Climate tipping points — too risky to bet against

Safe and just Earth system boundaries

The stability and resilience of the Earth system and human well-being are inseparably linked^1-3, yet their interdependencies are generally under-recognized; consequently, they are often treated independently^4,5. Here, we use modelling and literature assessment to quantify safe and just Earth system boundaries (ESBs) for climate, the biosphere, water and nutrient cycles, and aerosols at global and subglobal scales. We propose ESBs for maintaining the resilience and stability of the Earth system (safe ESBs) and minimizing exposure to significant harm to humans from Earth system change (a necessary but not sufficient condition for justice)⁴. The stricter of the safe or just boundaries sets the integrated safe and just ESB. Our findings show that justice considerations constrain the integrated ESBs more than safety considerations for climate and atmospheric aerosol loading. Seven of eight globally quantified safe and just ESBs and at least two regional safe and just ESBs in over half of global land area are already exceeded. We propose that our assessment provides a quantitative foundation for safeguarding the global commons for all people now and into the future.

Recent exposure to environmental stochasticity does not determine the demographic resilience of natural populations

Escalating climatic and anthropogenic pressures expose ecosystems worldwide to increasingly stochastic environments. Yet, our ability to forecast the responses of natural populations to this increased environmental stochasticity is impeded by a limited understanding of how exposure to stochastic environments shapes demographic resilience. Here, we test the association between local environmental stochasticity and the resilience attributes (e.g. resistance, recovery) of 2242 natural populations across 369 animal and plant species. Contrary to the assumption that past exposure to frequent environmental shifts confers a greater ability to cope with current and future global change, we illustrate how recent environmental stochasticity regimes from the past 50 years do not predict the inherent resistance or recovery potential of natural populations. Instead, demographic resilience is strongly predicted by the phylogenetic relatedness among species, with survival and developmental investments shaping their responses to environmental stochasticity. Accordingly, our findings suggest that demographic resilience is a consequence of evolutionary processes and/or deep-time environmental regimes, rather than recent-past experiences.

More than unfamiliar environmental connection to super typhoon climatology

This study employs a refined geometric variability model to look at the environmental relationship to super typhoon climatology, which is one of the major concerns about climate change and disasters. It is noted that adding only several recent years leads to a remarkable weakening of the environmental explanatory power on super typhoon climatology. Looking into the annual covariance elements, we find that the recent observations showing a group of outlying events with a particular drift are more than unfamiliar compared to the former stable relationship from 1985 through 2012. Greater uncertainty thereby amplifies concerns about the looming climate crisis.

Carbonic Anhydrase Enhanced UV-Crosslinked PEG-DA/PEO Extruded Hydrogel Flexible Filaments and Durable Grids for CO2 Capture

In this study, poly (ethylene glycol) diacrylate/poly (ethylene oxide) (PEG-DA/PEO) interpenetrating polymer network hydrogels (IPNH) were extruded into 1D filaments and 2D grids. The suitability of this system for enzyme immobilization and CO₂ capture application was validated. IPNH chemical composition was verified spectroscopically using FTIR. The extruded filament had an average tensile strength of 6.5 MPa and elongation at break of 80%. IPNH filament can be twisted and bent and therefore is suitable for further processing using conventional textile fabrication methods. Initial activity recovery of the entrapped carbonic anhydrase (CA) calculated from esterase activity, showed a decrease with an increase in enzyme dose, while activity retention of high enzyme dose samples was over 87% after 150 days of repeated washing and testing. IPNH 2D grids that were assembled into spiral roll structured packings exhibited increased CO₂ capture efficiency with increasing enzyme dose. Long-term CO₂ capture performance of the CA immobilized IPNH structured packing was tested in a continuous solvent recirculation experiment for 1032 h, where 52% of the initial CO₂ capture performance and 34% of the enzyme contribution were retained. These results demonstrate the feasibility of using rapid UV-crosslinking to form enzyme-immobilized hydrogels by a geometrically-controllable extrusion process that uses analogous linear polymers for both viscosity enhancement and chain entanglement purposes, and achieves high activity retention and performance stability of the immobilized CA. Potential uses for this system extend to 3D printing inks and enzyme immobilization matrices for such diverse applications as biocatalytic reactors and biosensor fabrication.

A multi-modal machine learning approach to detect extreme rainfall events in Sicily

In 2021 almost 300 mm of rain, nearly half of the average annual rainfall, fell near Catania (Sicily Island, Italy). Such events took place in just a few hours, with dramatic consequences on the environmental, social, economic, and health systems of the region. These phenomena are now very common in various countries all around the world: this is the reason why, detecting local extreme rainfall events is a crucial prerequisite for planning actions, able to reverse possibly intensified dramatic future scenarios. In this paper, the Affinity Propagation algorithm, a clustering algorithm grounded on machine learning, was applied, to the best of our knowledge, for the first time, to detect extreme rainfall areas in Sicily. This was possible by using a high-frequency, large dataset we collected, ranging from 2009 to 2021 which we named RSE (the Rainfall Sicily Extreme dataset). Weather indicators were then been employed to validate the results, thus confirming the presence of recent anomalous rainfall events in eastern Sicily. We believe that easy-to-use and multi-modal data science techniques, such as the one proposed in this study, could give rise to significant improvements in policy-making for successfully contrasting climate change.

