Comments 1 to 8:

1. From Peru at 16:03 PM on 7 October, 2012
   I found in WUWT this paper that claims to found paleoclimate evidence (from the Eocene-Oligocene transition)for a 1ºC climate sensitivity: New paper on climate sensitivity estimates 1.1 ± 0.4 °C for a doubling of CO2 Is based on this paper: Estimate of climate sensitivity from carbonate microfossils dated near the Eocene-Oligocene global cooling I have read the paper, and it seems weird to me. The author seems to have just picked some data from other papers, in particular: Zachos, et al. (Paleoceanography,1996) "High resolution (104 years) deep-sea foraminiferal stable isotope records of the Eocene-Oligocene climate transition" Pearson, et al. (Nature 2009) "Atmospheric carbon dioxide through the Eocene-Oligocene climate transition" From the first one the author got the deep ocean temperatures (from deep sea sedimentary cores in Antartica and Namibia) and from the second he got the approximate CO2 concentrations during that time. The main claim of the paper is that 33 million years ago there was a rapid (in less than 50 000 years) pulse of CO2 increase, from 780 ppm to 1140 ppm (about half the amount of CO2 liberated during the PETM) yet the deep southern Ocean just warmed little over 1ºC. Any idea about the reliability of the data or about what happened 33 million years ago?
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2. Rob Painting at 19:03 PM on 7 October, 2012
   From Peru - Seems very much like problematic material. Asten cites Lindzen & Choi (2011) without any discussion of its many flaws - see Lindzen and Choi 2011 - Party Like It's 2009. That should immediately raise concern. On a positive note, the paper is still open for comments, so those inclined have an opportunity to submit a reply. I suspect the paleo data, like Lindzen & Choi, has been cherry-picked to arrive at a pre-determined destination. Indeed, Asten's public comments on this topic (see here) are at odds with the bulk of paleo research.
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3. chris at 19:45 PM on 7 October, 2012
   As Rob has pointed out the Lindzen and Choi analysis is completely unreliable as an estimate of climate sensitivy both because of fatal methodological flaws but also due to the fact that his method (analysis of immediate changes in radiative response at the top of the atmosphere due to changes in surface temperature) can address only the rapid atmospheric response and doesn't say too much about responses occurring on the decadal (let alone 1000's of years!) timescale. Several papers have addressed the flaws in Lindzen's methods and these should certainly be known to a scientist making an honest and informed foray into this topic. The Chylek estimate cited by Asten is highly flawed (cherrypicked timepoints) as described by Hargreaves and Annan in Climate of the Past. The Douglass and Christy estimate is simply silly - they determine their estimate from the temperature variation during the period of satellite observation 1979-2007. …and so on… You simply can’t cite papers in the scientific literature that have been shown to be fundamentally incorrect, as if these still constitute valid elements of the evidence-base that informs current understanding. I expect these aspects of his paper will have to be fundamentally redone before the paper is considered suitable for publishing. And that’s not to address what may or may not be fundamental flaws in the work itself (I’ve only seen the paper for half an hour!). Dr Asten has published a smattering of scientific papers since 1973 largely in fields related to studying microseismic behaviour. No evidence in his published work over 40 years that he has any particular expertise in analysis of paleo data for addressing climate sensitivity, and judging by the work he’s cited he hasn’t got a very good understanding of the strengths and limitations of previous work on this subject…
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4. Riccardo at 21:50 PM on 7 October, 2012
   After a cursory reaading of the paper I noticed the following. The conclusions stands on essentially two choices. 1) the time intervals. In the paper Asten admit it's not based on any sound criterion. He first says: "Following the temperature drop to a minimum at 33.4 Ma a step change of duration about 150 000 yr is evident on the smoothed data." In other words, eyeballing the smoothed curve he sees a step change and that's good enough. Then, assuming the step change, he makes "some subjective choice on the position of time segments labelled a, b, c on Fig. 1, [...]". Again, we have to live with it. 2) CO2 concentration. The three segments are supposed to be "representative samples before, during and after the temperature change associated with the CO2 pulse shown in Fig. 4." But looking at fig. 4 they do not match, segments a and b have the same, higher CO2 concentration. For some reason, Asten averages the CO2 concentration during time intervals a and b (see table 1) contraddicting what he said on the step change between segments a and b. But then he added one more time interval before a to average its CO2 concentration with that of segment c. Either the rationale of this procedure is beyond my comprehension or I'd call the conclusions rather weak.
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5. chriskoz at 00:14 AM on 8 October, 2012
   Interesting to note is that the cranks at WUWT must go back 33Ma in search of some cherry (or rather statistically insignifficant straw-data in this case) to support their pre-conceived viewpoint that CS must be low. We know they deny a well understood and far more accurate, ice-core data supported research for the last 800ka. I don't need to mention how irrational is to look for answers about CS in Miocene hothouse and try to project results at today, as Miocene climate was totally different. I wonder how far those cranks would have to reach for some new straw data, when paleo guys start obtaining better proxies for Miocene and better quantifying the differences between then hothouse and now interglacial climates.
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6. Pete Dunkelberg at 01:52 AM on 8 October, 2012
   This new paper: Impact of melt ponds on Arctic sea ice simulations from 1990 to 2007, Flocco et al. 2012, Abstract:

   The extent and thickness of the Arctic sea ice cover has decreased dramatically in the past few decades with minima in sea ice extent in September 2007 and 2011 and climate models did not predict this decline. One of the processes poorly represented in sea ice models is the formation and evolution of melt ponds. Melt ponds form on Arctic sea ice during the melting season and their presence affects the heat and mass balances of the ice cover, mainly by decreasing the value of the surface albedo by up to 20%. We have developed a melt pond model suitable for forecasting the presence of melt ponds based on sea ice conditions. This model has been incorporated into the Los Alamos CICE sea ice model, the sea ice component of several IPCC climate models. Simulations for the period 1990 to 2007 are in good agreement with observed ice concentration. In comparison to simulations without ponds, the September ice volume is nearly 40 % lower. Sensitivity studies within the range of uncertainty reveal that, of the parameters pertinent to the present melt pond parameterization and for our prescribed atmospheric and oceanic forcing, variations of optical properties and the amount of snowfall have the strongest impact on sea ice extent and volume. We conclude that melt ponds will play an increasingly important role in the melting of the Arctic ice cover and their incorporation in the sea ice component of Global Circulation Models is essential for accurate future sea ice forecasts.

   discussed at Climate Central, looks helpful for understanding rapid changes in the Arctic.
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7. mspelto at 22:58 PM on 8 October, 2012
   For next week's roundup take note of the change on Thwaites Glacier, Antarctica.
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   Moderator Response: [JH] Thanks for the tip.
8. EliRabett at 12:51 PM on 9 October, 2012
   Not quite sure why anyone should be surprised by the aerosol aging paper
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