H Flohn: background to a geophysical model of the initiation of the next glaciation

Quaternary Research, 4, 385-404, 1974.


Evidence of (at least) five rapid hemispheric coolings of about 5oC during the last 105 yr has been found, each event spread over not more than about a century, as examples of a global-scale climatic intransitivity. Only some of them lead to a complete glaciation at the northern continents, others ended after a few centuries by a sudden warming ("abortive glaciation"). Starting from a modified version of Wilson's hypothesis of Antarctic ice surges, an air-sea interaction model with realistic geophysical parameters is outlined to interpret the sudden initiation of the North American ice sheet. Special attention is given to the Atlantic section, where the climatic anomalies during the last glaciation appear to have been significantly larger than in other sections.

Not much hint of excitement in the abstract. But to continue, he is interested in "when will the present interglacial end?". His facts:

  1. Since about 1945, global cooling on a scale of 0.01 oC/y...
  2. Climatic optimum 6-7000 yr ago. Last interglacial 10,000 yr long.
  3. Tropical ocean temperatures as high as today on 10% of last 400 kyr.
  4. General agreemnet that the present warm epoch has reached its final phase, and that - disregarding possible man-made effects - the natural end of this interglacial is "undoubtedly near". The timescale of this transition may be a few millenia, perhaps only centuries. [my emphasis].

Later on, he asserts that available evidence is incompatible with Milankovitch.

So... were was Flohn on prediction? Firstly, his predictions hold only disregarding possible man-made effects: it is not clear whether he believes man-made effects would be small, or whether his is just an academic exercise. Secondly, even if we do disregard possible man-made effects his strongest conclusion is only that "The timescale of this transition may be a few millenia, perhaps only centuries.

So, all in all, nothing new (for us; the paper contains scientific content not relevant to the was-a-new-ice-age discussion): the idea that the current interglacial would "naturally" end soonish is familiar, as is the fact that people knew that anthropogenic effects need to be taken into account.