Warm and Cool Periods are governed by glaciers in the northern hemisphere. When glaciers melt or grow, they’ll change the Earth’s moment of inertia.
This solar Irradiance graph shows where volcanic activity up to 1816 influence solar radiation. Then came the Little Ice Age. And around 1910 warming started.
What’s interesting about this graph is that it suggests that global warming is happening while the Earth is moving away from the Sun.
When warming started around 1910, the Moon had made its closest approach to the Earth in about 1,000 years.
When the Moon’s orbit moves closer to the Earth, it is because the Earth is spinning a little faster. It’s possible that the Earth’s gravity is dependent on its rotational velocity.
Evidence of this is after the rare Super Moon of 1910, the waters adjacent to Greenland’s southern coast below 60° N. latitude suddenly warmed during the 1920’s and 1930’s.
(PDF) The regime shift of the 1920s and 1930s in the North Atlantic https://share.google/pj4vaKyb63KJ7tFZy
Deep sea vents release heat causing glacial melt. Research I have done online suggests a magnitude 6.p earthquake or better around Greenland.This in turn causes tectonic plate uplift which slows both the north pacific and north atlantic currents releasing more heat into the Arctic