Day Four at AGU didn’t have as much climate stuff as the first three days. Aside from Al Gore, I went to a number of ice core and ocean sediment presentations.
First I heard the end of a presentation on lake sediments, saying that there were more droughts/century in the past in New England.
Then a modeler who discussed a supposed reconciliation between GISS model E and Dasuopu results. The GISS unit cell was 4 degrees lat and 5 degrees longitude, with the relevant gridcell assigned an altitude of 4000 meters. An article by Bradley et al was mentioned, as was Hansen PNAS 2006 for a supposed difference in temperature trend between E and W Pacific. She said that they could not replicate a result of Guiot et al and did not pursue that line further.
Then to D. Schneider from Colorado who discussed high-resolution Antarctic ice cores over the past two centuries (GRL Aug 2006) referring to Law Dome, Dronning Maud, ITASE 2001-1, ITASE 2001-5 and Siple Dome, analyzing dO18 and dD. He did principal components analysis and claimed the ability to reconstruct the Southern Annular Mode. The ice cores had an anti-correlation of -0.6 in the interior and +0.2 on the outside of the annulus. The PC1 had no trend over the 19th and 20th century. However the late 19th century was lower than the earlier 19th century or the 20th century. This negligible bit of red noise was noted up as a trend.
Then to Urman who discussed tropical ice cores and cyclones. He put up a correlation map between cyclone activity and PAC1 SSTs. More cyclones started further east in Nino years and fewer in Nina years. The Nina typhoons were more zonal, while Nino typhoons often went further north. He asked whether ice cores could clarify the dispute between Webster and Chan 2006 as to whether typhoon data from the 1950s showing elevated typhoon levels was valid. He showed a graph with strong decadal correlation between Quelccaya dO18 and PAC2 SST (0.893 — definitely a high correlation) and with NW typhoons (0.58). His legend said that he used centered 5-year averages. SM note: Quelccaya precipitation actually comes from the Atlantic and even from the Amazon basin from the South American monsoon. So there are a couple of legs to this proposed teleconnection.
Then I went to a session describing an ocean sediment core from Kau Bay, Indonesia, a closed basin of about 470 m in depth with a sill of only 40 m depth. The anoxic depth had been surveyed a couple of times — anoxic levels began at relatively shallow depths in a 1930 survey after a strong El Nino; only at the base in 1985 after a Nina; and once again at higher depths in 2003 after a Nino. She suggested a steady reduction in Nino frequency since about 700 BP. I left the session early to wait for Al Gore.
After the Gore speech, I went to some ice core posters. Kreutz described a new core from Mount Logan. There are now 4 cores from this area — 3 taken around 2002-3. We’ve discussed Fisher’s core from the Summit which has a sharp decrease in dO18 in the mid-19th century through the 20th. A shorter core (showing the same phenomenon) had been taken in 1980 — so this has been known to (say) Lonnie Thompson for some time. The new Fisher core was also from the Summit. The Kreutz core (Eclipse) was taken at a lower elevation and showed less centennial-scale variability. Kreutz and Fisher have concluded that the higher elevation core is reflecting precipitation from a much greater distance while the lower cores are more local. He showed a panel of comparanda from Seager et al (which is a version of the Graham-Hughes presentation discussed previously).
A nearby poster showed temperature estimates from several Canadian Arctic cores — Hudson Strait, Baffin Island, Beaufort Sea. The estimates were done from dinoflagellate cysts; sedimentation rates were 1.7- 4 mm/year, sampled every 10 cm, thus about 20 years resolution. He reported that temperatures in the Hudson Strait about 4000 years ago were up to 11 degrees C higher (!), but not much difference at the Beaufort Sea. The explanation for this was that the warm Greenland Current penetrated much further north into Canadian Arctic waters at this time (as seen trough North Atlantic flora).
Nearby was a poster for a short drill core from the Pamirs from a very large glacier. The reconnaissance was done by a group from the University of Idaho. Their glacier was 1 km thick — pretty remarkable. (The day before, Lonnie Thompson said that the 160 meter thick Quelccaya glacier was as good as it gets.) They are trying to get NSF funding — I hope that they get it. Maybe they will even archive their sample results before 20 years has passed.
Then to poster 1234 -Neny Fjord, Norway had a thick (12 m ) Holocene sequence with basal C14 date of 8060 C14 BP. 1235 — a record from Cabo Frio at the South Atlantic Convergence Zone.
Then to a presentation by Nicola Scafetta on his latest thoughts on solar-climate relationships building on several earlier articles. He made the obvious point that forcing factors prior to the 20th century were agreed to be solar and volcanic. Thus variation in a reconstruction — whatever the merit of the reconstruction — had to result from these factors. He then took the view that feedback to solar forcing should be deduced from this information rather than on a priori grounds. He then used the various temperature and solar reconstructions to give bounds to each. Of the temperature reconstructions, Mann and Jones 2003 was at one end of variability (0.2 deg C) and Moberg at the other end (0.8 deg C). (As an aside, in the discussion of reconstructions here, I’ve not really tried to assess the knock-on impact in attribution studies, although I’m obviously aware of the issue; for those who say that these reconstructions don’t “matter”, here’s a case where they are being used for forcing attribution.) e also noted the big differences between variability in different iterations of solar reconstructions, with Lean et al 2005 being much less variable than the earlier versions. He also drew attention to the lag factor between forcing and temperature (his tau) resulting from ocean inertia. He mentioned that a tau of 10 was held to be sensible for physical reasons, but that the tau from some solar proxy-temperature proxy combinations was much less. (He noted that differences for solar variability resulted even from interpretations of ACRIM where an adjustment in the middle of the record was not without controversy and led to different knock-on results.) The tau of MJ03-Lean 2000 was 0.75; 3.75. Scafetta had an interesting graphic showing the GISS model against actuals — something dear to Willis’ heart. Prior to 1958 in this graphic, the GISS reconstruction was really bad. He mentioned a possible feedback from solar forcing onto cloud cover.
I browsed more ice core and sediment posters for a while. One that caught my eye was from Wyss Yin of Hong Kong (U43B-0858) who had a theory of why CO2 levels rose in interglacials. He was a geologist who had studied dozens of boreholes in the Hong Kong shelf. He pointed out much loess had been de-calcified. He proposed that dropping ocean levels led to exposed continental shelfs, that this exposed marine pyrite, which then oxidized and dissolved carbonates yielding carbon dioxide. I don’t know whether this can be reconciled with timing (and, in particular, with the ice core information.) However, there are many Pleistocene loess exposures and lots of potential information to be assimilated.