Use the jumper battery to start the engine, then disconnect it and leave the engine running (with no current drain such as lights, heater fan, radio, etc). (mechanics.stackexchange.com)
I am a hero, all because I opened the doors and left the engine running. (automobilemag.com)
By leaving their engines idling for long periods, drivers contribute to air pollution, waste fuel, and produce noise and fumes that harm the environment and public health. (sciencedaily.com)