Anthropogenic atmospheric deposition caused the nutrient and toxic metal enrichment of the enclosed lakes in North China

Anthropogenic emissions have resulted in increases in the atmospheric fluxes of both nutrient and toxic elements. However, the long-term geochemical impacts on lake sediments of deposition activities have not been clearly clarified. We selected two small enclosed lakes in northern China-Gonghai, strongly influenced by anthropogenic activities, and Yueliang lake, relatively weakly influenced by anthropogenic activities-to reconstruct historical trends of atmospheric deposition on the geochemistry of the recent sediments. The results showed an abrupt rise in the nutrient levels in Gonghai and the enrichment of toxic metal elements from 1950 (the Anthropocene) onwards. While, at Yueliang lake, the rise on TN was from 1990 onwards. These consequences are attributable to the aggravation of anthropogenic atmospheric deposition in N, P and toxic metals, from fertilizer consumption, mining and coal combustion. The intensity of anthropogenic deposition is considerable, which leave a significant stratigraphic signal of the Anthropocene in lake sediments.

Stabilization of mineral-associated organic carbon in Pleistocene permafrost

Ice-rich Pleistocene-age permafrost is particularly vulnerable to rapid thaw, which may quickly expose a large pool of sedimentary organic matter (OM) to microbial degradation and lead to emissions of climate-sensitive greenhouse gases. Protective physico-chemical mechanisms may, however, restrict microbial accessibility and reduce OM decomposition; mechanisms that may be influenced by changing environmental conditions during sediment deposition. Here we study different OM fractions in Siberian permafrost deposited during colder and warmer periods of the past 55,000 years. Among known stabilization mechanisms, the occlusion of OM in aggregates is of minor importance, while 33-74% of the organic carbon is associated with small, <6.3 µm mineral particles. Preservation of carbon in mineral-associated OM is enhanced by reactive iron minerals particularly during cold and dry climate, reflected by low microbial CO₂ production in incubation experiments. Warmer and wetter conditions reduce OM stabilization, shown by more decomposed mineral-associated OM and up to 30% higher CO₂ production. This shows that considering the stability and bioavailability of Pleistocene-age permafrost carbon is important for predicting future climate-carbon feedback.

Assessing the contribution of global wildfire biomass burning to BaP contamination in the Arctic

Polycyclic aromatic hydrocarbons (PAHs) have become cause for growing concern in the Arctic ecosystems, partly due to their stable levels despite global emission reduction. Wildfire is considered one of the primary sources that influence PAH levels and trends in the Arctic, but quantitative investigations of this influence are still lacking. This study estimates the global emissions of benzo[a]pyrene (BaP), a congener of PAHs with high carcinogenicity, from forest and grassland fires from 2001 to 2020 and simulates the contributions of wildfire-induced BaP emissions from different source regions to BaP contamination in the Arctic. We find that global wildfires contributed 29.3% to annual averaging BaP concentrations in the Arctic from 2001 to 2020. Additionally, we show that wildfires contributed significantly to BaP concentrations in the Arctic after 2011, enhancing it from 10.1% in 2011 to 83.9% in 2020. Our results reveal that wildfires accounted for 94.2% and 50.8% of BaP levels in the Asian Arctic during boreal summer and autumn, respectively, and 74.2% and 14.5% in the North American Arctic for the same seasons. The source-tagging approach identified that local wildfire biomass emissions were the largest source of BaP in the Arctic, accounting for 65.7% of its concentration, followed by those of Northern Asia (17.8%) and Northern North America (13.7%). Our findings anticipate wildfires to play a larger role in Arctic PAH contaminations alongside continually decreasing anthropogenic emissions and climate warming in the future.

A Method of Evaluating Safe Operating Space: Focus on Geographic Regions, Income Levels and Developing Pathway

Safe and Just Space (SJS) is a framework for determining the range where the use of natural resources within the Earth's carrying capacity can maintain human well-being. However, there has been no systematic monitoring and evaluation of their sustainability across time and space. Here we developed and applied a model and a sustainable development human safe operation space (SDHSOS) index to assess the sustainability capacity and development path of 149 countries from 2000 to 2018. The results demonstrate that (1) The overall sustainable development capacity of all countries is at the middle or lower level and that it has increased over time. (2) The sustainability of natural and socio-economic dimensions and their degree of change show obvious geographic differences and income differences. (3) The national development path divided by income is characterized by a decline in natural environment dimensions and an increase in socio-economic dimensions, which mainly reflects a traditional development path model that promotes social welfare at the expense of the natural environment. This study suggests that nations can accurately identify development characteristics, expand their comparative advantages is the key to improving sustainable development capabilities.

Biocatalytic Membranes for Carbon Capture and Utilization

Innovative carbon capture technologies that capture CO₂ from large point sources and directly from air are urgently needed to combat the climate crisis. Likewise, corresponding technologies are needed to convert this captured CO₂ into valuable chemical feedstocks and products that replace current fossil-based materials to close the loop in creating viable pathways for a renewable economy. Biocatalytic membranes that combine high reaction rates and enzyme selectivity with modularity, scalability, and membrane compactness show promise for both CO₂ capture and utilization. This review presents a systematic examination of technologies under development for CO₂ capture and utilization that employ both enzymes and membranes. CO₂ capture membranes are categorized by their mode of action as CO₂ separation membranes, including mixed matrix membranes (MMM) and liquid membranes (LM), or as CO₂ gas-liquid membrane contactors (GLMC). Because they selectively catalyze molecular reactions involving CO₂, the two main classes of enzymes used for enhancing membrane function are carbonic anhydrase (CA) and formate dehydrogenase (FDH). Small organic molecules designed to mimic CA enzyme active sites are also being developed. CO₂ conversion membranes are described according to membrane functionality, the location of enzymes relative to the membrane, which includes different immobilization strategies, and regeneration methods for cofactors. Parameters crucial for the performance of these hybrid systems are discussed with tabulated examples. Progress and challenges are discussed, and perspectives on future research directions are provided.

