Each unit of electricity produced by NG is a 50% cut in released carbon and a step towards renewables.
And, unlike coal plants, you can shut down gas turbines when demand is low. Coal plants are kept spinning 24 hours a day even if there is no use for the power, so we would probably get a greater than 50% cut in emissions.
Great thoughts on transitioning from coal, nuclear and Natural Gas
Hybrid gas/thermal solar turbines... Throw in a very large measure of efficiency as well as the ability for co-generation.
Run the turbines as much as possible on solar produced steam, switch to NG when the sun goes away.
That creates a gas turbine system that uses 25% or so less gas (and produces less CO2) and makes thermal solar much more affordable because the turbines aren't sitting idle for large parts of the day.
Natural gas, wind, and solar can be installed quite rapidly and can get us off of coal faster than any other method... Then as we reduce our need for natural gas we can start replacing a meaningful percentage with biogas from sewage systems, agricultural wastes, manure, etc... read full and comment here