Not quite. There's still the matter of the Callendar effect: CO2 increases. -> World warms a litte. -> Baseline level of water vapor in the atmosphere increase

Not quite. There's still the matter of the Callendar effect: CO2 increases. -> World warms a litte. -> Baseline level of water vapor in the atmosphere increases. -> water warms a little more. -> Baseline level of water level... That's where computer modeling becomes important.