged everything to suit the conclusion including scrapping the correlation between all the effects within a 24 hour cycle and one rotation of the planet.
Inversion indeed !,it is as though the world was intellectually upside down !.
My error in previous post. In fact Antarctica has stronger greenhouse effect in summer. (Fig. 1) The ozone hole stratospheric cooling is apparent in Fig. 2. More incident solar radiation in summer results to warmer surface temperature than winter and more upwelling surface radiation but relatively cool troposphere due to ozone depletion cooling results to less increase in downwelling surface radiation.
Policycritic, this model polar vortex: http://oi62.tinypic.com/2wc4j83.jpg
On the edges of the vortex are jet streams whose speed depends on the temperature gradient. So this looks during the polar night: http://oi61.tinypic.com/15579jl.jpg
However, the distribution of ozone over the Arctic Circle is not uniform. So it looked on December 16. http://oi62.tinypic.com/5pezck.jpg
You can see that the jet stream encounters an obstacle, which causes the slow down. Here you can see it. http://oi59.tinypic.com/119t742.jpg
Where the jet stream slows down, warm air could get into the polar circle. This is seen perfectly on the animation polar vortex at the height of 15 km. http://earth.nullschool.net/#current/wind/isobaric/70hPa/orthographic=25.14,96.29,419
Directs the jet stream circulation in the troposphere. http://earth.nullschool.net/#current/wind/isobaric/250hPa/orthographic=25.14,96.29,318
Thank you.
Chuck L
my apologies then – a case of mistaken identity. Added 2 + 2 and got 5 (not for the first time).
@MaxLD-None of that data satisfies my concerns with spatial sampling. In fact, it makes my concerns worse, since it appears people draw sweeping conclusions about the Arctic atmosphere on the basis of a handful of locations.
ES says:
February 4, 2014 at 10:22 am
I understand that there is a variety of information on polar temperature inversions. I never said that there were not temperature inversions in the Arctic.
What I said was that the CERES data shows a difference between the Arctic and the Antarctic. In the Antarctic, the inversion is strong enough and persistent enough that over large areas, the monthly average of the CERES shows an actual inversion in the temperatures, with the atmosphere ON AVERAGE FOR THE MONTH being warmer than the surface over a large contiguous area.
In the Arctic, on the other hand, there are much smaller, non-contiguous areas where that is true. But it is not true over a large contiguous area as it is in the Antarctic
So I am not saying that there are no temperature inversions in the Arctic, quite the opposite in fact. I’m just pointing out that they are much less pervasive than in the Antarctic.
w.
ren says:
February 4, 2014 at 10:51 am
Ren, I’m willing to work through bad english, that’s why I asked what it was that you meant.
w.
Michael D Smith says:
February 4, 2014 at 11:20 am
Thanks, Michael. The authors claim that the tropics is better at radiating away heat than the poles. The only way to determine that is with percentages.
w.
Steven Mosher says:
February 4, 2014 at 5:57 pm
Awww, nuts. Mosh is back in his cryptic phase again. He’s a brilliant guy but you wouldn’t know it from some of his comments.
Mosh, if the CERES data is the “wrong data to detect inversions”, then why does it detect them so well in the Antarctic?
w.
Matthew R Marler says:
February 4, 2014 at 11:19 am
Make you a deal, Matthew. You re-write it in letter form, and send it off to Nature Geo, we’ll both sign it. I’ll provide whatever might be necessary in the way of graphs and data, although usually they don’t like those in letters …
I went through this exercise in a more formal manner with Nature when I submitted a “Communications Arising”. It was peer-reviewed, raised interesting points … and after publication, it sunk without a trace.
Then another author and I submitted a letter to some journal about some piece of rampant bogosity they’d published … the journal couldn’t be bothered.
Sadly, these days it seems to be something of a black eye for a journal to receive a letter pointing out that one of their papers is not the holy grail …
Anyhow, if you want to give it a shot, let’s go for it.
w.
george e. smith says:
February 4, 2014 at 12:21 pm
Good question, George. The Stefan-Boltzmann equation doesn’t deal with “black bodies” per se. Instead, what they found is that the radiation of any solid body can be calculated as
Radiation equals 0.0000000567 times emissivity times temperature to the fourth power.
or as it is normally written
W = σ ε T4
As you point out, the emissivity of any real object is always less than 1. However, in the longwave frequencies of interest, the emissivity of natural objects is quite close to 1, even objects that reflect strongly in visible light. In the 9-12 micron range, for example, the emissivity of snow is 0.986, of cotton plants is 0.98, of human skin is 0.98, of coniferous needles is 0.971, and so on.
As a result, as Geiger said in his canonical text which is my bible on these matters, “The Climate Near The Ground”,
HTH,
w.