Introducing the Atmosphere

A while back I introduced the ocean. a bit. Time for the atmosphere, which turns out to be much simpler than the ocean, or maybe that just is a matter of being more subtle.

In the ocean, we have names for areas bounded (usually) by land. This doesn't work for the atmosphere, since it covers the whole earth. It does turn out, however, that the circulation itself (as for the Southern Ocean) helps divide the atmosphere. For a first approximation, little air crosses the equator. (Some does, to be sure.) So we can divide the atmosphere to northern and southern hemisphere circulations. Even though the two hemispheres are greatly different in their amounts and distribution of land and ocean, it turns out that their major circulation is quite similar.

In both hemispheres, air rises from the equator, move towards higher latitude at elevation (5-15 km, 3-9 miles up) and then sinks to the surface around 30 degrees latitude (north or south). The surface circulation is from that sinking latitude back towards the equator. This is the Hadley cell. There's a similar cell between about 60 degrees latitude and the pole, called the Ferrel cell. In between the two is not so much a cell as a storm zone.

A couple of questions I haven't seen firmly answered (I do have leads on a couple of papers, but haven't read them yet) are: Why are the circulations so similar between the hemispheres? Why are there 3 zones of circulation instead of 2, 4, 5, 75, ...?

In the vertical ... how high is up? :-) There's actually a way of approaching this by way of a different question:

What is the atmosphere made of? If we sample air all around the world, and through all levels of the atmosphere, we discover a few striking things. First, only 3 gases account for almost the entire atmosphere -- Nitrogen (N2), Oxygen (O2), and Argon (Ar). They are, in order, 78%, 21%, and 1% of the atmosphere in terms of counting molecules, and 76%, 23%, and 1% by mass. Note that these figures have been rounded, but also note that they do add to 100%. A further feature is that this proportion is constant throughout the atmosphere -- until you get to about 100 km (about 60 miles) up. Above that point heavier gases separate from lighter ones.

So that's our answer to 'how high is up?' -- about 100 km.

But back to the matter of what the atmosphere is made of. We've all heard about water (H2O), Carbon dioxide (CO2), and Ozone (O3) and how important they are. They are indeed important. But, added up through the atmosphere, they account for only about 0.24% of the molecules. Considering all gases, only about 1 in 400 molecules is not one of the big 3 of Nitrogen, Oxygen, or Argon.

Yet it is these other, rare, molecules which account for almost all the interesting processes in the atmosphere! This includes rain, hurricanes, the fact that the earth is not frozen, protecting surface life from solar ultraviolet, constructing the stratosphere, ...

Ok, the stratosphere brings us back to the vertical structure of the atmosphere. Starting from the surface, we have the troposphere. Here's where almost all the weather happens, and temperatures generally decrease with height. (So it's usually cooler in the mountains than the flat land around them.) In the stratosphere, temperatures are constant or increasing with height. Above this is the mesosphere, where temperatures go back to decreasing with height. The top of the mesosphere is that 100 km (or so) boundary. Above this, things get very different, and usually are studied by people who aren't meteorologists or climatologists. (Aeronomers, chemists, physicists instead.)

The stratosphere being a warm place, compared to the air above or below it, is because of the ozone absorbing ultraviolet. Without the ozone (and the chemistry that maintains that molecule), there's nothing to be absorbing energy to warm the layer. At most, ozone is about 12 parts per million of the molecules in that layer (0.0012 % !)

Since my first cut is always to take a look at the largest scale things, the most common, and such, we're already done. 3 molecules make up almost all of the atmosphere (N2, O2, Ar), there are 3 circulation zones between equator and pole in each hemisphere, there are 3 layers in the vertical, and the atmosphere goes up about 100 km.

To understand most of what's interesting, we have to get much more subtle. Always a fun and interesting thing to find that understanding some very small part of a big system will let us understand a lot about that large system.

The question place #1

I'll put this up as a collecting spot for questions. If you have questions about science, drop them here. Some I'll be able to answer in new posts, some, maybe readers here will be able to make progress with.

Science not politics

Continuing with Dave's comments about climate science:

Secondly you have a topic that's polarized many different groups, and many an individual will merely argue a point because a group they might relate to is arguing the same point.

Many people have vested interests relating to climate change and thoughts about what, if anything, to do about it. That does produce politics, in that groups of people with interests act politically.

But the science is the science, and respects no party, no nation, no religion, etc.

This does make for the problem that groups with interests other than explaining and discussing the best science also establish web sites, write editorials, produce shows, etc. to propagandize their views, distorting and lying about the science along the way. So if you're interested in the science, you have to work harder to find it than in something which doesn't scare people. You also have to work harder to disentangle the parts of an article that are science from those which are opinion, wishful thinking, and such.

One thing which I think is helpful in deciding about sources is to, first, hold your nose about their political viewpoints. This can be hard when the politics are greatly different from yours, but bear with it. As you read through, look for scientific claims, or claims which the author thinks are scientific. As you find them, go hit the literature on the topic and see if the author has represented the point correctly. It may sound like a lot of work, but in practice, most web sites which are more concerned about their politics than the science display this fairly quickly by lies and distortions, and some are at an extremely basic level. Basic enough that you can check the truth of it by looking at a textbook from 30 years ago (before the topic was getting nearly as much press, but well after the scientific basics were understood). If not an outright lie, very often what you'll see is a quote selected from a scientific article and removed from its context. Once you find the context, you see that the original author's intent was quite different than the bit quoted.

