This is in reference to a discussion at:
Tallbloke’s blog by Stephen Wilde. My response is something of a tome so I am going to post it here. I don’t do this stuff for a living so take this in the spirit of me possibly talking through my pants a bit. The approach is one from first principles and from some additional reading on the subject. So, here we go:
i) The stratosphere and the mesosphere actually cooled when the sun was more active and are now warming now that the sun is less active. There must be something else going on to account for that.
Yes, there could well be other things involved. But, an increase in UV should increase excitation in the stratosphere and increase temperature from where it would be without it. There may be other things going on that influence that however, and swamp that. In other words, the stratosphere cooled while the sun was active, yes, but maybe it was still warmer than it would have been and might have cooled even MORE if the sun were not so active.
I would wonder about such things as stratospheric injections of materials from volcanism over decadal scales. It takes much longer for things to work out of the stratosphere than it does from the troposphere where it washes out fairly quickly. What has the decadal rate of volcanic stratospheric injection of material been over time?
What impacts have changes in meteor induced materials had on decadal scales? The water vapor in the mesosphere comes mainly from space debris (bits of ice from tiny cometlets, for example). How has the composition of the mesosphere changed over decadal scales? Have we been hitting more comet debris, less?
ii) The jet streams moved poleward and the polar vortexes shrank when the sun was more active. That is a critical point for diagnostic purposes and I need to explain in some detail why it is so critical.
This is to be expected when we get a net increase in energy into the system. The Hadley cell expands, the Ferrel cell moves Northward, and the Polar cell shrinks with the net result moving the circumpolar jet North. That jet is at the boundary of the Ferrel and Polar cell. The entire Ferrel cell moves North so the jets associated with it move North. We also saw the ITCZ move North at the same time so we saw a greening of areas in Africa that experienced extreme drought in the 1970’s.
i) Taking the stratosphere as a whole (rather than splitting it into latitudinal sections) it actually appears to have cooled during the late 20th century period of more active sun and now appears to be warming slightly with a less active sun.
This may not be a valid way of looking at things. I would want to know the stratospheric temperature at each cell. It could be that a heating of the Hadley cell and the resulting shift of the Ferrel cell Northward cause a strengthining of the polar jet which acts to more efficiently sequester the polar stratosphere from lower latitude mixing with warmer air. This MIGHT result in the polar stratosphere cooling more than the equatorial stratosphere warms. In other words, there might be a net cooling when the entire stratosphere is taken as a whole but this might actually be due to extreme cooling in only a small portion of it. So if 1/3 of the stratosphere warms by 2 degrees, 1/3 has overall no change, and 1/3 cools by 3 degrees, we will see a net cooling while the temperature variations haven’t been even. A warming in one area could CAUSE a cooling in another.
(Note that I have typed this as I am reading so it is subject to subsequent “aha!” moments and possibly even contradictions!)
iii) The distance of the jet stream latitudinal shifting from the peak of the Mediaeval [sic] Warm Period to the depths of the Little Ice Age is in my opinion far greater than could be explained simply by the small differential between solar effects on UV at the equator and solar effects on UV at the poles.
It doesn’t really have much to do with what goes on at the poles as it does what goes on in the equatorial region, to my mind. It is the Hadley cell that seems to drive everything else. It is a conservation of energy thing. When the energy input in the tropical summer hemisphere declines, the Hadley cell in that hemisphere shrinks or the Northern edge moves Southward. The Northern edge of the Hadley cell seems to situate itself where it needs to be to dissipate surface heating. If you increase tropical solar heating, the Hadley cell expands Northward into cooler territory to dissipate the heat.
The Ferrel cell seems to undergo less change in size and is simply pushed northward or slides southward in response to being pushed around by Hadley. The Polar cell seems to me to respond as the one that gives up ground or expands. When it shrinks, like the skater pulling in her arms, the polar jet gets smaller (moves northward) but increases in velocity. This acts to more effectively sequester polar air from the lower latitudes which does things like reduces the O3 content of the air in winter. The impact of that is to reduce a primary greenhouse gas at the poles and allow for more efficient radiation of heat into space. So we have several things going on at the same time. Hadley expands in response to heating. Ferrel moves North. Polar becomes a more efficient radiator (lack of O3 possibly resulting in greater stratospheric cooling as there is now less greenhouse gas there absorbing LWIR from the surface). In the meantime, the tropical seas are warming resulting in an increase in the temperature of the Gulf Stream, possibly resulting in a greater melting of sea ice. This increased open water area combined with less greenhouse gas in the stratosphere might result in greater overall radiation of heat into space. Note how that in recent years the maximum sea ice has declined but the difference between minimum and maximum has increased. Not also the same response from snow cover. We have a greater difference between minimum and maximum snow cover in summer/winter. So maybe we have more heat coming North in summer but it is more efficiently radiated in winter.
iv) The solar effect on stratospheric ozone on the height of the tropopause at the equator would be heavily modulated by ocean surface temperatures so that the poleward pressure on the jet streams would be inconsistent. In fact I think that the effect of ocean sea surface variability on the height of the tropopause at the equator would be far greater than the solar UV effects.
