That's not longer a clear cut yes/no poll. Choose the wording as you like Dave, but must leave just two options, IMO.
The answers are not the problem, the question is.
Nothing is "sure", so by default the answer can be nothing but "no", whichever words you want to use.
That is not to say that anthropogenic global warming (that is what we're talking about, right?) is not occurring, or that the global warming that is occurring is not anthropogenic, just that we can never be certain.
However, all the data we have point that way, and if it looks like a duck, quacks like a duck and has face like a duck, it's most likely a duck*.
Instead of complaining about Dave adding another answer as an option, perhaps you should work on the question itself.
* It could also be our supreme reptilian overlord in a duck body.