A perspective on iron (Fe) in the atmosphere: air quality, climate, and the ocean

As scientists engage in research motivated by climate change and the impacts of pollution on air, water, and human health, we increasingly recognize the need for the scientific community to improve communication and knowledge exchange across disciplines to address pressing and outstanding research questions holistically. Our professional paths have crossed because our research activities focus on the chemical reactivity of Fe-containing minerals in air and water, and at the air-sea interface. (Photo)chemical reactions driven by Fe can take place at the surface of the particles/droplets or within the condensed phase. The extent and rates of these reactions are influenced by water content and biogeochemical activity ubiquitous in these systems. One of these reactions is the production of reactive oxygen species (ROS) that cause damage to respiratory organs. Another is that the reactivity of Fe and organics in aerosol particles alter surficial physicochemical properties that impact aerosol-radiation and aerosol-cloud interactions. Also, upon deposition, aerosol particles influence ocean biogeochemical processes because micronutrients such as Fe or toxic elements such as copper become bioavailable. We provide a perspective on these topics and future research directions on the reactivity of Fe in atmospheric aerosol systems, from sources to short- and long-term impacts at the sinks with emphasis on needs to enhance the predictive power of atmospheric and ocean models.

The stability and collapse of marine ecosystems during the Permian-Triassic mass extinction

The history of Earth's biodiversity is punctuated episodically by mass extinctions. These are characterized by major declines of taxon richness, but the accompanying ecological collapse has rarely been evaluated quantitatively. The Permian-Triassic mass extinction (PTME; ∼252 mya), as the greatest known extinction, permanently altered marine ecosystems and paved the way for the transition from Paleozoic to Mesozoic evolutionary faunas. Thus, the PTME offers a window into the relationship between taxon richness and ecological dynamics of ecosystems during a severe extinction. However, the accompanying ecological collapse through the PTME has not been evaluated in detail. Here, using food-web models and a marine paleocommunity dataset spanning the PTME, we show that after the first extinction phase, community stability decreased only slightly despite the loss of more than half of taxonomic diversity, while community stability significantly decreased in the second phase. Thus, taxonomic and ecological changes were unequivocally decoupled, with species richness declining severely ∼61 ka earlier than the collapse of marine ecosystem stability, implying that in major catastrophes, a biodiversity crash may be the harbinger of a more devastating ecosystem collapse.

Prehistoric pathways to Anthropocene adaptation: Evidence from the Red River Delta, Vietnam

Over the past twenty years, government advisory bodies have placed increasing emphasis on the need for adaptive measures in response to the effects of human-induced climate change. Integrated Assessment Models (IAMs), which incorporate macroeconomic and climate variables, feature prominently in advisory content, though they rarely draw on data from outside strictly constrained hypothetical systems. This has led to assertions that they are not well-suited to approximate complex systemic human-environment processes. Modular, interdisciplinary approaches have offered a way to address this shortcoming; however, beyond climate records, prehistoric data continue to be under-utilised in developing such models. In this paper we highlight the contribution that archaeology and palaeoecology can make to the development of the next generation IAMs that are expected to enhance provision for more local and pro-active adaptations to future climate change. We present data from one of Southeast Asia's most heavily developed river deltas: the Red River (Song Hong) Delta, in Vietnam and localised analysis from the Tràng An Landscape Complex World Heritage Site, on the delta's southern margin. Comparison is made between Shared Socio-economic Pathways (SSP) 5-8.5 and SSP2-4.5 emission projection models and the Mid-Holocene inundation of the Red River Basin. We highlight the value to taking a scientific long view of coastal evolution through an illustrative set of eight research foci where palaeo-data can bring new and localised empirical data to bear on future risk management planning. We proceed to demonstrate the applicability of palaeoenvironmental, zooarchaeological and historical evidence to management and the development of sustainable conservation strategies using Tràng An as a case study. In so doing, we further highlight the importance of knowledge exchange between scientific, corporate, non-governmental, local, and state stakeholders to achieve tangible results on the ground.

World Energy Economics and Geopolitics amid COVID-19 and Post-COVID-19 Policy Direction

COVID-19 has placed a focus on the global energy industry. The global energy system in 2020 and beyond was covered in this article. The epidemic had immediate implications on energy demand, particularly for oil, and on energy bills. According to the IEA, understanding the development of the low-carbon energy system and the eventual demise of the current system based on fossil fuels is crucial for predicting the future of global energy geopolitics. Since renewables are the goal of post-COVID-19, geopolitical tensions between nations that produce fossil fuels have been brought to light. Three guidelines are suggested in this paper for the switch to renewable energy sources in order to slow global warming. First, place a focus on immediate policy changes that have a long-term impact on the energy transition. Utilize the upcoming midterm energy transition opportunities. Fresh, uncompromised policy frameworks should be developed. As the pandemic scenario is almost settled, additional research is needed to comprehend the widespread and catastrophic repercussions of post-COVID-19 on energy geopolitics, including variations in energy demand and price, wake of economic recovery, macroeconomic instability, Ukraine crisis and anticipating geopolitical consequences for renewables and fossil fuel economics. More national and regional focus is needed on long-term policy designs and justifications. The effectiveness of altering the sustainable development objectives related to energy or maintaining the current goals with the suggested policy design can also be examined in further research. Key challenges and recommendations are highlighted in order to ensure a successful long-term energy transition that can serve as a reference for energy policymakers in all countries.

Better insurance could effectively mitigate the increase in economic growth losses from U.S. hurricanes under global warming

Global warming is likely to increase the proportion of intense hurricanes in the North Atlantic. Here, we analyze how this may affect economic growth. To this end, we introduce an event-based macroeconomic growth model that temporally resolves how growth depends on the heterogeneity of hurricane shocks. For the United States, we find that economic growth losses scale superlinearly with shock heterogeneity. We explain this by a disproportional increase of indirect losses with the magnitude of direct damage, which can lead to an incomplete recovery of the economy between consecutive intense landfall events. On the basis of two different methods to estimate the future frequency increase of intense hurricanes, we project annual growth losses to increase between 10 and 146% in a 2°C world compared to the period 1980-2014. Our modeling suggests that higher insurance coverage can compensate for this climate change-induced increase in growth losses.

