Is Winter the Greenest Season?

The Minnesota weather decided to bestow a favor on us today. Around noon, it warmed up to a balmy -20. Add the freezing temperature to the piles of snow and the sheets of ice covering the roads, and people don’t seem to be getting out much.
And this makes me wonder, is winter our greenest season? People are still driving- we have to get to work. But more carpools appear to be popping up, and a larger number of my colleagues are talking about taking the bus. Either they don’t trust themselves on the road, or more often, they don’t trust other drivers’ abilities on the ice. And even those who are driving are doing so less than before. Work is a requirement, but other pursuits are being put on hold or largely omitted. It’s just too much hassle to fight the wind, the roads and the cold to make going out to dinner worthwhile.
I see car after car in the parking lots buried in days worth of snow. Clearly, they’ve not been driven. With the driving rate down, carbon emissions must have dropped. And I’m just guessing here, but I don’t think anyone is using their car’s air conditioner.
Carbon Dioxide (from exhaust) and CFCs (from air conditioners) are two of the worst offenders of greenhouse gas pollution. So have we (or more accurately, has the winter weather) made a sizeable dent in the amount of pollutants our cars send into the atmosphere?
I can’t seem to find studies that address this specific question, though logic leads me to believe the answer is yes.
However, total carbon emissions go up during the winter due to residential heating needs. According to Rupert Posner, Australian Director of the Climate Group, “Cold weather generally does result in higher greenhouse gas emissions as we have our heaters running that bit harder.” ( http://www.theclimategroup.org/news_and_events/greenhouse_indicator_winter08/Editorial ).
Perhaps as the weather warms up, we can continue our winter driving habits of carpooling, using public transport, and walking. Combine this with lowering the heat in our homes, and we might be able to slow the rate of greenhouse gas build up.
And for now, let’s remember to turn on the heat only as needed. Put on a sweatshirt rather than adjust the thermostat, so we don’t undo all of winter’s hard environmental work.