> Just to be clear: the idea that you "have to" use Kelvin or Rankine for temperature differences is objectively false. It's perfectly coherent to have a temperature difference of 5 degrees Celsius. You can add it to a temperature of 20 degrees Celsius, and you'll get a temperature of 25 degrees Celsius. We never need to bring some external unit into this picture: not in real life, and not in well written software interfaces.

It’s not that hard, you structure providing the definition of Celsius can just simply have Kelvin as its gauge at the relationship would be trivial to handle in software.
As for the rest, Let’s agree to disagree.



> The idea that it "shouldn't be strange to a climate scientist" that temperature differences in Celsius don't exist is, of course, patently absurd. Climate science as a vocation has chosen to communicate the thresholds for temperature differences in units of degrees Celsius. Here is just one example: https://www.un.org/en/climatechange/science/climate-issues/degrees-matter

I think there’s a big difference between Scientists and laypersons, and just because you see literature being written this way it doesn’t mean it is technically correct.
The target audience here is people who deal with these numbers in an informed manner, those would be scientists and engineers not layperson.

> I'll reiterate my call for you to explain how you think a hypothetical standard units library ought to tell its users how to convert temperature differences from Celsius to Fahrenheit. Seriously: what line of code do you want to tell them to write?

You don’t have temperature in Celsius or Fahrenheit.