Priming sugar

I am going to bottle a belgian here soon and so I looked at the calculation for priming sugar additions. I see that changing the temperature makes a significant difference in the amount of sugar , but why? Also when is this temp measured? is it what temp I intend to store the bottles at while carbing?

The temperature for priming is the temperature of the beer when you prime it.  It makes a significant difference because there can be 1.0 Volumes or more of CO2 left in the beer from the fermenting process.  Depending on temperature, the beer will contain more or less CO2 when you prime it and seal the bottle.

Cheers!
Brad

You can't just take the temp of the beer though. What you need is the warmest temperature the beer held last during any active fermentation. IOW, if I ferment, then condition at 60° and chill before priming (weird I know, but as an example) I can't use "42°" for my priming calculations, since it likely only has the CO2 of a 60° beer, albeit better held in suspension.
Definitely no easy way to figure it all, and racking will release "some" of the CO2.
Wait - I have an idea! KEG!!!