Sunday, December 23, 2007

AGU: the science

OK, enough joking around. I was actually there for work, having received a generous invitation to present at the session on "Climate Sensitivity From Modeling, Current Observations, and Paleoclimate Data."

We've often thought about going to the AGU Fall Meeting, since while we are in Japan it's actually more convenient than the EGU, but never previously got round to it. The organisation is rather different to the EGU, and took a bit of getting used to. For some reason, the poster sessions are not clearly linked to their corresponding oral sessions (the code numbers indicate the section and the time, but eg there is no obvious link between U43A and U51B, despite them being posters and oral session on the same topic). They don't even arrange things in alphabetical order in the book. There is also no Climate section and very little Nonlinear Geophysics (the two most interesting sections in the EGU), but a whole lot of Paleoclimate.

Here are some highlights from my notes. Errors and omissions all mine, of course.

After a couple of paleoclimate talks first thing on Monday morning I ducked into a rather bizarre session entitled "Navigating a Career in the Geosciences: Strategies for Success." It started off with some important successful guy telling us how the rewards would come if we just put in enough hard work and perseverance and were prepared to take our chances. He told us his own life story of how there were not enough jobs in his PhD speciality, so he changed topics. Then he found funding hard to come by in his next he changed again, becoming Director of NCAR. Why didn't we all think of that? The next presentation was a similar pep-talk from another senior professor about how great life was if only one persevered, but the last talk actually did have some useful content based on real research about what distinguishes the more successful from the less. But I'm hardly going to give away the secrets to you lot :-) One of the most important factors seemed to be the Y chromosome, which reliably distinguishes the "outstanding" from the merely "hard working" (Trix and Psenka, 2003). Later on that day, a session on extremes had Tom Knutson sounding rather sceptical about whether or not hurricanes were likely to increase much (and he thought it would take some time to see a signal in the data).

Tuesday morning started with a session on aerosols, not really my thing but I'd spotted both Schwartz and Chylek were presenting, so I turned up to listen. Steve Schwartz presented his sensitivity analysis, but admitted it had received a lot of criticism and he would not "bet the ranch" on it, which probably defused some potential criticisms (in the questions after someone did say that they thought his detrending was a dodgy step). Later on in the week I spoke to him in person, he said he'd just got our comment and hadn't yet planned his reply. Petr Chylek presented a somewhat similar paper from in the same special issue of JGR (guest editor: P Chylek) which I'll probably blog about in more detail later. I got the impression of a bit of a clique separate from mainstream climate science here. Someone in the audience actually asked where they might get the opposing point of view. It wasn't 100% clear what they meant by "opposing", but one good answer might be chapters 9 and 10 of the IPCC AR4 WG1, or indeed the whole book. There was also a session concerning use of the multimodel ensemble (ie the AR4 runs), which I am getting interested in. In fact there were a few sessions with this sort of flavour that during the week.

After 2 consecutive 10h days and fairly late nights, Wednesday morning had nothing much of interest so we had a lie-in (and tested the crappy hotel gym). The afternoon had some stuff on ocean tracers, including some adjustments to the ocean heat content data, and also estimates of ocean mixing based on various other tracers (tritium from bombs, helium from the mantle). This is something I've tried to point out to some climate sensitivity estimation people who claim that we can't say much about the ocean mixing rate (and thus heat uptake, which affects climate sensitivity estimates) because the temperature data are so uncertain. Even if the direct measurements of temperature are uncertain, we have other evidence about the mixing rate, which they studiously choose to ignore!

Thursday morning had some fun stuff on carbon sequestration, including various air capture schemes. I'm not really convinced that these make sense, but I've nothing against their consideration. Rather than harvesting and burying biomass, it might be simpler to just use it for energy in place of the fossil fuels. In the afternoon we had the exciting session on "Tipping points", which started off with a well-attended talk by Jim Hansen. He didn't actually talk about tipping points in much detail but argued for a rapid halt to coal use (unless sequestration-enabled).

Friday morning was our big thrill of the week, with presentations in the session on climate sensitivity. I was due to talk 2nd up, immediately after Jim Hansen, which (as is generally the case in these situations) I presumed would mean a mass exodus throughout my talk. I consoled myself with the thought that at least most would hear the start of it. Anyway, we arrived bright and early, checked that our presentations were set up and bagged good seats. At about 8:02 the convenor stood up, and said that she was very very sorry, but unfortunately Jim Hansen's presentation wasn't ready yet, so we would have to start with the 2nd presentation! Well at least that saved me another 15 minutes of nerves, and since Hansen's presentation was "in the pipeline" people didn't have time to run out for a coffee so I had a packed house. When initially invited, I'd really planned to steal jules' paleo work and talk about that, but then she also got a talking slot in the same session so I had to leave that in her hands and revamped the "Can we believe in high climate sensitivity" stuff instead. I had some fun reading a bit of Steven Goodman's Nature letter ("This technique would be a wonderful contribution to science were it not based on a patently fallacious argument, almost as old as probability itself") against a back-drop of quotes from the recent climate science literature all claiming that uniform priors represent a state of pure ignorance (this of course being the patently fallacious argument Goodman was ridiculing). Lest anyone think I was picking on anyone in particular, I quoted from 3 papers from largely different groups, plus an extract from the Nobel-winning consensus of 2500 climate scientists otherwise known as the IPCC AR4. However I had noticed that Myles Allen was supposed to be talking straight after me, and I was disappointed that he did not attend and defend his beliefs. I guess if I keep on turning up to the major conferences we can't continue to miss each other indefinitely. The rest of the session had a mix of old and new stuff, nothing too revolutionary. We wound down with a session on geoengineering which was fun.

Nameable names that I met for the first time (mostly very briefly) included, in no particular order: Steve Schwartz, Ray Pierrehumbert, Michael Tobis, Michael Mann and of course there were numerous others I've met before. The weather was great and SF is easily the nicest city I've visited in the USA (not that I'm very well travelled over there) so we thoroughly enjoyed ourselves. On scientific grounds, I think I prefer the EGU, but maybe that is partly a matter of familiarity.

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