Natural gas, with its reputation as a linchpin in the effort to wean the nation off dirtier fossil fuels and reduce global warming, may not be as clean over all as its proponents say.

Even as natural gas production in the United States increases and Washington gives it a warm embrace as a crucial component of America’s energy future, two coming studies try to poke holes in the clean-and-green reputation of natural gas. They suggest that the rush to develop the nation’s vast, unconventional sources of natural gas is logistically impractical and likely to do more to heat up the planet than mining and burning coal.

The problem, the studies suggest, is that planet-warming methane, the chief component of natural gas, is escaping into the atmosphere in far larger quantities than previously thought, with as much as 7.9 percent of it puffing out from shale gas wells, intentionally vented or flared, or seeping from loose pipe fittings along gas distribution lines. This offsets natural gas’s most important advantage as an energy source: it burns cleaner than other fossil fuels and releases lower carbon dioxide emissions.

“The old dogma of natural gas being better than coal in terms of greenhouse gas emissions gets stated over and over without qualification,” said Robert Howarth, a professor of ecology and environmental biology at Cornell University and the lead author of one of the studies. Mr. Howarth said his analysis, which looked specifically at methane leakage rates in unconventional shale gas development, was among the first of its kind and that much more research was needed.