Collaborative Research: DRU: An Improved Model of Endogenous Technical Change Considering Uncertain R&D Returns and Uncertain Climate Response

设计应对全球气候变化的措施需要分析工具，这些工具可以帮助决策者了解政策成本与避免气候变化带来的收益之间的权衡。然而，成本和收益都是不确定的。迄今为止，气候变化研究中使用的模型还不能代表所有关键的不确定性。一个重要的疏漏是对旨在改进能源技术的研究和发展（R&amp；D）回报的不确定性的表述。对研发的研究表明，这种回报是不确定的，而且是高度倾斜的（即，取得重大突破的可能性很小）。忽视这种不确定性而只关注平均效应，将对实现特定目标所需的减排量或短期排放限制与能源技术研发投资之间的相对平衡产生有偏差的估计。本研究将通过开发一个明确表示研发回报不确定性的模型框架来改进决策者可用的分析工具。技术变革的表现及其与研发支出的关系将根据美国专利的历史经验进行校准。该模式还将通过将不确定性限制在与20世纪气候一致的范围内，改善对温室气体排放的气候响应中不确定性的表征。这些组成部分将被整合到一个单一框架中，该框架可用于探索在不确定情况下有关减排和研发支出的决策。本研究结果将改进用于气候变化评估的分析设施。预计新工具将通过消除当前模型中的偏差，在减排时间和技术研发投资方面提供更好的指导。

Designing a response to global climate change requires analysis tools that can help decision makers understand the tradeoffs between the cost of a policy and its benefit in the form of avoided climate change. Both the costs and the benefits, however, are uncertain. To date, models used in studies of climate change have not represented all the critical uncertainties. One important omission is the representation of uncertainty in returns to research and development (R&D) directed to the improvement of energy technologies. Studies on R&D have shown that such returns are uncertain and highly skewed (i.e., have a small probability of a very large breakthrough). Ignoring this uncertainty and focusing on the average effect will produce biased estimates of the emissions reductions required to meet particular targets or the relative balance between near-term emissions constraints and investments in energy technology R&D.This research will improve the analysis tools available to decision makers by developing a model framework that explicitly represents the uncertainty in the returns to R&D. The representation of technical change and its relation to R&D expenditure will be calibrated to historical experience with U.S. patents. The model will also improve the representation of the uncertainty in the climate response to greenhouse gas emissions by constraining that uncertainty to a range consistent with 20th century climate. These components will be integrated into a single framework that can be used to explore decision making about emissions reductions and R&D expenditures under uncertainty.The results of this research will improve the analysis facilities that are applied to climate change assessment. The new tools are expected to give improved guidance in the timing of emissions reductions and investments in technology R&D by eliminating biases in current models.