Introduction

Why we need to talk about tipping points

The 21st century has already witnessed extraordinary, abrupt and potentially irreversible changes in the world around us. With global warming now at around 1.2°C above the pre-industrial level, massive coral reef die-off events are occurring, the Amazon rainforest is suffering droughts, large regions of permafrost are thawing, and part of the West Antarctic Ice Sheet may be irreversibly retreating, to name but a few of the tumultuous changes happening in the Earth system.

In the last decade, climate impacts have escalated, harming the economy and resulting in  insurance being withdrawn from some of the most vulnerable communities. The global financial crisis of 2007-2008 and ensuing Great Recession have shown us how fragile the economy can be, and the COVID-19 pandemic gave us all a profound lesson in abrupt, cascading change. At the same time, we have started to see evidence of accelerating social and technological change towards sustainability, including numerous political declarations of a ‘climate emergency’ and exponential growth of renewable energy deployment.

All of this experience challenges a worldview that many of us were brought up with – to see the world like a machine. The world is not behaving in a linear fashion. Instead, our expectations of smooth, predictable and reversible changes are being confronted with a reality of abrupt, unexpected and irreversible ones. We wrote this report during 2023 against a backdrop of unprecedented climate extremes, including severe heat waves across much of Asia, massive loss of Antarctic seaice, and Canadian forest fires way off the scale of even recent experience. 

The pace and scale of these events has attracted use of the term ‘tipping points’ – originally popularised by Malcolm Gladwell – which describes the phenomenon that occurs when a small change makes a big difference to a system. Tipping points in the Earth system are arguably the biggest risk we face in a changing world, because they can lead to profound damages that are abrupt or irreversible – or both. The level of global warming that could trigger known climate tipping points is uncertain; there is little assessment of tipping point impacts and even less consideration of who or what is most vulnerable to those impacts. Yet we know enough to argue that any credible climate change risk assessment must consider the risks from climate tipping points – as they could profoundly affect the economy and societies.

For too long, the climate change assessment process has tended to focus on the most likely outcome, rather than evaluating the highest-risk outcomes. But this is poor risk assessment and it is leaving society ill equipped for what lies ahead.

Furthermore, while climate tipping points are often portrayed as ‘high-impact, low-likelihood events’, some are rapidly becoming ‘high-impact, high-likelihood events’. 

The risks from anthropogenically triggered Earth system tipping points, and our perception of them, may in turn influence tipping points in human systems. These ‘social tipping points’ can take many forms – from the escalation of wars to the sudden uptake of new technologies. The global financial crisis and the COVID-19 pandemic demonstrated how undesirable impacts can cascade through our networked world. But this potential also exists for desirable impacts. The same feedback principles underlie both undesirable tipping points in the Earth system and those in human systems, both desirable and undesirable. 

As experience starts to show how risks can cascade between the different realms of climate, ecology and human society, there is a growing sense that we are in a ‘polycrisis’. But experience has barely scratched the surface of what could occur as the impacts of global change – especially climate change – accelerate and accumulate. Hence, there is an urgent need to assess how Earth system tipping points can impact human systems, especially whether and how they could trigger undesirable social tipping points. This is essential information to enable mitigation of the worst impacts and to build resilience to impacts that cannot be avoided.

Growing recognition and knowledge of tipping point risks in turn begs the question of how best to govern those risks. Can our current institutions and processes deal with tipping point risks? Or do the unusual qualities of tipping points (abruptness, irreversibility, unpredictability, and having large but unevenly distributed impacts) demand new governance approaches? 

Against this backdrop of profound risks, the opportunities for creating and enabling ‘positive tipping points’ to accelerate action to tackle climate change, biodiversity loss and other sustainability challenges are just starting to be widely recognised. They may offer the most credible way of achieving the acceleration of action that is required – by leveraging strongly reinforcing feedback processes that are self-propelling.

When presented with such complexity and tumultuous change, we cannot continue  looking at the world in an outdated way. We need an effective and comprehensive risk assessment of ‘negative’ tipping points; we need an opportunity analysis of realised and potential ‘positive’ tipping points; and we need to consider how to navigate both, in a just way, in the face of uncertainty. The experience of the author team tells us many people are hungry for this knowledge.

