The idea of the carbon budget is a powerful conceptual tool to define and quantify the climate challenge. Whilst scientists present the carbon budget as the geophysical foundation for global net-zero targets, the financial metaphor of a budget implies figuratively the existence of a ‘budget manager’ who oversees the budget balance. Using this fictive character of budget manager as a heuristic device, the paper analyses the roles of carbon dioxide removal (CDR) and solar radiation management (SRM) under a carbon budget. We argue that both CDR and SRM can be understood as ‘technologies of offset’. CDR offsets positive carbon emissions by negative emissions, whereas SRM offsets the warming from positive greenhouse gas forcing by the induced cooling from negative forcing. These offset technologies serve as flexible budgeting tools in two different strategies for budget management: they offer the promise of achieving a balanced budget, but also introduce the possibility for running a budget deficit. The lure of offsetting rests on the flexibility of keeping up an ‘appearance’ of delivering a given budget whilst at the same time easing budget constraints for a certain period of time. The political side-effect of offsetting is to change the stringency of budgetary constraints from being regulated by geophysics to being adjustable by human discretion. As a result, a budget deficit can be normalised as an acceptable fiscal condition. We suggest that the behavioural tendency of policymakers to avoid blame could lead them to resort to using offset technologies to circumvent the admission of failure to secure a given temperature target.

碳预算的想法是定义和量化气候挑战的强大概念工具。虽然科学家们将碳预算作为全球净零目标的地球物理基础，但预算的财务隐喻形象地暗示了监督预算平衡的“预算经理”的存在。使用预算管理器的这种虚构特征作为启发式装置，本文分析了碳预算下二氧化碳去除 (CDR) 和太阳辐射管理 (SRM) 的作用。我们认为 CDR 和 SRM 都可以理解为“抵消技术”。CDR通过负排放抵消正碳排放，而SRM通过负强迫引起的冷却抵消正温室气体强迫引起的变暖。这些抵消技术在两种不同的预算管理策略中充当灵活的预算工具：它们提供实现平衡预算的承诺，但也引入了运行预算赤字的可能性。抵消的诱惑在于保持交付给定预算的“外观”的灵活性，同时在一定时期内放松预算限制。抵消的政治副作用是将预算约束的严格程度从由地球物理学调节变为由人类自由裁量权调节。因此，预算赤字可以正常化为可接受的财政状况。