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Solar climate intervention refers to a group of methods for reducing climate risks associated with anthropogenic warming by reflecting sunlight. Marine cloud brightening (MCB), one such approach, proposes to inject sea‐salt aerosol into one or more regional marine boundary layer to increase marine cloud reflectivity. Here, we assess the potential influence of various MCB experiments on Africa's climate using simulations from the Community Earth System Model (CESM2) with the Community Atmosphere Model (CAM6) as its atmospheric component. We analyzed four idealized MCB experiments under a medium‐range background forcing scenario (SSP2‐4.5), which brighten clouds over three subtropical ocean regions: (a) Northeast Pacific (MCBNEP); (b) Southeast Pacific (MCBSEP); (c) Southeast Atlantic (MCBSEA); and (d) these three regions simultaneously (MCBALL). Our results suggest that the climate impacts of MCB in Africa are highly sensitive to the deployment region. MCBSEP would produce the strongest global cooling effect and thus could be the most effective in decreasing temperatures, increasing precipitation, and reducing the intensity and frequency of temperature and precipitation extremes across most parts of Africa, especially West Africa, in the future (2035–2054) compared to the historical climate (1995–2014). MCB in other regions produces less cooling and wetting despite similar radiative forcings. While the projected changes under MCBALL are similar to those of MCBSEP, MCBNEP and MCBSEA could see more residual warming and induce a warmer future than under SSP2‐4.5 in some regions across Africa. All MCB experiments are more effective in cooling maximum temperature and related extremes than minimum temperature and related extremes. Plain Language Summary: We investigate the potential impact of artificially increasing marine cloud reflectivity on Africa's climate. Human influence on the climate is projected to increase the risk of damaging extreme events across the globe. In Africa, one of the most vulnerable regions to climate change, these impacts are already being felt, especially among communities least able to adapt. It is possible to increase the reflectivity of marine clouds by spraying them with sea salt particulates. This approach was proposed as one possible way of reducing warming by reducing the amount of sunlight reaching the earth's surface. The potential implications of such initiatives for the climate system remain uncertain, especially in Africa. In this study, we analyzed a climate model, that simulates increased reflectivity of clouds to assess the potential impacts of artificially brightening clouds over different subtropical marine regions on the African climate, focusing on mean and extreme precipitation and temperature events. Our results suggest that the impact of artificially increasing marine cloud reflectivity depends on the marine region of intervention. Key Points: The climate impacts of Marine Cloud Brightening (MCB) in Africa are highly sensitive to the deployment regionMCB in the Southeast Pacific could effectively cool Africa and reduces temperature and precipitation extremesIn this study, MCB is more effective in cooling maximum temperature and related extremes than minimum temperature and related extremes [ABSTRACT FROM AUTHOR]

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]

We assess the daily characteristics of recent past precipitation over Africa by means of a large ensemble of observational products, including reanalysis, gauge‐based, and satellite‐based products. The spatial distribution of seasonal mean precipitation varies considerably amongst products especially over areas where gauge networks are sparse. Large uncertainties in the annual precipitation cycle are visible in particular over the Ethiopian Highlands, the eastern Sahel, the coasts of the Gulf of Guinea, and the Horn of Africa. Interannual variability shows large differences especially amongst reanalysis data sets whereas satellite and gauge‐based products usually show more consistent results. Plain Language Summary: Southern Africa and the Atlas region show the largest agreement amongst different products for most of the precipitation characteristics, including annual time series and trends, spatial and temporal correlations, and indices of mean and extreme events. Over other regions, discrepancies amongst different products are larger, especially for indices based on short time scales, in particular, over the regions affected by the monsoon (the Sahel, the coasts of the Gulf of Guinea, and Central Africa). Observed precipitation characteristics have been compared to the results of state‐of‐the‐art regional climate models (RCMs). Given the impossibility to select a single "best" observation data set for a realistic representation of all precipitation characteristics, our results show that comparing model results to a very limited set of observations is not only pointless, but it can be even misleading. When similarly large ensembles of model results and observations are compared, our findings show that RCMs are able to reproduce daily precipitation characteristics as well as the observations. Key Points: Precipitation over Africa is assessed by means of a large ensemble of reanalysis, gauge‐based, and satellite‐based productsSouthern Africa and the Atlas region show the largest agreement amongst different products for most of the precipitation characteristicsSimilarly large ensembles of regional models are able to reproduce daily precipitation characteristics as well as the observations [ABSTRACT FROM AUTHOR]

