Live (almost) from AGU–Dispatch #2

Before I get started with a few hasty remarks on today’s events, let me remind you that Lonnie Thompson’s Frontiers in Geophysics lecture will be webcast live on Wednesday at 1815 Pacific time. A link to the webcast can be found here. The lecture is entitled “Abrupt Climate Change and Our Future”. At the same page you’ll find links to Arvidson’s Whipple lecture on Mars exploration, which will be webcast at 14:20. Enjoy! Wish you were here.

Now, let me say at once how inspiring it is to see so much first-rate innovative science arrayed here. There are a lot of geophysicists in the world, and most of them are very, very good. It is especially encouraging to see so much new, young talent in all areas. I spend all too much of my time on RealClimate writing about bad science, it is great to come here and get a reality check.

I spent a fair chunk of my morning at the session at which I myself was giving a talk. This session was “Studying Climate Dynamics with Idealized Atmospheric GCM’s,” and was one of the few sessions devoted to basic fluid dynamical issues having a bearing on how climate works. By “idealized GCM’s” one means things like simplifying the radiation or continental configurations or thermodynamics, but retaining all or most of the fluid dynamics. What this really is about is how to design GCM simulations so as to test hypotheses and develop general understanding. That sort of thing doesn’t usually come from the fanciest and most comprehensive model. This session included such things as the way storm scale (“baroclinic”) eddy feedback helps determine the North Atlantic Oscillation. or how the sharpness of tropical sea surface temperature gradients determine the nature of the Intertropical Convergence Zone (an especially fascinating talk by Tim Dunkerton and colleagues). I myself was presenting a potpourri of some of the dynamical issues in my work on Titan and on the Snowball Earth postglacial hothouse — e.g. the reason that precipitation fails to rise as fast as Clausius-Clapeyron would suggest (which has some commonalities with methane precipitation limitation on Titan, where you only have 2 Watts per square meter to drive all the hydrological cycle). We had a quite good audience, but not the kind of SRO crowd that the Greenland Glacier session had. It can’t escape one’s attention that the amount of interest in and attention paid to basic fluid dynamical issues in climate is a lot less than what is going into some other areas. Someday, the balance will need to be restored. One problem is that fluid dynamics is really hard, and it is even harder to get into the newspaper with it, because it’s hard to explain to people. That makes it have less flash, though it’s none the less important to the understanding of climate. Still, a good time was had by all.

For me, the high point of the day (apart from an impromptu and wide-ranging conversation with Kevin Zahnle on SO2 photolysis, problems that have emerged with some classic Methane Early Earth radiative calculations, the possibilities of N2O as a greenhouse gas on the young Earth, and the general issue of oxygenation of planets) was Mark Serreze’s Nye Lecture on Arctic climate change. The tough part of that was that (as seems to be a law of the Universe) the Gods of Scheduling at AGU scheduled Mark’s talk right on top of David Lea’s Emiliani lecture on tropical climate change during the Last Glacial Maximum. So, one had to decide whether to go Cold or go Warm. I had been struggling with this decision all day, but in the end the decision was made for me since Mark’s talk was closer to the beer and by the time I was done talking to Kevin, there was no time to get over to Moscone West for David’s talk.

Needless to say, Mark spoke to a huge ballroom, and it was packed to the gills. This really is the Year of the Ice. He opened by showing some quotes from his earlier papers. Seven years ago, big changes in the arctic were clearly observable, but he wouldn’t have said with confidence that they were due to anthropogenic global warming (AGW). The problem is that the Arctic is subject to a lot of natural variability, notably the North Atlantic Oscillation (NAO). There was NAO-related warming in the period 1920-1940, so how could we know that the current warming wasn’t part of the same thing?

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