In the midst of the Steven Postrel flap, the journal Nature comes out with an intriguing study that tentatively predicts a change in ocean circulation patterns will cool warming trends in the northern hemisphere in the next decade. The study emphasizes the novelty of making such a prediction, and concludes, given a gazillion caveats, that global warming temperature signals could plateau for several years while the ocean's circulatory system undergoes a periodic oscillation.


Blog entries should have pictures even when they have nothing to do with the content, or as in this case, make a visual case that is totally nonsensical to the post.

What's interesting to watch in the blogosphere and media is how poorly public discussion can withstand any level of complexity beyond the zero-sum, binary nature of most national issues: Republican/Democrat, global warming hysteric/denier, tall/short, sea/firmament, etc. Warming and cooling need not be mutually exclusive, as counterintuitive as that sounds. You can have both at the same time, a short term (decadal) cooling signal that masks the anthropogenic warming trend. When the IPCC reviews climate models, it presents the total anthropogenic forcing as net. Notice in this chart from the 2007 IPCC report how aerosols (in blue) reduce the gross radiative forcing:



This is another reason to raise an eyebrow at rhetoric like that which popped up over in the comments section of Tom Levenson's Inverse Square blog (see post below). To talk monolithically about global warming or regional cooling (note, the issue here isn't "global cooling") doesn't provide an adequate picture. It's possible in the next decade the meridional overturning circulation will lower the temperature in the Northern Hemisphere. It's "very likely" to use the IPCC's restrained phrase, that warming will continue after the natural ocean state switches again. Natural climate variability (annual or decadal time scales) shouldn't be confused with climate change, which is happening at the same time, but will also "very likely" go on for thousands of years. The "global cooling" I wrote about yesterday, in the 3rd quarter of the last century, might even have been caused by a similar flip in ocean circulation — a natural trend toward global cooling masking an "unnatural" warming trend, something I read today (Will add link later, when have materials handy).

Andy Revkin over at Dot-Earth posed a question today about how climate activists will or won't be able to integrate studies like this cooling picture into their own heated rhetoric. Here's my post in his comments section:

“Can Climate Campaigns Withstand a Cooling test?”

Whatever you think about this or that climate campaign, you have to acknowledge the paradox at their core — at the core of any advocacy honestly based on accumulated scientific research. I suppose by definition, campaigns are dogmatic, with focus-group-tested messages and enough Kool Aid to go around. Science on the other hand is this shape-shifting, self-destroying, self-perpetuating bee swarm that eschews dogma (officially, anyway) and drives without prejudice into the unknown (officially, anyway). Staying “on message” must be tough when the swarm must pivot around a new landscape feature.

The hope would be that this interesting paper in Nature leads the more hysterical of the groups both left and right of the meridional overturning circulation (That includes you, Mr. Ebell) to think a little harder about what science is and isn’t, and about what a novel peer-reviewed paper is and isn’t. It’s worth tying this conversation into the groundswell of activities now occurring in the realm of scientific literacy, from the 2005 Rising Above the Gathering Storm report to the end of last year and early this year, when two Hollywood screenwriters signed on pretty much the entire U.S. scientific establishment in support of a debate on science-and-technology issues among the presidential candidates. The latter hasn’t happened, and the initiative has its serious critics, but it’s a sign of how hungry scientists are to let people know what they actually do for a living. [Disclosure: My name is in there someplace among the several hundred thousand blogger-endorsers.]

So, to answer the question, if climate campaigns don’t have enough room to accommodate natural climate variation — and several hundred thousand other issues — into their messaging, a breeze of cooler air, even a virtual one wafting in from an ocean model still in beta-testing, might be the best thing that has happened to this conversation in a while.