Why do I need less priming sugar when bottling a colder beer?

I will be bottling an American Wheat today. I usually bring the carboy out in the garage the night before bottling to let everything settle before I bottle the next day. I brought the carboy outside last night and it got down to about 45F last night and right now it is 49F. So, I know that you need to use less priming sugar when the beer temp at bottling is colder.

Beermith says that bottling at 50F requires 4.13 ounces compared to 5.20 ounces at 70F. Why the big difference in amount of priming sugar when bottling cold? The beer will be at 70F after it is bottled.

Because colder beer absorbs and retains more CO2. While your beer is fermenting, there's a constant supply of CO2 that bubbles through it that creates the airlock activity. Some of this CO2 doesn't make it to the surface, but stays in solution in the beer. More of it stays in solution at colder temperatures.

There's a discussion about this in the Science forum.
If your beer is still fermenting, it will reach a new CO2 equilbrium at the lower temperature.
I don't think this would happen overnight, so I would use the previous temperature to calculate priming sugar.

Thanks. I went and searched for the link. They sure explored the idea of priming sugar in that thread. Wow!