Quantitative risk analysis has long underpinned public trust in experts who interpret and address environmental disputes. However, in the uncertain and complex context of responding to a changing climate, it has been argued that trust in scientific expertise must be warranted on norms other than experts’ competence in quantifying risk. Nowhere is this more evident than in the case of solar geoengineering. Much like abrupt climate change, solar geoengineering involves potential nonlinear or threshold responses, where both the triggering points and the system’s reactions are poorly understood, leaving risks inadequately characterized. In this paper, we examine climate model experiments with solar geoengineering to understand how expertise is justified in the absence of reliable risk assessments. We argue that these experts enact a specific norm of competence, which holds that trust should be warranted not on their ability to quantify risk, but to render unknown unknowns into known unknowns.

Over the past two decades, the concept of ‘tipping points’ has gained prominence in natural and socialsciences. A growing field within social science applies the concept in ways similar to natural science,aiming to identify and amplify societal tipping points in response to ecological ones. The paperexamines the use of societal tipping points in the context of climate change, focusing on how theconcept is mobilized in public discourse. We analyse how agency and cause–effect explanations areassigned and ordered in representations of climate crisis responses, contributing to debates about thefunction and adequacy of the tipping point concept. Through a narrative analysis of media articles inSweden, we identify three public narratives: social, techno-economic and political tipping points.These narratives show how responses to climate are framed, emphasising the roles of socialmovements, technological innovation and political intervention. Social tipping points, which peakedaround 2018, are portrayed as catalysts for societal change driven by collective action and shifts inpublic norms. The analysis suggests that tipping points operate as both an analytical concept and arhetorical device shaping understandings of climate change, while also raising concerns about theiruse in social science and conceptual dilution.

As large-scale climate interventions such as solar geoengineering gain traction in formal assessment processes, the role of computer-based models in shaping anticipatory governance remains underexplored. This paper examines how model intercomparison projects serve as infrastructural sites for synchronization, aligning diverse scientific, technical, and political timelines to facilitate expert foresight. Through an analysis of the Geoengineering Model Intercomparison Project, we demonstrate how the organization of data through experimental protocols and historical simulations is a contested practice where experts negotiate shared schedules and rhythms of anticipation. Our findings reveal that many practices for synchronization are mundane and happen outside formal models. Despite the highly technical nature of computer-based modelling, with its emphasis on the uniform temporality of numerical calculation, we argue that important to the synchronization of deployment scenarios is the exercise of practical judgement, as experts discern and seize opportunities to reorient collective expectations about the future. By foregrounding this kairological dimension to knowledge infrastructures, we highlight the politics of anticipation that experts are engaged in, influencing how societies perceive and respond to the feasibility of large-scale climate interventions.

Two decades after the tipping points became part of climate policy discussions, this study examines how the relation between societal tipping points and climate tipping points is understood in public discourse. We analyze views on how political and social actions might impact the race between negative climate tipping points and positive societal tipping points, drawing on a global sample of 10 news outlets from 2020 to 2024. In line with previous research, our findings suggest that “Tipping point” rarely implies an irreversible, self-reinforcing process. Three discursive tensions stem from the concept's ambiguous ontology: the kind of transition envisioned, agency of actors and politics needed, and means for change. Positive tipping points offer a discursive balance, allowing discussions on negative climate tipping points without excessive pessimism. The paper ends with a reflection on whether this shift may dilute the focus on risks and promotes a depoliticized belief that incremental changes will lead to a conflict-free transition.

We have followed with great interest the responses to our article in Dialogues on Climate Change con-cerning societal tipping points in public debate, as well as the reflections offered on their relationship toclimate tipping points and their implications for society. In this response, we underscore the strengths ofthe four responses our article received and critically assess whether early opportunity signals can beapplied to transformations in social systems, and whether such systems can be modelled in ways analogousto physical climate systems. Finally, we outline potential directions for future research on societal tippingpoints.

Carbon dioxide removal (CDR) approaches are becoming increasingly central to visions of decarbonizing national economies. The past few years have seen an increasing number of countries committed to net-zero targets, preceded by a surge of modelled 1.5°C scenarios envisioning large-scale future CDR deployment. The prospect of CDR deployment raises new complex socio-ecological challenges, and presents new deep uncertainties. These complexities, challenges and uncertainties cannot be investigated using solely the techno-economic modelling and environmental risk-assessment methods that currently dominate the construction of policy-relevant knowledge on CDR. Social sciences and the humanities perspectives on CDR are often restricted to instrumental tasks such as investigating public acceptance, overcoming social resistance or supporting the development of integrated assessment models. There is a need for more diverse investigations of CDR which include not only environmental and techno-economic dimensions, but also explore key societal complexities, challenges and uncertainties. Against this backdrop, we call for submissions on CDR stemming from perspectives within the social sciences and humanities. We encourage novel empirical and theoretical contributions on:

– CDR-related policy design or analyses of recent policy developments at sub-national, national and international levels of governance, e.g., in context of climate targets and strategies, climate tipping points, mitigation deterrence or societal transformations.

– Construction of knowledge in scientific discourse, e.g., critical reflections on the scenario/pathway literature and integrated assessment modeling, science communications, IPCC processes or science-policy relations.

– Historical and contemporary experiences of CDR in different cultural, geographical and political contexts, e.g. case studies, experience from developing countries, equity and responsibility distribution in North-South relations or geopolitical implications.

