What tinnitus was politely trying to tell you is that you royally screwed up that calculation. To convert a temperature from Fahrenheit to Celsius you do as you say: subtract 32 (because 32 F = 0 C), then multiply by 5/9 to get to the right scale. To covert a temperature difference from F to C there is no subtraction - you just do the multiplication by 5/9. Which means that the Arctic was actually a whopping 25 degrees Celsius above average.
