Greenhouse gasses are generated by old codgers on allotments growing tomatoes in grow-bags in their B&Q greenhouses.
Ultra-Low-Frequency electromagnetic Boredom Waves are generated by 'The Archers' on Radio 4, and these spill out of the speakers of their paint-spattered 1960's Pye five-transistor radios, pooling in the stacks of cracked plastic flower pots strewn all over the place. Overnight as the temperature drops, the waves react with the plastic of the grow-bags, using discarded Werthers wrappers as a catalyst, to produce greenhouse gasses.
Greenhouse gasses cause heating because the molecules have a spare carbon atom that sticks out like a splinter and catches on clouds, isobars, ozones, etc creating sparks. Oxygen in the air catches fire from the sparks creating hot Aurora Borealises, heating up the planet.