Companies bet carbon labels can help the climate. Will consumers catch on?

The world is littered with labels — markers that tell you how many calories are in a candy bar or if a tomato is organic.

Now, companies are creating labels to show consumers the environmental costs of their daily habits. Carbon labels have already cropped up on salads, sneakers and even face creams. Unilever, the maker of Dove soap and Lipton teas, has said it will add labels to all of its 70,000 products.