Abstract: Global climate change has sparked widespread concern worldwide, with the international community calling for strict control of energy-related carbon dioxide emissions to mitigate climate change. As the key implementers of policy objectives, resolute investments in energy-saving and emission reduction technologies not only directly impact the Chinese government's ability to achieve emission reduction targets but also determine the implementation of the fundamental national policies of resource conservation and environmental protection. Various uncertainties related to climate change may further increase the risks faced by firms in their decisions regarding energy-saving and emission reduction investments. While scholars have demonstrated the impact of various uncertainty factors on firm investment decisions, the research on the uncertainty stemming from climate change and its influence on firm decisions regarding energy-saving and emission reduction investments remains limited. There is a lack of a comprehensive understanding of the costs and uncertainties faced by micro-level entities, such as firms, in their efforts to mitigate climate change. Particularly, among the various uncertainty factors, the size of the discount rate can directly affect decision-makers' estimates of the relationship between future returns and current costs and, consequently, determine their optimal investment decisions. Currently, there is scarce research that analyzes decision-makers' responses to climate change uncertainty by introducing discount rates in option value models. Therefore, an in-depth exploration of the mechanisms behind firm decisions on energy-saving and emission reduction technology investments, in conjunction with option value models, holds theoretical and practical significance for further improving China's energy-saving and emission reduction policies, developing a low-carbon economy, mitigating climate change, and accelerating the construction of an ecological civilization.
Based on the option value theory, this paper proposes energy-saving and emission reduction investment decision-making rules for firms to respond to climate change uncertainty based on production levels. Under the rule, industrial firms could deal with the uncertainty of climate change according to their outputs. First, we propose a traditional firm investment rule. Second, we develop an output decision model considering the uncertainties faced by industrial firms. Based on uncertainty models of emissions reduction and various cost function formulations, a novel optimal investment rule for implementing energy-saving and emission-reduction actions “based on firm's production scale” has been derived. Finally, based on the theoretical model we develop, we perform a numerical simulation and, in particular, explore the impacts of uncertainty and social discount rate on firms' optimal investment decisions. Further, we also investigate the dynamic path of firms' option value, which shows the applicability of this new investment rule.
Combining theoretical analysis with numerical simulation results, we find that the greater the uncertainty faced by firms, the higher the threshold for deciding whether to invest in emission reduction projects. As a result, the option value of holding emission reduction investment opportunities by firms increases, thus increasing the likelihood of firms adopting a cautious approach of observing and waiting before taking emission reduction actions. This result suggests that uncertainty could increase the probability that firms wait and delay to invest in emission reduction actions. Considering that the impact of global climate change becomes more and more obvious, future policy uncertainty will become a key factor affecting firms' emission reduction investment decisions. By considering both of the uncertainty of climate change and discount rate, the proposed investment rule can provide decision-making support for optimal investment of firms in dealing with climate change.

Key words: uncertainty, discount rate, carbon emission reduction, firm-level investment decision, option value, climate change

摘要： 全球气候变化引起了世界各地的广泛关注,国际社会呼吁严格控制与能源相关的二氧化碳排放,企业实施节能减排投资是减缓气候变化的重要策略。基于期权价值理论,本文提出了一个企业依据产出水平应对气候变化不确定性的节能减排投资决策规则。首先给出了一个传统的企业投资决策规则;然后在期权价值理论基础上,构建了一个不确定性产出模型,并分别基于不同的减排成本函数形式,推导出新的企业最优减排项目投资规则;最后进行数值模拟,分析了气候变化不确定性和社会贴现率等因素对企业最优投资时点的影响及企业投资期权价值的动态变化路径,验证了该投资规则的适用性。本研究设计的企业最优适应性投资规则考虑了气候变化的不确定性和贴现率,可以为企业应对气候变化的投资决策提供理论指导,具有重要的实践意义。

关键词: 不确定性, 贴现率, 节能减排, 企业投资决策, 期权价值, 气候变化