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Abstract

Geological storage and mineralization of CO2 in mafic/ultramafic reservoirs faces challenges including limited effective porosity, permeability, and rock reactivity; difficulties in using seawater for CO2 capture; and uncontrolled carbonation. This study introduces a CO2 capture, storage, and mineralization approach with the utilization of biobased biodegradable chelating agents and seawater. An acidic chelating agent solution is used to increase effective porosity and permeability through enhanced mineral dissolution. For instance, applying an acidic N,N-Bis(carboxymethyl)-L-glutamate solution to a porous basalt increased effective porosity by 16% and permeability by 26-fold in 120 hours. Subsequently, alkaline chelating agent–containing seawater improves CO2 capture and storage by inhibiting mineralization, thus maintaining injectivity while providing ions for mineralization and further expanding storage space. Last, controlled mineralization is achieved by adjusting chelating agent biodegradation. Promising CO2 storage and mineralization capacities two orders higher than current techniques, this approach reduces required reservoir volume while enhancing efficiency.

Abstract

The fast rollout of hydrogen generation, transport, and storage infrastructure has become a top priority of the European Union and its member states. Planning hydrogen infrastructure requires a thorough understanding of the future role of hydrogen in the energy system. At the same time, there is still huge uncertainty about the future demand for hydrogen and its overall role. An energy systems analysis is conducted with high temporal and spatial as well as technological resolution under alternative demand scenarios. An energy system model is used to optimize the entire European energy system with hourly time resolution and high spatial consideration of renewable energy potentials. The hydrogen demand in the five scenarios ranges from about 700 TWh for mainly industrial uses to 2800 TWh in all sectors in the EU27 + UK by 2050. The results show that an integrated European hydrogen system is a robust element of the cost-optimal system design in all scenarios. This encompasses flexible electrolyzers at the most favorable wind and solar locations, long-distance hydrogen transport network, large-scale seasonal underground storage, and electricity generation for peak demand periods. Conclusions about the individual components are provided and high-resolution data on hydrogen demand are available for future research.

Editor’s summary

Forever chemicals such as per- and polyfluoroalkyl substances (PFAS) are potential hazards for the environment and human health. The detection of PFAS in groundwater is particularly concerning, especially for drinking water sources. Tokranov et al. compiled a large database of US groundwater observations as the basis for a model to estimate the probability of PFAS contamination based on well depth. The data come from a range of well types, including those for observation, domestic tap water, and public water supply. The model highlights that about 80 million people in the conterminous US rely on groundwater with detectable amounts of PFAS before treatment. —Brent Grocholski

Abstract

Per- and polyfluoroalkyl substances (PFAS), known colloquially as “forever chemicals,” have been associated with adverse human health effects and have contaminated drinking water supplies across the United States owing to their long-term and widespread use. People in the United States may unknowingly be drinking water that contains PFAS because of a lack of systematic analysis, particularly in domestic water supplies. We present an extreme gradient–boosting model for predicting the occurrence of PFAS in groundwater at the depths of drinking water supply for the conterminous United States. Our model results indicate that 71 million to 95 million people in the conterminous United States potentially rely on groundwater with detectable concentrations of PFAS for their drinking water supplies before any treatment.

Abstract

Climate change affects marine organisms, causing migrations, biomass reduction and extinctions1,2. However, the abilities of marine species to adapt to these changes remain poorly constrained on both geological and anthropogenic timescales. Here we combine the fossil record and a global trait-based plankton model to study optimal temperatures of marine calcifying zooplankton (foraminifera, Rhizaria) through time. The results show that spinose foraminifera with algal symbionts acclimatized to deglacial warming at the end of the Last Glacial Maximum (LGM, 19–21 thousand years ago, ka), whereas foraminifera without symbionts (non-spinose or spinose) kept the same thermal preference and migrated polewards. However, when forcing the trait-based plankton model with rapid transient warming over the coming century (1.5 °C, 2 °C, 3 °C and 4 °C relative to pre-industrial baseline), the model suggests that the acclimatization capacities of all ecogroups are limited and insufficient to track warming rates. Therefore, foraminifera are projected to migrate polewards and reduce their global carbon biomass by 5.7–15.1% (depending on the warming) by 2100 relative to 1900–1950. Our study highlights the different challenges posed by anthropogenic and geological warming for marine plankton and their ecosystem functions.

