The popularity of the term polycrisis suggests a growing demand for new thinking about the world's intersecting crises, but loose and haphazard uses of the concept impede knowledge generation. The special issue, ‘Polycrisis in the Anthropocene’, aims to close the gap. This introductory comment first elaborates upon three key contributions of the lead article ‘Global Polycrisis: The Causal mechanisms of Crisis Entanglement’: a conceptualization of crisis as systemic disequilibrium; the distinction between the slow-moving stresses and the fast-moving trigger events that interact to generate a crisis; and a grammar with which to map the causality of crisis interactions. The commentary then explores three key debates around the polycrisis concept: Are we in a polycrisis, at risk of a polycrisis, or neither? Is the present polycrisis truly unique and unprecedented? And where are power and agency in a systemic approach to polycrisis? These ongoing debates suggest promising directions for polycrisis research that could feature in this special issue and advance the field of polycrisis analysis.

This commentary introduces the special issue ‘Polycrisis in the Anthropocene’ by elaborating upon three major contributions of its lead article, ‘Global Polycrisis: The Causal Mechanisms of Crisis Entanglement’, and exploring three key debates surrounding the polycrisis concept. It invites others to contribute to the special issue in order to advance polycrisis analysis, build a community of knowledge and practice, and generate new insights and strategies with which to address the world's worsening crises.

The popularity of the term polycrisis suggests a growing demand for new thinking about the world's intersecting crises, but loose and haphazard uses of the concept impede knowledge generation. The special issue, ‘Polycrisis in the Anthropocene’, aims to close the gap. This introductory comment first elaborates upon three key contributions of the lead article ‘Global Polycrisis: The Causal mechanisms of Crisis Entanglement’: a conceptualization of crisis as systemic disequilibrium; the distinction between the slow-moving stresses and the fast-moving trigger events that interact to generate a crisis; and a grammar with which to map the causality of crisis interactions. The commentary then explores three key debates around the polycrisis concept: Are we in a polycrisis, at risk of a polycrisis, or neither? Is the present polycrisis truly unique and unprecedented? And where are power and agency in a systemic approach to polycrisis? These ongoing debates suggest promising directions for polycrisis research that could feature in this special issue and advance the field of polycrisis analysis.

Inviting contributions and debates to Global Sustainability journal's special issue ‘Polycrisis in the Anthropocene’.

Information on social aspects of climate change intervention, such as behavioral choices and public acceptance, are often not included in global climate models. As a result, they have been critiqued for not adequately reflecting ‘real world’ conditions. At the same time, these models are important and influential policy tools. To improve these models, calls are being made for more interaction – or integration – between the social science and modelling research communities. Yet, it remains unclear how to achieve this. Responding to this gap, we explore what kind of integration is currently taking place, how, and opportunities for further development.

The importance of social drivers of climate change interventions, or social aspects, is currently underrepresented in computational modelling projections. These parameters are largely excluded from estimates of technical mitigation potential, feasibility, and tools like integrated assessment models (IAMs) and other large-scale models that influence the development of climate policies and notable bodies like the Intergovernmental Panel on Climate Change. This paper contributes to calls being made within the research community to address this gap and strengthen linkages between modelling practices and social science insights. Using nature-based solutions (NbS) as a framing, we present the results of a critical literature review and interviews with multidisciplinary experts reflecting on the current state of integration around IAMs and opportunities to better capture social aspects within large-scale modelling processes. Our findings confirm the need to incorporate social aspects in IAMs, but highlight that how this happens in practice may depend on context, project objectives, or pragmatic choices rather than conceptual notions about what ‘good’ integration is. Nevertheless, some integration strategies are better than others, and concerns about data limitations and low capacity of the IAM community for engaging in integration can be overcome with sufficient support and complementary efforts from the broader research community.

Integrating social aspects in large-scale models requires complementary efforts from the broader research community.

In 2015, the United Nations articulated the ambition to move toward a prosperous, socially inclusive, and environmentally sustainable future for all by adopting the Sustainable Development Goals (SDGs). However, little is known about the pathways that could lead to their concurrent achievement. We provide an overview of the current literature on quantitative pathways toward the SDGs, indicate the commonly used methods and indicators, and identify the most comprehensive pathways that have been published to date. Our results indicate that there is a need for more scenarios toward the full set of SDGs, using a wider range of underlying narratives.

