See the article 28 July 2013 in NYT by Anthony R. Ingraffea:
http://www.nytimes.com/2013/07/29/opinion/gangplank-to-a-warm-future.html

As I explain in my book Toxic Capitalism, fracking (hydraulic fracturing) might be a great new technology but if not done properly it carries very heavy risks for the environment. One of the dangers I mention is methane.

As Ingraffea mentions, methane is a far more powerful greenhouse gas than carbon dioxide, though it doesn’t last nearly as long in the atmosphere. Still, over a 20-year period, one pound of it traps as much heat as at least 72 pounds of carbon dioxide. Its potency declines, but even after a century, it is at least 25 times as powerful as carbon dioxide. When burned, natural gas emits half the carbon dioxide of coal, but methane leakage eviscerates this advantage because of its heat-trapping power. This is the gas that is released into the atmosphere unburned as part of the fracking process, and also from pipelines, compressors and processing units.

A 2011 study from the National Center for Atmospheric Research concluded that unless leaks can be kept below 2%, gas coming from fracking lacks any climate advantage over coal. And a study released this May by Climate Central, a group of scientists and journalists studying climate change, concluded that the 50% climate advantage of natural gas over coal is unlikely to be achieved over the next three to four decades.

But be sure, the fracking lobby does not want to talk about this.

Our solution? Waste less, consume wisely, reduce energy consumption, and don’t cut corners in the quest for energy and raw materials.