Doubling down on nutations

Kelsey et al have replied to Eric Wolff’s comment on their Climate of the Past Discussion Paper which I discussed yesterday. Wolff is concerned that the paper’s opening statement that “The existence of a ~1470 year cycle of abrupt climate change is well-established” does not reflect recent literature, citing multiple papers to make this point.

Kelsey’s response is “Please see references from highly ranked publications referenced in this article” followed by a list of papers (one of which, as Wolff points out in his subsequent reply, does not exist). This is not a response that indicates she is open to input from reviewers.

But what about these nutations which Kelsey et al think are, together with sunspots, driving the DO cycles. Nutations are wobbles in the Earth’s orbit caused by the gravitational pull of the Sun and the Moon on the Earth’s equatorial bulge. This wobble will cause a redistribution of insolation over the Earth, just like the obliquity and precession components of Milankovitch cycles. The key question is by how much? Is it enough, in conjunction with sunspots, to cause the DO cycles? The paper does not explore this critical question.

For reference, the obliquity cycle changes the angle at which the Earth’s angle tilts from 22.1° and 24.5°. The latitudinal component of the 18.6-year nutation is ±9.2″ (i.e. 9.2/60/60 = ±0.0025°). This causes the Tropic of Cancer (where the Sun is directly overhead at noon on the summer solstice) to move by a few hundred metres. It should be fairly obvious that insolation does not vary appreciably over such short distances. Nutation will also be linked to some changes in tidal amplitude, but it is really hard to imagine an 18.6-year cycle having much effect on millennial timescales.

I had expected A. M. Kelsey to be a retired engineer. Actually, she is a PhD student at the University of Queensland studying the palaeoecology and palaeoclimatology of Fraser Island in southern Queensland. Her coauthors are her supervisors – who I think are somewhat remiss for allowing her to submit this paper.

Why am I interested in this dubious paper? Three main reasons:

  • If nutations and sunspots caused DO cycles then our climate is far more sensitive to forcings than anybody thinks it is.
  • Climate change deniers will probably use it to argue our climate is only sensitive to sunspots and nutations and that greenhouse gas forcings are somehow insignificant.
  • The open peer review process at Climate of the Past gives a window onto how peer review copes with “interesting” papers.

About richard telford

Ecologist with interests in quantitative methods and palaeoenvironments
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One Response to Doubling down on nutations

  1. The periodic influences of the moon are well accepted. See the cyclical relationship between the moon, earth, and sun which drives the ocean tides.

    Yet AGW denialists such as Richard Lindzen can not see the same relation in other climate measures. Lindzen, who formulated the foundational theory of the Quais-biennial Oscillations (QBO) in upper atmospheric winds, completely missed the lunar connection to QBO cycles.

    This is all in the context of the 40+ years since Lindzen wrote these words:

    “5. Lunar semidiurnal tide : One rationale for studying tides is that they are motion systems for which we know the periods perfectly, and the forcing almost as well (this is certainly the case for gravitational tides). Thus, it is relatively easy to isolate tidal phenomena in the data, to calculate tidal responses in the atmosphere, and to compare the two. Briefly, conditions for comparing theory and observation are relatively ideal. Moreover, if theory is incapable of explaining observations for such a simple system, we may plausibly be concerned with our ability to explain more complicated systems. Lunar tides are especially well suited to such studies since it is unlikely that lunar periods could be produced by anything other than the lunar tidal potential. The only drawback in observing lunar tidal phenomena in the atmosphere is their weak amplitude, but with sufficiently long records this problem can be overcome [viz. discussion in Chapman and Lindaen (1970)] at least in analyses of the surface pressure oscillation. ” — from Lindzen, Richard S., and Siu-Shung Hong. “Effects of mean winds and horizontal temperature gradients on solar and lunar semidiurnal tides in the atmosphere.” Journal of the Atmospheric Sciences 31.5 (1974): 1421-1446.

    Lindzen has been wrong on so many theories (Iris cloud hypothesis, etc) that its not surprising that his QBO model is likely wrong. So there is always room for new physics-based applications of “numberology”.

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