a single statement to which you, presumably, want to attach some single truth value
It would be a probability, actually, and it would need a lot of tightening up before it would make any sense even to try to attach any definite probability to it. (Though I might be happy to say things like “any reasonable tightening-up will yield a statement to which I assign p>=0.9 or so”.)
your statement consists of multiple claims from radically different categories
Yes, it does.
For the avoidance of doubt, in writing down a conjunction of three simpler propositions I was not making any sort of claim that they are of the same sort, or that they are equally probable, or that they are equivalent to one another, or that it would not often be best to treat individual ones (or indeed further-broken-down ones) separately.
Jamming three very different claims together and treating them as a single statement doesn’t look helpful to me.
It seems perfectly reasonable to me. It would be unhelpful to insist that the subsidiary claims can’t be considered separately (though each of them is somewhat dependent on its predecessors; it doesn’t make sense to ask why the climate has been warming if in fact it hasn’t, and it’s risky at best to forecast something whose causes and mechanisms are a mystery to you) but, I repeat, I am not in any way doing that. It would be unhelpful to conflate the evidence for one sub-claim with that for another; that’s another thing I am not (so far as I know) doing. But … unhelpful simply to write down a conjunction of three closely related claims? Really?
In what sense (other than writing it down, and suggesting that it summarizes what is generally meant by “global warming” when people say they do or don’t believe it) am I treating it as a single unit?
It would be a probability, actually, and it would need a lot of tightening up before it would make any sense even to try to attach any definite probability to it. (Though I might be happy to say things like “any reasonable tightening-up will yield a statement to which I assign p>=0.9 or so”.)
Yes, it does.
For the avoidance of doubt, in writing down a conjunction of three simpler propositions I was not making any sort of claim that they are of the same sort, or that they are equally probable, or that they are equivalent to one another, or that it would not often be best to treat individual ones (or indeed further-broken-down ones) separately.
It seems perfectly reasonable to me. It would be unhelpful to insist that the subsidiary claims can’t be considered separately (though each of them is somewhat dependent on its predecessors; it doesn’t make sense to ask why the climate has been warming if in fact it hasn’t, and it’s risky at best to forecast something whose causes and mechanisms are a mystery to you) but, I repeat, I am not in any way doing that. It would be unhelpful to conflate the evidence for one sub-claim with that for another; that’s another thing I am not (so far as I know) doing. But … unhelpful simply to write down a conjunction of three closely related claims? Really?
You can, of course, write down anything you want. But I believe that treating that conjunction as a single “unit” is unhelpful, yes.
In what sense (other than writing it down, and suggesting that it summarizes what is generally meant by “global warming” when people say they do or don’t believe it) am I treating it as a single unit?
As I mentioned, I don’t want to restart the discussion. Feel free to discard my observation if you don’t find it useful.