Warming from greenhouse gases is the driver of the warming, but there are multiplies. Most obvious one is water vapour which is a very powerful greenhouse gas.

Warming from greenhouse gases is the driver of the warming, but there are multiplies. Most obvious one is water vapour which is a very powerful greenhouse gas. So the warming caused by the raised CO2 enables more water vapour in the air (warmer air can take up more water) which amplifies the greenhouse effect. Then come all the secondary effects like melting of highly reflective ice and others.