In our recently published work, we incorporated planetary boundaries in the optimization of the United States (US) power sector in 2030. Yang claims there is a double-counting error in our results and encourages us to minimize direct emissions instead of life cycle emissions in our model. Here, we argue that Yang's main criticism based on the risk of double-counting emissions when multiple sectors are simultaneously optimized does not apply to our case study, in which only one sector – the power sector – is analyzed. To assess the implications of Yang's suggestion to minimize direct emissions, we repeated the calculations optimizing direct emissions instead of life cycle emissions. We found that this approach is unable to discriminate effectively between electricity production technologies and, consequently, leads to a suboptimal mix with impacts on climate change, ocean acidification and freshwater use 102, 33 and 1.5 times the limits, respectively, whereas our original solution meets all planetary boundaries concurrently. Our findings imply that Yang's suggestion of optimizing direct emissions in energy systems models might not the best way forward in single-sector studies like ours.

中文翻译：

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回复能源环境的杨扬（Y. Yang）所作的“关于在全球范围内推动可持续发展的评论”。科学，2020，13，DOI：10.1039 / C9EE01176E

在我们最近发表的工作中，我们在2030年将行星边界纳入了美国（US）电力部门的优化。Yang声称我们的结果存在重复计算误差，并鼓励我们将直接排放量而不是生命周期排放量降至最低我们的模型。在这里，我们认为，杨的主要批评是基于多个部门同时优化时的重复计算排放风险，这一点不适用于我们的案例研究，在该案例研究中，仅分析了一个部门（电力部门）。为了评估Yang提出的将直接排放量降至最低的建议的含义，我们重复了优化直接排放量而不是生命周期排放量的计算。我们发现，这种方法无法有效地区分电力生产技术，因此，导致混合效果欠佳，对气候变化，海洋酸化和淡水使用的影响分别是限值的102倍，33倍和1.5倍，而我们的原始解决方案同时满足所有行星边界的要求。我们的发现表明，杨的建议对能源系统模型中的直接排放进行优化可能不是像我们这样的单部门研究的最佳方法。