Open Mind

Open Thread #7

October 23, 2008 · 17 Comments

Open thread #6 is getting pretty big, which can make the page load slowly for some users. So here’s open thread #7.

Categories: Global Warming

17 responses so far ↓

  • johnG // October 23, 2008 at 2:48 pm

    Thank you for your blog, and in general, thanks to all of the scientists/bloggers for this free college education you offer.
    Question: I’m creating an animated illustration of the Milankovic cycles and am having trouble understanding the orbital characteristics that correspond to the precession values I find under this topic in wikipedia. For example, wikipedia shows precession changing from -0.06 to 0.06. What does this number describe? (I understand tilt and eccentricity, but my artist background fails at precession).

    Thanks in advance.

    [Response: The quantity called "precession" in climate is the product of the eccentricity and the sine of the angle between the longitude of perihelion and the longitude of the equinox; it's an indicator of the magnitude of the impact on high-latitude climate forcing due to precession of the equinoxes (in the astronomical sense). There's more about the topic here and here.]

  • Ben Lankamp // October 23, 2008 at 6:27 pm

    A few weeks ago I was looking for global averaged radiosonde temperature data from the various homogenization efforts available, on a monthly timescale. Although this data is available, I found it is not in a ready-to-use format e.g. for importing in R. So I decided to gather the raw data and create a data file with the five major homogenizations of the last years. I put the file on-line for download, see link, for anyone who might be interested in it as well. You may notice that RATPAC is not in the file, I am working on that. Notice #1: there is no guarantee this compilation file will be updated in the future, right now data is available up to June 2008 (HadAT2). Notice #2: there is no guarantee this file is without errors, but I did find long-term trends were not different from those mentioned in the related articles.

  • chriscolose // October 24, 2008 at 3:57 am

    Two things Tamino

    Could you briefly reply to Lucia’s new post on the Santer paper

    I know it’s Lucia, but I wonder about her “merging” of three different data sets with different base periods and her discussion on volcanic forcing

    Secondly, do you have any primary references on discussion of Milankovitch cycles from a more mathematical basis?


  • David B. Benson // October 24, 2008 at 7:09 pm

    chriscolose // October 24, 2008 at 3:57 am —

    has lots of references. Try some.

  • David B. Benson // October 25, 2008 at 12:32 am

    I just remebered that LaGrande et al., with Gavin Schmidt as one of the co-authors, did a model study of the 8.2 kybp event, considering this event to have enough proxies to be well characterized. I obtained a copy of

    Consistent simulations of multiple proxy responses
    to an abrupt climate change event
    A. N. LeGrande, G. A. Schmidt, D. T. Shindell, C. V. Field, R. L. Miller, D. M. Koch, G. Faluvegi, and G. Hoffmann


    TO the extent that I can follow this paper, it appears that the event onset (cooling) proceeded at over -1 K per decade in the North Atlantic and around -0.2 K per decade at Amersee, Germany. (See Figure 1). The GISP2 ice core temperature proxy gives about -3 K total excursion, but (possibly due to smearing on the record) over much longer than three decades.

    In the GISP2 proxy, the subsequent warming (the point here) proceeds at about 3/4 to 1/2 the rate of the prior cooling; the record is similar in shape to the excepted response to volcanic forcing, but both larger in magnitude and over a longer time.

    While it is certainly correct to state that the warming over the past century (or even 140 years) is the largest fast excursion since the recovery from the 8.2 kybp event. from this model study it appears that the high rates in the GISP2 data are only representative of the North Atlantic, not the global surface temperature. So it is probably the case that the current warming is proceeding faster, on the centennial scale, than any warming since (at least) the recovery from Younger Dryas. (But Younger Dryas wasn’t global either, so I now have no prior precident any more recent than about 74–71 kybp, the recovery from the Mt. Toba super-eruption.)

  • Hank Roberts // October 25, 2008 at 1:08 am

    One of two cites I posted at RC in a reply to Ike, arguing that temperate forests rebuild topsoil and so even a “mature” forest is not carbon neutral and ripe for clearcutting (as the industry has been arguing)

  • nanny_govt_sucks // October 25, 2008 at 10:10 am

    Less Ice In Arctic Ocean 6000-7000 Years Ago

    “ScienceDaily (Oct. 20, 2008) — Recent mapping of a number of raised beach ridges on the north coast of Greenland suggests that the ice cover in the Arctic Ocean was greatly reduced some 6000-7000 years ago. The Arctic Ocean may have been periodically ice free.”

  • Hank Roberts // October 25, 2008 at 4:15 pm

  • David B. Benson // October 25, 2008 at 9:52 pm

    “Part of the problem is refereeing. Many (I think most) papers in refereed journals are not refereed. There is a persumptive referee who looks at the paper, reads the introduction and the statements of results, glances at the proofs, and, if everything seems okay, recommends publication. Some referees do check proofs line-by-line, but many do not. When I read a journal article, I often find mistakes. Whether I can fix them is irrelevant. The literature is unreliable.”

    Melvyn B. Nathanson, from “Desperately Seeking Mathematical Truth” in the August 2008 issue of the Notices of the American Mathematical Society (as Opinion, not an Editorial).

    His speciality must have lower standards than the parts of mathematics I have read. I recall no mistakes at all, beyond some easily fixable typos.

  • Rick Brown // October 26, 2008 at 6:26 pm

    Hank, the timber industry’s arguments in favor of cutting mature and old-growth forests fail on many points. My slightly longer post at RC hasn’t shown up, but you can download my paper “Implications of Climate Change for Conservation, Restoration and Management of National Forests” at Pages 13-19 address some of the issues around carbon accounting for forests, including the fallacies of the industry’s arguments.

  • Hank Roberts // October 26, 2008 at 7:16 pm

    Thank you Rick. Great resource, delighted to see you here and at RC.

  • dhogaza // October 26, 2008 at 7:53 pm

    Rick Brown! Who’s been fighting the old growth wars in the PNW for what, 30 years, man?

    Welcome aboard!

  • Rick Brown // October 26, 2008 at 10:22 pm

    I’m not sure I wanted to be reminded how long it’s been, but thanks dhogaza, the same one. I spend more time than I probably should at RC, but check in here only sporadically I’m afraid. And thanks Hank, I’m glad you find the paper useful.

  • dhogaza // October 27, 2008 at 4:13 am

    I spend more time than I probably should at RC

    Good folk, there, but you can add considerably to any analysis of consequences in the biosphere, especially regarding ecosystems of the PNW of course.

    I think the time’s well-spent. The press pays attention, [edit]

    Glad to see you’re well and still in the fight.

  • David B. Benson // October 27, 2008 at 9:51 pm

    I notice that Nanny hasn’t been around lately.

    Stock market?

  • Hank Roberts // October 28, 2008 at 3:55 pm

    In science, a good paper is one that leads others into productive areas for further research — whether the first paper got it right, or just got lucky:

  • HankRoberts // October 29, 2008 at 1:33 am

    PCA in use:

    ________excerpt follows_____
    The researchers looked at six properties of the galaxies, including luminosity, mass of hydrogen, inclination and optical radius, the measure of part of the galaxy responsible for a certain percentage of its light. Many of these properties were already known to be related to one another, and the researchers discovered a new correlation, between luminosity and optical radius. But the bulk of their work, which is published in Nature, consisted of a statistical study of all the correlations using a technique called principal component analysis.

    The analysis shows that these properties are controlled by a single parameter. From their data, the researchers cannot say for certain what this parameter is….

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