With the 1.5^oC global warming target set to be breached in the next decade, and as the impacts of this warming across the world become more deleterious, Climate Intervention (CI) and in particular Solar Radiation Modification (SRM) will become the subject of global political discussion. While low latitude, developing countries have the most to gain or lose from CI and SRM, they are underrepresented in current discussions, however, decisions regarding development and implementation/rejection of SRM require that these countries be at the center of such conversations.

Preparing the African voice for this discussion is essential and requires a well-resourced and well-connected African research community that understands the regional impacts of global warming and how CI may mitigate or exacerbate these impacts. While there are many SRM research projects around Africa facilitated by the DEGREES Initiative, a coordinated CI research community does not yet exist.

Here we present results from a project that aims to transition the current loose research network into a well-structured CI and SRM research coalition, nurturing an expert SRM community in Africa over the next 5-10 years.

The main component of the project is a workshop that will bring together African CI and SRM researchers alongside representatives of the World Climate Research Programme, the Coordinated Regional Downscaling Experiment (CORDEX-Africa) and International African research institutions. The workshop will discuss how to build, grow, and sustain a coalition of African SRM researchers, considering its research and capacity-building activities, its initial composition, and its structure. The workshop will also develop an initial roadmap of activities for the coalition and consider potential funding sources to support it. Furthermore, we will explore using a research hub model as a vehicle through which the coalition, its activities and growth is supported.

The insights and outcomes from these discussions will be synthesized into a white paper outlining the goals and principles of the coalition, with concrete recommendations for next steps. Key messages of the white paper will be presented in this session.

The work is pioneering and entrepreneurial and we know of no other efforts like this. In fact, we believe this would be the first continental scale SRM research coalition in the world, let alone in the Global South.

How to cite: Lennard, C., Abiodun, B., and Parker, A.: Developing an African Climate Intervention Research Coalition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4373, https://doi.org/10.5194/egusphere-egu24-4373, 2024.

Model of stratospheric aerosol injection deployment scenarios have often assumed that a global sunscreen could be applied to the earth on relatively short notice, perhaps in response to a climate emergency.  This emergency response framing confuse the time scales associated with the commencement of such a program.  Once deployed, stratospheric aerosols could cool the earth quite quickly, but such a deployment would require aircraft and other infrastructure that does not currently exist.  Given the span required to develop and certify a novel aircraft program and thereafter to build a fleet numbering in the hundreds, scenario builders should assume a roughly two-decade interval between a funded launch decision and the attainment of a target level of cooling.

How to cite: Smith, W.: An assessment of the infrastructural and temporal barriers constraining a near-term implementation of a global stratospheric aerosol injection program, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2221, https://doi.org/10.5194/egusphere-egu24-2221, 2024.

Modelling of marine cloud brightening (MCB), a form of solar radiation modification, has thus far proven challenging due to the incongruous nature of the scales required. The microphysics of the cloud droplets and aerosols can only be resolved at really small scales, but just as important are the large-scale impacts on circulation and radiation. Large eddy simulations (LES) seem best placed to deal with this problem; they can resolve circulation an turbulence, but also have small enough grid boxes that useful parametrisation of microphysics can be made. When coupled to parcel models their representation of microphysical processes can be improved even further, although at a computational cost. There have been multiple studies of MCB in LES so far, but with wide-ranging background conditions and experimental designs. This leads to varying results that are challenging to compare. The aim of this study is to directly compare the results of at least two LES models, MONC and DALES, for an MCB experiment. They will first be compared with a historic data set, before being configured to ran the MCB experiment. It is hoped that MONC can also be coupled to a parcel model to improve its representation of cloud microphysics.

How to cite: Smith, W. M.: Comparison of marine cloud brightening in large eddy simulations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-4102, https://doi.org/10.5194/egusphere-egu24-4102, 2024.

