Well, double is 100% hotter. How would you express temperatures 1% hotter than today's average? Are you saying that can't be expressed?
Most physical quantities use a scale where zero means "none of what you are measuring", so any multiplication makes sense because saying something like "twice as long" would be the same physical length whether you used meters, inches, miles or cubits. Fahrenheit and Celsius don't start counting from a real zero point, therefore multiplication or percentage changes don't make any sense in them. You can only do that in a scale where zero means zero like in Kelvin. (or at least that's what I had beaten into me in a few physics and thermodynamics classes).