No, it's a silly distinction you're making between science and scientists.
No, it isn't.
Science is prescriptive whenever scientists want it to be.
No, science is never prescriptive. This is what people mean when they say, "Science is descriptive, not prescriptive." A trivial observation that you seem unable to grasp.
Scientists often testify before policy makers. Sometimes they're just reporting findings, usually they're there as advocates for something.
How about that. Depending on the questions asked, sometimes people provide facts, sometimes they offer opinions. What an earthshaking observation.
Q: Is the climate, in general warming?
A: Yes, that is a scientific fact.
Q: Are humans responsible?
A: Yes, that's established beyond any reasonable doubt at this point.
Q: What should we do?
A: Well, scientifically speaking... if we don't do anything, things will be bad. If we do something, the problem can be mitigated.
Q: STOP WAFFLING! What should we do?
A: Well, on the whole, I think we should do something. This is not a scientific result. Science does not provide values. But I, as a human being, can differentiate between a bad outcome and a not so bad outcome. I prefer the not so bad outcome.