Solid particles, such as alumina, calcite, and diamond, have been proposed as an alternative material for the stratospheric aerosol injection (SAI) studies. The traditional SAI set-up based on sulphate aerosols was shown to have several limitations such as stratospheric heating, due to absorption of long wave radiation, or ozone depletion, due to chlorine activation at the particle surfaces. Solid particles are thought to potentially overcome these limitations by having better optical properties and/or larger chemical inertness. In our work, we use for the first time a fully coupled atmosphere-ocean-aerosol-chemistry-climate model SOCOLv4.0, which incorporates a solid particle emission scheme, to assess the SAI effects of the alumina, calcite, and diamond. For each solid particle type, we followed the GeoMIP protocols and performed G4 and G6 experiments, which are cooling efficiency calibration runs and the transient ensemble runs to bring decadal surface temperatures of the SSP5 scenario to the ones from the SSP2 scenario, respectively. For all considered SAI substances, we find that the resulting burden is close to the yearly emission quantity, suggesting an average lifetime of approximately one year. Diamond has the highest burden-per-emission ratio, suggesting a higher lifetime, which is explained by its small particle radius. Sulfur, alumina, and calcite provide very similar cooling per emission, while diamond has a cooling efficiency of about a factor of three higher. Diamond also has the lowest absorption in the long wave, which allows it to show the weakest heating of the lower stratosphere, no increase in the stratospheric water vapour, and smallest dynamical effects on ozone. In terms of surface climate artifacts, those species that show the weakest heating in the stratosphere (calcite and diamond) also show the least anomalies in atmospheric and oceanic circulation patterns compared to the SSP2 scenario. Information on the interaction between alumina, calcite and ozone-relevant chemical cycles is available, but has not been sufficient so far for implementing their ozone chemistry with high confidence in the results. Additional laboratory studies, thus, are required for further modelling research on this subject.

How to cite: Sukhodolov, T., Vattioni, S., Stefanetti, F., Schuring, I., Sedlacek, J., and Chiodo, G.: Solid particle SAI with a fully coupled atmosphere-ocean-aerosol-chemistry-climate model SOCOLv4.0, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18905, https://doi.org/10.5194/egusphere-egu24-18905, 2024.

Potential SRM deployment scenarios are increasingly discussed in the literature and an effort to construct plausible scenarios is underway in the scientific community. Such deployment scenarios underpin the design of possible governance mechanisms of SRM. A wide range of possible scenarios can be envisaged, including unilateral deployment by one actor, uncooperative multi-actor deployment, global centralized deployment or a global moratorium. In order to inform the current dialogue on governance, we explore in this work the behavior of a system where two uncooperative actors deploy SRM. We rely on a simple four-box climate model that responds to stratospheric aerosol injection (SAI) in the northern and southern hemispheres, including the oceanic response. The stratospheric aerosol optical depth has been parameterized with impulse response functions fitted on IPSL-CM6A-LR runs with injections at different latitudes. We couple this model to a control module in order to investigate different controlled SRM deployment strategies, reflecting potential governance scenarios. The two actors inject varying amounts of aerosols in the stratosphere to reach their own climate target which is unknown by the other actor. The climate target can be a temperature target (change of the temperature with respect to the initial state) or a monsoon target (variability of the monsoon index). Depending on the objectives and the characteristics of the deployment strategies by the two actors, we construct several experiments that result in i) involuntary cooperation between the two actors, ii) conflicting behaviors, or ii) one actor taking advantage of the other (free riding). We have also constructed experiments mimicking political decision-making timescales and potential perceived failure of SRM, causing more or less random interruptions of the injections. Although the scenarios are highly idealized and do not represent a realistic implementation of SRM, they help to understand the potential, synergies, risks and challenges of a decentralized, uncooperative deployment of SRM. We will discuss how the analysis of this type of experiments can inform the discussion on potential SRM governance strategies. Our future plans include adding a parametrization of the sea level rise and of ocean acidification into the model to investigate the behavior of these parameters as a result of the different SRM deployment and governance strategies. The simple model could also be used for educational purposes, for example to inform and to train decision-makers on SRM climate intervention and its effects and consequences.

