???全世界都在爭先恐后地利用可再生能源，美國卻落在了后面。頁巖天然氣工業的異軍突起進一步影響了美國可再生能源的前景，并有可能將可再生能源打入冷宮。

????很多有影響力的評論家都對頁巖氣的低碳排放及其經濟潛力大加贊美。即使是一開始支持可再生能源的奧巴馬總統也轉變了立場，他在2012年的國情咨文中表示要大力發展頁巖氣，而涉及可再生能源的部分卻只有只言片語。

????頁巖氣之所以在美國受到如此青睞，主要原因包括兩個方面。首先，天然氣造成的二氧化碳污染是燃煤的一半，天然氣正在逐步成為能源工業的燃料選擇，這一點毫無疑問。然而，電力行業的二氧化碳排放量大約占全美二氧化碳排放總量的40%，比美國經濟領域中的任何一個行業都要多，包括交通運輸業。雖然核能發電的二氧化碳排放量要比天然氣少得多，但在日本福島發生核泄漏事故后，核電業遭遇了前所未有的寒冬。

????此外，對于嚴重依賴傳統燃料的交通運輸業來說，其二氧化碳排放量占到全國總量的大約30%。要想找到一種既滿足大眾市場要求，又符合成本效益的替代方案還需要等待很多年。燃煤污染太嚴重，核能利用與交通運輸業又陷入困局，太陽能和風能尚未發展成熟，如此一來，選擇天然氣也就成了一種對抗氣候變化的折衷辦法了。

????然而這種設想是否切實有效？《環境研究通訊》（Environmental Research Letters）期刊指出，如果真的要在本世紀內實現給地球降溫的目標，就必須盡快大規模綜合部署礦藏資源、風能、太陽能和核能，而不是天然氣。該刊通過一個例子進一步提醒，假如在未來40年內安裝一萬億瓦特的天然氣發電廠，到2112年，和燃煤發電廠相比，天然氣發電讓全球變暖趨勢減緩程度也就不到十分之一。

????麻省理工學院（MIT）最近一項研究聲稱，頁巖氣的運用抑制了可再生能源的發展，它只能算是向低碳未來前進的一個“短期性”過渡方案。夸大其價值可能會嚴重妨礙碳收集和碳封存等低排放科技的發展。

????太陽能和風能還未發展到黃金成熟期的想法是一種謬見。美國太陽能產業正在遭遇危機，原因并不是太陽能電池的發展尚未成熟，而是另有原因。一方面，美國人對于新事物的迷戀已經讓我們在前沿太陽能科技領域投入了無數資金，成果卻并不顯著。而另一方面，中國提升了傳統多晶硅的能效，并占領了全球太陽能電池50%的市場份額。

????其次，我們沒能采納一種傳導性生態系統理念，該系統應該包括長期的行業激勵、稅收返還和聯邦可再生能源配額標準，并在石油和天然氣定價時考慮各自的環境成本。第三，堅持在海外生產而非本地生產使得我們仍然能夠保持創新力，但這最終也將使得寶貴的知識產權和工作機會流向國外。

????頁巖氣的迅猛發展也只是最近幾年的事。而風力發電之路雖然崎嶇，但卻卓有成效。一路從明尼蘇達到德克薩斯州遍布著的大規模風力發電廠儼然已使美國成為“風能界的沙特阿拉伯”。但聯邦政策的不確定性嚴重制約了風能行業的發展潛力。

???The world is scrambling to deploy renewable sources of energy, but America has fallen behind. The upstart natural gas from shale industry has only further increased the prospect of depressing renewables in America, and potentially shoving them into cold storage.

????Influential commentators have extolled shale gas' low carbon footprint, as well as its economic potential. Even President Obama, who initially embraced renewables, has ardently converted to shale in his 2012 State of the Union address, while throwing renewables a few crumbs.

????Shale gas' allure is two-fold. First, natural gas, which causes about half as much CO2 pollution as coal, is slowly but surely becoming the power industry's fuel of choice. Nevertheless, the electric power sector contributes about 40% of the nation's total CO2 emissions. That total is greater than any other sector of the U.S. economy, including transportation. Nuclear generation, which is much less carbon-intensive than natural gas, is facing a chilly winter post-Fukushima.

????Further, the transportation sector, which accounts for roughly 30% of the country's CO2 emissions, is heavily reliant on conventional fuels. A mass-market, cost-effective alternative to them is many years away. With coal so dirty, and nuclear energy and transportation mired, natural gas is seen as a halfway measure to combat climate change until solar and wind energies mature.

????But how valid is this assumption? An Environmental Research Letters paper argues that to achieve substantial temperature reductions this century, it will take a rapid and massive deployment of a mix of conservation, wind, solar, and nuclear energy -- not natural gas. If a trillion watts of gas-fired generation were installed over the next 40 years, the decline in warming by 2112 would only be within a tenth of a degree of that induced by coal-fired plants, it cautions.

????A new MIT study asserts that shale use suppresses the development of renewables, and that it can only be a "short-term" bridge to a low-carbon future. Treating it otherwise could altogether stunt the development of lower-emission technologies like carbon capture and sequestration.

????That solar and wind are unready for prime time is a myth. Solar energy is facing a crisis in the country, not because solar cells are unproven, but due to other factors. First, America's fascination for the new, new thing has made us sink billions, with few obvious results, into cutting-edge solar technologies. The Chinese, on the other hand, have improved the efficiency of traditional polysilicon, and captured 50% of the world's solar cell market.

????Second, our failure to put in place a conducive ecosystem, whether it includes long-term industry incentives, feed-in tariffs, a federal renewable portfolio standard, or pricing oil and gas fairly by incorporating the costs of their environmental damage. Third, by persisting in manufacturing overseas and not locally, we will still continue to innovate, but end up exporting precious intellectual property and jobs.

????Wind turbines too are rugged and effective. While shale has gushed only in the last few years, a powerful wind corridor has always existed all the way from Minnesota to Texas, making the U.S. the "Saudi Arabia of Wind," but an uncertain federal policy has strangled its potential.