Natural gas extraction and post-closure methane emissions

In North Carolina, much opposition to fracking has reflected concern over air, water, and soil contamination.  At the national level, debate has also swirled around the potential impact of natural gas extraction on the global climate.  A recent PhD dissertation from Princeton University attaches numbers to a concern that has largely escaped notice until now: the potential impact of methane leaking, not from active wells, but from old wells that have ceased production.