Confidence in the understanding of past climate change and changes
in orbital forcing is strengthened by the improved ability of current models to simulate past climate conditions.
Based just
on orbital forcing, and following previous ice age cycles, we are due for a long period of gradual cooling to the next ice age.
This
supported orbital forcing of the ice ages and led to speculation that another ice age was inevitable as the planet moved toward the corresponding configuration.
They accounted for the
known orbital forcing and also considered other possible feedbacks, such as the aerosol loading of the atmosphere.
The «forcing bands» it mentions appear to be those of the various
interacting orbital forcings, not the orbital, albedo and GHG forcings I have argued about.
The albedo and CO2 feedbacks amplified
weak orbital forcings, the feedbacks necessarily changing slowly over millennia, at the pace of orbital changes.
First of all, simplify by imagining a box
with orbital forcing as input and an (unobserable) temperature as output; the water vapor feed back is inside and is effectively instaneous on the scale of millennia appropriate for considerring ice age variations.
A look at the increasing temperature response to the same
orbital forcings as average temperature dropped shows that climate sensitivity became significantly larger during the Pleistocene ice ages.
While orbital forcing favours predictability at the scales it acts, the overview of climate variability at all scales suggests a big picture of irregular change and uncertainty of Earth's climate.
Predicted changes in
orbital forcing suggest that the next glacial period would begin at least 50,000 years from now, even in absence of human - made global warming (see Milankovitch cycles).
Moreover, anthropogenic forcing from increased greenhouse gases might
outweigh orbital forcing for as long as intensive use of fossil fuels continues [9].
Isotopious @ 43 — It is generally agreed that orbital forcing [at high northern latitudes] is the cause of the changes between the three states of interglacial / interstade (mild glacial) / stade (full glacial).
The theory of
direct orbital forcing is obvously incorrect, since integral of insolation does not change for more than 0.1 % during eccentiricity variations.
Now one way to study this is to take the average temperature of each millenium of the record: doing so shows the most recent millenium was the coolest and the one just previous next so; this is in keeping with
orbital forcing theory.
In a short piece in the PAGES Newsletter, George Denton, Wally Broecker and I linked this excess ice and
orbital forcing through ocean circulation to control of CO2, and others are surely thinking along the same lines.
Nor, I fear is your analysis of
orbital forcing quite right; see David Archer's new book «The Long Thaw» or various of his papers; these may be obtained from his publications web page.
Strong positive feedbacks to the initial regional and
seasonal orbital forcing are necessary to account for the eventual * global * glacial / interglacial climate shift.