Methane hot spot in US is 3x expected size:

One area in the United States is spewing vast amounts of methane, a potent greenhouse gas, into the atmosphere far faster than expected, US space agency researchers said Thursday. Satellite data show more than triple the estimated amount of methane is coming from near the Four Corners intersection of Arizona, Colorado, New Mexico and Utah. 
The study by NASA and the University of Michigan spanned the years of 2003-2009, before hydraulic fracturing for natural gas began in earnest in the area, signaling that fracking is not to blame. Rather, the persistence of the emissions "indicates that the source is likely from established gas, coal, and coalbed methane mining and processing," said the study in Geophysical Research Letters, a journal of the American Geophysical Union. 
The hot spot area is about 2,500 square miles (6,500 square kilometers), and each year has released about 0.59 million metric tons of methane into the atmosphere. "This is almost 3.5 times the estimate for the same area in the European Union’s widely used Emissions Database for Global Atmospheric Research," said the study.