The Celsius temperature scale is an interval scale [0] which means that it is possible to calculate differences but not ratios. The Kelvin temperature scale is a ratio scale [0] (it has an "absolute zero") that allows to do that.

Beside that if there are uncertainties involved, one should do proper propagation of uncertainty anyways. [1]

[0] https://en.wikipedia.org/wiki/Level_of_measurement

[1] https://en.wikipedia.org/wiki/Propagation_of_uncertainty