Want to do your part to fight global warming?   If you live where it's frosty, maybe you should consider relocating to the Sunbelt.

That's one way of reading an analysis published in the current issue of Cities, the International Journal of Urban Policy and Planning (abstract only, must pay to see full text).

Heating and air conditioning account for over half of residential energy use, according to the "viewpoint" article by Michael Sivak, a professor with the University of Michigan's Transportation Research Institute.

Sivak looked at energy demand for the 50 largest metropolitan areas in the United States, where more than half the population lives.  He toted up the heating and cooling degree days for the metro areas as an indicator of how much residents would crank up their AC or furnace, depending on the weather. 

(Heating degree days are an index of the energy needed to heat buildings, he notes, while cooling degree days are a ranking of how much juice it would take to chiill a sun-baked building.)

San Diego came out best in Sivak's ranking, with the lowest combined heating and cooling score, while Minneapolis fared worst.  Baltimore came in 30th, two notches below Washington and just ahead of New York and Philadelphia.

The 25 metro areas with the lowest combined energy demand are all in the Sunbelt, with the exception of Portland and Seattle in the balmy Northwest.  The chilliest metro areas turn out to have much higher overall energy demand - heating apparently consumes a lot more energy than cooling does.

Of course, as anyone knows who's argued with a roommate over where to set the thermostat, people vary in how much heat or cold they can take.  The amount of energy needed to keep a home warm or cool also depends on how well insulated it is, and on the efficiency of the home's appliances, air conditioning and furnace.

So maybe instead of bailing out the Big Three automakers, Congress should offer incentives for everyone living in Detroit to move south.  While we're at it, clear out those big cities in the frigid Midwest and Northeast.  And since Baltimore is a bit on the chilly side right now as well, perhaps we ought to start packing, too, and get across the Potomac.  Imagine what that would do for the slumping real estate market in all those Sunbelt cities! 

But before we force everyone to live where it's warm, maybe we ought to do what we can to trim our residential carbon footprint.  Get a home energy audit.  Upgrade insulation.  Get more energy- efficient windows and appliances.  

Or, if a new furnace is not your idea of a holiday gift and you really can't afford anything else right now, turn down the thermostat and put on an extra sweater.