Just another thought

The problem of gathering evidence for global warming has been cooking in my mind for some time. (1960?)

The real problem is to get a long series of measurements of the whole planet.
My thinking goes like this:  We have good data on day length back to Galileo
and his ephemeris of the moons of Jupiter.
Water etc. expands when warmed.  The expansion of the seas will change the moment of inertia of the planet.  This will slow the rotation and lengthen the day.  Global warming will show as an error in the ephemeris of the moons of Jupiter.  The ephemeris has been an important navigation tool.  It will have recorded corrections back almost to the start.
Proof or disproof of global warming.