Abstract

Large stocks of soil carbon (C) and nitrogen (N) in northern permafrost soils are vulnerable to remobilization under climate change. However, there are large uncertainties in present-day greenhouse gas (GHG) budgets. We compare bottom-up (data-driven upscaling and process-based models) and top-down (atmospheric inversion models) budgets of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) as well as lateral fluxes of C and N across the region over 2000–2020. Bottom-up approaches estimate higher land-to-atmosphere fluxes for all GHGs. Both bottom-up and top-down approaches show a sink of CO2 in natural ecosystems (bottom-up: −29 (−709, 455), top-down: −587 (−862, −312) Tg CO2-C yr−1) and sources of CH4 (bottom-up: 38 (22, 53), top-down: 15 (11, 18) Tg CH4-C yr−1) and N2O (bottom-up: 0.7 (0.1, 1.3), top-down: 0.09 (−0.19, 0.37) Tg N2O-N yr−1). The combined global warming potential of all three gases (GWP-100) cannot be distinguished from neutral. Over shorter timescales (GWP-20), the region is a net GHG source because CH4 dominates the total forcing. The net CO2 sink in Boreal forests and wetlands is largely offset by fires and inland water CO2 emissions as well as CH4 emissions from wetlands and inland waters, with a smaller contribution from N2O emissions. Priorities for future research include the representation of inland waters in process-based models and the compilation of process-model ensembles for CH4 and N2O. Discrepancies between bottom-up and top-down methods call for analyses of how prior flux ensembles impact inversion budgets, more and well-distributed in situ GHG measurements and improved resolution in upscaling techniques. Key Points

The northern terrestrial permafrost region was a weak annual CO2 sink and stable source of CH4 and N2O during the time period 2000–2020

The global warming potential is indistinguishable from neutral over a 100 years time period but a net source of warming over a 20 year period

Bottom-up and top-down methods yield different magnitudes of estimates that cannot be fully reconciled

Plain Language Summary

The northern permafrost region covers large areas and stores very large amounts of carbon and nitrogen in soils and sediments. With climate change, there is concern that thawing permafrost will release greenhouse gases into the atmosphere, shifting the region from long-term cooling of the global climate to a net warming effect. In this study, we used different techniques to assess the greenhouse gas budgets of carbon dioxide, methane and nitrous oxide for the time period 2000‒2020. We find that the region is a net sink of carbon dioxide, mainly in boreal forests and wetlands, while carbon dioxide is emitted from inland waters and fires affecting both forest and tundra. Lakes and wetlands are strong sources of methane, which contributes to warm the climate significantly, especially over shorter timescales. Nitrous oxide is emitted at low rates across the region, with a relatively limited impact on climate. In summary, the climate warming from the northern permafrost region is likely close to neutral when calculated over a 100 years time window, but it warms the climate when calculated over a 20 years time window.

We report three major and confronting environmental issues that have received little attention and require urgent action. First, we review the evidence that future environmental conditions will be far more dangerous than currently believed. The scale of the threats to the biosphere and all its lifeforms—including humanity—is in fact so great that it is difficult to grasp for even well-informed experts. Second, we ask what political or economic system, or leadership, is prepared to handle the predicted disasters, or even capable of such action. Third, this dire situation places an extraordinary responsibility on scientists to speak out candidly and accurately when engaging with government, business, and the public. We especially draw attention to the lack of appreciation of the enormous challenges to creating a sustainable future. The added stresses to human health, wealth, and well-being will perversely diminish our political capacity to mitigate the erosion of ecosystem services on which society depends. The science underlying these issues is strong, but awareness is weak. Without fully appreciating and broadcasting the scale of the problems and the enormity of the solutions required, society will fail to achieve even modest sustainability goals.

