Exactly. To what do you calibrate the instrument you use to measure the standard?
Calibration . . . the fly in the ointment when it comes to how the “average global warming” has been measured over the past 100 years by different types of thermometers that cannot be calibrated all the same way. Add to that the unscientific “averaging” of temperatures around the globe, and your single degree Celsius of alleged “average warming” over such a long period of time becomes utterly meaningless and unavoidably questionable.
Never mind the alleged fluctuations of the weight of the standard kilogram. How do the scientists know that the earth’s gravity itself has not varied by a few degrees of force? It has not necessarily been established that a certain mass has to exert a uniform force of gravitational attraction after all.