The climate story on natural gas is gnarlier than ever. First there was a paper from Robert Howarth of Cornell claiming that natural gas from fracking is worse than coal, as far as net warming effect on the earth. Now the Department of Energy's National Energy Technology Laboratory (NETL) has fired back, sort of, with a report that seems to have already been in progress when Howarth published his.

NETL says that when natural gas is used to produce electricity, it results in 50 percent less greenhouse-gas emissions than coal over a 20-year time horizon, and 54 percent less when looked at over a century.

This is good news for those who would like to see us use natural gas as an immediate, drop-in replacement for coal in power generation. But it doesn't change the fact that fracking is one of the nastier means of resource extraction we have, with a potentially enormous footprint in areas of the U.S. that are already fairly densely inhabited.

Plus, there's a sleeping dragon when it comes to natural gas: The distribution systems are leaky. Howarth told this reporter that natural gas distribution systems in, for example, Philadelphia could lose as much as 3 percent of the gas they transport. Most of the gas used in this country is put through these systems, rather than used for electricity production, which means there is potentially a large source of losses directly to the atmosphere that we haven't even accounted for yet.

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