Caroline Zimm’s research while affiliated with International Institute for Applied Systems Analysis and other places

The authors are all devoted energy system and sustainability transformation scholars, who collaborate regularly and actively at global and local levels to advance the knowledge space of demand-side solutions and policies. They are members of a growing bottom-up initiative, the Energy Demand Changes Induced by Technological and Social Innovations (EDITS) network (https://iiasa.ac.at/projects/edits), which builds on various research disciplines to facilitate advances in modeling, data compilation, and analysis of the scope and breadth of the potential contributions of demand-side solutions for climate change mitigation, improved wellbeing for all, and sustainability, complementing supply-side solutions for decarbonizing the energy and material systems.

Biophysical tipping points pose existential threats to current and future generations, both human and non-human, with those currently underserved being the most vulnerable. Social tipping points, as deliberate interventions into systems with the expectation of non-linear impacts and widespread change, have the potential to address some of these challenges. However, the imperative to act cannot increase risks nor perpetuate unjust or inequitable outcomes through the creation of sacrifice zones. In this paper we argue that considerations of what needs to change, who is being asked to change and where the change or its impacts will be felt and by whom, are fundamental questions that require a level of reflexivity and systemic understanding in decision-making. All actors have a role to play in ensuring that justice, equity and ethics are incorporated in each and every intervention. Enabling social tipping points towards radical transformations could benefit from more diverse perspectives to open up the solution space, with a particular emphasis on the inclusion of marginalised voices. We conclude that taking a cautious step back to explore all options, not just those that seem to offer a quick fix could offer a more substantial route into thinking through tipping points and create a more equitable as well as sustainable future.

The costs of climate change are often estimated in monetary terms, but this raises ethical issues. Here we express them in terms of numbers of people left outside the ‘human climate niche’—defined as the historically highly conserved distribution of relative human population density with respect to mean annual temperature. We show that climate change has already put ~9% of people (>600 million) outside this niche. By end-of-century (2080–2100), current policies leading to around 2.7 °C global warming could leave one-third (22–39%) of people outside the niche. Reducing global warming from 2.7 to 1.5 °C results in a ~5-fold decrease in the population exposed to unprecedented heat (mean annual temperature ≥29 °C). The lifetime emissions of ~3.5 global average citizens today (or ~1.2 average US citizens) expose one future person to unprecedented heat by end-of-century. That person comes from a place where emissions today are around half of the global average. These results highlight the need for more decisive policy action to limit the human costs and inequities of climate change.

The UN 2030 Agenda includes 17 Sustainable Development Goals towards improving access to resources and services, reducing environmental degradation and bringing down inequality. However, there is debate on the magnitude of the environmental burden that would arise from meeting the needs of the poorest, especially compared to much larger burdens from the rich. We first show that the ‘Great Acceleration’ of human impacts is characterized by a ‘Great Inequality’ in utilising and damaging the environment. We then operationalize ‘just access’ to minimum energy, water, food and infrastructure. Third, in an unequal world, we show that hypothetically meeting ‘just access’ would add 2-26% to current impacts on the Earth’s natural systems of climate, water, land and nutrients. These additional impacts, hypothetically caused by about a third of humanity, equal those currently caused by the wealthiest 1-4%. Nevertheless, achieving ‘just access’ calls for redistribution within stable Earth System Boundaries.

The UN 2030 Agenda’s 17 Sustainable Development Goals (SDGs) and the COVID-19 pandemic share two important characteristics. They are global challenges that if not met, pose risks to all citizens. Furthermore, responses need to be system-level, rather than sectoral. COVID-19 has illuminated three complementary, compelling actions that can address these challenges—work across silos; visibly use science in policy; and harness simultaneous global interruption to habits. This commentary describes these using worked examples and suggests actions for policymakers and other leaders. Acknowledging that the full SDG agenda is of much broader multidimensional scope than the COVID-19 pandemic, the SDG examples focus on environmental sustainability.

With the establishment of the sustainable development goals (SDGs), countries worldwide agreed to a prosperous, socially inclusive, and environmentally sustainable future for all. This ambition, however, exposes a critical gap in science-based insights, namely on how to achieve the 17 SDGs simultaneously. Quantitative goal-seeking scenario studies could help explore the needed systems' transformations. This requires a clear definition of the "target space." The 169 targets and 232 indicators used for monitoring SDG implementation cannot be used for this; they are too many, too broad, unstructured, and sometimes not formulated quantitatively. Here, we propose a streamlined set of science-based indicators and associated target values that are quantifiable and actionable to make scenario analysis meaningful, relevant, and simple enough to be transparent and communicable. The 36 targets are based on the SDGs, existing multilateral agreements, literature, and expert assessment. They include 2050 as a longer-term reference point. This target space can guide researchers in developing new sustainable development pathways.