You confuse overpopulation with overcrowding.

Yes, how does biological weapons sound? Solve our population problem instantly, cheap and self replicating. Nobody would believe we scientists are the ones doing it because we've taught them to dismiss all conspiracies as theories.
It's awesome to be able to throw away all ethics to achieve this and yet conveniently we could blame it on nature and god's wrath.

That is exactly how I would do it if I am a scientist being given this task and  I am left with no morally acceptable choice to save the planet.

Won't work. To make something you have to take it from somewhere. Everything is taken from the earth. But there's a limit to how much we can take.

Unless we have a 'replicator' like in the Star Trek, there's no way we can solve this without taking from the planet even more.