[mhb]

The mild winter is an effect because of the time period at which they're looking. Without additional data, one might expect that global warming implies both warmer winters and warmer summers.

Total heating in winter uses more energy than cooling in summer because there is a bigger difference between the outdoor temperature and the target temperature in winter than in summer. Just based on this article, one would expect the delta of warmer winters and warmer summers to roughly offset each other.

So it doesn't seem sound to conclude, based on this article, that, if the CO2 emissions were looked at over a full year, that the warmer winter would result in a net CO2 reduction.

[bromley]

Also, cooling systems are generally less efficient than heating systems, which would increase summer energy consumption (and CO2) more than the reduction in winter.

That's assuming the overall US climate (by which I mean population- or energy-consumption-weighted degree days) necessitated similar amounts of winter heating and summer cooling.

[millerski150]

I agree global warming does imply warmer winters and summers. I'm not sure if you're addressing the article or what I wrote, but if you look at C02 emissions over a full year, I doubt the warmer winter would result in a reduction of total annual C02 production, because summers will now require more energy & C02 (to cool). I'm saying the title is misleading because just because a small reduction in the US' winter's C02 doesn't mean the planet is cooling (or global warming is reversing) ... especially if you factor in developing world emission growth, which I didn't mention before.