

Wikipedia says:

Dansgaard–Oeschger events (often abbreviated D–O events) are rapid climate fluctuations that occurred 25 times during the last glacial period. Some scientists say that the events occur quasi-periodically with a recurrence time being a multiple of 1,470 years, but this is debated. —

The 25 occurrences of 1470 years are represented in this synodic chart posted in the comments of our 2018 blog post:

Possible origin of Dansgaard-Oeschger abrupt climate events.

Re. the ‘debate’, let’s take a line from this paper:

On the 1470-year pacing of Dansgaard-Oeschger warm events

Michael Schulz

First published: 01 May 2002

Citations: 99

‘a fundamental pacing period of ~1470 years seems to control the timing of the onset of the Dansgaard-Oeschger events.’

Another study: Timing of abrupt climate change: A precise clock

Stefan Rahmstorf

First published: 21 May 2003

An analysis of the GISP2 ice core record from Greenland reveals that abrupt climate events appear to be paced by a 1,470-year cycle with a period that is probably stable to within a few percent; with 95% confidence the period is maintained to better than 12% over at least 23 cycles. This highly precise clock points to an origin outside the Earth system; oscillatory modes within the Earth system can be expected to be far more irregular in period.

[bold added]

However, researchers often admit defeat when looking for a viable mechanism to explain its regularity, or just say there isn’t one to date.



Returning to the synodics chart, a relevant number doesn’t appear in it. The Jupiter-Saturn conjunction of 19.865~ years is an important period in the solar system, and it returns to almost the same position after every three occurrences, as Johannes Kepler noted with his ‘trigon’, centuries ago.

We can work out the rate of movement per conjunction in degrees:

360 – ((360 / S) * J-S) = 117.147 degrees

(360 / 117.147) * J-S = 61.046482y (‘JS-360’)

[Data: https://ssd.jpl.nasa.gov/?planet_phys_par ]

Then, from the chart:

1470*25 / ‘JS-360’ = 602.00029

Check: (602*360) / 117.147 = 1849.983 (1850 J-S, see chart)

Since ‘JS-360’ is almost exactly a whole number (602), the Jupiter-Saturn conjunction should be in its original position at the end of the 25 D-O cycles.

Adding 602 to the orbits of each planet = multiples of 25:

223(N) + 602 = 825 (25*33) = 1850-1025(S-N)

[33 = 74-41]

1248(S) + 602 = 1850 (25*74)

3098(J) + 602 = 3700 (25*74*2)

Another way to get multiples of 25:

Add 2 to each orbit number (see chart), and subtract 2 from 602.

More on the 602 number:

602 = 14*43

14*61.046482y = 854.651y

43 J-S = 854.197y

These two results are only about half a year apart, and we find:

43*43 = 1849 J-S

Add 1 = 1850 J-S completing the 25 D-O cycle.

43*61.046482y = 2625 years (2624.9987)

1470:2625 = 14:25 ratio

1470*25 = 2625*14 (hence 602 of ‘JS-360’ = 14*43)

Obliquity note:

28 D-O = 41160 years, a fair match to the expected 41 kyr period.

One paper refers to a fit between D-O and obliquity.

Others support the notion of a link — possibly a topic for another post.

(28*25*1470 = 1,029,000 years)

Example of a 1470 year period from Arnholm’s solar simulator — click on image to enlarge:



Showing Neptune, Jupiter, Saturn and Earth.

* * *

Another one — Jupiter, Neptune, Saturn