The interconnected global emergencies of climate change, food security and health: a call to action by the Science for Africa Foundation

The evidence is clear that climate change is the greatest challenge facing mankind today. Africa is disproportionately burdened by multiple direct and cascading impacts of the climate crisis. Global investments for climate change adaptation, however, have not prioritized Africa adequately and there is a significant knowledge gap in understanding the context and science of climate change and sustainable solutions for the continent's adaptation. Solutions for adaptation and resilience are made complex by an urgent need for accelerated economic growth, rapid population expansion and urbanization, habitat and biodiversity loss and dwindling financing.  There are also challenges in matching policies, wavering commitments and actions with good science that focuses on sustainable lives, livelihoods and ecosystem preservation. The solutions must come from where the impacts are felt. The Science for Africa Foundation supports African researchers and institutions to lead in the science that addresses African priority development areas and has set climate change as a strategic priority. This call to action, by the SFA Foundation, outlines key areas that its strategy addresses through programs that support African scientific excellence, leadership and the best of Africa's research to understand the science of climate change and its impacts; collate and assess evidence for policy; grow high level technical capacity on the continent; and create innovative priority actions for Africa.

Underestimated permafrost degradation: Improving the TTOP model based on soil thermal conductivity

Under the continuing influence of global warming, resolving the inconsistency of permafrost degradation rates and quantifying the spatial distribution characteristics are critical for high-altitude water cycle processes. The dynamics of permafrost degradation are mainly manifested in soil temperature, which can be measured with high accuracy and high temporal resolution. This study considered the influence of soil thermal conductivity (K) by periodic land surface temperature (LST), improved the static output of the temperature at the top of permafrost (TTOP) model, and verified the reliability of the TTOP model improvement by the Kappa coefficient. The results showed that from 2000 to 2020, the extent of dynamically simulated permafrost was 5.42 × 105 km2 less than that of static simulated permafrost, and the linear degradation rate doubled. The degraded permafrost showed an increasing degradation from southeast to northwest. Among them, the degradation in the Nujiang River and the Changjiang River north of the Nyainqentanglha Mountain has exacerbated the permafrost degradation in the hinterland of the Qiangtang Plateau. Based on the AWI-CM-1-1-MR LST from CMIP6, SSP126 to SSP585 dynamic simulation results of permafrost indicate that the extent will decrease by 11.35 % by 2100. Overall, the extent and rate of permafrost degradation, considering high spatiotemporal resolution, were twice as fast as expected. Our results will inform policymakers with a more accurate spatiotemporal distribution of frozen soil types in high-altitude regions and characteristics of permafrost degradation within the watershed.

Decadal-centennial-scale solar-linked climate variations and millennial-scale internal oscillations during the Early Cretaceous

Understanding climate variability and stability under extremely warm 'greenhouse' conditions in the past is essential for future climate predictions. However, information on millennial-scale (and shorter) climate variability during such periods is scarce, owing to a lack of suitable high-resolution, deep-time archives. Here we present a continuous record of decadal- to orbital-scale continental climate variability from annually laminated lacustrine deposits formed during the late Early Cretaceous (123-120 Ma: late Barremian-early Aptian) in southeastern Mongolia. Inter-annual changes in lake algal productivity for a 1091-year interval reveal a pronounced solar influence on decadal- to centennial-scale climatic variations (including the ~ 11-year Schwabe cycle). Decadally-resolved Ca/Ti ratios (proxy for evaporation/precipitation changes) for a ~ 355-kyr long interval further indicate millennial-scale (~ 1000-2000-yr) extreme drought events in inner-continental areas of mid-latitude palaeo-Asia during the Cretaceous. Millennial-scale oscillations in Ca/Ti ratio show distinct amplitude modulation (AM) induced by the precession, obliquity and short eccentricity cycles. Similar millennial-scale AM by Milankovitch cycle band was also previously observed in the abrupt climatic oscillations (known as Dansgaard-Oeschger events) in the 'intermediate glacial' state of the late Pleistocene, and in their potential analogues in the Jurassic 'greenhouse'. Our findings indicate that external solar activity forcing was effective on decadal-centennial timescales, whilst the millennial-scale variations were likely amplified by internal process such as changes in deep-water formation strength, even during the Cretaceous 'greenhouse' period.

Machine learning prediction of connectivity, biodiversity and resilience in the Coral Triangle

Even optimistic climate scenarios predict catastrophic consequences for coral reef ecosystems by 2100. Understanding how reef connectivity, biodiversity and resilience are shaped by climate variability would improve chances to establish sustainable management practices. In this regard, ecoregionalization and connectivity are pivotal to designating effective marine protected areas. Here, machine learning algorithms and physical intuition are applied to sea surface temperature anomaly data over a twenty-four-year period to extract ecoregions and assess connectivity and bleaching recovery potential in the Coral Triangle and surrounding oceans. Furthermore, the impacts of the El Niño Southern Oscillation (ENSO) on biodiversity and resilience are quantified. We find that resilience is higher for reefs north of the Equator and that the extraordinary biodiversity of the Coral Triangle is dynamic in time and space, and benefits from ENSO. The large-scale exchange of genetic material is enhanced between the Indian Ocean and the Coral Triangle during La Niña years, and between the Coral Triangle and the central Pacific in neutral conditions. Through machine learning the outstanding biodiversity of the Coral Triangle, its evolution and the increase of species richness are contextualized through geological times, while offering new hope for monitoring its future.

