If you have any links I'd be very interested to see them. Happy to be proven wrong here, but when most (all?) of the research is based in modelling I don't see how you'd prove causation, especially in such a large system that you can't test with and without the intervention in question.
By related to I assume you mean correlates with though. To be fair, we can't say there is a causal link (even if it does seem very likely).
We can TOTALLY say that there's a causal link, it's been proven by scientific stories
If you have any links I'd be very interested to see them. Happy to be proven wrong here, but when most (all?) of the research is based in modelling I don't see how you'd prove causation, especially in such a large system that you can't test with and without the intervention in question.