Multi-annual predictions of hot, dry and hot-dry compound extremes

Abstract. Hot-dry compound extremes have recently gained increasing attention due to their potential impacts on environments and societies. For these reasons, assessing climate predictions is essential to providing reliable information on such extremes. However, despite several studies focusing on compound extremes in the past and climate projections, little is known on a multi-annual timescale. At this regard, decadal climate predictions have been produced to provide useful information for this specific timescale. Thus, we evaluate the ability of the CMIP6 multi-model decadal climate hindcast in predicting hot-dry climate extremes, as well as their hot and dry univariate counterparts for the forecast years 2–5. The multi-model skillfully predicts hot-dry compound extremes and hot extremes over most land regions, while the skill is more limited for dry extremes. However, we find only small and spatially limited improvements from the initialisation of the hindcasts, especially for the hot-dry compound extremes, with most of the skill coming from external forcings, especially long-term trends. Finally, we find the decadal hindcast to be able to reproduce the connections between the compound extremes and their hot and dry univariate components. Evaluations such as this of decadal hindcast are an essential tool to establish the potential and the limits of these products, a necessary step to provide reliable and useful information regarding such impactful extremes.