Across continental Africa, more than 300 new hydropower projects are under consideration to meet the future energy demand that is expected based on the growing population and increasing energy access. Yet large uncertainties associated with hydroclimatic and socioeconomic changes challenge hydropower planning. In this work, we show that only 40 to 68% of the candidate hydropower capacity in Africa is economically attractive. By analyzing the African energy systems' development from 2020 to 2050 for different scenarios of energy demand, land-use change, and climate impacts on water availability, we find that wind and solar outcompete hydropower by 2030. An additional 1.8 to 4% increase in annual continental investment ensures reliability against future hydroclimatic variability. However, cooperation between countries is needed to overcome the divergent spatial distribution of investment costs and potential energy deficits.

Carbon-emitting technologies often cost less than carbon-emission-free alternatives; this difference in cost is known as the Green Premium. Innovations that decrease the Green Premium contribute to achieving climate goals, but a conceptual framework to quantify that contribution has been lacking. Here, we devise a framework to translate reductions in the Green Premium into equivalent reductions in carbon emissions. We introduce a new integrated assessment model designed for teaching and communication, the Climate Optimized INvestment model, to facilitate transparent investigation of cost-saving innovation. We look at consequences of introducing a new technology with potential for learning and improvement for scenarios with three levels of stringency of carbon constraint: an Unlimited budget scenario in which carbon emissions abatement is determined only by balancing marginal costs; a Large budget scenario with a maximum budget for future cumulative emissions equivalent to 50 times the initial-year emissions; and a Small budget scenario with a maximum budget for future cumulative emissions equivalent to 15 times the initial-year emissions. At all of these stringency levels, we find the least-cost solutions involve investing in a learning subsidy to bring the cost of the new technology down the learning curve. Reducing the Green Premium can lead to enhanced carbon abatement, lower abatement costs even after reaching net-zero emissions, less climate damage, and increased net-present-value of consumption. We find both the value of Green Premium reductions and the value of carbon dioxide removal are greater under more stringent mitigation targets. Our study suggests a crucial role for both public and private sectors in promoting and developing innovations that can contribute to achieving zero emissions goals.

Plans for decarbonized electricity systems rely on projections of highly uncertain future technology costs. We use a stylized model to investigate the influence of future cost uncertainty, as represented by different projections in the National Renewable Energy Laboratory 2021 Annual Technology Baseline dataset, on technology mixes comprising least-cost decarbonized electricity systems. Our analysis shows that given the level of future cost uncertainty as represented by these projections, it is not possible to predict with confidence which technologies will play a dominant role in future least-cost carbon emission-free energy systems. Successful efforts to reduce costs of individual technologies may or may not lead to system cost reductions and widespread deployments, depending on the success of cost-reduction efforts for competing and complementary technologies. These results suggest a portfolio approach to reducing technology costs. Reliance on uncertain cost breakthroughs risks costly outcomes. Iterative decision-making with learning can help mitigate these risks.

Efforts to make food systems more sustainable have emphasized reducing adverse environmental impacts of agriculture. In contrast, chemical and biological processes that could produce food without agriculture have received comparatively little attention or resources. Although there is a possibility that someday a wide array of attractive foods could be produced chemosynthetically, here we show that dietary fats could be synthesized with <0.8 g CO2-eq kcal(-1), which is much less than the >1.5 g CO2-eq kcal(-1) now emitted to produce palm oil in Brazil or Indonesia. Although scaling up such synthesis could disrupt agricultural economies and depend on consumer acceptance, the enormous potential reductions in greenhouse gas emissions as well as in land and water use represent a realistic possibility for mitigating the environmental footprint of agriculture over the coming decade.

