[17] “Americans' Preference for Environmental Protection vs. Economic Growth, 1984 -2019,” Gallup Poll, https: // news. gallup. com/ poll/ 248243/ preference-environment economy-largest -2000. aspx.
[18] 页岩气是包含于沉积岩中的天然气。与埋藏于渗透岩中、易于开采的传统天然气不同，页岩气所处的岩层渗透性很低，孔隙少。因此其开采更为复杂，需要水力压裂等专门技术，把水和化合物以高压注入，以碎裂岩层。
[19] 页岩气的环境影响仍存在激烈争议。Robert Howarth及其合作者指出，与传统天然气开采相比，水利压力排放的甲烷至少多出30%，另外我们知道，甲烷造成的温室效应比二氧化碳更为严重。还有，水力压裂技术也存在争议，因为可能导致地下水污染。参见: Robert W. Howarth, Renee Santoro, and Anthony Ingraffea,“Methane and the Greenhouse-Gas Footprint of Natural Gas from Shale Formations,” Climatic Change 106, no. 4（2011）:679 -690.
[20] Daron Acemoglu, Philippe Aghion, Lint Barrage, and David Hémous,“Climate Change, Directed Innovation, and Energy Transition: The Long-Run Consequences of the Shale Gas Revolution,”2019 Meeting Papers, No. 1302, Society for Economic Dynamics. https: // scholar. harvard. edu/ aghion/ publications / climate change-directed-innovation-and-energy-transition-long-run-consequences.
