Institute for Atmospheric and Climate Science, ETH Zurich, Universitätstrasse 16, CH-8092 Zürich, Switzerland.
Nature. 2013 Jan 3;493(7430):79-83. doi: 10.1038/nature11787.
For more than a decade, the target of keeping global warming below 2 °C has been a key focus of the international climate debate. In response, the scientific community has published a number of scenario studies that estimate the costs of achieving such a target. Producing these estimates remains a challenge, particularly because of relatively well known, but poorly quantified, uncertainties, and owing to limited integration of scientific knowledge across disciplines. The integrated assessment community, on the one hand, has extensively assessed the influence of technological and socio-economic uncertainties on low-carbon scenarios and associated costs. The climate modelling community, on the other hand, has spent years improving its understanding of the geophysical response of the Earth system to emissions of greenhouse gases. This geophysical response remains a key uncertainty in the cost of mitigation scenarios but has been integrated with assessments of other uncertainties in only a rudimentary manner, that is, for equilibrium conditions. Here we bridge this gap between the two research communities by generating distributions of the costs associated with limiting transient global temperature increase to below specific values, taking into account uncertainties in four factors: geophysical, technological, social and political. We find that political choices that delay mitigation have the largest effect on the cost-risk distribution, followed by geophysical uncertainties, social factors influencing future energy demand and, lastly, technological uncertainties surrounding the availability of greenhouse gas mitigation options. Our information on temperature risk and mitigation costs provides crucial information for policy-making, because it clarifies the relative importance of mitigation costs, energy demand and the timing of global action in reducing the risk of exceeding a global temperature increase of 2 °C, or other limits such as 3 °C or 1.5 °C, across a wide range of scenarios.
在过去的十年中，将全球变暖控制在 2°C 以下一直是国际气候辩论的一个关键焦点。为此，科学界已经发布了许多情景研究，这些研究估计了实现这一目标的成本。产生这些估计仍然是一个挑战，特别是因为存在相对知名但量化程度较差的不确定性，并且由于跨学科的科学知识有限整合。一方面，综合评估界广泛评估了技术和社会经济不确定性对低碳情景及其相关成本的影响。另一方面，气候建模界多年来一直在努力提高对地球系统对温室气体排放的地球物理响应的理解。这种地球物理响应仍然是缓解情景成本的一个关键不确定性，但仅在初步基础上与其他不确定性的评估相结合，也就是说，仅在平衡条件下。在这里，我们通过生成与将瞬态全球温度升高限制在特定值以下相关的成本分布来弥合这两个研究界之间的差距，同时考虑了四个因素的不确定性：地球物理、技术、社会和政治。我们发现，延迟缓解的政治选择对成本风险分布的影响最大，其次是地球物理不确定性、影响未来能源需求的社会因素，以及最后是围绕温室气体缓解选择的可用性的技术不确定性。我们有关温度风险和缓解成本的信息为决策提供了至关重要的信息，因为它阐明了在降低超过 2°C 全球升温或其他限制（如 3°C 或 1.5°C）的风险方面，缓解成本、能源需求和全球行动的时间在广泛的情景中的相对重要性。