The 2022 Indus floods in Pakistan underscore the urgency of adapting to more frequent and severe natural disasters in a warming world. Post-disaster reconstruction offers a chance to built-in adaptation measures, but identifying feasible and cost-effective adaptation options is challenging, especially in data-scarce regions. Here we employ a high-resolution rapid assessment of flood stages combined with demographic data to identify adaptation opportunities and costs for the Indus floodplains. Under a plausible set of assumptions, we find that rebuilding houses in a flood-proof, elevated manner ('moving up') or (temporary) relocation ('moving over') could have protected 13%, respectively 16% of people affected during the 2022 floods, while the remaining 70% of people were exposed to shallow water levels that could have been addressed with low-cost adaptation. Implementing these measures during ongoing reconstruction could be an effective adaptation to future floods but will come with substantial costs. Rebuilding in a flood-proofed manner ('moving up') alone would already increase costs by 26%-63% ($1.5bn-$3.6bn) compared to estimated reconstruction costs without adaptation ($5.8bn). Additional costs would be incurred by relocation and adaptation of other infrastructure. The absence of local flood stage and socio-economic data creates uncertainty and points to future research avenues. Yet, our prototype approach demonstrates the value of rapid assessments for guiding post-disaster adaptation of livelihoods to future floods.

Potential temporal and causal connections among various geologic events have long been discussed in the geological literature. More recently, signs of common periodicities in these episodes have been reported. In this study of correlation and cyclicity of geologic occurrences, we review and synthesize previous work, and utilize the newest data for various major events over the the last 260 My. These include, 1) high-quality radio-isotopic age determinations (U-Pb zircon and 40Ar/39Ar) for continental flood-basalt (CFB) eruptions; 2) the dates of widespread intervals of ocean anoxia; 3) the latest published dates of marine and non-marine extinction events, 4) hyper-thermal climate intervals and 5) the occurrences of stratigraphic Hg anomalies, and non-radiogenic Os -isotope anomalies as potential proxies for large-scale basaltic volcanism. Times of at least 13 of 17 intervals of anoxic oceans are marked by stratigraphic Hg-anomalies, pointing to contemporaneous LIP eruptions, and 5 anoxic intervals in the warm Cretaceous Period are correlated with marine Os-isotope ratios suggesting potential LIP hydrothermal activity. Nine of the ocean-anoxic intervals are thus far correlated with times of marine-extinction episodes, and 8 of those anoxia/extinction co-events are significantly correlated with the ages of the well-dated CFB eruptions. Seven of the marine-extinction events and associated CFB volcanism are coeval with extinctions of non-marine vertebrates, supporting global catastrophic volcano-climatic episodes devastating both marine and terrestrial environments.New digital circular spectral analyses revealed significant underlying cycles of-32.5 My and -26.2 My in the ages of the anoxic events and marine extinctions. Spectral analysis of the latest high-quality ages of the CFBs resulted in similar significant periodicities of 32.8 My and 12.9 My (-26.2/2 My harmonic). High-frequency periods at various harmonics appear at-6.4 My, 8.4 My and 9.7 My in each of the three spectra.These findings support a multi-factor extinction scenario in which release of massive amounts of CO2 and perhaps CH4 mostly from CFB magmas (and in some cases sub-volcanic intrusions into carbon-rich deposits), led to very warm climate intervals with near-lethal to lethal hyper-thermal conditions on land and in the sea. Concurrent release of halogens from CFB eruptions could also have decimated the global ozone layer. In many cases, the warm oceans became acidic, and developed anoxic to euxinic conditions, even up to the ocean surface, contributing to the causes of the marine extinctions. Additionally, four extinction events (late Eocene, end -Cretaceous, end-Jurassic and mid-Norian) correlate closely with the ages of the 4 largest impacts (craters >= 100 km in diameter) over the same period, capable of producing severe climatic effects and extinctions.The potential dominant underlying-33-My and 26-My cycles, reported in these and other correlated tectonic, climatic, and biotic events over the last 260 My and beyond, are likely related to the Earth's tectonic-volcanic rhythms, but the similarities with known Milankovitch Earth orbital periods and their amplitude modulations, and with known Galactic cycles, suggest that, contrary to conventional wisdom, the geological events and cycles may be paced by astronomical factors.

