Is precession the cause of global warming?
It can't be.
If it were, then we would expect (in the simplest case, no secondary effects) global temperature to follow a simple sine curve with a 26,000 year period. It doesn't.
Some people will come up with a thousand half-baked but plausible-sounding ideas that explain part of the data.
I suspect the truth is people tend make up their minds about what is true then look for data to support it.
Whilst it is true that precession will have an effect due to the unequal irradiation of relative amounts of land and sea at differing inclinations, the effect is small (tiny?) compared to that caused by increasing (evidenced) rises in