The Paris Agreement requires countries to articulate near-term emissions reduction strategies through to 2025 or 2030 by communicating nationally determined contributions (NDCs), as well as encouraging the formulation of long-term low-emission development strategies (Article 4.19)¹. In response, many countries have either submitted or are preparing mid-century strategies². Most NDCs set high-level near-term goals—such as limits on emissions or emissions intensity³—which do not provide information about the extent to which they lay the foundations of technology, infrastructure and institutions for deeper reductions in the future, which is a key question for decision makers. Here, using a state-level model of the US embedded within a global integrated assessment model^4,5, we demonstrate that although the US NDC lies on a straight-line emissions pathway towards its mid-century strategy, the resulting energy system transitions involve nonlinear transformations. The rates of capacity additions and capital investments in electricity generation beyond 2025 are more than three times the rates during the next decade. Our results demonstrate the need for global stocktaking exercises to evaluate the NDCs using metrics broader than emissions to better illuminate their effectiveness in addressing the Paris Agreement’s long-term goals^6,7.

中文翻译：

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衡量从国家确定的贡献到本世纪中期战略的进展

《巴黎协定》要求各国通过传达国家自主贡献（NDC），并鼓励制定长期低排放发展战略（第4.19条）¹，阐明到2025年或2030年的近期减排战略。作为回应，许多国家已经提交或正在准备本世纪中叶的战略²。大多数NDC都设定了近期的高层目标，例如排放限制或排放强度³-这些信息未提供有关它们在多大程度上奠定了技术，基础设施和机构的基础，以便在将来进一步深化减排，这对于决策者来说是一个关键问题。在这里，使用嵌入在全球综合评估模型中的美国的州级模型^4,5，我们证明，尽管美国NDC处于通往本世纪中叶战略的直线排放路径上，但由此产生的能源系统转换涉及非线性转换。2025年以后的发电能力增加和资本投资率是下一个十年的三倍以上。我们的结果表明，需要进行全球盘点活动，以使用比排放量更广泛的指标来评估NDC，以更好地阐明其在实现《巴黎协定》的长期目标^6,7方面的有效性。