中文摘要
为更好地理解一大类气候—增长模型的结构与核心机制，我们从增长理论的视角研究气候与经济动态综合模型（DICE）的一个简化版本。我们通过解析证明，该模型具有一个鞍点稳定稳态的连续统。存量变量的初始条件向来难以校准，而这些初始条件对长期经济与气候结果至关重要。然而，我们也证明，资本初始存量设定错误所产生的影响显著小于初始CO2存量设定错误的影响。这些洞见对于延迟实施气候政策的后果以及最优碳税具有重要含义。利用一个经校准、并针对大转型进行数值求解的模型版本，我们表明，推迟最优气候政策会同时提高峰值温度和稳态温度。这些发现可推广至大量解析与数值综合评估模型。经由有限振幅脉冲响应（FAIR）碳循环模型扩展后的简单DICE模型，在跨越数个世纪的时间跨度上呈现出稳态的连续统。峰值温度与长期温度取决于初始条件，这一结果在DICE-2023中也得到印证。我们进一步表明，尽管存在转型动态，碳的社会成本与GDP之比大体保持恒定；然而，其水平取决于最优政策实施的时间。
Abstract
ABSTRACT To better understand the structure and core mechanisms of a broad class of climate‐growth models, we study a simplified version of the dynamic integrated model of climate and the economy (DICE) through the lens of growth theory. We analytically show that this model features a continuum of saddle‐point stable steady states. Initial conditions of stock variables, which are notoriously difficult to calibrate, matter for long‐run economic and climate outcomes. However, we also demonstrate that a misspecified initial stock of capital has a significantly smaller impact than a misspecified initial CO 2 stock. These insights have important implications for the consequences of delayed climate policy implementation and the optimal carbon tax. Using a calibrated version of the model, solved numerically for the big transition, we show that postponing optimal climate policy raises both peak temperature and the steady‐state temperature. The findings extend to a large set of analytical and numerical integrated assessment models. The simple DICE, augmented by the finite amplitude impulse‐response (FAIR) carbon cycle model, exhibits a continuum of steady states over time horizons spanning several centuries. Peak and long‐run temperatures depend on initial conditions, a result that is also confirmed for DICE‐2023. We further show that the social cost of carbon to GDP ratio is largely constant despite transitional dynamics; however, its level depends on the timing of optimal policy implementation.