The demand for local warehouses to speed up those orders also has an effect, Carnegie Mellon's Costa Samaras said. Those buildings need power, heat and cooling, and that means more emissions.

This doesn't mean you'll have to permanently settle on slow deliveries if you want to be kind to the planet, but it may be a while before emissions are less of an issue. Courier companies are gradually switching to hybrid and electric delivery trucks that improve their side of the equation, while the rise of delivery drones could also help. However, the data suggests that efforts to pursue carbon-neutral shipping are not only necessary, but might not be going far enough to catch up with increasing demand.