Analysis of Compound Climate Extremes and Exposed Population in Africa Under Two Different Emission Scenarios

Abstract

It is well established that Africa is particularly exposed to climate extremes including heat waves, droughts, and intense rainfall events. How exposed Africa is to the co-occurrence of these events is however virtually unknown. This study provides the first analysis of projected changes in the co-occurrence of five such compound climate extremes in Africa, under a low (RCP2.6) and high (RCP8.5) emissions scenario. These changes are combined with population projections for a low (SSP1) and high (SSP3) population growth scenario, in order to provide estimates of the number of people that may be exposed to such events at the end of the 21st century. We make use of an ensemble of regional climate projections from the Coordinated Output for Regional Evaluations (CORE) project embedded in the Coordinated Regional Climate Downscaling Experiment (CORDEX) framework. This ensemble comprises five different Earth System Model/Regional Climate Model (ESM/RCM) combinations with three different ESMs and two RCMs. We show that all five compound climate extremes will increase in frequency, with changes being greater under RCP8.5 than RCP2.6. Moreover, populations exposed to these changes are greater under RCP8.5/SSP3, than RCP2.6/SSP1, increasing by 47-and 12-fold, respectively, compared to the present-day. Regions of Africa that are particularly exposed are West Africa, Central-East Africa, and Northeast and Southeast Africa. Increased exposure is mainly driven by the interaction between climate and population growth, and the effect of population alone. This has important policy implications in relation to climate mitigation and adaptation. Plain Language Summary It is well known that Africa is exposed to a range of different climate hazards including droughts, heat waves, and extreme rainfall events, which cause major social and economic suffering. It is, however, largely unknown how exposed the African population is to the co-occurrence of such climate hazards. This is important because compound events will likely increase the suffering far and above that caused by individual climate hazards. In this study, we provide an analysis of potential changes in five different compound events, and the exposure of the African population to them, at the end of this century. Combining exposure to all compound events, the results show that compared to the present-day, the exposure of the African population may increase by 12-and 47-fold in the best-and worst-case scenarios, respectively. The spatial distribution of changes shows that West Africa and central and eastern regions of Africa may be particularly exposed. Increased exposure is mainly caused by the interaction between climate and population growth, and the effect of population alone. These results imply that any policy response designed to reduce exposure needs to address both climatic and socioeconomic factors.

Increasing Compound Heat and Precipitation Extremes Elevated by Urbanization in South China

“…Compound events are defined as comprising a combination of two or more different extremes occurring coincidentally or sequentially within a certain period of time (Mueller and Seneviratne, 2012;AghaKouchak et al, 2014;Leonard et al, 2014;Wahl et al, 2015). These extremes are considered contributing to complex interactions of multiple hazards such as widespread wildfires (Witte et al, 2011), large-scale air pollution (Konovalov et al, 2011) to human society/ ecosystems (Weber et al, 2020). In this study, compound heat and precipitation extremes are defined for each station individually.…”

“…Extreme climate and weather events often occur simultaneously or sequentially within a short period of time, known as compound events (Leonard et al, 2014). As a combination of two or more extremes (e.g., preconditioned heat and subsequent extreme precipitation), compound events often result in larger impacts than individual events (Zscheischler et al, 2018;Weber et al, 2020). Moreover, the hazards resulting from interacted climate extremes may further intensify the magnitude and severity of the risks caused by individual events (Leonard et al, 2014;Alizadeh et al, 2020).…”

“…A compound event with low temperatures, strong wind, and following extreme precipitation in Queensland of Australia caused the deaths of half a million cattle (Cowan et al, 2019). While most existing studies paid much attention to individual events, few focused on compound events with magnified impacts compared to the individual events (Weber et al, 2020).…”

Deciphering Impacts and Human Responses to a Changing Climate in East Africa

“…As a region, East Africa is considered a hot-spot of compound events due to increased population exposure resulting from extreme weather and population growth (Weber et al, 2020). Although parts of the region are well-represented in the literature, the evidence on drivers of climate-related human mobility beyond voluntary migration, direct and indirect factors, and their interlinkages remain inconclusive and context-specific (van der Land et al, 2018;Groth et al, 2020).…”

Assessing mean climate change signals in the global CORDEX-CORE ensemble

“…For example, using CORDEX-CORE, it will now be possible to assess future climate (mean, extremes and hazards) worldwide at an unprecedented resolution of 0.22 • using an homogeneous, consistent ensemble, e.g., (Ciarlo et al 2020;Weber et al 2020). It also complements the ensemble of RCM simulations for regions with a small ensemble size (e.g., Central America (Cavazos et al 2020)).…”