The climate change I'm talking about is going from indoors to outdoors, or when the seasons change from cool to hot. Just the other day I played outside for a few hours. It was relatively cool, in the evening but quite humid. Everything was fine. A few days later I took the bass out of the case the action was noticeably higher. I left it for a few days but it never rebounded and I had to readjust it. It seems that you have a bass in the air conditioning and take it outside for a while and then back to the same conditions the neck would return to its previous state? Obviously not! This has happened a couple of times before, usually around a gig, meaning I've taken the bass out of the house for a while. But its not always a problem. Most perplexing. Other instruments don't seem to care as much, or at all. I'm assuming its humidity doing this and not some other agent. I'm also assuming there's not much I can do about it or we'd all be doing it. Sigh.