As far as I'm aware, clean coal usually does not refer to the CO2 emissions of the coal, but instead to the particulate emissions and the like. As such, while it will significantly reduce local pollution problems (relative to traditional coal technologies), it will have no direct effect on global warming. In fact, it may indirectly make global warming worse, because the absence of a smelly plant belching nasty black smoke may make people less willing to switch from coal to renewable resources like solar, wind, and biomass.
edit:
Jyush, look up marine cement... we can make carbon-neutral concrete today. Depending on the engineering characteristics needed, we may even be able to make carbon-negative