None of the recent climate models or any of the resent so called climate scientists attempt to explain why Earth's temperature dramatically rises and then suddenly falls every 110,000 years. (I assume this is because it suggests that human induced CO2 has little to do with Earth's climate variations.)
Wallace S. Broecker, thinks the 110,000 year climate cycle has more to do with the oceanic conveyor. He says: "We have clear evidence that different parts of the earth's climate system are linked in very subtle yet dramatic ways. The climate system has jumped from one mode of operation to another in the past. We are trying to understand how the earth's climate system is engineered, so we can understand what it takes to trigger mode switches. Until we do, we cannot make good predictions about future climate change."
Others, like S. Eldredge and G. Riel, think it has more to do with cyclic changes in the Earth's orbit. They claim three orbital variations contribute to the interglacials. (An interglacial period is when the Earth is warmer.) The first variation is a change in the Earth's orbit around the sun, or eccentricity. The second is a shift in the tilt of the Earth's axis, the obliquity. The third is precession, or wobbling motion of Earth's axis. Warm summers in the northern hemisphere occur when that hemisphere is tilted toward the sun and the Earth is nearest to the sun in its elliptical orbit. Cool summers occur when the Earth is farthest from the sun during that season. These effects are more pronounced when the eccentricity of the orbit is large. When the obliquity is large, seasonal changes are more extreme.
This would certainly explain why the North pole is shrinking and the South pole is expanding. If we combine both observations we get a somewhat pausable explanation as to why Earth suddenly shifts between glacial and interglacial periods over a 110,000 year cycle....
When the obital variations are such that the top end of Earth is both closer to the sun and tilted more towared the sun, the hotter northern hemisphere summers eventually melt the North pole. This unlocks the Artic circle and allows the Atlantic ocean currents to flow in. This change of current flow disrupts the oceanic conveyor which relies on the Atlantic warmer top currents to cool, sink and then return back toward Africa. Without the oceanic conveyor bringing the deep water in the pacific up to the surface, less CO2 effervesces out of the ocean from the subsea volcanic vents. The Pacific Ocean instead becomes a carbon sink which causes the atmospheric CO2 level to plunge.
Without the oceanic conveyor functioning, the surface water nearer to the equator become hotter and the surface water nearer to the poles becomes colder. This both increases the global cloud cover and re-freezes the North pole. Both have the effect of reflecting more sunlight away from Earth and lowering the surface temperature considerably. Consequently another glacial period begins.
It takes another 90,000-100,000 years for Earth's orbital variations to become such that the oceanic conveyor restarts itself to bring on another interglacial period and thus repeat the cycle
How bad does it get during a glacial period? Pretty bad. Snow above 1km everywhere. Most of Asia Europe, etc in permafrost. When the north pole melts, expect the sea level to rise another 5 m. When the big freeze begins, expect the sea level to fall 125m. Australia can expect 90% less precipitation. Would pumping more CO2 into the atmosphere help? Unlikely. It would be quickly absorbed by the ocean. The only hope might be to restart the oceanic conveyor sooner rather than later.
