Water vapor is more complex than CO2 alone. Water vapor creates clouds both high and low, water clouds and ice clouds, day clouds and night clouds. Without the water vapor effects, the CO2 wouldn't be causing much warming. But water vapor effects vary much more than CO2 effects.
Water vapor effects also include thunderstorms and hurricanes, which move around hot tropical air and have a net cooling effect on the earth, by moving hot air to a higher altitude. Or so it seems.
So climate is in chaos, limited by the laws of thermodynamics.
Speaking of water, it appears that some significant fraction of the heat is going into the deeper oceans. We're not sure how much, not sure how it gets there, and not sure how long it will stay. These are all open research questions.
So while sensitivity shows no sign of being negative, it isn't very predictable. And, in fact, estimates of sensitivity have been wandering up and down for some time now. We need to know the sensitivity of the temperature of air at the earth's surface to CO2, water vapor, methane, and so on. But the total energy added can distribute to the deep sea as well, so surface temps aren't simply dependent on energy added.
The amount of energy that would raise the air temperature by two degrees, would only raise the deep sea temp by a tiny fraction of that, due to the difference in the heat capacity of water vs air. So temperature-change is not related to the energy added in a simple way.
Whatever the answer, it ain't simple.