Anthropogenic warming is projected to increase the magnitude and frequency of extreme events, whose impacts are already being felt in vulnerable regions in sub‐Saharan Africa. Solar radiation management (SRM) has been proposed as an interim measure to offset warming while emissions are reduced; however, the impact of stratospheric SRM on regional climate extremes have not yet been explored, particularly in the Paris agreement context. We investigate the potential impact of SRM on temperature and rainfall means and extremes over sub‐Saharan Africa using simulations from the Geoengineering Large Ensemble. We found SRM significantly reduces temperature means and extremes; however, the effect on precipitation is not as linear. The results should be interpreted with caution as they are particular to this approach of SRM and this modelling experiment. Plain Language Summary: We investigate the potential impact of artificially reducing the amount of sunlight that reaches the Earth's surface on the climate over sub‐Saharan Africa. Human induced warming is projected to increase the magnitude and frequency of extreme events, whose impacts are already being felt in vulnerable regions in sub‐Saharan Africa. Large volcanic eruptions can reduce the global mean temperature. Similarly, the continuous injection of microscopic particles in the upper atmosphere to artificially reduce some of the amount of sunlight reaching the Earth's surface has been proposed as a measure to reduce global temperature while emissions are reduced. The impact of such actions on regional climate extremes is still unclear especially in sub‐Saharan Africa. We analyzed climate model simulations from the Geoengineering Large Ensemble to explore the projected impact of artificial sunlight reduction on climate extremes sub‐Saharan Africa with continued emissions of greenhouse gases. We found that artificially altering the sunlight reduces mean and extreme temperatures, while the effect on rainfall is not as linear and remains uncertain. Key Points: The benefit of SRM as mitigation strategy is larger for temperature than precipitation over AfricaThere is a regional diversity in the response to SRMSRM is effective over Central and East Africa while changes over West and Southern Africa are mixed [ABSTRACT FROM AUTHOR]

Understanding the processes responsible for precipitation and its future change is important to develop plausible and sustainable climate change adaptation strategies, especially in regions with few available observed data like Congo Basin (CB). This paper investigates the atmospheric circulation processes associated with climate model biases in CB rainfall, and explores drivers of projected rainfall changes. Here we use an ensemble of simulations from the Swedish Regional Climate Model (RCM) RCA4, driven by eight General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Phase 5 (CMIP5), for the 1.5 ∘ C and 2 ∘ C global warming levels (GWLs), and under the representative concentration pathways (RCPs) 4.5 and 8.5. RCA4 captures reasonably well the observed patterns of CB rainfall seasonality, but shows dry biases independent of seasons and large scale driving atmospheric conditions. While simulations mimic observed peaks in transition seasons (March–May and September–November), the rain-belt is misplaced southward (northward) in December–February (June–August), reducing the latitudinal extent of rainfall. Moreover, ERA-Interim reanalysis driven RCM simulation and RCM–GCM combinations show similar results, indicating the dominance of systematic biases. Modelled dry biases are associated with dry upper-tropospheric layers, resulting from a western outflow stronger than the eastern inflow and related to the northern component of African Easterly Jet. From the analysis of the climate change signal, we found that regional scale responses to anthropogenic forcings vary across GWLs and seasons. Changes of rainfall and moisture divergence are correlated, with values higher in March–May than in September–November, and larger for global warming of 2.0 ∘ C than at 1.5 ∘ C . There is an increase of zonal moisture divergence fluxes in upper atmospheric layers ( > 700 hPa ) under RCP8.5 compared to RCP4.5. Moreover, it is found that additional warming of 0.5 ∘ C will change the hydrological cycle and water availability in the CB, with potential to cause challenges to water resource management, agriculture, hydro-power generation, sanitation and ecosystems. [ABSTRACT FROM AUTHOR]