>>maybe he missed the fact that the Paris Deal was not binding

Sorry I already responded before I saw this.

Agreed. And each nation gets to set and alter its own targets. So why pull out altogether?

IMHO a lot of this revolves around the negativity directed at Trump since he won. The recent decapitation stunt is widely deplored, but simply reflects the idea that it's open season on Trump. I perceive a distinct European hostility towards the US that actually has existed for a while, but is displayed in its full glory now that it's cool to attack Trump.

From his POV: he can see that European "allies" have not met their NATO contributions, so perhaps he feels the Paris nationally determined contributions (NDC) will go the same way, with US feet held to the fire to meet its targets while everybody else freeloads.

That is the precedent displaced to him by the Europeans and he won't have been impressed by their snarky response when he pointed it out.

My thought: he saw little value in another treaty with antagonists whose own recent track record of meeting obligations, is poor. Recent lashings-out would have reinforced this.

He's a proud man. Just as it's a role for management to sort the unusual egos of very smart people doing the best work, international politicians ought to see that lashing out at Trump reliably causes him to raise the draw bridge.

Seems to me that all those who enjoy lashing out at the man, might like to take a look in the mirror and ask themselves what they thought would happen when they kept poking the bear.