Tree hugger or not, we’re all aware by now of the undeniable global warming crisis. While there are many causes for the climate change, many are quick to point fingers at the airline industry (even though, according to an NPR report I heard earlier this week, travel accounts for less than 4 percent of the world’s carbon emissions.)

With so much focus on climate change in today’s world, a recent Consumer Reports analysis grabbed my attention: what is the “greenest” way to travel? To determine this, they went to Web sites that help consumers calculate carbon output, and the results varied dramatically.

Bill McGee of USA Today conducted much of the research for this study, which he outlined in his On the Road column. The bottom line, he writes, is that “if you're using carbon calculators to determine what your offsetting tab should be, you'd better cross-check your math.”