As you proceed with this, you'll find some sites are very prone to distortion or lying, and some are, if not doing it, then at least only doing it on such a subtle level that you can't detect it. Eliminating the most egregious (and those who quote the same lines -- there's very little originality, so learning a few facts suffices to eliminate a lot of the bad sites) narrows the field greatly, and productively. The difficult part is where you have to eliminate sites whose politics you generally like. On the other hand, if you want your car fixed, you go to your mechanic, not to your representative (aside from the times they're the same person :-). Scientists working in the area are better sources than political groups anyhow.

After you start to understand the science, you have separate questions. (for all 'you', including me). I don't think the responses are dictated by the science. Once you understand the science and the probable outcomes, now you have to ask the questions of what is morally appropriate, what is politically appropriate, what is economically appropriate, and so on, by way of responses (including 'do nothing'). Different people, even if agreed on the science, will (and should) disagree here. But, if the discussion were to be based on our best understanding of the science, I think we'd be far better off.

Happy 4th of July!

4th of July now, I'm back from my travels, and celebrating the date. One thing I do on the 4th is to re-read the Declaration of Independence and the Constitution. Actually, not so much the declaration as the Constitution. While the Declaration did prompt the following events, it is the Constitution which really defined who we were or at least wanted to be. Much of the better part our history is a matter of applying the ideals of the Constitution to a greater fraction of the people.

I've also started fooling with genealogy in the past year, most of which I won't inflict on you as it's really only of interest to me (and perhaps some of my relatives). (But the story of my ancestor at the bombing of Fort McHenry ... surely that's of interest to all? ... well, maybe not.) One thing I've taken as given is that, ultimately, I'm related to everybody, and have ancestors from everywhere. One thing that means is that in every war, I figure I have relatives on both sides. For our revolution, this turns out to be true within a single family. My great-to-the-something ancestor Zeboath Brittain and the other two older brothers fought for the revolution, while the three younger brothers fought for the Empire. After the Empire lost, they moved to Nova Scotia. Dad, William, was also an empire loyalist, outspokenly so and jailed for it a time or two during the war. But he stayed (along with his wife, who was apparently equally vocal in favor of the revolution) after the war settled down.

It's a reminder, though, that the decision to revolt was not very clear-cut at the time. Rather few participated on either side, and among those families that did, it doesn't seem very one-sided as to which side they'd go for. This is part of the answer, I guess, as to why Canada neither joined in the rebellion, nor conducted their own later (by the way, happy Canada day 3 days late). A different genealogical perspective is that post-revolution, the life expectancy of USAns plummeted. Or maybe that's just my ancestors (though I doubt it).

Since we're in July, also a happy Bastille day (early, July 14th) to my French friends. (My known French ancestors were out of the country before the revolution; but 60+% of my ancestors are still unknown, so I'll assume some were still there.) During my recent vacation/working trip, I was in France (Paris and Perros-Guirec Brittany) for a week. Walked down from the Arc de Triumphe to the Place de la Concorde, among other things. No visit to the Bastille, but my wife and I did visit Versailles, which had its own drama in the Revolution. It's more than a little odd to think about how the support of France (Louis XVI, draining coffers and raising taxes) for our revolution helped bring about its revolution. Worked out better for us than France, or at least Louis.

Anyhow, whether it's "Libertie, Egalitie, Fraternitie", "We hold these truths to be self-evident ...", "We the people of the United States of America, in order to form a more perfect union, ...", this is a good time to think about what our ideals are, the best possible arrangements for our societies is, and how to move from where we are currently to where that better situation is.

Cheers!

Climate is a messy business

I'll be making a number of posts prompted by a note from Dave in a different area. It'll be a number of posts because I'd like to take some care on each of the points.

Let's start with:
This topic of global warming has alot of problems... First of all you have a complicated science. It's not likely alot of people will truly understand the science well enough to be able to argue the points.

Climate certainly is a messy business. One of the things that makes it interesting to those of us who work on it is precisely that. Wherever you look, you find something that affects climate, regardless of whether you look at permafrost, sea ice, forests, farms, rivers, factories, sunspots, volcanoes, dust, glaciers, ...

So certainly we have a complicated science and certainly few people are going to understand enough of it to argue the finer points. This is true within the science as well, as few who study volcanoes and their climate effects are going to be able to argue the finer points about the role of sea ice in climate, or vice versa.

What does an honest and interested person do then? Two things as I see it. First, not all the science involved is difficult. For those parts of the science, learn the science. Anybody who can get through normal life, cook a recipe, balance a checkbook, etc., can understand the basics. One source is Jan Schloerer's summary at http://www.radix.net/~bobg/faqs/scq.basics.html Jan was not a climate scientist, but, as I said, you don't need to be one to understand the basics. One thing he did do (see his acknowledgements, for instance) is check with people who were to ensure that he'd gotten the science right (or at least correct given the limits of writing a general audience description). I'll come back to basics in a minute.

Second, for things that aren't elementary, start looking to expert opinion. No different than if your car is acting up and you can't figure out why, or you've got something like a cold but it isn't going away like one should. You go find an auto mechanic or doctor and use their expertise. If your concern is, instead, about climate, then find some climate scientists. While there aren't that many (even counting worldwide) they do exist. And it's not that hard to find their professional understanding. You'll see it more directly in journals like Science and Nature than Scientific American or Discover. But both can be gotten fairly easily, and both include summaries of the science which are written for laymen.

You can also look to the IPCC reports, the fourth having been issued recently. The first was the best, I think, in terms of explaining the science to non-professionals. As the basics haven't changed since then, you might want to look for the first edition. The summary for policymakers, in each edition, is the most readable and aimed for non-professionals. The drawback is that it necessarily includes fewer details about the science. Nevertheless, it (the IPCC report) does represent as good a summary of the state of the science as you'll find.