Who this report is for

This report is for all those concerned with tackling escalating Earth system change and mobilising transformative social change to alter that trajectory, achieve sustainability and promote social justice. 

Our primary audience is decision makers, including policymakers and leaders in the public, private and voluntary sectors. Governance has a particular social position and collective responsibility to lead in the protection of public goods and the effective distribution of public money. Leaders in other sectors can play an equally vital role in creating (or inhibiting) transformative change through the mobilisation of human capital and private finance. Those in the media can choose to amplify (or not) key risk and opportunity information. But we also want to reach a broad audience. As citizens, all of us can contribute to transformative social change, and we can also seek to influence those who are more powerful than us. 

The authors and origins of this report 

A total of 200 researchers have contributed to this report, which was initiated alongside an international meeting on ‘Tipping Points: from climate crisis to positive transformation’ at the University of Exeter, UK, in September 2022. The meeting and associated recent research on tipping points attracted widespread interest and media attention. The meeting also served to crystallise a community of tipping point researchers – making it clear that there was both a niche to fill with this report, and a community ready to fill it. A core writing team was formed, from the University of Exeter and international partners, and an open call was made for researchers to contribute their expertise to the report and a corresponding special issue of the open-access journal Earth System Dynamics on ‘Tipping Points in the Anthropocene’. Consequently, most of the research content of this report has undergone, or is undergoing, peer review. 

Aims of this report

Our overarching aim is to provide a first-ever comprehensive (but not exhaustive) assessment of currently recognised tipping points in the Earth system and in human systems that are relevant to urgent contemporary global change – especially climate change and biodiversity loss – and associated transformative social change.

The report aims to help improve climate risk assessment by comprehensively assessing the risks from Earth system tipping points. It considers the systemic risks of how Earth system tipping points can impact human systems, especially whether and how they could trigger undesirable social tipping points. Then it aims to assess how to govern the risks from Earth system tipping points. It further aims to synthesise knowledge of positive tipping points and their potential to accelerate transformative social change, as well as explain how to govern these opportunities (and their associated risks), building in part on our previous ‘Breakthrough Effect’ report with SYSTEMIQ (Meldrum et al., 2023).

This report as a whole is intended to provide a foundation for future regular updates on the status of tipping points in the Earth system and in human systems. At the time of writing, there is a shortage of assessment of these, particularly at the level of synthesis across the climate, ecological and social realms. There is a proposal under consideration for an IPCC Special Report on Tipping Points, which we support. That would have a different style and emphasis and would be subject to inter-governmental approval. We trust that this report would provide a useful stepping stone.

Scope

The report’s title conveys that we are concerned with tipping points associated with global change and ones whose consequences are (or have the potential to be) of global interest or concern. It does not imply that the tipping mechanisms are global in scale, although this possibility is assessed within the report. Some tipping points have global consequences; others with (potentially) global implications start out on a much smaller scale and warrant our consideration. There are many smaller-scale tipping points that are important in a regional and/or cultural context but may not be (or ever become) of global interest. The dividing line of inclusion is necessarily imprecise. We include some case studies of fairly localised tipping points with what we assess to be considerable potential to spread. We expect that with further research such selections will change.

Style and structure

The report tackles diverse subject matter and complex concepts, and marshalls myriad data. It is drawn from an extensive and growing body of academic research, but is written for a non-academic audience. Hence we have worked hard to ensure it is comprehensible. 

To this end, it adopts a layered structure. After this introductory section there are four major sections. Each begins with an introduction to and synthesis of its subject matter, drawing out key messages and recommendations. Each section is divided into chapters and each chapter delves into greater detail on key target systems or issues, as well as containing a summary of key messages and recommendations.

The report broadly proceeds from tipping point risks to opportunities. It starts in the biophysical science realm of tipping points in the Earth system, zooms into the social science of undesirable tipping points in social systems, considers the governance of Earth system tipping points, then shifts to considering positive tipping points in social systems and their governance. 

Before launching in, we define the key concepts and terms related to tipping points that are used throughout this report. We also outline in a little more depth some key aspects of our approach, including some key risk, equity and justice considerations across both negative and positive tipping points.