U.S. carbon-dioxide emissions have dropped 13 percent since 2007. He mentions the usual factors: the recession, better fuel-efficiency for cars and trucks, the switch from coal to natural gas.
By now, the shale-gas story is well-known. Four years ago, natural gas cost around $9 per million British thermal units — too costly for most electricity needs. But recently, thanks to big advances in drilling techniques, companies have been able to extract gas from shale-rock formations in places like Texas and Pennsylvania. Natural gas prices dropped below $2 per million BTUs last year. As a result, electric utilities switched from coal to cleaner natural gas, which emits less carbon when burned. And there is plenty of it – because of fracking we have unlocked a treasure-trove of natural gas- enough to power us for another 200 years.