Home Not Cooling Evenly

I have a running joke about my house:  I think they installed the insulation backwards, because in the winter, the house is colder then it is outside, and in the summer it is hotter.  Though not completely accurate, I have always been perplexed by the thermal dynamics of this property.

Lets start off with some background.  Like most of the Washington, DC, area (and east coast cities) my home is a "town" house.  Generally speaking, a town house is wider than a "row" house.  A town house is typically two rooms wide, whereas a row house is one room wide.  In both cases, the home would be several stories tall and several rooms deep-- potentially half a city block deep.  (In Tennessee, a house that is one room wide and several rooms deep is called a "shotgun" house, because you could shoot your shotgun in the front door, and blow out the back door.  Sigh...  Tennessee was such a fun place.)

In my case, when you walk in the front door, you can turn right to the living room, walk down a flight of stairs to the master suite, or walk up half a flight to the kitchen, dining room, family room.  So, that's two and a half stories.  From the downstairs master suite, you can go down another level to the computer bunker (ie: basement.)  From the kitchen, you can go up a story to more bedrooms. Thus, we're at four and a half stories.  Turns out there is enough room in the roof, for another 15x17 room, but its never been built out.

The dominate feature of the town house, is the pseudo-spiral staircase.  I call it pseudo-spiral, because its a rectangular box, the size of an elevator shaft, running from bottom to top.  There are three stairs, a set of four stairs at 45 degree angles, then three stairs, and two stairs at 45 degrees.  (If your not good at geometry, you just climbed one story and turned 270 degrees, so you are facing to the left of where you started.)  There is a small landing, and then another sequence of steps.  Repeat this once down and twice up.

I call it the M.C. Escher house:
 

But here's what you really need to know about the house:  Using my new Harbor Freight Non-contact Laser Thermometer, I have verified that at the lowest climate controlled point of the house, to the highest climate controlled point in the house, there is a thirty degree temperature variation.

Yes, that right: 30 degrees Fahrenheit!  With the thermostat set on 85 degrees, and an outside temperature of 75 degrees, the baseboard of the master suite is 65 degrees.  The largest bedroom upstairs has a 12 foot vaulted ceiling.  At the peak of the ceiling, the temperature is 95 degrees.  And these are ambient temperatures-- the AC is not running!

First questions: Why such a huge temperature variation?  Simple answer:  Heat rises, so the stairwell acts as a ventilation silo that allows all the hot air to rise, and cool air to sink.

Second question:  How do I fix it?

And so we begin...