The phrase
"glacial climate" refers to a very cold and icy climate, similar to the conditions experienced during an ice age.
Full definition
Ganopolski, A. and S. Rahmstorf, 2001: Rapid changes
of glacial climate simulated in a coupled climate model.
Braun, H., M. Christl, S. Rahmstorf, A. Ganopolski, A. Mangini, C. Kubatzki, K. Roth, and B. Kromer, 2005: Solar forcing of
abrupt glacial climate change in a coupled climate system model.
However, the global dust burden and associated radiative forcing are substantially higher
during glacial climates, so that the amplification of the dust load by this feedback is larger.
But the calculations can only be done well when the temperature change is large, notably at glacial terminations (the gradual change from
cold glacial climate to warm interglacial climate).
Should it be attained, this state would be more «symmetric» than the present climate, with comparable areas of ice / sea - ice cover in each hemisphere, and would represent the culmination of 50 million years of evolution from bipolar nonglacial climates to
bipolar glacial climates.
Now an interesting new paper in Nature [subscription] suggests that a rapid natural transition towards a
stable glacial climate, with permanent ice sheets covering large parts of North America and Eurasia, could indeed be ahead.
Release from the combined environmental stresses of a frigid,
glacial climate near sea - level and a major impact in low latitudes may have been a factor influencing subsequent Ediacaran biotic evolution.»
However,
at glacial climate, the AMOC experiences an intermediate stage — with a rapid intensification period of ~ 300 years — and a large overshoot response.
In Possible solar origin of the 1,470 -
year glacial climate cycle demonstrated in a coupled model, Holger Braun, Marcus Christl, Stefan Rahmstorf, Andrey Ganopolski, Augusto Mangini, Claudia Kubatzki, Kurt Roth & Bernd Kromer postulated that the combination of the 210 year DeVries — Suess and the 87 year Gleissberg cycle could tip nonlinear fresh water influxes and subsequent changes in Thermohaline Circulation triggering Dansgaard - Oeschger events.
He thinks that we can look to paleoclimate as evidence for abrupt climate change — and indeed we can — but the examples he has to use are those of abrupt change during deglaciation (YD) or
during glacial climate (D - O; Heinrich; Bond).
«the 1,470 - year climate response in the simulation is restricted to
glacial climate and can not be excited for substantially different (such as Holocene) boundary conditions... Thus, our mechanism for the glacial, 1,470 - year climate cycle is also consistent with the lack of a clear and pronounced 1,470 - year cycle in Holocene climate archives.»
Surprises that could change this include going into
a glacial climate state, which had the mysterious ability to draw down CO2 in the past, or uptake by the terrestrial biosphere.
The clues from the paleo - record indicate that there is likely a bi-modal spectrum of overturning states in
glacial climates, but there is no evidence of such multiple steady states in the Holocene.
Both panels are reconstructions of oxygen concentrations in the California Margin during a cold,
glacial climate (left, 18,000 years ago) and a warm, interglacial climate (right, 14,000 years ago; Moffitt et al. 2015a).
We are in
a glacial climate as long as we have ice in our polar regions and we are more likely to have another ice age than become too warm.
Discrepancies in
the glacial climate simulations are further amplified by short integration times, as the deep ocean equilibrates on millennial timescales.
Probably not how «culture arose... in the depths of
the glacial climate.»
Culture... arose about 40 thousand years ago, in the depths of
the glacial climate... Civilized humanity has never seen a climate change as severe as global warming.
«the 1,470 - year climate response in the simulation is restricted to
glacial climate and can not be excited for substantially different (such as Holocene) boundary conditions... Thus, our mechanism for the glacial, 1,470 - year climate cycle is also consistent with the lack of a clear and pronounced 1,470 - year cycle in Holocene climate archives.»
1997 Gerard C. Bond, et al., «A Pervasive Millennial - Scale Cycle in North Atlantic Holocene and
Glacial Climates.»