Smoke without fire
Surprisingly, global action on ozone depletion was initiated without finding a smoking gun.
Mandated by the UN, the coalition forces invaded Iraq in 2003, to destroy its "chemical weapons of mass destruction," without finding a smoking gun. That's the negative; there's also been a positive. Thirty years ago, member-states of the UN reached amazing consensus without any sign of a smoking gun and sealed a deal to initiate daring action. To dramatise the story, 24 countries on that day decided to start destroying what could be called "chemical weapons of mass destruction" that were being emitted, albeit unintentionally, in millions of tonnes annually and getting "stocked" in the sky. Those groups of chemicals were called ozone-depleting substances, mainly chlorofluorocarbons (CFCs), which were predicted to be the cause of the destruction of the Earth's defence system – the stratospheric ozone layer.