Let's take a very crude stab at a first order analysis.
Suppose that in order to overcome the natural energy input that drives weather and thus hope to exert some effect and a control, Man must add an additional, say, 10%. An overhead Sun bathes the Earth with about 1,000 Watts per square meter. And so Man's input energy would have to be some 100 W/m^2. If an area of, say, 100 km on a side were to be targeted, that's an area of 10^10 (10 billion) square meters. The added 10^2 W/m^2 over 10^10 m^2 is a total input of 10^12, or one trillion Watts. That's a thousand thousand megawatts! I guess back in the 60's/early '70s the US had installed a good number of nuclear power plants, eh?
My point is this. The energy density of the atmosphere is considerable. Man's puny output can apply but a tiny ripple. (Greenhouse gases are another thing entirely.) Over large cities we can see subtle influences, to be sure, such as a heat island effects. But that doesn't amount to what we'd call a meaningful modification of weather that could be 'weaponized.' And that's involving the Sun (warming the seriously denuded land replaced by a conurbation) and the waste energy of Man in concert.
Cranks who think we have an abundance of energy to surreptitiously beam into the sky as laser emission and thereby alter weather on any meaningful scale clearly do not grasp basic physics.