Ecological integrity and conservation challenges in a rapidly changing Arctic: A call for new approaches in large intact landscapes

Intactness is a commonly used measure of ecological integrity, especially when evaluating conservation status at the landscape scale. We argue that in the large and relatively unfragmented landscapes of the Arctic and sub-Arctic, intactness provides only partial insight for managers charged with maintaining ecological integrity. A recent landscape assessment suggests that 95% of Alaska shows no measured direct or indirect impacts of human development on the landscape. However, the current exceptionally high levels of intactness in Alaska, and throughout the Arctic and sub-Arctic, do not adequately reflect impacts to the region's ecological integrity caused by indirect stressors, such as a rapidly changing climate and the subsequent loss of the cryosphere. Thus, it can be difficult to measure, and manage, some of the conservation challenges presented by the ecological context of these systems. The dominant drivers of change, and their associated ecological and socioeconomic impacts, vary as systems decline in ecological integrity from very high to high, and to intermediate levels, but this is not well understood in the literature. Arctic and sub-Arctic systems, as well as other large intact areas, provide unique opportunities for conservation planning, but require tools and approaches appropriate to unfragmented landscapes undergoing rapid climate-driven ecological transformation. We conclude with possible directions for developing more appropriate metrics for measuring ecological integrity in these systems.

Tipping points ahead? How laypeople respond to linear versus nonlinear climate change predictions

We investigate whether communication strategies that portray climate change as a nonlinear phenomenon provoke increases in laypeople's climate change risk perceptions. In a high-powered, preregistered online experiment, participants were exposed to linear or nonlinear predictions of future temperature increases that would be expected if global greenhouse gas emissions were not reduced. We hypothesized that the type of climate change portrayal would impact perceptions of qualitative risk characteristics (catastrophic potential, controllability of consequences) which would, in turn, affect laypeople's holistic risk perceptions. The results of the study indicate that the type of climate change portrayal did not affect perceptions of risk or other social-cognitive variables such as efficacy beliefs. While participants who were exposed to a nonlinear portrayal of climate change perceived abrupt changes in the climate system as more likely, they did not perceive the consequences of climate change as less controllable or more catastrophic. Notably, however, participants who had been exposed to a linear or nonlinear portrayal of climate change were willing to donate more money to environmental organizations than participants who had not been presented with a climate-related message. Limitations of the present study and directions for future research are discussed.

Role of space station instruments for improving tropical carbon flux estimates using atmospheric data

The tropics is the nexus for many of the remaining gaps in our knowledge of environmental science, including the carbon cycle and atmospheric chemistry, with dire consequences for our ability to describe the Earth system response to a warming world. Difficulties associated with accessibility, coordinated funding models and economic instabilities preclude the establishment of a dense pan-tropical ground-based atmospheric measurement network that would otherwise help to describe the evolving state of tropical ecosystems and the associated biosphere-atmosphere fluxes on decadal timescales. The growing number of relevant sensors aboard sun-synchronous polar orbiters provide invaluable information over the remote tropics, but a large fraction of the data collected along their orbits is from higher latitudes. The International Space Station (ISS), which is in a low-inclination, precessing orbit, has already demonstrated value as a proving ground for Earth observing atmospheric sensors and as a testbed for new technology. Because low-inclination orbits spend more time collecting data over the tropics, we argue that the ISS and its successors, offer key opportunities to host new Earth-observing atmospheric sensors that can lead to a step change in our understanding of tropical carbon fluxes.

Spatioselective surface chemistry for the production of functional and chemically anisotropic nanocellulose colloids

Maximizing the benefits of nanomaterials from biomass requires unique considerations associated with their native chemical and physical structure. Both cellulose nanofibrils and nanocrystals are extracted from cellulose fibers via a top-down approach and have significantly advanced materials chemistry and set new benchmarks in the last decade. One major challenge has been to prepare defined and selectively modified nanocelluloses, which would, e.g., allow optimal particle interactions and thereby further improve the properties of processed materials. At the molecular and crystallite level, the surface of nanocelluloses offers an alternating chemical structure and functional groups of different reactivity, enabling straightforward avenues towards chemically anisotropic and molecularly patterned nanoparticles via spatioselective chemical modification. In this review, we will explain the influence and role of the multiscale hierarchy of cellulose fibers in chemical modifications, and critically discuss recent advances in selective surface chemistry of nanocelluloses. Finally, we will demonstrate the potential of those chemically anisotropic nanocelluloses in materials science and discuss challenges and opportunities in this field.

Climatic threshold of crop production and climate change adaptation: A case of winter wheat production in China

Global climate change has adversely affected agricultural production. Identifying the climatic threshold is critical to judge the impact and risk of climate change and proactively adapt agriculture. However, the climatic threshold of agriculture, especially crop production, remains unclear. To bridge this gap, taking winter wheat production from 1978 to 2017 in China as an example, this study clarified the definition of the climatic threshold of crop production and calculated it based on a mechanism model considering multiple factors and their synergies. The results showed that (1) the climate presented a warmer and wetter trend from 1978 to 2017, especially after 1996. (2) Water, fertilizer, and winter wheat yields increased significantly (22.4 mm/decade, 96.4 kg/ha·decade, and 674.2 kg/ha·decade, respectively, p &lt; 0.01). (3) The average optimal temperature and water thresholds for winter wheat were 7.3°C and 569 mm, respectively. The temperature rise was unfavorable for winter wheat production, and the water supply increase was beneficial to winter wheat production. (4) Increasing irrigation and fertilization could raise the optimal temperature threshold and adapt to climate warming in most provinces, while Shandong and Shaanxi both needed to reduce fertilization. We established a generalized method for calculating the climatic threshold of agricultural production and found that multifactor synergistic effects could influence the climatic threshold. The climatic threshold of winter wheat changed with different adaptation levels. However, considering the limitations in resource availability and environmental capacity, increasing the use efficiency of water and fertilizer is more important for adapting to climate change in the future.

