The remaining carbon budget for limiting global warming to 1.5 degrees Celsius will probably be exhausted within this decade^1,2. Carbon debt³ generated thereafter will need to be compensated by net-negative emissions⁴. However, economic policy instruments to guarantee potentially very costly net carbon dioxide removal (CDR) have not yet been devised. Here we propose intertemporal instruments to provide the basis for widely applied carbon taxes and emission trading systems to finance a net-negative carbon economy⁵. We investigate an idealized market approach to incentivize the repayment of previously accrued carbon debt by establishing the responsibility of emitters for the net removal of carbon dioxide through ‘carbon removal obligations’ (CROs). Inherent risks, such as the risk of default by carbon debtors, are addressed by pricing atmospheric CO₂ storage through interest on carbon debt. In contrast to the prevailing literature on emission pathways, we find that interest payments for CROs induce substantially more-ambitious near-term decarbonization that is complemented by earlier and less-aggressive deployment of CDR. We conclude that CROs will need to become an integral part of the global climate policy mix if we are to ensure the viability of ambitious climate targets and an equitable distribution of mitigation efforts across generations.

将全球变暖限制在 1.5 摄氏度的剩余碳预算可能会在这十年内用尽^1,2。此后产生的碳债务³将需要通过净负排放⁴来补偿。然而，尚未设计出经济政策工具来保证可能非常昂贵的净二氧化碳清除 (CDR)。在这里，我们提出跨期工具，为广泛应用的碳税和排放交易系统提供基础，为净负碳经济提供资金⁵. 我们研究了一种理想化的市场方法，通过建立排放者通过“碳清除义务”（CRO）净清除二氧化碳的责任来激励偿还先前累积的碳债务。固有风险，例如碳债务人的违约风险，通过对大气 CO _{2定价来解决}通过碳债务利息进行储存。与关于排放路径的流行文献相比，我们发现 CRO 的利息支付会引发更加雄心勃勃的近期脱碳，而 CDR 的更早和更不积极的部署是其补充。我们的结论是，如果我们要确保雄心勃勃的气候目标的可行性和在几代人之间公平分配减缓努力，CRO 将需要成为全球气候政策组合的一个组成部分。