27 January 2006

We're Number 1!

Rule No. 1: Everybody loves a good list.
Rule No. 2: Criteria for inclusion and/or ranking of lists need have absolutely no grounding in reality.

That's a lesson I learned about a decade ago during one of my stints as a newspaper reporter and editor. The boss had us compile "top 10" lists of just about anything, even though we were ostensibly a serious paper covering Canada's Parliament. We didn't have to consult any authority, just arbitrarily arrange 10 topical items relevant to the issue at hand and presto: a user-friendly guide to whatever it is we're supposed to be experts on.

Judaism figured this out a long time ago. The 10 Commandments are much easier to digest than theological tracts, and even though the last two are really just variations on the same prohibition (coveting), the authors knew that a nice round 10 was more attractive than nine. And the No. 1 rule is always the most important -- Yahweh being a jealous god and all.

David Letterman's Top 10 lists appeal to the same innate sensibilities. Despite the fact that his writers rarely make No. 1 the funniest item, you have to count backwards, because, again, No. 1 is supposed to be the most important.

Science section editors are no less immune from the temptation to rank. And so it is, climate change being such a hot topic these days, that each year they run the latest list of the top warmest years on record. A story that says the year that just drew to a close is No. 1 is too good to resist.

Which explains why in the past week or so, many a story found its way onto science pages and websites proclaiming 2005 the warmest year on record. Here's a typical example. But only a few days earlier, from similar sources, came stories claiming 2005 was tied (with 1998) for second warmest year (See here and here.) So what was it?

Actually, it's not important. The fact that it was pretty darn close to the warmest year on record is enough to warrant concern, given the climatological predictions that things are only going to get hotter as the century unfolds. Resisting the temptation to get all hot and bothered about whether 1998 or 2005 was No. 1, which is what good science journalists should do, is apparently too difficult for even the best of us.

The problem is that it leaves reportage open to the like of Steven Milloy and his "junk science" acolytes. Just this week he posted a PC vs Not PC comparison belittling the "2005 was warmest year on record" story.

It's only when you get into the details that the story actually acquires some gravitas. For example, the press release from NASA on which the latest story is based, actually gets into a very interesting and provocative point. The basic idea is this: 1998 was an El Nino year, meaning much of the world was warmer than usual because of a weather pattern unrelated to anthrogenic climate change. 2005 wasn't an El Nino year, and yet it still tied (or topped) 1998. That means
...what's significant, regardless of whether 2005 is first or second warmest, is that global warmth has returned to about the level of 1998 without the help of an El Nino.
Now, consider that El Nino is just an irregular but recurring phenomenon that merely redistributes heat from the western side of the Pacific to the East. (Thanks to Gavin at Real Climate for helping me with this one.) So how does its presence or absence change global warming? The answer is that El Ninos not only move heat across the Pacific, they vent some heat from the ocean into the atmosphere. And most of our global warming measurements are based primarily on what's going on in the air, not the oceans.

The implications for climatology are not insignificant. Roger Pielke Sr., the sometimes controversial researcher who heads up a climate change research group at Colorado State University (and who resigned last year from the federal Climate Change Science Program Committee), says this bias in favor of atmospheric temperature is a serious obstacle to good science. On his blog, he wrote recently that "a more meaningful metric than global average temperature to assess global warming is ocean heat content."

I think it safe to say that debate over how to measure climate, which is very real, is far more interesting and consequential than a headline-grabbing list. All of which is not to say that lists aren't useful things through which necessary attention can be focused. But it's probably a good idea not to take most of them too seriously without looking closely at the criteria involved in assembling them.

By the way, after 2005 and 1998, the next three warmest years on record, according to just about everyone, are, in descending order of heat content, 2002, 2003 and 2004. I mean, hey -- everybody loves a list.

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