How to cite: Boucher, O., Määttänen, A., Lurton, T., and Ravetta, F.: Idealized modeling of uncooperative two-actor SRM deployment, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6144, https://doi.org/10.5194/egusphere-egu24-6144, 2024.

Diffuse radiation, which is modulated by cloud and aerosol conditions, can have varied impacts on gross primary production (GPP), with the specific impacts depending on vegetation density, environmental conditions, and the specific physiological characteristics of plants. To quantify the sensitivity of GPP variation to changes in diffuse radiation at the global scale, we use several reanalysis datasets and a satellite-derived products with distinct characterizations of the division between direct beam and diffuse radiation, to force the Energy Exascale Earth System Model Land Model (herein ELM). We find large variations in the range of GPP due to the change in ratio of diffuse radiation to the total downward shortwave radiation (or diffuse fraction). The research implies substantial control of diffuse radiation on atmosphere–biosphere interaction, and demonstrates the importance of thoroughly and systematically validating the simulated diffuse radiation by atmosphere modules, along with assessing the ecosystem responses to the diffuse radiation variations within global land models.

How to cite: Shi, M. and Chakraborty, T.: Diffuse radiation characterized gross primary production over the globe, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20697, https://doi.org/10.5194/egusphere-egu24-20697, 2024.

Several geoengineering projects are designed to modify solar radiation to limit global warming. These changes in solar radiation can have impacts on ecohydrological systems which are poorly quantified. In this study, CMIP6 outputs were used to calculate sensitivities of global and local near-surface meteorological variables to solar radiation changes. These sensitivities were applied to the currently observed climate to perturb meteorological variables in response to changes in solar radiation. These new conditions were used as inputs to a mechanistic ecohydrological model (T&C) to analyze the partitioning and changes in energy and water fluxes and the response of vegetation productivity in different biomes and climates. Specifically, we run two simulation scenarios to understand the solar radiation impacts on ecohydrological systems. The first scenario focuses only on changes in solar radiation, while the second scenario considers the combined effects of solar radiation changes and its climate feedback. The results show that, in the absence of climate feedback, changes in solar radiation are mainly reflected in changes in sensible heat, with less impact on the hydrological cycle, and vegetation productivity is positively and linearly correlated with changes in solar radiation. When climate feedback is included, the effects on latent heat and hydrologic variables are more pronounced, and the response of vegetation productivity to negative and positive solar radiation changes tend to be asymmetric. These results provide a basis for how land-surface processes could respond to regional brightening and dimming and future solar geoengineering programs.

How to cite: Wang, Y., Meili, N., and Fatichi, S.: Exploring the impacts of changes in solar radiation on ecohydrological variables, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7258, https://doi.org/10.5194/egusphere-egu24-7258, 2024.

Clouds play a vital role in the Earth's radiation budget, with low-level clouds having a net cooling effect. Evidence shows that forests alter low-level clouds' formation and physical properties (e.g., [1-3]). In their turn, clouds modify radiation transfer, influencing near-surface variables and forest carbon uptake. Shallow cumulus clouds can enhance photosynthesis due to the diffuse fertilization effect, and the relative increase in photosynthesis is most significant in boreal forests compared to other ecosystems [4]. All this evidence suggests a strong atmosphere-biosphere link for boreal forests. 

We use long-term observations at SMEAR II station in Finland and satellite data sets to study how air mass transformation over boreal forests changes the optical properties of low-level clouds. Further, we assess the dynamics of photosynthesis and net ecosystem exchange in response to changing cloud properties and near-surface variables under different low-level clouds. We show that stratus clouds dampen photosynthesis, and the effect is amplified with the time spent by an air mass over a forest. Oppositely, cumulus clouds enhance photosynthesis compared to the clear sky conditions. If an air mass is exposed to the boreal forest for several days, and cumulus clouds form during the daytime, photosynthesis is efficient, and clouds' transmittance somewhat decreases. Our results suggest that shallow cumulus clouds formed in an air mass interacting with boreal forest can become more reflective. At the same time, these clouds provide ideal conditions for enhanced boreal forest carbon uptake.

