No basic disagreement with you work in fact I was impressed!

I do have a comment though, the 20 watt swing from the ellipticity of the earth’s orbit would effect the northern and southern hemispheres differently since the north is predominately land and the south is predominantly water. The south is closer to the sum in the winter so the water would absorb more heat and there is more water. This would set up a flow of water based on the heat imbalance. This maybe part of what you have found?