Climate Letter #1854

This is a continuation from yesterday’s discussion. For several months I have not written about the temperature feedback loop that is an implicit reality within the full chain of events described yesterday. In short, the way air pressure sets up in response to all the 500hPa levels, which vary by altitude within a zone extending between about three and four miles above sea level, directly affects the strength and positioning of jetstream wind pathways. Variations in the jetstream wind pattern, in turn, have a direct effect on the movement of precipitable water (PW) concentrations existing at that same high altitude. The way such movement proceeds, in turn, has a direct effect on temperatures at (and also below) the surface, as a result of PW’s greenhouse energy effect. Large changes in surface air temperature, in turn, have a direct effect on 500hPa levels directly above, a result of normal in-depth molecular expansion or contraction of the gases of all kinds from which air is composed. When all is said and done, through the normal operations of a cause-and-effect chain reaction, warmer air at the surface will help to cause an increase in the amount of greenhouse energy it is immediately exposed to, which by definition creates a feedback loop. Everything in the chain is naturally reversed when surface air becomes colder.

I think this is good information, but what can we do with it? None of the activity is exclusive. That is, all of the component parts of this chain of events are individually affected by other considerations of some import, which may or may not add to the specified feedback effect. Also, examples of warming feedbacks and cooling feedbacks are both found to exist in abundance, as contemporaries. How well do they offset each other? Is one of the two intrinsically more powerful or more durable than the other? Questions like this, correctly answered, should eventually have an effect on our understanding of future expectations for climate change. I don’t personally have any such specifics in mind, and will not try to make predictions, but I can still offer some perspectives on the processes involved, including many details, and will continue on that course.

The 500hPa air pressure “thing” is both vitally important and the hardest of all components to get one’s head around. I think the U of Maine people have done a marvelous job of creating visual representation, using color coding on a simple map of the world. Anyone can see how many different changes unfold from day to day and season to season. Some day I hope we will be able to see how annual changes have transpired for any given day of the year over many decades, making valid trend analysis a real possibility.

One thing seems certain. In the dead of winter, when the circle of pressure readings around either pole, as viewed out to the edge of the green zone, is tightly compact, with the inner blue part all deeply shaded, the well-knit processes in place are not easily dislodged. The surrounding jetstream winds should inevitably remain strong and tightly wrapped. A cold type of feedback loop can then be assumed operative at an effective maximum, and nothing much can stop it until stronger sunshine has returned in full force. We’re only now getting a good taste of this latter development in Antarctica, well into the summer season. The Arctic is meanwhile having a terrible time putting together a compact zone of pressures anything like the one Antarctica has had for months and is finally coming out of. There is not much time left, and the strange activities of the “stratospheric vortex” are clearly not helping. Without development of a cold feedback loop, subsurface ground and water temperatures could effectively end up higher than normal when summer begins, allowing a durable increase in the amount of outbound radiation that is normally reserved more for solar-based effects.

Carl