不确定气候下的脱碳投资策略（英）-2025_19页_2mb

Decarbonization Investment Strategies Under Climate Uncertainty and Adjustment Costs

Introduction
The paper explores optimal decarbonization investment strategies, accounting for climate uncertainty and adjustment costs (e.g., training costs for clean technology adoption). It establishes a modeling framework that investigates how these factors impact investment pathways, cumulative emissions, and sectoral allocation of abatement efforts.

Key Findings

1. Impact of Uncertainty and Adjustment Costs

   • Climate uncertainty increases the cost of achieving climate targets, especially when adjustment costs are present.
   • Investment pathways are front-loaded due to the need to hedge against worst-case scenarios, particularly for hard-to-abate sectors (e.g., heavy industry and agriculture).

2. Temporal and Sectoral Implications

   • Delayed learning of the true carbon budget exacerbates the need for early investment, as policymakers must prepare for potential catastrophes over longer periods.
   • Hard-to-abate sectors experience a "U-shaped" investment profile, shifting from bell-shaped to declining pathways under uncertainty, while easy-to-abate sectors (e.g., energy) show steeper declines in investment after learning.

3. Carbon Price Dynamics

   • Climate uncertainty results in a "heavy-tailed" distribution of carbon prices, with higher average prices when learning is delayed. This symmetry in risk (favoring caution over optimism) drives aggressive early investments.

Model and Methodology

• The framework integrates adjustment costs (via convex investment costs) and climate uncertainty (via stochastic optimization) into economic models of abatement investment.
• Calibration uses sectoral marginal abatement costs from the IPCC, Gaussian approximations of carbon budget uncertainty, and a 2% social discount rate.

Policy Implications

1. Adjustment costs and climate uncertainty necessitate robust, front-loaded investment strategies to avoid overly costly transitions.
2. Early resolution of climate uncertainty can yield substantial cost savings.
3. Models ignoring capital accumulation and adjustment costs may underestimate near-term investment needs.
4. Hard-to-abate sectors require tailored investment policies to address stranded assets and facilitate decarbonization.

Conclusion
The study advocates for integrating adjustment costs and climate uncertainty into climate policy frameworks to optimize decarbonization investment, emphasizing the urgency of early action to mitigate risks and leverage economies of scale.