這項(xiàng)研究的幾個(gè)重要特征使其與美國(guó)氣候和能源選擇的其他評(píng)估不同。?首先，我們的研究明確側(cè)重于政策設(shè)計(jì)和評(píng)估。許多先前的研究已經(jīng)檢驗(yàn)了替代燃料、新技術(shù)和未來(lái)減少石油使用和二氧化碳排放的途徑的技術(shù)可行性。然而，必須超越工程估計(jì)或特定燃料和技術(shù)的可得性，考慮將導(dǎo)致這些減少的機(jī)制，即推動(dòng)私營(yíng)市場(chǎng)變化的具體政府政策工具，這是我們的關(guān)鍵重點(diǎn)。如果不了解這些政策是如何運(yùn)作的，決策者就無(wú)法明確地指導(dǎo)如何向前發(fā)展。?第二，我們采用一致的經(jīng)濟(jì)建模方法，這是研究的基礎(chǔ)。這種模型，我們稱(chēng)之為NEMS-RFF，是美國(guó)能源部/能源信息管理局國(guó)家能源建模系統(tǒng)（NEMS）的RFF版本。我們?cè)贠nLocation，Inc.的幫助下開(kāi)發(fā)了這個(gè)版本。通過(guò)使用相同的模型和相同的基本假設(shè)，我們可以對(duì)不同的策略進(jìn)行評(píng)分，從而進(jìn)行蘋(píng)果對(duì)蘋(píng)果的比較。我們的得分基于兩個(gè)有效性指標(biāo)：石油消耗量減少1桶，二氧化碳排放量減少1噸，以及每項(xiàng)政策的成本。?第三，這項(xiàng)研究范圍廣泛，考慮到了一系列廣泛的政策。與其他一些研究不同，我們還研究了一系列橫切策略，這些策略組合了多個(gè)單獨(dú)的策略。我們針對(duì)一個(gè)參考案例，研究了35項(xiàng)政策，包括4項(xiàng)交叉政策選擇。盡管沒(méi)有一項(xiàng)研究能夠完全全面，但我們認(rèn)為，這份報(bào)告涵蓋了決策者目前面臨的許多相關(guān)能源政策選擇。?第四，這項(xiàng)研究的一個(gè)特點(diǎn)是根據(jù)基本的微觀經(jīng)濟(jì)原則，對(duì)經(jīng)濟(jì)或“福利”成本進(jìn)行審查，其中成本是社會(huì)為實(shí)現(xiàn)特定的石油使用和/或二氧化碳排放減少而放棄的資源的價(jià)值。例如，這些成本可能包括使用更清潔但更昂貴的燃料生產(chǎn)電力、減少駕駛或采用更節(jié)能的技術(shù)。許多研究都是根據(jù)一種燃料替代另一種燃料或一種節(jié)能技術(shù)替代另一種效率較低的燃料的情況來(lái)計(jì)算直接支出變化。其他國(guó)家，特別是那些著眼于碳稅或總量管制和貿(mào)易計(jì)劃等基礎(chǔ)廣泛的政策的國(guó)家，評(píng)估國(guó)內(nèi)生產(chǎn)總值（GDP）的變化。盡管如此

Several important features of this study distinguish it from other assessments of U.S. climate and energy options.  ?First, our research focuses explicitly on policy design and evaluation. Many previous stud-ies have examined the technical feasibility  of alternative fuels, new technologies, and future pathways to reduce oil use and CO2 emissions. However, it is essential to look beyond engineering estimates or availability of particular fuels and technologies, and consider the mechanisms that will bring about those reductions, namely, the specific government policy instruments that will drive changes in private markets, our key focus. Without an understanding of how these policies work, decisionmakers have no clear guidance on how to move forward.  ?Second, we use a consistent economic model-ing approach, which is the backbone of the study. This model, which we call NEMS-RFF, is an RFF version of the U.S. Department of Energy/Energy Information Administration’s National Energy Modeling System (NEMS). We developed this version with the assistance of OnLocation, Inc. By using the same model with the same underlying assumptions, we can score different policies, making apples-to-apples comparisons. We based our scores on two effectiveness metrics—reduction in    barrels of oil consumed1 and reduction in tons of CO2 emitted—as well as the cost of each policy.  ?Third, the study is wide-ranging, taking into account a broad menu of policies. Unlike some other studies, we also examine an array of crosscutting policies that combine multiple individual policies. We examined 35 policy sce-narios, including 4 crosscutting policy options, against a reference case. Although no study can be completely comprehensive, we believe this report covers many of the relevant energy policy options currently facing policymakers.  ?Fourth, a hallmark of this study is its examina-tion of economic or “welfare” costs, based on fundamental microeconomic principles in which cost is the value of the resources that society gives up to achieve a given reduction in oil use and/or CO2 emissions. These costs could include, for example, producing elec-tricity with cleaner but more expensive fuels, driving less, or adopting more energy-efficient technologies. Many studies calculate direct expenditure changes from scenarios in which one fuel substitutes for another or one energy-efficient technology replaces another, less efficient one. Others, particularly those looking at broad-based policies such as carbon taxes or cap-and-trade programs, assess changes in gross domestic product (GDP). Although such