High future discounting rates favor inaction on present expending while lower rates advise for a more immediate political action. A possible approach to this key issue in global economy is to take historical time series for nominal interest rates and inflation, and to construct then real interest rates and finally obtaining the resulting discount rate according to a specific stochastic model. Extended periods of negative real interest rates, in which inflation dominates over nominal rates, are commonly observed, occurring in many epochs and in all countries. This feature leads us to choose a well-known model in statistical physics, the Ornstein-Uhlenbeck model, as a basic dynamical tool in which real interest rates randomly fluctuate and can become negative, even if they tend to revert to a positive mean value. By covering 14 countries over hundreds of years we suggest different scenarios and include an error analysis in order to consider the impact of statistical uncertainty in our results. We find that only 4 of the countries have positive long-run discount rates while the other ten countries have negative rates. Even if one rejects the countries where hyperinflation has occurred, our results support the need to consider low discounting rates. The results provided by these fourteen countries significantly increase the priority of confronting global actions such as climate change mitigation. We finally extend the analysis by first allowing for fluctuations of the mean level in the Ornstein-Uhlenbeck model and secondly by considering modified versions of the Feller and lognormal models. In both cases, results remain basically unchanged thus demonstrating the robustness of the results presented.

中文翻译：

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统计分析和随机利率模型​​，用于评估对减缓气候变化影响的未来

较高的未来贴现率有利于对当前支出不作为，而较低的利率则建议采取更直接的政治行动。解决全球经济中这一关键问题的一种可能方法是取名义利率和通货膨胀的历史时间序列，然后构建实际利率，最后根据特定的随机模型获得由此产生的贴现率。在许多时代和所有国家，普遍观察到长期负实际利率，其中通货膨胀主导名义利率。这一特征使我们选择统计物理学中的一个著名模型 Ornstein-Uhlenbeck 模型作为基本的动态工具，在该模型中，实际利率随机波动并可能变为负值，即使它们倾向于恢复为正平均值。通过覆盖 14 个国家数百年，我们提出了不同的方案，并包括错误分析，以考虑统计不确定性对我们结果的影响。我们发现只有 4 个国家的长期贴现率为正，而其他 10 个国家的利率为负。即使人们拒绝发生恶性通货膨胀的国家，我们的结果也支持考虑低贴现率的必要性。这 14 个国家提供的结果显着提高了应对气候变化减缓等全球行动的优先级。我们最终通过首先考虑 Ornstein-Uhlenbeck 模型中平均水平的波动来扩展分析，其次通过考虑 Feller 和对数正态模型的修改版本。在这两种情况下，