References

[1] Teuling, A. J., Taylor, C. M., Meirink, J. F., Melsen, L. A., Miralles, D. G., van Heerwaarden, C. C., Vautard, R., Stegehuis, A. I., Nabuurs, G.-J., and de Arellano, J. V.-G.: Observational evidence for cloud cover enhancement over western European forests, Nat. Commun., 8, 14065, 2017. 

[2] Yli-Juuti, T., Mielonen, T., Heikkinen, L., Arola, A., Ehn, M., Isokääntä, S., Keskinen, H.-M., Kulmala, M., Laakso, A., Lipponen, A., Luoma, K., Mikkonen, S., Nieminen, T., Paasonen, P., Petäjä, T., Romakkaniemi, S., Tonttila, J., Kokkola, H., and Virtanen, A.: Significance of the organic aerosol driven climate feedback in the boreal area, Nat. Commun., 12, 5637,  2021. 

[3] Petäjä, T., Tabakova, K., Manninen, A., Ezhova, E., O'Connor, E., Moisseev, D., Sinclair, V. A., Backman, J., Levula, J., Luoma, K., Virkkula, A., Paramonov, M., Räty, M., Äijälä, M., Heikkinen, L., Ehn, M., Sipilä, M., Yli-Juuti, T., Virtanen, A., Ritsche, M., Hickmon, N., Pulik, G., Rosenfeld, D., Worsnop, D. R., Bäck, J., Kulmala, M., and Kerminen, V.-M.: Influence of biogenic emissions from boreal forests on aerosol–cloud interactions, Nat. Geosci., 15, 42–47,  2022. 

[4] Zhou, H., Yue, X., Lei, Y., Zhang, T., Tian, C., Ma, Y., & Cao, Y.: Responses of gross primary productivity to diffuse radiation at global FLUXNET sites. Atmospheric Environment, 244, 117905, 2021.

How to cite: Ezhova, E., Aarne, A., Arola, A., Liponen, A., Lintunen, A., Yli-Juuti, T., Bäck, J., Kokkola, H., Kerminen, V.-M., Petäjä, T., Virtanen, A., and Kulmala, M.: Links between boreal forest and clouds inferred from long-term atmospheric observations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12943, https://doi.org/10.5194/egusphere-egu24-12943, 2024.

Atmospheric transmittance, encompassing parameters such as the clearness index, cloudiness index, and transmitting index, plays a pivotal role in the transfer of electromagnetic energy in the atmosphere. This research aimed to enhance our understanding of solar energy availability by investigating these transmittance indices across specific locations in Nigeria's diverse climatic zones. By analyzing satellite hourly data from MERRA-2 spanning ten years, the diurnal and spatial distribution patterns of solar radiation parameters and transmittance indices were examined. The research identified distinct patterns in the radiation parameters and transmittance indices. In the morning hours, radiation parameters exhibited an increasing trend from coastal to inland locations, while the afternoon period showed a reverse pattern for diffuse solar radiation. Clearness and transmitting coefficient demonstrated consistent increases from the coast inland during both morning and afternoon hours, whereas the cloudiness index displayed an opposite pattern. Moreover, the transmittance indices showed a gradual reduction from west to east during the evening. Coastal regions experienced average annual values of 100W/m2 for diffuse solar radiation, 1443W/m2 for direct solar radiation, and 500W/m2 for global solar radiation, while Sahelian regions recorded 104W/m2, 2081W/m2, and 678W/m2, respectively. The clearness index ranged from 0.35 to 0.54, the cloudiness index ranged from 0.15 to 0.46, and the transmitting coefficient ranged from 0.19 to 0.45 across the studied locations. The observed distribution patterns provide valuable insights into solar energy availability within Nigeria's climatic zones. The contrasting patterns between morning and afternoon periods suggest variations in atmospheric conditions. Importantly, the study emphasizes the significance of the transmitting coefficient in characterizing atmospheric transmittance and its role in defining radiation transfer variables. In conclusion, this research contributes to existing knowledge by evaluating atmospheric transmittance indices and their distribution patterns in specific locations across Nigeria. The findings underscore the importance of considering the transmitting coefficient alongside other parameters to accurately assess solar energy availability. Understanding these indices and their variations is essential for the effective utilization and management of solar energy resources.

