Right now geologically speaking talking about the last 10 million years, the last 10,000 years
is part of an extended warm period at the end of a long cooling trend. Geologically there have
been several extended hot periods, where the earth was covered in tropical swampy lands with
shallow warm seas which changed little for tens of million years- up to 120 million years..
The Mississippian an Pennsylvanian periods best illustrate that. In recent history there have
been 5 well documented glacial periods ( two more less well documented periods preceded
those 5) , interrupted by warm interglacial periods.
The periods have been getting shorter in a logarithmic basis. This is shown below in table form, and with the figure.
GLACIATION Global Glacial periods and intervals
Plot of log interglacial period is a virtually straight line, Giving 21.07 thousand
years expected interglacial period from start of the warming 20.0 thousand years ago.
This analysis gives us 1070 years more interglacial, (21.07 - 20.0) but the troubling part is that the
probable error (inaccuracy of data is ±1000 years) is about the same as the answer, meaning it could
start any time. Other attempts to get better resolution all came to the same problem with the answer.
We are due for a glacial period any time now.
There is worse news. The ice cores, the Vostok Greenland and Antarctic ice cores, when analyzed year
by year t show a temperature spike of VERY short duration at the start of major glacial periods. It appears
that the start of the glacial period is precipitous, lasting no more than a decade. For example the Dover
straights between England and France froze solid in less that a decade at the start of the last Wurm glacial
period. That was preceded by a 10 degree spike lasting about 20 years, followed by a crash of over 15
degrees that lead to total glaciation. Below note the spikes.
There is a mechanism for this spike causing a strong reversal. In any system LeChatlier's principle states
that any system in equilibrium will react to a change by shifting equilibrium so as to minimize the change.
The warming causes flooding which in turn causes a new set of ocean currents that in turn shift weather
patterns total to a new track. The rain winds shift south to Africa. That causes cloud cover which rejects
heat over much of Europe. Thus it snows, and snows, and that white cover also rejects incoming heat
leading to the Norse "Fribble Winter" - the year there was no summer. That can build the beginning of a
major glacier in that one year, leading to a thermal catastrophe. Thus the new equilibrium is established
that caused the Sahara to bloom as a fertile grassland, millennia ago, and caused Canada and Scandinavia
to be under an ice blanket a half mile deep.
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