I've given thought to this but didn't follow through yet because of it being near 0 degrees out lately.
I have two cold air returns which I felt would be more than enough current to pull the warm air up the staircase.
We've just moved into a fully remodeled home and have found that the upstairs is FREEZING. So, I ran a few tests to see what was going on.
Basically there is an open staircase which is very warm until midway up - It is like hitting a wall of cold air after that.
I took a lighter and lit...