I need some help on this one. I’m not getting the connection between ocean surface temperature and stratosperhic heating from solar UV. Yes, I do get the notion of an impact on the height of the tropopause but not the connection of how it impacts stratospheric heating by UV.
What you are calling the “jet” is basically the zonal flow of the Ferrel cell. When I think of the “jet” I think of the polar jet because I think that is the one that is showing the greatest response to things. The Ferrel cell is simply being pushed
Northward or allowed to settle Southward in response to tropical temperatures.
One problem is that I can’t find the data set I want in order to explore the relationship I am looking for. UAH has “Tropics” and “NoPole” but they do not spit Northern tropics and Southern Tropics. I want to see the relationships between the Tropics, the temperature region, and polar area per hemisphere. I can get both tropics, extratropical, and polar but that mixes things up that don’t belong with each other in looking at how I want to see the response.
v) The actual shrinking of the polar vortexes seems unlikely just from poleward pressure from the slightly lower tropopause at the equator given that the polar tropopause should also have been lowering to some extent (but less) at the same time. More likely some additional process from above encouraged the polar vortex to shrink at the same time as the jets were pushed poleward.
The polar jet is getting squeezed Northward by the Ferrel cell being pushed Northward by the expansion of the tropical Hadley cell, I think.
Also, one can not model the entire planet as a ball because the two hemispheres are much different. The NH had a lot more land. The SH has a lot more water. The SH will absorb a lot more heat in a given situation than the NH will. That is one reason why I believe we see the net impact of global ocean circulation as that of moving heat from the Southern Hemisphere to the Northern, it is trying to balance the heat in the system via circulation of the oceans. The air circulation between hemispheres is more sequestered but we have a significant meridional flow of water between hemispheres. Deep water surfaces in the SH, picks up heat as it migrates to the NH, gives up that heat in the northern polar region, and sinks for another go-round.
My proposition is that instead the latitudinal shifts are a result of two separate forces acting together (hence the high mobility of the jets latitudinally) when the sun is more active with one being a cooling effect at high levels over the poles pulling the jets poleward and the other being a warming effect at low levels over the equator pushing the jets poleward at the same time.
Well, you seem to have what is going on correct to some extent (well, not that I am a judge of “correct” but we seem to be in agreement as to what is happening. We just seem to disagree on cause/effect. The simply expansion of the Hadley cell in response to an increase in tropical energy maybe be enough to explain all of this. If the cooling of the polar cell is greater as a result than the warming of the tropical cell, we get the net stratospheric cooling.
Another way of looking at it is that when the Ferrel cell is pushed Northward, the polar troposphere bulges upward (but little changes in the Ferrel cell troposphere). This increase in altude of the troposphere could result in a net increase in radiative cooling until the Arctic ocean freezes over. At that point convection pretty much stops in the Arctic and the net flow of air is one if sinking. The more ice-free the Arctic, the longer convection continues. The South pole would behave somewhat differently in this respect as it is situated on a permanent ice cap.
Once the Arctic Ocean freezes over, the tropospheric boundary begins to sink and convection in the NH polar region stops. The strong polar jet prevents warm air from farther South from migrating into the polar region and convecting upwards. It acts to cut off the polar region. In the spring when convection gets started again we finally see this sequestered mass of O3 depleted air finally spill out of the polar region where it manifests as “the ozone hole” that might drift over the higher latitude temperate region until it mixes in and dissipates. This generally doesn’t happen until about the time the North pole is receiving 24hr sun.
The cooling effect appears to be dominant over longer time periods to give the observed cooling of the stratosphere and mesosphere when the sun is more active.
Again, I would like to see this broken down by region by hemisphere in order to verify some hunches but I don’t have access to the data I would need.
Nonetheless there is still overall system warming with the more active sun because of the extra
energy going into the oceans due to the jets shifting poleward thereby reducing total cloudiness and albedo as shown in the illustration at the head of this article.
Generally an increase in energy in the oceans will lead to an increase in clouds, not a decrease. For example, during El Nino we see increased equatorial Pacific clouds and during La Nina we see decreased clouds. Stronger winds prevent the formation of towering convection columns and shear them before they can form. But that is more a surface formation of trade winds, in that case, not jets far aloft.
Note that the solar UV warming effect on ozone in the stratosphere becomes weaker as one approaches the poles whereas the solar proton destruction of ozone in the mesosphere becomes stronger as one approaches the poles.
Well, there’s a bit of positive feedback potentially going on here. O3 is a rather potent greenhouse gas. If you have increased O3 production, you have an increase in radiative warming. As you move toward the poles you get a double-whammy in that reduced O3 production results in less O3 absorption of LWIR so the rate of temperature change is not linear with the rate of change in UV.
The temperature differential between surface and stratosphere will increase either if the surface warms or if the stratosphere cools so a higher tropopause (globally averaged – never mind the latitudinal variations) and a poleward shift of the jets is consistent either with AGW theory which proposes a warming of the troposphere from human CO2 or in accordance with my hypothesis which proposes a cooling of the stratosphere from some natural solar induced process when the sun is more active.