Thermal acclimation and metabolic scaling of a groundwater asellid in the climate change scenario

Metabolic rate has long been used in animal adaptation and performance studies, and individual oxygen consumption is used as proxy of metabolic rate. Stygofauna are organisms adapted to groundwater with presumably lower metabolic rates than their surface relatives. How stygofauna will cope with global temperature increase remains unpredictable. We studied the thermal acclimation and metabolic scaling with body mass of a stygobitic crustacean, Proasellus lusitanicus, in the climate change scenario. We measured oxygen consumption rates in a thermal ramp-up experiment over four assay temperatures and tested two hypotheses: (i) P. lusitanicus exhibits narrow thermal plasticity, inadequate for coping with a fast-increasing thermal regime; and (ii) oxygen consumption rates scale with the body mass by a factor close to 0.75, as commonly observed in other animals. Our results show that P. lusitanicus has low thermal plasticity in a fast-increasing thermal regime. Our data also suggest that oxygen consumption rates of this species do not follow mass-dependent scaling, potentially representing a new trait of metabolic optimization in groundwater habitats, which are often limited in food and oxygen. Species with limited dispersal capacities and rigid metabolic guilds face extinction risk due to climate change and omitting groundwater ecosystems from climate change agendas emphasizes the unprotected status of stygofauna.

Near-term climate risks and solar radiation modification: a roadmap approach for physical sciences research

Current impacts and escalating risks of climate change require strong and decisive action to reduce greenhouse gas (GHG) emissions. They also highlight the urgency of research to enhance safety for human and natural systems, especially for those most vulnerable. This is reflected in two recent US National Academies of Science, Engineering, and Medicine studies that recommended a national focus on advancing our understanding of how to manage urgent current and future climate risks, and the study of approaches for increasing the reflection of sunlight from the atmosphere to reduce global warming, a process referred to as sunlight reflection modification (SRM). Here, we build on these recommendations by proposing a roadmap approach for the planning, coordination, and delivery of research to support a robust scientific assessment of SRM to reduce near-term climate risks in a defined timeframe. This approach is designed to support the evaluation of SRM as a possible rapid, temporary, additive measure to reduce catastrophic impacts from anthropogenic climate change, not as a substitute for aggressive GHG mitigation. Assessing SRM is proposed to be undertaken in the context of climate hazard risks through 2050, weighing the impacts associated with likely climate change trajectories against scenarios of possible SRM implementations. Provided that research is undertaken openly and that scientific resources are made widely available, the transparency of the process and the evidence generated would contribute to the democratization of information, participation by diverse stakeholders, more informed decision-making, and better opportunities for all people to weigh SRM options against climate change risks.

Vapour pressure deficit determines critical thresholds for global coffee production under climate change

Our understanding of the impact of climate change on global coffee production is largely based on studies focusing on temperature and precipitation, but other climate indicators could trigger critical threshold changes in productivity. Here, using generalized additive models and threshold regression, we investigate temperature, precipitation, soil moisture and vapour pressure deficit (VPD) effects on global Arabica coffee productivity. We show that VPD during fruit development is a key indicator of global coffee productivity, with yield declining rapidly above 0.82 kPa. The risk of exceeding this threshold rises sharply for most countries we assess, if global warming exceeds 2 °C. At 2.9 °C, countries making up 90% of global supply are more likely than not to exceed the VPD threshold. The inclusion of VPD and the identification of thresholds appear critical for understanding climate change impacts on coffee and for the design of adaptation strategies.

Opportunities to tackle short-lived climate pollutants and other greenhouse gases for China

To limit the global temperature increase to below 1.5 °C, it is critical to reduce not only carbon dioxide (CO₂), but also specific non-CO₂ greenhouse gases (GHGs) and precursors, including some short-lived climate pollutants (SLCPs). These include emissions of black carbon, methane (CH4), tropospheric ozone, and fluorinated gases such as hydrofluorocarbons (HFCs). As the largest CH4 emitter and second-largest HFCs emitter, China plays a critical role in global efforts to reduce SLCPs and has acknowledged the need to reduce non-CO₂ GHGs in its 2060 carbon neutrality goal. This study reviewed leading international experiences with SLCP reduction to identify global best practices to inform target development and policy actions in China and elsewhere. We used bottom-up modeling and scenario analysis to evaluate pathways of non-CO₂ emission mitigation in China to 2050, drawing on mitigation measures developed through updated 2030 and 2050 cost curves. We identified a cost-effective reduction potential of 35 % for methane, 30 % for fluorinated gases, and 40 % for nitrous oxides-another potent GHG-in 2030 relative to 2015 levels for China under a Deep Non-CO₂ Mitigation scenario. Annual total reduction potential of 1080 million metric tons of CO₂ equivalent is also possible by 2030. For long-term targets, progress made on reducing SLCPs could help China reach its carbon neutrality target by 2060. While some uncertainties regarding the long-term mitigation potential of SLCPs remain, our analyses suggest that the fast adoption of available cost-effective technologies could allow China to reduce its non-CO₂ GHGs by 56 % by 2050.

