Natural gas has been true boon to emissions. When the rest of the civilized world was adopting more nuclear energy, American politicians representing their constituents were determined to kill it. President Bill Clinton and Senator John Kerry were cheered by their voters when they announced an end to nuclear science in America in the early 1990s. As a result, America built more coal and that led to America leading the world in CO2 emissions.

But in the 2000s, a natural gas revolution took hold. By the end of the first decade, American CO2 emissions were back at early 1990s levels and coal emissions were back to early 1980s levels. Nuclear energy would still be better but the administration blocks it at every turn, and they are not fans of fracking, but they like taking credit for lower emissions. 

A pair of Duke researchers say that natural gas alone will not be enough to stop global warming and that more government restrictions on CO2 are needed - and they even posit that nuclear could fill that gap. 

 Credit and link: DOI: 10.1021/es4046154 

Since natural gas is abundant and less expensive, it will encourage greater natural gas consumption and less of fuels such as coal - but it also means less demand foe emissions-free energy such a nuclear power.  The net effect on the climate will depend on whether the greenhouse emissions from natural gas -- including carbon dioxide and methane -- are low enough to be a trade-off for not implementing lower emissions energy sources. 

To most in business, there is little point in talking about what works better but will never get built. As we have seen with NASA and nuclear energy, the administration makes a habit of lauding something in speeches and announcing new projects, while canceling existing ones. The Constellation program and MOX are recent examples for each.

Most evidence indicates that natural gas as a substitute for coal in electricity production, gasoline in transport, and electricity in buildings decreases greenhouse gases. But natural gas production and consumption has higher emissions than renewables and nuclear power.

Natural gas is clearly a cleaner, inexpensive replacement for fuels such as coal and oil that emit more carbon dioxide and local air pollutants - that is why environmentalists touted it for decades. But extracting, processing and transporting it can result in lost methane - methane is a potent greenhouse gas, it has 23X the impact of CO2 on global warming, but it is also much shorter-lived and obviously it can be better captured, since natural gas is primarily methane, which would further lower costs.

Since the precise level of these methane emissions is uncertain, models are more guesses than projections. Even at the high end, methane is nowhere near as bad for long-term climate change as CO2.  

"We find that so far increased natural gas has mostly taken the place of coal, but looking forward there also may be increased consumption for sectors such as industry, as well as some degree of displacement of zero-emission sources such as renewables and nuclear," said Daniel Raimi, associate in research at Duke University. "The net effect on U.S. greenhouse gas emissions appears likely to be small in the absence of policies specifically directed at greenhouse gas mitigation."

By renewables, they mean solar and wind, and in an idealized case. Natural gas works right now, there is no capitalism-induced miraculous efficiency boost needed, the way there is for those.

Raimi and Richard Newell, Gendell Professor of Energy and Environmental Economics, created  two hypothetical futures: one where natural gas production and prices follow a "reference case" scenario, and another where increased shale gas production lowers prices and encourages increased consumption. They also account for a range of methane emissions scenarios, ranging from 25 percent below to 50 percent above the levels estimated by the U.S. Environmental Production Agency. 

"The fact that increased shale gas doesn't have a huge climate impact on its own doesn't mean it's not important. If broad climate policy is enacted, having abundant natural gas could be very helpful by making it cheaper for society to achieve climate goals," Newell said. "If natural gas is expensive, then it will be more costly to switch away from fuels that have higher greenhouse gas emissions, such as coal and oil. But keeping methane emissions low is essential to maximizing the potential benefits of natural gas."

The climate benefits of natural gas are reduced if there are a lot of methane emissions, but while "recent evidence suggests methane emissions may be higher than the EPA currently estimates, it's not clear how this new information will affect those estimates," Raimi said. "Reducing methane emissions is important, but even if methane emissions from natural gas systems are significantly higher than current EPA estimates, we did not find this significantly alters the impact of abundant natural gas on long-term national or global greenhouse gas emissions pathways."

Citation: Richard G. Newell, Daniel Raimi, 'Implications of Shale Gas Development for Climate Change', Environ. Sci. Technol., April 22 2014 DOI: 10.1021/es4046154