Net Social Benefits of Carbon Dioxide Removal: Carbon Cycle Feedbacks and Strategic Advantages (CDRecon)

为了保持将全球平均气温上升保持在2°C以下的机会并限制长期气候变化，从大气中去除二氧化碳（二氧化碳去除，CDR）并将其处置在非大气碳库中变得越来越必要。关于碳的社会成本的信息，即衡量向大气排放碳的成本，不足以评估碳减排的社会效益，因为还需要考虑非大气碳库的社会成本。将碳移到陆地生物圈的社会成本（例如，通过植树造林）或海洋（例如通过在沿海地区散布橄榄石）产生的碳循环反馈和饱和效应，这意味着减少碳排放的净社会效益低于所节省的（大气）碳社会成本。本项目CDRecon通过将动态经济模型与地球系统模型相结合，开发了一种新的CDR综合评估方法，以解决CDR非大气社会成本的两个问题：1） 什么样的碳循环模型适合于综合评估净 社会 CDR的好处？（二） 为CDR分配碳信用额的适当方案是什么？忽视非大气层的社会成本导致气候政策中CDR措施的份额和时间的估计不一致。但无论如何，气候政策在现实中是不完美的。非全球覆盖和非合作行为导致国际碳泄漏和搭便车。与减排和碳捕获和储存（CCS）相比，CDR允许从大气中去除扩散和过去的碳排放。因此，在处理与不完善的气候政策有关的问题方面，减少灾害风险提供了一些尚未开发的战略优势。然而，如果不考虑碳的非大气社会成本，它也可能增加进一步的缺陷。CDRecon将使用并进一步开发综合评估建模（IAM）、敏感性分析、前瞻性可计算一般均衡（CGE）模型、微分博弈分析和（随机）动态优化等方法，以解决有关最佳和非最佳的另外两个问题气候政策中的CDR：3） CDR如何影响全球协调的气候政策？四、 CDR如何影响国际碳泄漏和搭便车？CDRecon将研究最佳和非最佳CDR应用，后者是由于只关注大气社会成本而忽视碳循环反馈而产生的。

To maintain the chance of keeping the average global temperature increase below 2°C and to limit long-term climate change, removing carbon dioxide from the atmosphere (Carbon Dioxide Removal, CDR) and disposing of it in non-atmospheric carbon reservoirs is becoming increasingly necessary. Information on the social cost of carbon, i.e. measuring the cost of emitting carbon into the atmosphere, is not sufficient for assessing the social benefits of CDR because the social cost of non-atmospheric carbon reservoirs also needs to be taken into account. The social cost of removing carbon into the terrestrial biosphere (e.g., by afforestation) or the ocean (e.g. by spreading olivine in coastal areas) arises from carbon-cycle feedbacks and saturation effects, implying lower net social benefits of CDR than suggested by the saved (atmospheric) social cost of carbon. The present project, CDRecon, develops a new approach to an integrated assessment of CDR by combining dynamic economic modeling with earth system modeling to address two questions on Non-atmospheric Social Cost of CDR:1) What carbon cycle models are appropriate for integrated assessment of the net social benefits of CDR? 2) What is an appropriate scheme for assigning carbon credits to CDR? Neglecting non-atmospheric social cost results in inconsistent estimates with regard to the share and timing of CDR measures in climate policies. But climate policy is imperfect in reality anyway. Non-global coverage and non-cooperative behavior result in international carbon leakage and free-riding. In contrast to abatement and carbon capture and storage (CCS), CDR allows the removal of both, diffuse and past carbon emission from the atmosphere. Thus, CDR provides a number of unexplored strategic advantages in dealing with issues related to imperfect climate policies. Yet, if applied without accounting for the non-atmospheric social cost of carbon, it could also add a further dimension of imperfection. CDRecon will use and further develop methods of integrated assessment modeling (IAM), sensitivity analysis, forward-looking computable general equilibrium (CGE) models, differential game analysis, and (stochastic) dynamic optimization to address two further questions on Optimal and Non-optimal CDR in Climate Policies: 3) How is globally-coordinated climate policy affected by CDR?4) How is international carbon leakage and free-riding affected by CDR?CDRecon will study both, optimal and non-optimal CDR application, the latter arising from focusing only on the atmospheric social cost and neglecting carbon cycle feedbacks.