The slope of the temperature at all of these warming points, indicated by red arrows, are a measure of how fast ice retreats and earth warms when the Arctic is Closed. The slope of the temperature at all of these cooling points, indicated by blue arrows, are a measure of how fast ice advances and earth cools when the Arctic is Open and after because ice keeps advancing after the snowfall stops..
When the Arctic is Closed, the Sun always melts more ice than gets replaced each year.
When the Arctic is sufficiently Open, it always snows more than enough to replace the ice that the Sun melts each year.
The temperature of the earth can and does change rapidly. It is reasonable to assume that the heat balance stays close to equilibrium. This means that the heat balance at all the points along the horizonal line on this chart have approximately the same heat balance. That means that you cannot explain ice melting rapidly or ice volume building rapidly by the differences in heat balance. You can explain the temperature getting rapidly warmer or rapidly cooler by the advance and retreat of ice sheets. All the other explainations have major problems which includes timing. Sometimes they are in phase and sometimes they are out of phase with the actual changes they are supposed to cause.
Ice extent is ALWAYS in phase with Earth Temperature
At least this has been true for the 870 k years of Antarctic Ice Core Data and the 150 k years of Arctic Ice Core Data.