Carbon Dioxide Removal Model Intercomparison Assessment (CDR-MIA)

持续的人为温室气体排放正在改变气候，威胁着严重、普遍和不可逆转的影响。作为回应，人们越来越关注和研究消除二氧化碳(CDR)方法的潜力，使负排放能够补充二氧化碳减排努力。然而，对大规模CDR的潜在积极和消极影响仍然缺乏量化和阐明。该项目的主要目的是分析二氧化碳清除模型对比项目(CDR-MIP)第一阶段实验的结果，以更好地评估大规模CDR的潜力和风险。CDR-MIP是一项新的倡议，它将一套地球系统模型聚集在一个共同的框架内，以研究CDR。CDR-MIP的第一阶段包括两个理想化的实验，即直接捕获二氧化碳空气，以及植树造林和海洋碱化实验，旨在调查以下关键问题：(A)气候可逆性，在使用CDR将未来较高的大气CO2浓度恢复到较低(例如，当前或工业化前)水平的背景下，以及(B)不同CDR方法的潜在效力、反馈、时间尺度和副作用。虽然在设计CDR-MIP方面已经做了大量的工作，来自世界各地的一些建模团体已经同意进行模拟，但该项目目前完全是自愿的。因此，模型输出不太可能很快得到利用。因此，需要专门的资金来确保及时分析数据并向公众传播数据。我们还建议利用这些分析的结果，更好地限制CDR技术在综合评估模型(IAM)生成的共享社会经济路径(SSP)情景中的假定有效性，这些情景用于促进气候变化研究和评估。目前，当CDR被包括在IAM模拟中时，没有考虑到碳循环反馈，迫切需要填补这一知识空白。我们建议使用CDR-MIP分析的结果来计算基于碳循环反馈的CDR贴现率，然后将其用于校准和重新运行具有IAM的SSP场景。除此之外，还将设计、运行和评估新的实验，以调查碳循环和气候系统对同时实施多种CDR方法的响应。这些实验将在CDR-MIP实验的基础上，结合植树造林和人工海洋碱化等方法。随后的分析将允许将组合CDR的有效性和风险与单独实施的效果和风险进行比较。该项目的结果将提供对CDR的全面评估，可与SPP中的伙伴项目反复讨论。分析的结果也将提供给参加战略计划的其他项目。

Continued anthropogenic greenhouse gas emissions are changing the climate threatening severe, pervasive and irreversible impacts. In response, there is increasing focus and study on the potential of Carbon Dioxide Removal (CDR) methods to enable negative emissions to complement CO2 emission mitigation efforts. However, the potentially positive and negative impacts in response to large-scale CDR remain poorly quantified and elucidated. The main aim of this project is to analyze the output from the Carbon Dioxide Removal Model Intercomparison Project (CDR-MIP) phase 1 experiments to better assess the potential, and risks of large-scale CDR. CDR-MIP is a new initiative that brings together a suite of Earth System Models in a common framework to investigate CDR. The 1st phase of CDR-MIP, which includes two idealized experiments of direct CO2 air-capture, as well as afforestation and ocean alkalinization ones, is designed to investigate key questions concerning (a) climate reversibility, in the context of using CDR to return high future atmospheric CO2 concentrations to a lower (e.g., present day or pre-industrial) level and (b) the potential efficacy, feedbacks, time scales, and side effects of different CDR methods. While a significant amount of work has gone into designing CDR-MIP and a number of modeling groups from around the world have agreed to run the simulations, the project is currently entirely voluntary. Thus, it is unlikely that the model output will be quickly utilized. Dedicated funding is therefore needed to ensure the timely analysis of data and its public dissemination. We propose to also use the results of these analyses to better constrain the assumed effectiveness of CDR technologies in the Integrated Assessment Model (IAM)-generated Shared Socioeconomic Pathway (SSP) scenarios that are used to facilitate climate change research and assessment. Currently, carbon cycle feedbacks are not accounted for when CDR is included in IAM simulations and there is an urgent need to fill this knowledge gap. We propose to do this by using the results from the CDR-MIP analyses to calculate a carbon cycle feedback based discount factor for CDR that will then be used to calibrate and re-run a SSP scenario with an IAM. In addition to this, new experiments will also be designed, run, and evaluated to investigate the response of the carbon cycle and climate system to the simultaneous implementation of multiple CDR methods. These experiments will build upon the CDR-MIP ones by combining some of the methods, such as afforestation and artificial ocean alkalinization. Subsequent analyses will allow the efficacy and risks of combined CDR to be compared to that of the individual implementations. Results of this project will provide a comprehensive assessment of CDR that can be discussed iteratively with partner projects in the SPP. Results of the analyses will also be made available to other projects participating in the SPP.