Aviation’s carbon footprint spreads beyond the exhaust spewing from the engines of high-flying passenger jets.

It’s also the ground operations of airports — everything from the buses ferrying passengers to their planes, to the little car with flashing lights that guides aircraft to their parking places, the electricity that powers the machines that make pricey cappuccinos in food concourses and the garbage removal that keeps airports clean.

To put that into concrete terms, while the aviation sector is responsible for about 2 percent of the world’s greenhouse gas output, airports account for about 5 percent of the sector’s total.