Probabilistic cost estimates for climate change mitigation

摘要

For more than a decade, the target of keeping global warming below 2 ℃ 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 ℃, or other limits such as 3 ℃ or 1.5 ℃, across a wide range of scenarios.%减缓气候变化的成本上所存在的不确定性是由rn地球物理学、技术、以及社会系统和政治上的rn不确定性决定的。通常，地球物理不确定性是rn与其他三方面的不确定性分开评估的，这使得rn对主要不确定性因素进行总体评估有困难。rnJoeri Rogeli及其同事利用一种综合模拟方法来rn计算在四个主要不确定性影响之下使气候保持rn在某个全球变暖阈限(比如说已经被讨论很多rn的2℃)之下所涉及的成本。他们发现，政治rn不确定性迄今对成本分布影响最大。作者根据rn他们的结果得出结论认为，如果要使2℃的目rn标变成现实，我们在2020年之前就必须走一rn条高效率的、低能源需求的路线，同时采取减rn缓气候变暖的措施。