From my experience, it's not the terrible twos it's the terrible threes. It's then that the tantrums started because they want to do so muc themselves but can't because they are only 3. It sounds to me like your son is very curious and likes to explore. That's a good thing! It will drive you nuts, but it's a good thing for him. LOL
You will just have to do preventative things like screwing the vents down and finding ways to limit where he can climb. At the same time, you find places and ways that it is ok to climb and explore. Redirect and show him what is ok and safe to do.

Good luck!

__________________