So what would disprove global warming?
In the view of the warm-mongers, nothing can possibly disprove it (and absolutely everything proves it unequivocally.)
First the phrase has to be defined: the rise in average temperature of the planet in response to manmade CO2
Disproving is hard when faced with a theory that morphs to fit the data. For example the climate modelers predicted that El Nino would become more common as the world heated rapidly. That prediction happened conveniently after the El Ninos of the 80's and 90's and relatively rapid warming.
More recently the modelers are predicting the opposite: more La Nina. Conveniently there has been more La Nina. They are of course careful to use phrases like "La Nina-like conditions". They use that to pretend that the "missing" heat is in the deep ocean, but in fact it is still missing.
The short answer is "global warming" is not a theory worthy of the name so there is no need to disprove it. "Climate change" is so loosely defined it cannot possibly be called a theory.
I'll add two more theories: "the rise in CO2 is manmade" and "CO2 absorbs IR". To disprove manmade CO2 one would have show net ocean outgassing of CO2, but most evidence points towards the opposite such as pH and isotope ratios. To disprove that CO2 causes warming, one would have to invalidate some basic physics about molecular structure and photon interaction. Since those are not visible one must use indirect evidence such as empirical measurements that show absorption of particular wavelengths when CO2 is in a tube and IR is sent through the tube (versus other gases in the tube). In short, there is almost no chance that either "manmade CO2" or "CO2 absorbs IR" will be disproven.
It should be kept in mind that CO2 absorbing certain IR frequencies efficiently in no way proves that "global warming" is real. But the underlying mechanics of manmade CO2 and CO2 absorption of IR are not easily disproven. So the easiest thing to do is show that CO2 warming is negligible. One really easy way is that temperatures have risen a negligible amount for 17 years (since 1996 which was actually a coolish year).