Potential for perceived failure of stratospheric aerosol injection deployment

As anthropogenic activities warm the Earth, the fundamental solution of reducing greenhouse gas emissions remains elusive. Given this mitigation gap, global warming may lead to intolerable climate changes as adaptive capacity is exceeded. Thus, there is emerging interest in solar radiation modification, which is the process of deliberately increasing Earth's albedo to cool the planet. Stratospheric aerosol injection (SAI)-the theoretical deployment of particles in the stratosphere to enhance reflection of incoming solar radiation-is one strategy to slow, pause, or reverse global warming. If SAI is ever pursued, it will likely be for a specific aim, such as affording time to implement mitigation strategies, lessening extremes, or reducing the odds of reaching a biogeophysical tipping point. Using an ensemble climate model experiment that simulates the deployment of SAI in the context of an intermediate greenhouse gas trajectory, we quantified the probability that internal climate variability masks the effectiveness of SAI deployment on regional temperatures. We found that while global temperature was stabilized, substantial land areas continued to experience warming. For example, in the SAI scenario we explored, up to 55% of the global population experienced rising temperatures over the decade following SAI deployment and large areas exhibited high probability of extremely hot years. These conditions could cause SAI to be perceived as a failure. Countries with the largest economies experienced some of the largest probabilities of this perceived failure. The potential for perceived failure could therefore have major implications for policy decisions in the years immediately following SAI deployment.

The economic and environmental analysis of solar energy development under climate impacts

Solar energy is a promising renewable technology to secure energy security and reduce emissions. While there are several solar energy studies, the intensified climate change has altered the climate pattern such as regional sunny hours and the strength of solar radiation. To investigate the impact of climate change on the regional solar energy potential, this study analyses the average sunny hour and solar radiation from monthly data from Jan. 2009 to Apr. 2021 and applies the ARIMA and ARDL models to predict the potential changes of these factors for the period of May 2021 to Dec. 2025. The results show the impact of climate change on solar energy generation potential is geographically different. Based on the historical data, the estimated electricity generation potential from conventional PV, PV/PCM, and PVT/PCM technologies are 2,636, 2,747, and 2868 kWh per m2, respectively. However, under climate impacts, their power potential will be greatly reduced to 2,422, 2,525, and 2636 kWh per m2. Specifically, the future power potential will decline up to 8%, and thus the policymakers should incorporate the climate influence on solar energy development and application to minimize power fluctuation.

Fires, vegetation, and human-The history of critical transitions during the last 1000 years in Northeastern Mongolia

Fires are natural phenomena that impact human behaviors, vegetation, and landscape functions. However, the long-term history of fire, especially in the permafrost marginal zone of Central Asia (Mongolia), is poorly understood. This paper presents the results of radiocarbon and short-lived radionuclides (²¹⁰Pb and ¹³⁷Cs) dating, pollen, geochemical, charcoal, and statistical analyses (Kohonen's artificial neural network) of sediment core obtained from Northern Mongolia (the Khentii Mountains region). Therefore, we present the first high-resolution fire history from Northern Mongolia covering the last 1000 years, based on a multiproxy analysis of peat archive data. The results revealed that most of the fires in the region were likely initiated by natural factors, which were probably related to heatwaves causing prolonged droughts. We have demonstrated the link between enhanced fires and "dzud", a local climatic phenomenon. The number of livestock, which has been increasing for several decades, and the observed climatic changes are superimposed to cause "dzud", a deadly combination of droughts and snowy winter, which affects fire intensity. We observed that the study area has a sensitive ecosystem that reacts quickly to climate change. In terms of changes in the vegetation, the reconstruction reflected climate variations during the last millennium, the degradation of permafrost and occurrence of fires. However, more sites with good chronologies are needed to thoroughly understand the spatial relationships between changing climate, permafrost degradation, and vegetation change, which ultimately affect the nomadic societies in the region of Central and Northern Mongolia.

Future land-use competition constrains natural climate solutions

Natural climate solutions (NCS) are an essential complement to climate mitigation and have been increasingly incorporated into international mitigation strategies. Yet, with the ongoing population growth, allocating natural areas for NCS may compete with other socioeconomic priorities, especially urban development and food security. Here, we projected the impacts of land-use competition incurred by cropland and urban expansion on the climate mitigation potential of NCS. We mapped the areas available for implementing 9 key NCS strategies and estimated their climate change mitigation potential. Then, we overlaid these areas with future cropland and urban expansion maps projected under three Shared Socioeconomic Pathway (SSP) scenarios (2020-2100) and calculated the resulting mitigation potential loss of each selected NCS strategy. Our results estimate a substantial reduction, 0.3-2.8 GtCO₂ yr^-1 or 4-39 %, in NCS mitigation potential, of which cropland expansion for fulfilling future food demand is the primary cause. This impact is particularly severe in the tropics where NCS hold the most abundant mitigation potential. Our findings highlight immediate actions prioritized to tropical areas are important to best realize NCS and are key to developing realistic and sustainable climate policies.

Exceeding 1.5°C global warming could trigger multiple climate tipping points

Climate tipping points occur when change in a part of the climate system becomes self-perpetuating beyond a warming threshold, leading to substantial Earth system impacts. Synthesizing paleoclimate, observational, and model-based studies, we provide a revised shortlist of global "core" tipping elements and regional "impact" tipping elements and their temperature thresholds. Current global warming of ~1.1°C above preindustrial temperatures already lies within the lower end of some tipping point uncertainty ranges. Several tipping points may be triggered in the Paris Agreement range of 1.5 to <2°C global warming, with many more likely at the 2 to 3°C of warming expected on current policy trajectories. This strengthens the evidence base for urgent action to mitigate climate change and to develop improved tipping point risk assessment, early warning capability, and adaptation strategies.