Abstract

Assessing compliance with the human-induced warming goal in the Paris Agreement requires transparent, robust and timely metrics. Linearity between increases in atmospheric CO2 and temperature offers a framework that appears to satisfy these criteria, producing human-induced warming estimates that are at least 30% more certain than alternative methods. Here, for 2023, we estimate humans have caused a global increase of 1.49 ± 0.11 °C relative to a pre-1700 baseline.

Abstract

When attempting to quantify future harms caused by carbon emissions and to set appropriate energy policies, it has been argued that the most important metric is the number of human deaths caused by climate change. Several studies have attempted to overcome the uncertainties associated with such forecasting. In this article, approaches to estimating future human death tolls from climate change relevant at any scale or location are compared and synthesized, and implications for energy policy are considered. Several studies are consistent with the “1000-ton rule,” according to which a future person is killed every time 1000 tons of fossil carbon are burned (order-of-magnitude estimate). If warming reaches or exceeds 2 °C this century, mainly richer humans will be responsible for killing roughly 1 billion mainly poorer humans through anthropogenic global warming, which is comparable with involuntary or negligent manslaughter. On this basis, relatively aggressive energy policies are summarized that would enable immediate and substantive decreases in carbon emissions. The limitations to such calculations are outlined and future work is recommended to accelerate the decarbonization of the global economy while minimizing the number of sacrificed human lives.

Keywords: carbon emissions; greenhouse gas emissions; global catastrophic risk; climate change; energy policy; human mortality; climate genocide

Depopulation projections are not based on facts.

Abstract

Estimates of current and future population exposure to both coastal and inland flooding do not exist consistently in all Small Island Developing States (SIDS), despite these being some of the places most at risk to climate change. This has primarily been due to a lack of suitable or complete data. In this paper, we utilise a ∼30 m global hydrodynamic flood model to estimate population exposure to coastal and inland flood hazard in all SIDS under present day, as well as under low, intermediate, and very high emissions climate change scenarios (SSP1-2.6, SSP2-4.5 and SSP5-8.5). Our analysis shows that present day population exposure to flooding in SIDS is high (19.5% total population: 100 year flood hazard), varies widely depending on the location (3%–66%), and increases under all three climate scenarios—even if global temperatures remain below 2 °C warming (range in percentage change between present day and SSP1-2.6: −4.5%–44%). We find that levels of flood hazard and population exposure are not strongly linked, and that indirect measures of exposure in common vulnerability or risk indicators do not adequately capture the complex drivers of flood hazard and population exposure in SIDS. The most exposed places under the lowest climate change scenario (SSP1-2.6) continue to be the most exposed under the highest climate change scenario (SSP5-8.5), meaning investment in adaptation in these locations is likely robust to climate scenario uncertainty.

Editor’s summary

The mid-Pleistocene transition (MPT), approximately 1.25 to 0.85 million years ago, was a period during which the glacial cycle changed from 41,000 years to 100,000 years in duration. It is widely believed that the cause of the MPT was a slowdown of deep ocean circulation punctuated by a collapse at about 0.90 million years ago. Hines et al. found no evidence of a dramatic change in deep ocean circulation over the MPT, only modest ocean circulation adjustments. Their data also illustrate how the deep ocean is able to sequester carbon dioxide without substantial changes in circulation geometry. —Jesse Smith

Abstract

The mid-Pleistocene transition (MPT) [~1.25 to 0.85 million years ago (Ma)] marks a shift in the character of glacial-interglacial climate (1, 2). One prevailing hypothesis for the origin of the MPT is that glacial deep ocean circulation fundamentally changed, marked by a circulation “crisis” at ~0.90 Ma (marine isotope stages 24 to 22) (3). Using high-resolution paired neodymium, carbon, and oxygen isotope data from the South Atlantic Ocean (Cape Basin) across the MPT, we find no evidence of a substantial change in deep ocean circulation. Before and during the early MPT (~1.30 to 1.12 Ma), the glacial deep ocean variability closely resembled that of the most recent glacial cycle. The carbon storage facilitated by developing deep ocean stratification across the MPT required only modest circulation adjustments.