Boulder, one of the first U.S. cities to do curbside recycling, has marketed itself as a place for health and the environment . The parking lot of its main retail district has reserved spaces for alternative-fuel vehicles. Now, the warm-up jerseys of the Rapids U-23 team implore fans to “Kick Global Warming.”

The new campaign was the idea of Ben Bressler, founder and director of an environmental travel company based in Boulder. It was inspired in part by his trip to the World Cup, where organizers declared their event carbon neutral. Any pollution generated by the games — from travel to the burning of stadium lights — was offset by donations to plant trees in Africa, or by replacing coal-powered stoves in Somalia with solar-powered grills.

Bressler decided to make his travel company carbon neutral in this same way, paying a third party to cover carbon emissions from plane trips and similar activities.