Whether there is global warming or not, a smaller global footprint by each person has a positive impact on the environment in general. And if your electricity bill is $5 cheaper because you diligently turn off the lights, there's one less scoop of coal out of the strip mine, and there's one more beer for you to drink.
"Oh Beautiful for smoggy skies, insecticided grain,
For strip-mined mountain's majesty above the asphalt plain.
America, America, man sheds his waste on thee,
And hides the pines with billboard signs, from sea to oily sea.”
George Carlin