How to cite: Obasi-oma, O., Emmanuel, I., Ojo, O., and Adeyemi, B.:  Evaluation of Some Atmospheric Transmittance Indices Over Nigeria, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8269, https://doi.org/10.5194/egusphere-egu24-8269, 2024.

Solar radiation modification (SRM) is increasingly discussed as a tool to reduce or avert global warming and concomitantly the risk of ice-sheet collapse, as is considered possible for the West Antarctic Ice Sheet (WAIS). While there is a growing body of literature on the climate impacts of various hypothetical SRM employment schemes, the concomitant effects on ice sheet dynamics are much less studied let alone understood. We present the first study explicitly modelling the Antarctic Ice Sheet response to global SRM-interventions with a continental scale ice sheet model. Intuitively, the question whether a WAIS collapse can be prevented depends on a manifold of factors such as ice sheet sensitivity, timing and design of the SRM-intervention and underlying climate scenarios. Our study suggests that safeguarding the WAIS from long-term collapse would either require rapid decarbonization efforts or quasi-immediate SRM-interventions. Both cases are either politically unrealistic or imprudent considering the precautionary principle. We discuss the response of the Antarctic Ice Sheet under various climate and SRM scenarios and the associated uncertainties which need to be resolved to get a more conclusive understanding on the impact of SRM-geoengineering strategies on earth’s two remaining large ice sheets. 

How to cite: Sutter, J., Frölicher, T., Jones, A., Wirths, C., and Stocker, T.: Could planetary scale solar radiation management prevent a West Antarctic Ice Sheet collapse? , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15763, https://doi.org/10.5194/egusphere-egu24-15763, 2024.

Heat transported in Circumpolar Deep Water is driving the break-up of ice shelves in the Amundsen Sea sector of Antarctica, that has been simulated to be unavoidable under all plausible greenhouse gas scenarios. However, climate intervention scenarios have not been considered. Solar geoengineering changes global thermal radiative balance, and atmospheric and oceanic transportation pathways. We simulate stratospheric aerosol injection (SAI) designed to reduce global mean temperatures from those under the unmitigated SSP5-8.5 scenario to those under the SSP2-4.5 scenario with six CMIP6-class Earth System Models. These consistently show intensified Antarctic polar vortex and sub-polar westerlies, which mitigates changes to easterly winds along the Amundsen Sea continental shelf compared with greenhouse gas scenarios. The models show significantly cooler Amundsen Sea waters and lower heat content at 300-600 m under SAI than with either solar dimming or the SSP5-8.5 unmitigated greenhouse gas scenarios. However, the heat content increases under all scenarios compared with present day suggesting that although vulnerable ice shelves would continue to thin, the rate would be lower for SAI even with SSP5-8.5 specified greenhouse gases, than for the moderate (SSP2-4.5) scenario. The simulations here use climate interventions designed for global temperature targets; interventions targeted at preserving the frozen high latitudes have also been proposed that might be expected to produce bigger local effects, but potentially deleterious impacts elsewhere. Considering the huge disruptions to society of ice sheet collapse, more research on avoiding them by intervention technology is a moral imperative. 