Well, I don’t believe you CAN “never mind the latitudinal variations” because I believe those are key to the entire process. You can, I believe, have a warming of the tropical stratosphere that RESULTS in a cooling of the polar stratosphere. What I would expect to see, though, is in the polar stratosphere a greater variation between winter/summer stratospheric temperature. A widening of the delta between summer and winter might be in the offing. But there are positive feedbacks and those throw things out of whack and make things a little less neat. An increase in equatorial O3 production could result in a decrease in polar O3 content aloft and change the overall radiative balance with the net impact being more heat migration from the tropics to the poles and out to space.
The jets were more poleward during the Mediaeval Warm Period hence the reported Viking settlements in Greenland so the temperature differential from surface to stratosphere must have increased then too and at that time there was no significant warming in the troposphere from human emissions thus the cause of the poleward jets back then must have been a net cooling of the stratosphere from entirely natural causes at a time of (then as now) a more active sun.
Or an increase in tropical energy moved the Northern edge of the Ferrel cell North of those Greenland settlements and caused an increase in heat transport Northward by the Gulf Stream at the same time as the Hadley cell expanded Northward in response to an increase in energy. During the LIA, the opposite would have happened.
Everything is, I think, hinging on the Hadley cell. Everything else is a reaction to that. Now what CAN happen with AGW is that an increase in radiative warming of the polar winter stratosphere can change things. The impact of AGW would be most apparent in polar winter. We would likely see little manifestation of it anywhere else in overall temperature change. But again, since there is little/no convection in the polar region and air flow is mostly cold, dry sinking air, I am not convinced of what noticeable impact that is going to have in the overall heat transfer of the planet.
That this process is actually going on with a reverse sign solar effect in the mesosphere (active sun causing cooling and quiet sun causing warming) has been discovered by Dr. Joanna Haigh who found that despite the quiet sun the amount of ozone in the mesosphere has been increasing with, presumably, a
warming effect in the mesosphere.
I would want to see that compared with changes in mesospheric water vapor. The mesosphere has more water than the stratosphere but it mainly comes from outer space. Little bits of ice that come flying into the atmosphere. We have seen
a global increase in the noctolucent clouds that form in the mesosphere from this water vapor. Have we been collecting an increasing amount of water? If so, this water will be broken down by UV into H2 and O with some of the O forming O3 and some forming O2. We might have a coincidence here that I would like to eliminate but again, I don’t know where to find data on mesospheric water content over time.
Even such things as waste dumps from peramently manned space operations and hydrogen fueled space shuttles might have an impact on the mesosphere. I will be curious to see if we have any changes after space shuttle flights terminate. The main engine was hydrogen and would have dumped a lot of extra water vapor into the mesosphere.
Changing the amount of water vapor in the mesosphere could have a significant impact on things as that would also change the amount of O3. Even dumping water into the stratosphere can have a disporportionate impact because it is so nearly completely dry that any water at all makes a huge difference, much more than increasing CO2.
the cooling effect in the upper atmosphere of the increased number of solar protons when the sun is more active is greater than the warming effect of more UV in the stratosphere below.
I suppose you might need to add the impact of Galactic protons, too.
During the latest Ulysses out-of-ecliptic orbit the solar wind density, pressure, and magnetic field strength have been the lowest ever observed in the history of space exploration. Since cosmic-ray particles respond to the heliospheric magnetic field in the expanding solar wind and its turbulence, the weak heliospheric magnetic field as well as the low plasma density and pressure are expected to cause the smallest modulation since the 1970s. In contrast to this expectation, the galactic cosmic-ray (GCR) proton flux at 2.5 GV measured by Ulysses in 2008 does not exceed the one observed in the 1990s significantly, while the 2.5 GV GCR electron intensity exceeds the one measured during the 1990s by 30%–40%. At true solar minimum conditions, however, the intensities of both electrons and protons are expected to be the same. In contrast to the 1987 solar minimum, the tilt angle of the solar magnetic field has remained at about 30″ in 2008. In order to compare the Ulysses measurements during the 2000 solar magnetic epoch with those obtained 20 years ago, the former have been corrected for the spacecraft trajectory using latitudinal gradients of 0.25% deg−1 and 0.19% deg−1 for protons and electrons, respectively, and a radial gradient of 3% AU−1. In 2008 and 1987, solar activity, as indicated by the sunspot number, was low. Thus, our observations confirm the prediction of modulation models that current sheet and gradient drifts prevent the GCR flux to rise to typical solar minimum values. In addition, measurements of electrons and protons allow us to predict that the 2.5 GV GCR proton intensity will increase by a factor of 1.3 if the tilt angle reaches values below 10″.
I think we both have noted some of the basic changes. We differ in our interpretation of cause/effect. I believe that there are several things working at the same time and that it isn’t tidy. There are some positive feedbacks going on, changes in solar activity causing changes in galactic rays, possible changes in debris fields though which the earth passes, injection of water vapor from spacecraft and aircraft, etc.
Overall, I believe you are seeing the same thing I am seeing. I want some data, though, that I think would be hard to find.