Tuesday, April 5, 2011

Starting to work with data

Let's suppose you have no particular axe to grind and are wondering about what 2011's average temperature will look like.  What are some things you would do?  First, of course, is try to get some data to work with.  I'm choosing the NCDC global land and sea temperatures, annual average.  If you prefer some other source, go with that.  And if you're interested in something entirely different than this, have a go with that data source.  I'll be talking about methods of dealing with data, not anything unique to annual average global mean 2 meter air temperatures.

Next is to do some basic looking around the data.  That includes plotting it, finding the maximum, the minimum, the average, and the standard deviation.  Since you're thinking about making a prediction of 2011, you also want to take a look at how things change from year to year.  What does the plot of year to year change look like?  What are the maximum, minimum, average, and standard deviations of change?

Monday, April 4, 2011

Messy Science

The type of science I like is what I call 'messy science'.  'Neat science' is the sort where you are looking at only one or maybe a few (easily counted) objects, which can be described by one or only a few number, like mass and momentum.  Celestial mechanics is a 'neat science' in this way, at least for the solar system.  Also, I hope, obvious is that being neat does not mean that it's easy.

Messy science is things like organismal biology or, for my own professional work, climate.  In climate, you can take something simple, like the rotation of the earth, and wind up with a lengthy list of things which affect it.  Conversely, you have a long list of things affected by it -- including the climate.  In What is a Day?, I mentioned a few things which affect the earth's rotation.

Another thing that is involved is the fact that the earth's inner core -- sitting about 5000 km below us -- rotates at a different rate than the crust.  In between the two is the liquid outer core, which has its own angular momentum, and whose top is about 3000 km below us.  More recent work (that paper was published in 2000) is now suggesting that one can learn about climate by studying the earth's core's rotation -- here for the press release, or here for the Dickey, Marcus, and deViron, 2011 paper: Air Temperature and Anthropogenic Forcing: Insights from the Solid Earth.

What a lovely, messy, situation!  We can look to the earth's core for signs about what is happening in climate!

I'll come back to this later for a discussion of the research paper itself.  Maybe, like many new ideas, it won't hold up.  If not, somebody else will get to write the paper which shows why not.  In the mean time, here's another candidate for the messiness of climate.  There's also another datum for how small the scientific community is.  I've met the lead author; it was she who explained to me how it was possible to measure length of day variations to such very high precision.

Friday, April 1, 2011

Says who?

I think citations are a greatly underappreciated part of scientific works.  They also, for some of the same reasons, provide a way of assessing the strength of a source even if you don't know the topic that's involved.

My first real introduction to citations as being important was when a history teacher of mine in college was concerned that I'd committed academic dishonesty -- failed to cite a source for something she felt was obscure.  After a nervous couple of minutes for me, we had a nice chat.  What I'd done was to mention, without citation, Newton's prism experiment.  I hadn't cited it because it was something I'd been seeing mentioned for years without citation, so figured counted as 'common knowledge' and not in need of a citation.  My history teacher, on the other hand, had never heard of it before, so was looking for the citation to the person who had discovered the experiment (perhaps a citation to Newton himself; I now have the right book -- Newton's Opticks).

So that's one use of citations -- avoid annoying your teacher.  Somewhat more generally, credit people for the work they do.  That's an important thing in being a scientist, as the people you're giving credit to are your colleagues.  Conversely, your colleagues will be peeved, to put it mildly, if you fail to credit them for their work.

The use at hand, as the title suggests, is to provide the backup for your claims.  You could avoid some of that by providing full descriptions yourself, but then your article becomes impossibly long.  Instead you can write something like "The earth is round[1] and rotates[2].", where you then give the full address to 1 and 2 somewhere later in the document (in print media days) or hyperlink the words directly.  An alternate that I prefer is to provide the direct 'who' and 'when', such as "The earth is round [c.f. e.g. Aristotle, ca. 322 BC*] and rotates [Foucault, 1851]."  In this way the reader immediately sees something about who your source is, and how old it is, and retains some merit even in a hyperlinking medium.

If you could read infinitely fast, it might be doable to simply read everything from everywhere.  But for us humans, some means of trimming the candidates to manageable volumes is needed.  So, for myself at least, if I'm trying to learn about a scientific topic, I head for scientific sources, or as close to the original as I can understand.

The bibliography/citation list is a quick way to figure this out.  Places that are citing wikipedia articles, newspaper editorials, and so forth, for most of what they have to say are not strong sources.  If the topic has scientific merit, there will be scientific papers on it.  If I couldn't read, or would have a hard time finding and reading, the original scientific papers (which is true in most fields), then I want to be learning from someone who could and did.  The strong source is one which is providing me the ability to go in to the literature and start learning about the particular part of the article which caught my attention.

This last is another important purpose of citation: It helps readers learn more.  I would rather be learning the science from an author who is trying to help me learn it.

Now for the mirror test: How do my own postings hold up to that standard?  In this post, it does ok, in the sense that this isn't about the content of science; it's my opinion of some things to consider in looking for sources from which to learn the science.  In the science posts, not always as well as I'd like.  So I'll take this post as a reminder to myself to include more references and links.

In my blogroll, two that are particularly good with their citations are Skeptical Science and RealClimate, though I think almost all are pretty good -- at least better than I.

*
c.f., I translate to myself as meaning 'See, for example'.  It means that there's more than one source, and this is either the one that I used (though I know there are more), or that for some reason I prefer it.
Update: my self-translation is incorrect, see Nick and Peter's comments.  What I really want is 'e.g.', for exempli gratia  (free example is my translation here, unfortunately, it's my son who is the latinist.)

ca means 'about' (circa).