The Globe and Mail reports in its Monday edition that on-line shopping is a convenience that comes with a climate cost. An Associated Press dispatch to The Globe says multiple factors shape the environmental toll of a delivery. These include the distance from a fulfilment centre, whether the shipment rides in a half-empty truck, how many trips a driver makes in the same area and the type of transportation used to move the package. When customers choose faster shipping and earlier delivery dates, the system shifts from optimized routing to whatever gets the package out fastest, and that means higher emissions, said Sreedevi Rajagopalan, a research scientist at MIT's Center for Transportation and Logistics. For example, trucks may leave warehouses before they are full and drivers might loop the same neighbourhood multiple times a day. One way companies such as Amazon try to minimize that is by placing their supply chain closer to customers. Their goal is to make the journey fast and effective, but reduce its emissions at the same time. Getting items to customers' doors from a fulfilment centre -- referred to as the "last mile" or "last kilometre" of shipping -- is one of the hardest stages to make less polluting.