How to cite: Moore, J., Chen, Y., Yue, C., Jevrejeva, S., Visioni, D., Uotilla, P., and Zhao, L.: Multi-model simulation of solar geoengineering indicates avoidable destabilization of the West Antarctic ice sheet, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7071, https://doi.org/10.5194/egusphere-egu24-7071, 2024.

In this work we apply GFDL Earth System Model (GFDL-ESM4.1) to explore the climate responses to a geoengineering scenario that aims to restrict global warming to 2.0°C above pre-industrial levels (1850–1900) under the CMIP6 overshoot scenario (SSP534-OS) . Simulations of this geoengineering scenario with the CESM Whole Atmosphere Community Climate Model (CESM2-WACCM6) showed nearly unchanged interhemispheric and pole-to-Equator surface temperature gradients relative to present-day conditions around 2020, and reduced global impacts, such as heatwaves, sea ice melting, and large shifts in precipitation patterns (Tilmes et al 2020). Here we implement the identical stratospheric forcing in the GFDL-ESM4.1 model and find excessive global surface cooling and reduced precipitation responses, compared to those projected in CESM2-WACCM. Notably, the Southern Hemisphere experiences more substantial cooling compared to the Northern Hemisphere, accompanied by a north-ward shift in the Intertropical Convergence Zone (ITCZ). These distinct climate responses between GFDL-ESM4.1 and CESM2-WACCM6 can be traced back to their different climate feedback parameters. Furthermore, our analysis reveals that spatially heterogeneous forcing within the geoengineering scenario results in diverse climate feedback parameters even just in one model, through varying surface warming and cooling patterns. This research highlights the importance of considering model structure uncertainties and spatial forcing patterns for a comprehensive evaluation of future scenarios and geoengineering strategies.

How to cite: Zhang, S., Naik, V., Paynter, D., Tilmes, S., and John, J.: Assessing GFDL-ESM4.1 Climate Responses to CESM2-WACCM6 Geoengineering Forcing for 2.0°C Warming Target, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-10285, https://doi.org/10.5194/egusphere-egu24-10285, 2024.

Global warming could surpass the 1.5 ^oC temperature target within a decade and even inevitably exceed 2 ^oC in this century, if fossil fuel emissions are not abated sufficiently and artificial interventions are not implemented. Even a temporary overshoot beyond 2 ^oC potentially disrupts the global carbon cycle, with the risk of irreversible and devastating changes to current terrestrial carbon sinks, such as the tropical forests and the northern high-latitude permafrost. Large-scale geoengineering is proposed as an adjunct to the conventional mitigation to partially counteract anthropogenic warming, and avoid dramatic alterations in the Earth system and the hazardous consequences. However, carbon dioxide removal and solar radiation modification differ in their role in interacting with the terrestrial carbon cycle, through directly interfering with the carbon cycle and indirect perturbation by changing the energy balance. The varied regional responses also affect the capacity of global carbon uptake, which further impacts on the efficacy of geoengineering. It's prudent to investigate the responses of the global terrestrial carbon balance in such context, i.e., the delayed consideration of solar radiation modification or carbon dioxide removal on top of various possible overshoot scenarios, to bring the global temperature back to and maintain the long-term targets.

How to cite: Chen, Y. and Ji, D.: Terrestrial carbon cycle response to solar radiation modification and carbon dioxide removal under potential temperature overshoots , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-613, https://doi.org/10.5194/egusphere-egu24-613, 2024.