Delayed use of bioenergy crops might threaten climate and food security

The potential of mitigation actions to limit global warming within 2 °C (ref. ¹) might rely on the abundant supply of biomass for large-scale bioenergy with carbon capture and storage (BECCS) that is assumed to scale up markedly in the future^2-5. However, the detrimental effects of climate change on crop yields may reduce the capacity of BECCS and threaten food security^6-8, thus creating an unrecognized positive feedback loop on global warming. We quantified the strength of this feedback by implementing the responses of crop yields to increases in growing-season temperature, atmospheric CO₂ concentration and intensity of nitrogen (N) fertilization in a compact Earth system model⁹. Exceeding a threshold of climate change would cause transformative changes in social-ecological systems by jeopardizing climate stability and threatening food security. If global mitigation alongside large-scale BECCS is delayed to 2060 when global warming exceeds about 2.5 °C, then the yields of agricultural residues for BECCS would be too low to meet the Paris goal of 2 °C by 2200. This risk of failure is amplified by the sustained demand for food, leading to an expansion of cropland or intensification of N fertilization to compensate for climate-induced yield losses. Our findings thereby reinforce the urgency of early mitigation, preferably by 2040, to avoid irreversible climate change and serious food crises unless other negative-emission technologies become available in the near future to compensate for the reduced capacity of BECCS.

Greenland Ice Core Record of Last Glacial Dust Sources and Atmospheric Circulation

Abrupt and large-scale climate changes have occurred repeatedly and within decades during the last glaciation. These events, where dramatic warming occurs over decades, are well represented in both Greenland ice core mineral dust and temperature records, suggesting a causal link. However, the feedbacks between atmospheric dust and climate change during these Dansgaard-Oeschger events are poorly known and the processes driving changes in atmospheric dust emission and transport remain elusive. Constraining dust provenance is key to resolving these gaps. Here, we present a multi-technique analysis of Greenland dust provenance using novel and established, source diagnostic isotopic tracers as well as results from a regional climate model including dust cycle simulations. We show that the existing dominant model for the provenance of Greenland dust as sourced from combined East Asian dust and Pacific volcanics is not supported. Rather, our clay mineralogical and Hf-Sr-Nd and D/H isotopic analyses from last glacial Greenland dust and an extensive range of Northern Hemisphere potential dust sources reveal three most likely scenarios (in order of probability): direct dust sourcing from the Taklimakan Desert in western China, direct sourcing from European glacial sources, or a mix of dust originating from Europe and North Africa. Furthermore, our regional climate modeling demonstrates the plausibility of European or mixed European/North African sources for the first time. We suggest that the origin of dust to Greenland is potentially more complex than previously recognized, demonstrating more uncertainty in our understanding dust climate feedbacks during abrupt events than previously understood.

Critical rates of climate warming and abrupt collapse of ecosystems

In the age of climate warming, comprehension of ecosystems’ future is one of the pressing challenges to humanity. While most studies on climate warming focus on the ‘magnitude of change’ of the Earth’s temperature, the ‘rate’ at which it is increasing cannot be ruled out. Rapid warming has already caused sudden ecosystem transitions at numerous biodiversity hot spots; a mechanistic understanding of such transitions is crucial. Here, we study a slow–fast consumer–resource ecosystem interacting in rapid warming scenarios. Employing geometric singular perturbation theory, we find that while a gradual change in mean temperature may accord population persistence, a critical warming rate can drive the resource’s sudden collapse, termed a warming-induced abrupt transition. This further triggers the bottom-up effect, resulting in the extinction of the consumer. The difference between the optimum temperature of the resource’s growth rate and the habitat temperature is crucial in deciding the critical rate of warming. Consequently, species inhabiting extreme temperature regions are more susceptible to warming-induced collapse than those within intermediate temperature ranges. We find that stochastic fluctuations in the system can advance warming-induced transitions, and the efficacy of generic early warning signals to anticipate sudden transitions is challenged.

Negotiating Sustainability Transitions: Why Does It Matter? What Are the Challenges? How to Proceed?

Why Does It Matter [...]

Research priorities for global food security under extreme events

Extreme events, such as those caused by climate change, economic or geopolitical shocks, and pest or disease epidemics, threaten global food security. The complexity of causation, as well as the myriad ways that an event, or a sequence of events, creates cascading and systemic impacts, poses significant challenges to food systems research and policy alike. To identify priority food security risks and research opportunities, we asked experts from a range of fields and geographies to describe key threats to global food security over the next two decades and to suggest key research questions and gaps on this topic. Here, we present a prioritization of threats to global food security from extreme events, as well as emerging research questions that highlight the conceptual and practical challenges that exist in designing, adopting, and governing resilient food systems. We hope that these findings help in directing research funding and resources toward food system transformations needed to help society tackle major food system risks and food insecurity under extreme events.

The Tragedy of Liberal Democratic Governance in the Face of Global Threats

In hindsight, the early response of liberal governments to the SARS-CoV-2 pandemic was chaotic and generally inefficient. Though one might be tempted to attribute these failures to the incompetence of certain political decision-makers, we propose another explanation. Global threats require a coordinated international response, which is only possible if the threat is perceived in the same way by all, and if government priorities are similar. The effectiveness of the response also relies on massive adhesion of citizens to the measures imposed, which in turn requires trust in government. Our hypothesis is that certain fundamental features of liberalism complicate such global and collective responses: neutrality of the state and primacy of the individual over collective society. Liberalism considers that institutions and public policy must not be designed to favor any specific conception of the common good. That which is best for all is usually determined by a "competition of opinions," which frequently leads to scientific expertise being considered as only one opinion among many. Liberalism also imposes strict respect for individual freedoms and private interests and tends to reject any form of collectivism or dictate imposed by the common good. In order to solve these structural problems and improve society's management of global threats, we make several proposals, such as the introduction of a minimal and consensual definition of the common good and the promotion of a health policy guided by One Health-like concepts. Overall, our analysis suggests that because political ideologies provide their own definitions of the common good and the place of scientific knowledge in the governance process and can thus affect the response to global threats, they should be urgently taken into consideration by public health experts.