There is plenty of evidence that leakyness is a common feature of natural gas infrastructure.
The Methane being leaked is 86x more potent than co2 over 20 years and 34x more potent over 100 years.
At 1% leakage todays natural gas emissions don't gain a climate advantage over coal until around 2100. At 2% leakage todays natural gas emissions are still significantly worse than coal in 2100.
https://www.technologynetworks.com/applied-sciences/news/glo...
http://theconversation.com/the-us-natural-gas-industry-is-le...