Cool charges us based on the footprint, and uses the money to buy emission permits away from tightly-regulated carbon markets in the U.S. There are only a certain number of permits available, and once Cooler buys up those permits, polluters have to find more sustainable ways to operate, stopping pollution at its source. This is a much more rigorous approach than carbon offsets, since offsets allow polluters to continue business as usual.
To learn more about Cooler, visit their website here.