he's not eating because he's three years old and got cold when you brought him home... this triggered his body to throw up a red flag that it may be breeding season... thus he won't eat. his feeding response is still there but there's no will to eat.
to say all carpets climb is a misnomer - only 1/3 of mine do at all.
that's my theory... there's really no way to even guess. just don't offer food for a couple weeks if his weight is fine.