Solar radiation management (SRM) has the potential to artificially cool the Earth by increasing the reflection of incoming sunlight. One commonly researched SRM strategy is stratospheric aerosol injection (SAI), which involves the injection of sulphate aerosols into the stratosphere that scatter incoming solar radiation, thus cooling the planet. There are large uncertainties in the potential impact that solar radiation management could have on the biosphere, and further work is required to improve our understanding of the risks associated with this form of climate intervention. This presentation examines the impact of SRM on vegetation carbon, net primary productivity, and land carbon. We take results from five 6th generation climate models (CMIP6) which ran experiments as part of the geoengineering model intercomparison project (GeoMIP) and compare them with a high emissions scenario (ssp585). The GeoMIP experiments aim to investigate the global effects of using stratospheric aerosol injections and directly decreasing solar irradiance to reduce global temperatures to a ‘middle of the road’ scenario (ssp245), but without reducing the high greenhouse gas concentrations. Compared to ssp585, we find that ssp585 plus SRM tends to increases global NPP and land carbon storage. The global patterns of change in vegetation carbon storage vary between the ESMs, but there is a widespread agreement that SRM would have a positive impact on carbon storage and NPP  in the Amazon rainforest.

How to cite: Parry, I., Ritchie, P., and Cox, P.: Analysing the impact of solar radiation management on the terrestrial biosphere in CMIP6 models, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15841, https://doi.org/10.5194/egusphere-egu24-15841, 2024.

Global warming will be devastating for agriculture in Africa, with consequent impacts on horticultural crop suitability. Horticultural crops are the main source of vitamins and antioxidants into our body and provide nutritional security. Stratospheric Aerosol Injection (SAI), which involves the injection of sulfur into the stratosphere to reduce incoming solar radiation to the earth surface, has been proposed as a strategy to reduce global warming rate, however, how this may affect horticultural crops, mango, orange and tomato, in Africa is still unknown. Our study examines the impact of climate change (GHG) and SAI on crop suitability and planting season in Africa. We used datasets from the Stratospheric Aerosol Geoengineering Large Ensembles (GLENS) project for the periods 2011-2030 and 2070-2089 as inputs into Ecocrop model to investigate GHG and SAI impacts on horticultural crops suitability in Africa. Our findings show GHG may lead to an increase of 3-4^oC in both minimum and mean temperature and a 5-10mm increase in total monthly rainfall in West, Central and East Africa but a decrease (10mm) in southern Africa. SAI intervention results in cooling over Africa of up to 3^oC in both minimum and mean temperature and may also lead to a decrease, 10-20mm in total monthly rainfall over the region by the end of century. The intervention may lead to an increase (~0.2) in Suitability Index Value (SIV) of mango and tomato over West and central Africa. However, a projected decrease (~0.3) in SIV is expected for mango and orange from Angola extending to northern Mozambique in southern Africa. In addition, no change in SIV is expected for the three crops in North Africa. SAI intervention may lead to 2-5% increase in suitable area for mango and tomato but a decrease (2%) for orange. The study provides information for decision-makers about choice of adaptation strategies to enhance regional economies and promote healthy nutrition in Africa.

Plain Abstract

Africa's agriculture will suffer greatly from global warming and affect horticulture crops. Our bodies get the majority of their vitamins and antioxidants from horticultural crops, which also offer nutritional security. Although, the injection of sulphur into the stratosphere has been put forward as an option to reduce effect of global warming but how this might impact horticultural crops, tomatoes, oranges, and mangoes, grown in Africa is still unknown. To examine the effects of climate change (GHG) and SAI horticultural crops suitability in Africa, we utilised information from the Stratospheric Aerosol Geoengineering Large Ensembles (GLENS) project for the periods 2011–2030 and 2070–2089 as inputs into the Ecocrop model. Over West and Central Africa, the Suitability Index Value (SIV) of tomatoes and mangoes may rise (~0.2) because of the intervention while for mango and orange a decline (~0.3) in SIV is anticipated from Angola to northern Mozambique in southern Africa. Mango and tomato suitable areas may rise by 2-5% because of SAI intervention but decrease by 2% for orange. Decision-makers can use the study's insights to choose adaption methods that will boost African regional economies and encourage a healthy diet. 

How to cite: Egbebiyi, T. S., Lennard, C., Quagraine, K., Odoulami, R. C., Pinto, I., Abiodun, B. J., Wolski, P., and Tilmes, S.: Potential Impact of Stratospheric Aerosol Injection on Horticulture Suitability in Africa?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-918, https://doi.org/10.5194/egusphere-egu24-918, 2024.