Movement of radioactive isotopes in the phloem tissue was investigated by the stripping technic similar to that used by Stout and Hoagland, i.e., the bark was separated from the wood and a piece of paraffined paper was inserted between them. When P32 was introduced to the leaves, it moved both upward and downward chiefly through the phloem tissue. C14 invariably moved in the phloem when supplied to the leaves in the form of C14O2. The simultaneous movement of these 2 radioactive tracers in opposite directions in the phloem was studied by supplying them separately to the leaves at each end of a stripped area. Their radioactivities were separated by the dry combustion method. Radioactivity due to C14 was re-covered in the BaCO3 fraction, while that due to P32 was re-tained in the ash. By carrying out this expt. under continuous light for a short period of time, considerable amt. of both P32 and C14 were found in the phloem of the stripped area. This is considered to be conclusive evidence for the simultaneous movement of P32 and C14 in opposite directions in the phloem tissue.

The Hill reaction was followed by the reduction of an oxidation-reduction dye, 2, 6-dichlorophenol indophenol. Samples of the mixture of the dye and chloroplasts were exposed to monochromatic light obtained from a Wood replica grating monochro-mator. The degree of dye reduction produced by exposure was measured with a Beckman spectrophotometer at the wave length corresponding to the absorption peak of the dye. The action spectrum of this reaction was obtained by plotting the effectiveness of light against wave length. This curve was compared with the absorption spectrum of chloroplast suspension and the photosynthetic action spectra of Chlorella and Ulva. Quantum requirement for this reaction was calculated. All findings are consistent with the view that Hill reaction is identical with the primary photochemical step of photosynthesis. The action spectrum of this reaction thus may be interpreted as a measure of the spectrum effectiveness for the photosynthetic process in chlorophasts of a higher plant.

Cuttings of garnet peridotite were collected between 603.2 and 683.5 in in the CCSD at Donghai. Minerals were separated by various methods and handpicked under a binocular microscope. The selected minerals were identified by SEM-EDS, microprobe, Laser Raman, and EDXD ( Synchrontron X-ray Diffraction). A number of unusual minerals have been recognized from the cuttings, e. g., moissanite, w stite, native Fe, native Cr, native Ni, native An, native Cu, native Al, taenite, kamacite, Ni-Fe-Cr alloy, Ni-Fe alloy, Fe-Cr alloy, Si-Fe alloy (Fe3Sgamma), and Co-Ni alloy. Two grains of Fe2P alloy (barringerite), have also been found. They are spheroidal in shape, with diameters of about 200 mu m, and they have identical hexagonal structures with cell parameters of a = 5.877 angstrom, c = 3.437 angstrom, and a: c = 1 :0.5848. They belong to space group P62m. This mineral, which is similar in structure and composition to artificial Fe2P (ICDD 83-2337), has previously only been found in meteorites. This is the first reported natural terrestrial occurrence of barringerite. Further study on its genesis and formational conditions is underway.

To evaluate the feasibility and capability of using filter-feeding bivalves as biofilters for organic waste derived from fish faeces and feed wastage in marine fish culture activities, a polyculture system comprising fish and green-lipped mussels Perna viridis was developed by transplantation of mussels into fish cages. As a control, mussels from the same population were simultaneously transplanted to a distant reference site free of effects from fish farming activities. After 3 mo acclimation, samples of mussel tissue, particulate organic matter (POM), fish feed and fish faeces were collected for measurements of carbon and nitrogen isotopic ratios and fatty acid profiles. Enrichment of C-13 and N-15 in mussel tissue collected inside the fish cages as compared to those at the reference site indicated the uptake and assimilation of isotopically heavier fish feed and fish faeces. Compared with mussels from the reference site, the pattern of fatty acid profiles and single fatty acids of mussels in fish cages also tended to be closer to fatty acid profiles of fish feed from fish farms. Based on the concentration-weighted isotope mixing model, the proportions of mussel biomass assimilated from POM, fish feed and fish faeces to mussel dietary consumption were 68.3, 27.5 and 4.2%, respectively. The direct uptake of organic waste from fish farms by filter-feeding mussels is different to their consumption of phytoplanktonic biomass, because the nutrient flux is shifted between these 2 distinct pathways.