The warming due to Co2 in the atmosphere, makes the warming due to water vapour worse.
There is nothing we can do to reduce water vapour in the atmosphere (unless you want to remove all the water out of all the world's oceans).
That is one of the reasons such a small concentration of CO2 can have such a large effect on the world's climate.
Thus the one and only thing we can do in connection with climate warming is reduce the concentration of CO2 in the atmosphere, by reducing our emissions.