Quantitative goal-seeking scenario studies could help to explore the needed systems' transformations to implement the 2030 Agenda for Sustainable Development by identifying enabling conditions and accounting for the synergies and trade-offs between the SDGs. Given that the SDGs were adopted some time ago, here, we review the existing global scenario literature to determine what it can offer in this context. We found only a few scenarios that address a large set of SDGs, while many more deal with specific clusters of 2–6 SDGs. We identified the most frequent clusters and compared the results of the most comprehensive sustainable development scenarios. The latter is complicated because of the diversity of methods, indicators, and assumptions used. Therefore, we suggest that an effort is needed to develop a wider set of scenarios that would achieve multiple SDGs, using a more standardized framework of targets and indicators.

This study reviews the current global pathways toward the SDGs and shows the need for a broader set of SDG scenarios.

In this paper, we explore how critically important ecosystems on the land provide evaporation to the atmosphere, which will later fall as precipitation elsewhere. Using a model-based analysis that tracks water flowing through the atmosphere, we find that more than two-thirds of the precipitation over critically important ecosystem areas is supplied by evaporation from other land. Likewise, more than 40% of the evaporation from critically important ecosystems falls as precipitation on other land. We conclude our work by discussing the policy implications for how these critically important ecosystems connect spatially distant wild and working lands via the atmospheric water cycle.

Global ecosystems are interconnected via atmospheric water vapor flows. Land use change can modify evaporation from land, altering atmospheric moisture recycling and potentially leading to significant changes in downwind precipitation and associated ecological impacts. We combine insights on global ecosystem-regulated moisture recycling with an analysis of critical natural assets (CNA, the 30% of global land providing most of nature's contributions to people) to reveal the sources and sinks of atmospheric water cycle regulation. We find that 65% of the precipitation over CNA is supplied by evaporation from other land areas. Likewise, CNA regions supply critical moisture as precipitation to terrestrial natural ecosystems and production systems worldwide, with 44% of CNA evaporation falling on terrestrial surfaces. Specifically, the Congo River basin emerges as a hotspot of overlap between local atmospheric water cycle maintenance and concentration of nature's contributions to people. Our results suggest global priority areas for conservation efforts beyond and in support of CNA, emphasizing the importance of sparsely populated managed forests and rangelands, along with wild forests, for fostering moisture recycling to and within CNA. This work also underlines the manifold benefits associated with achieving United Nations Sustainable Development Goal #15, to sustainably manage terrestrial life and conserve biodiversity.

Critically important ecosystems are essential for connecting distant landscapes via the atmospheric water cycle.

Scenarios compatible with the Paris agreement's temperature goal of 1.5 °C involve carbon dioxide removal measures – measures that actively remove CO2 from the atmosphere – on a massive scale. Such large-scale implementations raise significant ethical problems. Van Vuuren et al. (2018), as well as the current IPCC scenarios, show that reduction in energy and or food demand could reduce the need for such activities. There is some reluctance to discuss such societal changes. However, we argue that policy measures enabling societal changes are not necessarily ethically problematic. Therefore, they should be discussed alongside techno-optimistic approaches in any kind of discussions about how to respond to climate change.

The 1.5 °C goal has given impetus to carbon dioxide removal (CDR) measures, such as bioenergy combined with carbon capture and storage, or afforestation. However, land-based CDR options compete with food production and biodiversity protection. Van Vuuren et al. (2018) looked at alternative pathways including lifestyle changes, low-population projections, or non-CO2 greenhouse gas mitigation, to reach the 1.5 °C temperature objective. Underlined by the recently published IPCC AR6 WGIII report, they show that demand-side management measures are likely to reduce the need for CDR. Yet, policy measures entailed in these scenarios could be associated with ethical problems themselves. In this paper, we therefore investigate ethical implications of four alternative pathways as proposed by Van Vuuren et al. (2018). We find that emission reduction options such as lifestyle changes and reducing population, which are typically perceived as ethically problematic, might be less so on further inspection. In contrast, options associated with less societal transformation and more techno-optimistic approaches turn out to be in need of further scrutiny. The vast majority of emission reduction options considered are not intrinsically ethically problematic; rather everything rests on the precise implementation. Explicitly addressing ethical considerations when developing, advancing, and using integrated assessment scenarios could reignite debates about previously overlooked topics and thereby support necessary societal discourse.

Policy measures enabling societal changes are not necessarily as ethically problematic as commonly presumed and reduce the need for large-scale CDR.