San Jose Mercury News: Got climate guilt? Get out your credit card. If you’re concerned about the planetary impact of your driving, flying or other activities, you can buy carbon “offsets” – a kind of environmental pardon for buying a sport-utility vehicle or leaving the lights on. Heck, it’s easier than changing. Essentially, you’re contributing to a project that reduces earth-warming emissions to offset your own. But the fast-growing market for carbon offsets is confusing and lightly …