I have a friend who will never idle his car with the AC on. His justification: 10 minutes of discomfort isn't worth the emissions output. He knows it's a minuscule drop in the surface tension of a drop in the bucket of carbon output but he will never ever do it, no matter how hot it is. And he'll subject his passengers to discomfort in service of his principles.

At the same time he flys from LA to Europe 5+ times a year.

It's hard to truly live ethically in such a deeply unethical world.