– Political and public debates on or controversies over CDR, e.g. using discourse theory or critical science and technology studies (STS) to analyse mass media or social media, scientific trends, ideological connections to CDR or shifting power relations. 

Soil management is a strategy for improving soil suffering from problems such as low pH, nutrient deficiency, and erosion. The study evaluated the effects of human urine (HU), biogas slurry (BS), standard compost (StC), animal manure (AM), and synthetic fertilizer (SF) in comparison with no soil fertility management (NFM) on soil pH, cation exchange capacity (CEC), soil organic carbon (SOC), soil moisture content, nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sodium (Na), copper (Cu), zinc (Zn), manganese (Mn), and iron (Fe) in the Karagwe district, a Northwestern Tanzania. Four household farms representing each soil amendment type were selected for soil sampling. A total of 192 soil samples were collected and air-dried. After laboratory analysis, BS-enriched soil had the highest pH (6.558), CEC (23.945 cmol+/kg), SOC (5.573%), soil moisture (5.573%), N (0.497%), P (247.130 mg/kg), K (3.036 cmol+/kg), Ca (18.983 cmol+/kg), Mg (4.076 cmol+/kg), Na (2.960 cmol+/kg), and Cu (12.548 mg/kg). Similar soil properties were lower in NFM than in the other soils. The soil properties on the chosen farms did not differ significantly depending on the sampling zone for each organic fertilizer. Therefore, the result indicates that all evaluated organic fertilizers improved soil health compared to NFM, but BS and HU fertilizers led to relatively better soil health improvements than StC, AM, and SF.

The City of Stockholm aims to achieve net-zero emissions by 2030 by compensating for residual emissions using bioenergy with carbon capture and storage (BECCS). Relying heavily on negative emissions to reach the target, the city's strategy presents an interesting case of net-zero climate policymaking. Based on the analysis of interviews, City Council debates, and policy documents, the Stockholm case underscores the importance of understanding municipal climate policy in a multi-level policy setting, where the ability to govern emissions varies heavily between sectors depending on politics and policy at other levels of governance. Both waste incineration and road transport are perceived to include hard-to-abate emissions in 2030, partly due to governance linkages involving regional, national, and EU-level governing bodies. The energy utility, Stockholm Exergi, plans to implement BECCS, with funding from the EU and other public and private sources, at a heat and power plant. The unique opportunity to use BECCS as part of the city's net-zero target has made it possible to advance the net-zero goal from 2040 to 2030. However, there are risks that relying on BECCS may muffle public debate on what constitutes residual emissions in the city, subsequently leading to smaller municipal investments in emission reductions. Additionally, there are risks that the schedule for implementing BECCS is overly optimistic, meaning goal fulfilment may be threatened. However, this risk is not isolated to BECCS; similar risks are associated with combining fossil fuels with CCS. We recommend that the city critically examines the residual emissions, considers separate targets instead of a net-zero goal, and conducts risk assessments of key mitigation technologies to maintain its status as climate policy forerunner.

Soils require the application of biochar to improve degradation. The objective of this study was to evaluate the long-term effects of a field experiment on soil organic matter (SOM), soil organic carbon (SOC), and soil moisture content in Karagwe, Tanzania. Seven years ago, a field experiment was conducted using a Latin rectangle design with four replications. The treatments included carbonization and sanitation (CaSa) and carbonization and standard compost (CaSt), which were compared to control Andosols (CoA). A total of 96 soil samples were collected to determine SOM, SOC, and soil moisture content. The data were analyzed using one-way analysis of variance. The results showed that soil samples from the CaSa-treated soil had an increase in SOM content of 17.3%, an increase in stored SOC content of 10.0%, and an increase in soil moisture content of 6.3%. Compared with those in CoA, the CaSt-treated soil showed increases in SOM, SOC, and soil moisture of 14.4%, 8.4%, and 4.0%, respectively. Therefore, all treatments improved soil properties, with CaSa proving more effective in enhancing SOM, SOC, and soil moisture content compared to CaSt and CoA. In conclusion, CaSa is recommended for its sustainable ability to enhance Karagwean soil over time.

In this chapter, I will argue that scientific climate mitigation scenarios and pathways help create visions of the future, and that scenarios of a certain centrality or political and scientific le-gitimacy end up influencing the kinds of future developments deemed to be desirable or achiev-able. The argument will be supported by an overview of relevant research and is illustrated by an empirical study I conducted a couple of years ago with colleagues at Linköping University (Hansson et al., 2021). I will illustrate and discuss the construction of visions in the context of the IPCC reports. Engaging STS concepts, I reveal aspects of how relevant science is estab-lished. A point of departure, which I share with many STS scholars, is that scientific knowledge is negotiated and influenced by social processes and often co-constructed with politics (van Beek et al., 2022; Schenuit, 2023). I want to stress that such a point of departure does not mean that the ambition is to discredit the scientific validity of the IPCC. On the contrary, it is unavoid-able that science is situated in a cultural and political context. The boundaries between what is and is not considered scientific knowledge are blurry. It must be negotiated, especially when the scientific object is complex, in our case future development of the global climate in interaction with global society. Those interactions are inherently characterized by deep uncertainties and unpredictable social dynamics. Nevertheless, scientific communities have been tasked with the herculean mission to compile and analyze current understandings of climate change. Further-more, they are called upon to convey structured and transparent scenarios or pathways on how various futures may unfold. The main tools for that are integrated assessment models (IAMs) (IPCC, 2018). Therefore, my ambition is that STS-informed analyses can help society to open up and also improve scientific efforts to understand the future.