> "But the omega in your Ttt+ω2T=F(t) is not constant and the F(t) is not periodic, as there are e.g. terms −0.001t and −0.00007t2 and what you call TSI looks even more strange."
Those are drift terms to compensate for any long term trends, inconsequential really. The TSI is a periodic function that serves to replicate solar/sunspot activity.
So the forcing is essentially periodic, just as I stated when I set up the initial premise.