Science Please

by JS

Hilzoy on Will:

Where I come from, when someone writes something of the form: “P is not evidence for Q, and here’s why”, it is dishonest to quote that person saying P and use that quote as evidence for Q. If one of my students did this, I would grade her down considerably, and would drag her into my office for an unpleasant talk about basic scholarly standards. If she misused quotes in this way repeatedly, I might flunk her.

I don’t normally agree with George Will, and in fact I don’t in this case. I’m also not particularly interested in entering the climate debate on any side, but I find this piece of reasoning incomplete, and entirely indicative of why “scholarly standards” arguments always end up failing. This is a recapitulation of argument by authority, though in a unique form where the writer blithely assumes the authority of the original text.

“One important detail about the article in the Daily Tech is that the author is comparing the GLOBAL sea ice area from December 31, 2008 to same variable for December 31, 1979. In the context of climate change, GLOBAL sea ice area may not be the most relevant indicator. Almost all global climate models project a decrease in the Northern Hemisphere sea ice area over the next several decades under increasing greenhouse gas scenarios. But, the same model responses of the Southern Hemisphere sea ice are less certain. In fact, there have been some recent studies suggesting the amount of sea ice in the Southern Hemisphere may initially increase as a response to atmospheric warming through increased evaporation and subsequent snowfall onto the sea ice. (Details: http://www.sciencedaily.com/releases/2005/06/050630064726.htm )

Observed global sea ice area, defined here as a sum of N. Hemisphere and S. Hemisphere sea ice areas, is near or slightly lower than those observed in late 1979, as noted in the Daily Tech article. However, observed N. Hemisphere sea ice area is almost one million sq. km below values seen in late 1979 and S. Hemisphere sea ice area is about 0.5 million sq. km above that seen in late 1979, partly offsetting the N.Hemisphere reduction.”

Maybe in Hilzoy’s profession the authority of original texts are inviolate. In many disciplines this is probably a good default assumption. It is, however, not an appropriate view in science. This text attempts to make the argument that P is not evidence for Q, but it does so by referencing black box models of climate change. I personally think Hilzoy should flunk students who draw any conclusions about the relationship between P and Q without knowledge of the referenced climate models and their justification, including apparently, Hilzoy.

What I see happening, is that George Will and the Arctic Climate Research Center are essentially committing the same error by drawing conclusions about P (ice sheet levels) and Q (global warming/cooling) without any complete defense of the models and assumptions involved. By defending one side and not the other, Hilzoy is not applying an equal criterion of evidence to both parties in the debate.

Now you could argue that George Will is not a climate scientist, and that the Artic Climate Research Center is full of them, so we should believe ACRC’s claims without details. To an extent this is true, but I think it is incumbent on scientists to provide arguments with different levels of justification, so that individuals with different levels of sophistication can access and evaluate the claims given varying backgrounds. But ACRC type claims tend to bucket themselves into two categories: black box arguments (really press releases), and the relatively inaccessible scholarly work. The fact that there are no categories in between is somewhat troubling, especially considering how the policy debate would benefit from those kinds of expositions.