CO2 and the Last Glacial Maximum

Introduction

Often in the context of Anthropogenic Global Warming (AGW), comparisons are made to the changes of CO2 during the glacial cycles. Running the CRM models as in the last post, I compared runs for the Last Glacial Maximum and with variations holding a single component fixed in order to compare relative significance of glacial ice ( using 2010 instead of LGM ), CO2 ( using PreIndustrial instead of LGM ), Land Mask ( using 2010 land instead of the 5% increased land surface area from the LGM sea level fall ), and Orbit ( using the LGM orbit instead of LGM ).

The resulting annual mean radiance does not indicate a great deal of variance:

COMPARE_ANNUAL

AVERAGE_WRT_LGM

But as in the last post, the mean annual radiance obscures the dynamic seasonal variation of radiance:

PC_NET_RAD_ALL_MONTHS

This is seen in the depiction of the ranges of net radiance:

WARM_RANGE

And the more significant term is the maximum net radiance, specifically at the latitudes of ice accumulation:

MAX_HIGH_LAT_WRT_LGM

As to the glacial state, the most important factor appears to be the glacial state itself. This is consistent with stochastic resonance determining glacials, because there are two quasi stable solutions: non-glacial which tends to gravitate toward a non-glacial state, and glacial which feeds back to a continued glacial state. When snow and ice persisted for some period, feedback tended toward further accumulation. The effect of CO2 on maximum net radiance change is relatively small.

 

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