Coal production in Appalachia emits 1 million tons a year of potent greenhouse gas. It isn't CO2.

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5. It's Also About Efficiency

A coal plant recover only about 34% of the heat to electricity. Comparable combined cycle gas plants recover 67% of the heat and convert it to electricity. Smaller combined cycle gas systems like some universities use can covert over 80% of the heat into electricity or some other use (steam from the boiler for heat or something else).

Another side benefit from using gas is that it's generally cleaner than coal (just the combustion process, extraction/development emissions are something else). So as the US has switched from coal to gas, ozone forming precursors like nitrous oxides and particulates and sulfur dioxide pollution have gone down improving air quality, pollutant fall out (sulfates and nitrate loading) and visibilities. Unfortunately, the legacy of coal extraction, including acid mine runoff and scared landscapes will probably be around for centuries.

I don't think we'll ever completely wean ourselves off of fossil fuels. A renewable system will probably need some input from gas or diesel to maintain grid stability. I'm hopeful the next few decades will be transformative on how we produce and use energy.