According to the U.S. Energy Information Administration report the U.S. carbon dioxide emissions have dropped to their lowest point since 1994.
How is that possible, you ask? Well, the decline of coal as a power source and the increased use of natural gas is a big part of it.  With the increase of natural gas, energy related CO2 emissions have decreased over 12% since 2007. The U.S. produced 211.8 billion kilowatt hours more of electricity from natural gas in 2012, while coal power declined by 215.2 billion kilowatt hours, thanks to cheaper shale gas.
Annual Change in generation by fuel type in 2012
Currently about 40% of the world’s electricity is generated by burning coal, while about 21% is generated by burning natural gas; however, that number will continue to grow thanks to the lower natural gas prices and the continued lowering of emissions.
Power plants that run on natural gas not only emit half as much carbon dioxide, but they also emit five times less nitrogen oxide, 90 times less sulfur dioxides, and much lower levels of mercury than plants that burn coal. Burning coal produces more pollution and more greenhouse gases than burning natural gas.
The U.S. recently surpassed Russia to become the largest producer of natural gas in the world. But don’t fret; the globe has an estimated 850 trillion cubic meters of recoverable natural gas reserves, so there is plenty more to go around.