dichloromethane, a substance with uses varying from paint stripping to agricultural fumigation and the production of pharmaceuticals. The amount of this substance in the atmosphere decreased in the 1990s and early 2000s, but over the past decade dichloromethane became approximately 60% more abundant. "This was a major surprise to the scientific community and we were keen to discover the cause of this sudden increase," says Oram.

Solar panel manufacturing, among other things. The silicon cells are cleaned of chemical residues with dichloromethane, which is then evaporated off. It's also used in solvent vapor annealing processes used for depositing thin organic films, like anti-reflective coatings on the glass.

Knowing the Chinese, they probably don't keep too close a watch on whether the vapors end up the smoke stack, because it would cost more to clean it up.