The urgency to limit continued global mean temperature rise has prompted the emergence of methods of solar climate intervention (SCI) to cool the planet. Stratospheric aerosol injection (SAI) is a method of SCI that would cool the planet by injecting aerosols into the stratosphere to reflect a small amount of incoming solar radiation away from Earth. There is not yet a complete understanding of how the impacts and risks of SAI on human and natural systems compare to those of climate change alone. While there has been some work that has examined the potential impact of SAI on extreme weather events, none has thoroughly examined the potential impact of SAI on warm spells, defined as prolonged periods of anomalously warm temperature that may occur at any time of the year. Warm spells have detrimental impacts that are projected to worsen with continued climate warming including risks to human health, agriculture and ecosystems. Here, the impact of SAI on the frequency, magnitude, intensity, and duration of warm spells is investigated globally using the ARISE-SAI simulations. Specifically, future projections of warm spells under ARISE-SAI are compared to those under climate change alone following the moderate SSP2-4.5 emissions scenario.  The ARISE-SAI simulations indicate that increases in the frequency, magnitude, intensity and duration of warm spells could be limited if SAI were to be deployed, although there is significant regional variability. 

How to cite: Glade, I. and Hurrell, J.: Assessing the impact of stratospheric aerosol injection on warm spell characteristics, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1689, https://doi.org/10.5194/egusphere-egu24-1689, 2024.

Climate intervention through solar radiation modification is one proposed method for reducing climate risks from anthropogenic warming. Marine Cloud Brightening (MCB), one such approach, proposes to inject sea salt aerosol into a regional marine boundary layer to increase marine clouds' reflectivity. This study assessed the potential influence of four MCB experiments on the climate in Africa using simulations from the Community Earth System Model (CESM2) with the Community Atmospheric Model (CAM6). Four idealised MCB experiments were performed with the CESM2(CAM6) model under a medium-range background forcing scenario (SSP2-4.5) by setting cloud droplet number concentrations to 600 cm^-3 over three subtropical ocean regions: (a) Northeast Pacific (MCB_NEP); (b) Southeast Pacific (MCB_SEP); (c) Southeast Atlantic (MCB_SEA); and (d) the combination of these three regions (MCB_ALL). The CESM2(CAM6) model reproduces the observed spatial distribution and seasonal cycle of precipitation and minimum and maximum temperatures over Africa and its climatic zones well. The results suggest that MCB_SEP would induce the strongest global cooling effect and thus could be the most effective in decreasing (increasing) temperatures (precipitation) and associated extremes across most parts of the continent, especially over West Africa, in the future (2035-2054) while other regions could remain warmer or dryer compared to the historical climate (1995-2014). While the projected changes under MCB_ALL are similar to those of MCB_SEP, MCB_NEP and MCB_SEA could result in more warming and, in some regions of Africa, create a warmer future than under SSP2-4.5. Also, all MCB experiments are more effective in cooling maximum temperature and related extremes than minimum temperature and related extremes. These findings further suggest that the climate impacts of MCB in Africa are highly sensitive to the deployment region.

How to cite: Odoulami, R. C., Hirasawa, H., Kouadio, K., Patel, T. D., Quagraine, K. A., Pinto, I., Egbebiyi, T. S., Abiodun, B. J., Lennard, C., and New, M. G.: Africa's Climate Response to Marine Cloud Brightening, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-6419, https://doi.org/10.5194/egusphere-egu24-6419, 2024.

How to cite: Koesuma, S., Faqih, A., Hendri, H., Listyarini, J., Madi Astiani, A., Azzahra Kusuma, D., and Gernowo, R.: Tropical Cyclone-related Extreme Rainfall and Its Impact under Solar Radiation Management (SRM) in Eastern Indonesia Region , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20960, https://doi.org/10.5194/egusphere-egu24-20960, 2024.