Over the past decades, large variations of precipitation were observed in Africa, which often led to dramatic consequences for local society and economy. To avoid such disasters in the future, it is crucial to better anticipate the expected changes, especially in the current context of climate change and population growth. To this date, however, projections of precipitation over Africa are still associated with very large uncertainties. To better understand how this uncertainty can be reduced, this study uses an advanced Bayesian analysis of variance (ANOVA) method to characterize, for the first time in the regional climate projections of CORDEX-AFRICA, the different sources of uncertainty associated with the projections of precipitation over Africa. By 2090, the ensemble mean precipitation is projected to increase over the Horn of Africa from September to May and over the eastern Sahel and Guinea Coast from June to November. It is projected to decrease over the northern coast and southern Africa all year long, over western Sahel from March to August, and over the Sahel and Guinea Coast from March to May. Most of these projections however are not robust, i.e., the magnitude of change is smaller than the associated uncertainty. Over time, the relative contribution of internal variability (excluding interannual variability) to total uncertainty is moderate and quickly falls below 10%. By 2090, it is found that over the Horn of Africa, northern coast, southern Africa, and Sahel, most of the uncertainty results from a large dispersion across the driving Global Climate Models (in particular MIROC, CSIRO, CCCma, and IPSL), whereas over the tropics and parts of eastern Africa, most of the uncertainty results from a large dispersion across Regional Climate Models (in particular CLMcom).

中文翻译：

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评估 CORDEX-AFRICA 区域降水预测的不确定性

在过去的几十年里，在非洲观察到了大量的降水变化，这往往会给当地社会和经济带来巨大的后果。为了避免未来发生此类灾难，更好地预测预期变化至关重要，尤其是在当前气候变化和人口增长的背景下。然而，迄今为止，对非洲降水的预测仍然存在很大的不确定性。为了更好地了解如何减少这种不确定性，本研究首次使用先进的贝叶斯方差分析 (ANOVA) 方法在 CORDEX-AFRICA 的区域气候预测中表征与非洲降水。到 2090 年，预计 9 月至 5 月非洲之角以及 6 月至 11 月东萨赫勒和几内亚海岸的整体平均降水量将增加。预计全年北部海岸和南部非洲、萨赫勒西部地区从 3 月到 8 月以及萨赫勒和几内亚海岸从 3 月到 5 月都会减少。然而，大多数这些预测并不可靠，即变化的幅度小于相关的不确定性。随着时间的推移，内部变率（不包括年际变率）对总不确定性的相对贡献适中，并迅速降至 10% 以下。到 2090 年，发现在非洲之角、北部海岸、南部非洲和萨赫勒地区，大部分不确定性是由驱动全球气候模型（特别是 MIROC、CSIRO、