One of the essential prerequisites for the IPCC case for extended global warming is the claim that we face an extended Holocene because orbital geometry now is similar to the 400KY (Stage 11) interglacial which lasted for 28, 000 years.
Based on the paper by Berger and Loutre (2003) it is claimed that the extraordinarily long Stage 11 interglacial period resulted from the low orbital eccentricity at the time, and now we have similar eccentricity and should therefore expect an extended Holocene. (IPCC TS 6.4 1.5)
It is reported that “It is very unlikely that the earth would naturally enter another ice age for at least 30 000 years” (IPCC TS 6.2.4 “Robust Findings”)
This position is completely without merit.
An analysis of FIG 1. below shows the orbital forcing during the 400KY precedent compared to the present configuration and it can be seen that we are very close now to the tipping point like that which led Stage 11 into the following ice age.
FIG.1 QUINN, LEVINE, RAYMO ET AL ORBITAL GEOMETRY VS CLIMATE
(AA) Projection at present insolation, (BB) Projection of Glaciation, (X) Paillard
The position (X) shows the insolation maximum at 427KY which triggered the Stage 11deglaciation. (Paillard 1998) The following small dip in insolation was not sufficient to reverse the warming trend . “The Interglacial thus lasts an additional precessional cycle, yielding a total duration of 28 000 years.” (IPCC 18.104.22.168)
This is the so called precedent for an extended Holocene. This is the reason given by IPCC for the “Robust Finding” that it is very unlikely that the earth would enter another ice age for at least 30 000 years. But as shown in FIG.1 there is no such change in insolation now and Solar Forcing is in rapid decline.
Projecting present Solar forcing (insolation) (AA) back to the 400KY precedent we intercept at exactly 400KY which corresponds to the collapse of the Stage 11 interglacial climate as it enters the following ice age.
The collapse of the Stage 11 interglacial occurs when the insolation decline is similar to today.
From this analysis, based on the Solar Forcing from present global geometry which has been accepted as the external signal for climate, the contention that it is very unlikely the Earth would naturally enter another Ice Age for at least 30 000 years is unsafe.
There is good reason to expect the imminent termination of the interglacial because of the coincident action of 3 major cyclic processes.
1. Insolation in rapid decline similar to the 400KY precedent.
2. We are near the end of the nominal 100KY glaciation cycle.
3. The present interglacial is near the average age for termination.
We are also witnessing some major natural processes which occur at the end of each interglacial such as the slow down of the MOC and polar ice melt.
It is time to plan for the coming Ice Age.