Lasrick writes Energy expert H-Holger Rogner walks through the realities of the shale-gas boom, the 'game-changer' that has brought about a drop in energy prices and greatly reduced carbon emissions. But despite the positive impact on carbon emissions, Rogner points out that the cheap gas brought about by fracking shale may already be affecting investments into renewable energy, nuclear energy, and energy efficiency by offering more attractive investment opportunities: 'At today's prices of $4 to $5 per million British thermal units, gas-fired electricity holds a definite competitive advantage over new nuclear construction and unsubsidized renewables.' But natural gas is still a fossil fuel that emits carbon dioxide. 'A much higher share of natural gas in the energy mix would eventually raise emissions again, especially if gas not only displaces coal but also non-fossil energy sources. Moreover, methane, the chief component of natural gas, is itself a heat-trapping greenhouse gas with 25 times the warming effect of carbon dioxide. If total methane leakage—from drilling through end use—is greater than about 4 percent, that could negate any climate benefits of switching from coal and oil to gas.'