The welfare properties of climate targets
研究了气候模型中成本效益分析与成本有效性分析的不同约束（如辐射强迫、温度、累积排放）对最优碳价、排放和福利的影响，发现累积排放约束在1.5°C目标下福利最优，而带超调的辐射强迫约束福利损失最大。
Two approaches are predominant in climate models: cost–benefit and cost-effectiveness analysis. Cost–benefit analysis maximizes welfare, finding a trade-off between climate damages and emission abatement costs . By contrast, cost-effectiveness analysis minimizes abatement costs, omits damages but adds a climate constraint, such as a radiative forcing constraint, a temperature constraint or a cumulative emissions constraint. We analyse the impacts of these different constraints on optimal carbon prices, emissions and welfare. To do so, we fit a model with abatement costs, capital repurposing costs (stranded assets) and technological change on IPCC and NGFS scenarios. For scenarios reaching 1.5 °C in 2100, a constraint on cumulative emissions has the best welfare properties, followed by a temperature constraint with overshoot. A forcing constraint with overshoot has insufficient early abatement and large net negative emissions later on, leading to a substantial welfare loss of $23 Trillion. As to the paths reaching 2 °C, all cost-effectiveness analysis abate too late, but the welfare impact of this dynamic inefficiency is milder. Again, a forcing constraint with overshoot scores worst. We show that large negative emissions at the end of the century are never optimal and an artefact of constraints with overshoot.