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How does climate change research establish causality?

How does climate change research establish causality? For example, when it is said that human activity causes global warming, what sort of logic is used to justify this claim?

Let's not get into the debate of does it or not, it's tagged philosophy not politics :) I am asking how the mainstream climate change research community draws these inferences, not whether they are correct.

* Normally, causality between X and Y is established with direct controlled experiments where you change X and then look for a corresponding change in Y, which is absent when you don't change X. But even if you could do experiments on the whole planet, you only have the one, so what about the control?
* It's common to present simulations, but it's not clear to me how you would conclude that something which happens in a simulation *must* happen also in reality
* There are small scale experiments, but it's not clear to me how you would conclude that something which happens in an experimental model *must* happen also in the full system

Is causality taken to be "proven" in the sense that, although lack of causality has not been strictly falsified, given the quantity, diversity and precision of data, the simulations, the experiments, and logical reasoning from known principles, it seems incredibly unlikely that there isn't causality? So do we say global warming is *caused*, in the informal sense of (very) *probably caused*? Or is there actually hard evidence of the causality?