Climate Letter #1895

In yesterday’s letter I offered a speculation about what the high-altitude air pressure map would have looked like during the time of the Eocene when the polar regions had tropical climates.  No blue zone, no green zone, just a lot of red, and thus lots of precipitable water (PW) throughout the atmosphere.   That’s a pretty far-off extreme.  What about times closer to home, perhaps the next step beyond today?  Can we expect any significant changes that will need to be explained?  Well, in this morning’s science news there is a report about a fascinating new study where researchers had taken a close look at what the Arctic climate was like at the peak of the last interglacial period (Eemian), about 100,000 years ago. There was nothing tropical about it, but the landscape inside the Arctic Circle was far more lush and green than it is today.  I think you will find this interesting: https://phys.org/news/2021-03-arctic-lush-green.html.

How did temperatures get so warm for such a long period of time, probably for not less than a few thousand years? The authors take note of a feedback effect from all of the greenery, as it would have absorbed much more sunlight than bare or snow-covered tundra. Okay, but how did so much greenery get established in the first place? Nothing on that scale happened during the peak years of solar activity during the current (Holocene) interglacial. One possibility worth consideration is that the solar orbital effect may have been a little stronger and longer-lasting. That would give more time for feedbacks to grow from still more solar energy effects due to both the extra greenery and the extra sea ice melting. Next question—how does greenhouse gas fit into this picture? Ice core analysis tells us that both CO2 and methane reached peaks in the Eemian that were very close to the same as our pre-industrial levels, but no greater. As such, they were in no better position to add extra energy than they were for us in 1750. That seems to leave the burden of temperature warming that actually occurred mainly in the hands of solar energy in one form or another, with albedo effects taking the spotlight. Would that be enough to do the job of getting Arctic temperatures up by 5C, like it says in the study, keeping them there for maybe more than a thousand years?

I see one solid possibility for further enhancement, one that is not recognized by science so you do not have to believe it is true, but here is my case. It’s all about the greenhouse effect of holistic PW, which is quite unlike the greenhouse methodology of CO2, methane, and the rest of the well-mixed gases.  Moreover, I think PW is quite capable of acting independently, no matter what the others are doing. This means the progenitor of all PW, gaseous water vapor, is not simply a linear feedback created by the warming power of CO2.  Science is dead wrong about that, in more than one way.  PW is created in the first place by the warming power of everything that causes ice to melt or plain water to evaporate.  It’s called heat.  Heat is produced in a variety of ways by all sorts of things, including the sun. Once vapor is created its durability is subject to certain limitations, but these limitations, even if absolute, which I doubt, certainly do not apply to the various products of condensation that are partial components of any PW mix.

The Arctic was able to get warmer in the Eemian with no help at all from the well-mixed gases, because it could get all kinds of help from PW formation produced by heat and not subject to limited quantities.  This can include PW near the surface, PW in the tropics, and PW concentrations found at any level of the troposphere, at any latitude. In all situations the concentration is erratic with respect to atmospheric content, the exact opposite of all well-mixed gases. As a matter of fact, and I do mean fact, PW concentrations hovering over many locations, especially over Arctic locations, can double or more in just one or two days.  When they double the surface temperature can regularly be demonstrated to rise, temporarily, by a good 10C at the same time.  That’s a real increase, made of real heat, the kind you can feel. The kind that causes ice to melt, or more water to evaporate.

That brings up one more point, especially relevant to Arctic climate studies. High-altitude air pressure configuration also has an active role here, in part because of its propensity to change when surface temperatures change. Just as importantly, the configuration has an uncanny ability to regulate the movement of PW concentrations in the upper troposphere. When surface temperatures get warmer, for any reason, the configuration tends to make changes in the direction of weakness with respect to PW regulation. Weakness allows PW concentrations to gain more freedom of movement, enabling greater exercise of their greenhouse powers over selected regions of entry. The most sensitive part of the configuration is centered directly over the Arctic polar region, which PW concentrations usually find the most difficult to enter. For that reason a positive feedback loop can be created, mediated by the change in air pressure configuration. When the high Arctic surface gets warmer the resulting increase in PW entering over head causes yet more warming of the surface, and so on. As long as fresh supplies of PW keep arriving, this activity can be occurring even while the well-mixed greenhouse gases that are in place remain fixed. (More details about how this all works are described in previous letters.)

Carl