An analogy to global warming might help to further illuminate the issue:

Just because it snows one day, or even if it snows more than usual one winter, it can't be concluded that global warming is bunk and that global average temperature is not rising.

On the other hand, a drought in itself does not make global warming an infallible concept without some other contributions (e.g. empirical data). Notably, it also doesn't make sense given this hypothetical drought to disestablish the biggest polluters in hopes of somehow saving the smallest polluters, who are anyway potential "big polluters" themselves.