As the expansion of shale gas production has positioned the United States to become a potential net exporter of natural gas, the overall effect that increased exports would have on the climate has been in dispute.
Many aspects of an increased natural gas exports scenario would affect emissions. On the one hand, natural gas could partially displace the use of coal overseas in the generation of electricity. This would put downward pressure on emissions, as natural gas plants on average emit approximately 50 percent less carbon dioxide, or CO2, than coal plants.
On the other hand, methane, which is a potent, short-lived greenhouse gas with many times the warming potential of CO2, escapes into the atmosphere from leaks and intentional venting throughout the natural gas supply chain. Although cost-effective technologies exist that minimize the escape of methane, there is evidence that current levels of methane emissions can be high. Recent studies of air samples collected over natural gas production sites in the western United States reveal leakage rates of 4 percent at the Denver-Julesburg Basin and 6.2 percent to 11.7 percent at the Uinta Basin.
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