In addition, other studies have found basal rates change because of consistent exposure to heat and even food -- but the adaptation is much less.
However, I confess to being a little sloppy in the original post for this reason: I was allowing the basal metabolism number to fill in the gap on calorie burn during sleep and a few other "core" areas. I just didn't want to bog the thing down with being too specific.
I also didn't include the calorie burn required to digest food etc -- I felt the core point could be made even while excluding those values and allowing the basal rate to be their proxy.
So to clarify, while there is a small change to the basal rate in cold climates, the dominant reason our hypothetical man can go from 1,770 kcals per day at rest in temperate climes to, say, 2,500kcal burn in the subarctic has to do with the extra calories burned to maintain body temperature while at sleep -- and this is well documented in the literature.
Incidentally, it's also documented that acclimatized outdoors people spend roughly 30% fewer calories to maintain body heat at sleep in cold climate than non-acclimatized people. However that acclimatization benefit takes about a year to kick in.
Thanks for calling me on this one, Hoodoo -- I guess I should have made it clear from the start. As it was I didn't think anyone would read such a long post. Guess I was wrong