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The spatiotemporal variability of meteorological droughts, its changes and hot spots location across Africa are analysed for the period spanning 1928–2017 using the Standardized Precipitation Index (SPI) applied to the precipitation products from the Climatic Research Unit (CRU), University of Delaware (UDEL) and Global Precipitation Climatology Centre (GPCC). Spatially, an analysis based on rotational empirical orthogonal function identifies five regions of similar drought variability, namely the Sahel, East Africa, East Southern Africa, West Southern Africa and the Gulf of Guinea. Temporally, the most common periods of drought occurrence are the 1970s, the 1980s and, to a lesser extent, the 1990s. Changes in drought characteristics for the intermediate past (1958–1987) and recent past (1988–2017) compared to the far past (1928–1957) indicate robust increases of drought duration, frequency and severity in the Sahel, and to a lower extent in the Gulf of Guinea, some areas of Central Africa, part of Southern Africa and over Madagascar. These changes are stronger (weaker) along the Sahel during the intermediate past (recent past) and stronger (weaker) over Central and Southern Africa and Madagascar during the recent past (intermediate past). As a consequence, drought hot spots, mostly driven by severity during the regions' wet season, are identified in areas confined in the Sahel during the intermediate past and in regions mainly over Central and Southern Africa and Madagascar during the recent past. Our results are useful for drought disaster risk management across Africa and provide a valuable reference for future drought analysis under global warming conditions. [ABSTRACT FROM AUTHOR]

Global warming is likely to cause a progressive drought increase in some regions, but how population and natural resources will be affected is still underexplored. This study focuses on global population, forests, croplands and pastures exposure to meteorological drought hazard in the 21st century, expressed as frequency and severity of drought events. As input, we use a large ensemble of climate simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX), population projections from the NASA‐SEDAC dataset and land‐use projections from the Land‐Use Harmonization 2 project for 1981–2100. The exposure to drought hazard is presented for five Shared Socioeconomic Pathways (SSP1‐SSP5) at four Global Warming Levels (GWLs: 1.5°C to 4°C). Results show that considering only Standardized Precipitation Index (SPI; based on precipitation), the SSP3 at GWL4 projects the largest fraction of the global population (14%) to experience an increase in drought frequency and severity (versus 1981–2010), with this value increasing to 60% if temperature is considered (indirectly included in the Standardized Precipitation‐Evapotranspiration Index, SPEI). With SPEI, considering the highest GWL for each SSP, 8 (for SSP2, SSP4, SSP5) and 11 (SSP3) billion people, that is, more than 90%, will be affected by at least one unprecedented drought. For SSP5 at GWL4, approximately 2 × 106 km2 of forests and croplands (respectively, 6% and 11%) and 1.5 × 106 km2 of pastures (19%) will be exposed to increased drought frequency and severity according to SPI, but for SPEI this extent will rise to 17 × 106 km2 of forests (49%), 6 × 106 km2 of pastures (78%) and 12 × 106 km2 of croplands (67%), being mid‐latitudes the most affected. The projected likely increase of drought frequency and severity significantly increases population and land‐use exposure to drought, even at low GWLs, thus extensive mitigation and adaptation efforts are needed to avoid the most severe impacts of climate change. [ABSTRACT FROM AUTHOR]

Two questions motivated this study: 1) Will meteorological droughts become more frequent and severe during the twenty-first century? 2) Given the projected global temperature rise, to what extent does the inclusion of temperature (in addition to precipitation) in drought indicators play a role in future meteorological droughts? To answer, we analyzed the changes in drought frequency, severity, and historically undocumented extreme droughts over 1981–2100, using the standardized precipitation index (SPI; including precipitation only) and standardized precipitation-evapotranspiration index (SPEI; indirectly including temperature), and under two representative concentration pathways (RCP4.5 and RCP8.5). As input data, we employed 103 high-resolution (0.44°) simulations from the Coordinated Regional Climate Downscaling Experiment (CORDEX), based on a combination of 16 global circulation models (GCMs) and 20 regional circulation models (RCMs). This is the first study on global drought projections including RCMs based on such a large ensemble of RCMs. Based on precipitation only, ~15% of the global land is likely to experience more frequent and severe droughts during 2071–2100 versus 1981–2010 for both scenarios. This increase is larger (~47% under RCP4.5, ~49% under RCP8.5) when precipitation and temperature are used. Both SPI and SPEI project more frequent and severe droughts, especially under RCP8.5, over southern South America, the Mediterranean region, southern Africa, southeastern China, Japan, and southern Australia. A decrease in drought is projected for high latitudes in Northern Hemisphere and Southeast Asia. If temperature is included, drought characteristics are projected to increase over North America, Amazonia, central Europe and Asia, the Horn of Africa, India, and central Australia; if only precipitation is considered, they are found to decrease over those areas. [ABSTRACT FROM AUTHOR]

• Drought had most extensive impacts in parts of South Africa, Namibia and Botswana. • The response of vegetation to drought is weaker in Angola, Malawi and Madagascar. • The Community Earth System Model underestimates the magnitudes of drought impacts. • The model ensemble show a spread in vegetation response across biomes and seasons. Drought is a frequent disturbance in many regions of the globe and can have a particularly severe impact on vegetation. Over southern Africa, where drought is a regular occurrence, relatively little is known about how quickly vegetation responds to droughts. We characterized the meteorological drought occurrence in southern Africa from 1981 to 2005 and examined the impacts on vegetation productivity, as derived from satellite data. The spatio-temporal extent and severity of droughts were assessed at different timescales (1- to 18-month timescales) using the Standardized Precipitation Evapotranspiration Index (SPEI) and the Standardized Precipitation Index (SPI). Thereafter, we examined the impacts of droughts on southern African vegetation using the Normalized Difference Vegetation Index (NDVI). The results of this study show that southern African vegetation responds differently to drought over the different timescales. During the 1981–2005 period, droughts had extensive impacts over central parts of South Africa, Namibia and western areas of Botswana and the responses of vegetation varied according to season and biome, likely due to the differences in the levels of water needed by vegetation during various growth/phenological phases. In addition, the magnitude of the drought's impact on vegetation is sensitive to the type of drought index that is used to characterize its severity. We further investigated the response of vegetation as simulated by an Earth System Model (the Community Earth Systems Model, CESM) over the same period. The intensity of drought impacts on vegetation is underestimated by CESM, while the timescales at which vegetation responds to droughts are overestimated by it. Different model ensemble members show a substantial spread in the simulation of vegetation response across different biomes and seasons, which may be due to inherent errors and biases in the land component of the model (CLM4.5), or in the atmospheric model and/or the parameterizations. However, we demonstrate that the land component of the CESM (CLM4.5) does provide an adequate representation of the response of vegetation to drought and would provide useful information about the response of vegetation to future drought. If the uncertainties we identified could be reduced, a more realistic simulation of the vegetation response to drought could be realized. [ABSTRACT FROM AUTHOR]