Climate tipping points: retreating from the brink and accelerating positive change

Climate change is no longer a distant threat but is already making us face perilous “tipping points” that could alter our daily lives forever. James Dacey finds out how new research into human-climate systems could help us to avert disaster

“Flood warnings as heavy rain and thunderstorms hit”
“Torrential downpours trigger travel chaos”
“People stranded as flooding cuts off communities”

Stories about floods are a staple diet in the media. It’s hardly surprising given that heavy rain can have a huge impact on local communities – damaging homes, knocking out power lines and blocking roads. But imagine if an unfortunate combination of intense local flooding in one part of a country unleashed travel chaos across an entire nation.

Such an event is an example of a tipping point in a socioeconomic system – when a relatively small input triggers a disproportionately large outcome that brings about social and economic consequences that cannot be easily reversed. In this scenario, the trigger is flood waters within a relatively small area, and the tipping point is the loss of functionality of the national road network. If people cannot travel, then economic and social activity quickly grinds to a halt. Yes, the floodwaters will subside, but to prevent a similar outcome happening again, the road system would need to be redesigned.

In physics, tipping points – or critical points – are commonplace. They can be found in all sorts of phase transitions, whether it’s a liquid turning to gas, or the sudden magnetization of ferroelectric materials (see box below). But the rising interest in nonlinearity in a social context can be linked to Malcolm Gladwell’s 2000 bestselling “pop-sociology” book The Tipping Point. It deconstructed several confounding social trends, including the dramatic decline in New York City’s crime rates in the 1990s, and the unexpected (and unrelated) resurgence of Hush Puppies shoes that same decade.

Within a few years, the tipping-point concept had also entered climate conversations. Fears grew around catastrophic events with limited reversibility, such as the large-scale dieback of the Amazon rainforest (when plant health progressively deteriorates, sometimes resulting in organism death), and the melting of ice sheets that in turn cause global sea levels to rise. Those concerns led a team of environmental scientists in the UK and Germany to warn in 2008 that “society may be lulled into a false sense of security by smooth projections of global change” (PNAS 105 1786). They defined a “tipping element” as a subcontinental subsystem of the Earth that can be switched – under certain circumstances – into a qualitatively different state by small perturbations.

People are already being forced to flee their homes due to rising sea levels, while farmland is being abandoned because of drought

In recent years, the tipping-point concept has extended to human–climate systems, and its terminology even features in reports by the Intergovernmental Panel on Climate Change. The wider impact of local flooding is just one of many potential socioeconomic tipping points triggered by changes in the climate. In fact, people are already being forced to flee their homes due to rising sea levels, while farmland is being abandoned because of drought, and ski resorts are losing their snow because of global warming. But in an attempt to foresee dangerous thresholds and prevent us from crossing them, an entirely new academic field is emerging, in which researchers from across the social and physical sciences are investigating the complex interactions between climate and socioeconomic systems.

The road to a tipping point

One recent study in this growing field assessed the robustness of European road networks to floods (Transportation Research Part D 108 103332). Led by Kees van Ginkel – a climate adaptation and risk management researcher at the Deltares Institute in the Netherlands – the study found that small mountainous countries, such as Slovenia, Macedonia and Albania, are particularly vulnerable, with the worst 5% of one-in-a-hundred-year floods in localized areas potentially isolating entire regions due to a lack of resilience in the road network. Due to the limited number of connections between key economic centres in these nations, an estimated, 32–41% of drivers would have to take detours – many of them extreme – bringing social and economic disruption.

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In contrast, road networks in wealthier, larger nations – such as the UK, Germany and France – are generally more robust, although even they can still have local vulnerabilities. Two days of heavy rainfall over central Europe in July 2021, for example, led to extreme flooding in which at least 222 people were killed in Germany and Belgium, with severe infrastructure damage across a wider region. Much of the devastation occurred in the German states of North Rhine-Westphalia and Rhineland-Palatinate, where steep narrow valleys created funnel-like effects. What’s more, flood-water levels were heightened because soils were largely saturated prior to the record-breaking July rainfall in the catchment areas of the Ahr and Erft rivers. Floods and landslides led to road closures, which cut off evacuation routes for several villages.

The models used by today’s social-tipping researchers have similarities with recent developments in network theory and critical transitions in physical systems. Van Ginkel’s road study, for instance, adopted a network percolation approach, which is used in physics to model phase transitions in materials. This approach can describe, for example, how a solution of polymers will turn into a rigid gel once enough chains have linked together, with the switch occurring at what is known as a “percolation point”.

Crucially, van Ginkel’s group adapted the physical model to make it relevant for policymakers. That’s because in human systems, unacceptable tipping points can be reached long before the mathematical percolation point. “In our study, the true percolation point is where the whole country is basically flooded – and if that did happen then the lack of a road network is no longer your biggest problem,” he says.

Instead, social tipping points are defined by human factors – in this case, the large loss of functionality of a national road network during a flood, as defined by cut-off routes, route changes and overall delay times. Van Ginkel says that national road authorities are likely already aware of some of the vulnerabilities his group’s study reveals. The value, he says, is that it enables comparisons to be made between nations, which could be useful for policymakers, or for business investors.

For many systems, the tipping point may not be directly triggered by the climate. As van Ginkel points out, it could be due to a policy change that removes support for communities facing the impacts of slow and steady climate changes. Agricultural workers in increasingly arid regions who rely on government subsidies, for example, would be exposed to accumulated slow-onset impacts of climate change if their support was suddenly removed. In other words: the nonlinearity exists in the social system.

Tipping points in physical systems

In physics, the idea of phase transitions or critical points crops up in many contexts. In condensed-matter physics, a material can suddenly switch into a fundamentally different state at critical temperatures, a liquid can become a gas, while a standard metal can transform into a superconductor. Statistical mechanics offers a way of understanding phase transitions via the Ising model, originally developed to explain the spontaneous magnetization in ferromagnetic film.

A related theory, percolation theory, is used to model the sudden emergence of long-range connectivity across a system of random disconnected clusters. Percolation theory has been used to study everything from fracture propagation in materials, to the spread of forest fires and the fragmentation of biological viruses. Today, some of these statistical physics tools are being repurposed to investigate social dynamics – from the way news spreads on social media, to voting patterns and the complex interactions between climate and socioeconomic systems.

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Not just doom and gloom

Social tipping-point studies do not only expose vulnerabilities and predict catastrophes. They also help us to understand the mechanics of desirable rapid social change. Why, for example, did it quickly become unthinkable to allow smoking in public spaces after decades of tolerance? Why did the protest of one Swedish pupil energize a generation to campaign about climate threats? Or why did it take a pandemic for hybrid working to become widely adopted?

The simple answer to such questions is that the time was right – but that’s only obvious in hindsight. The more pertinent question for changemakers is: how can you “tip” social and economic systems to facilitate rapid progressive change?

In Gladwell’s The Tipping Point he argues that successful interventions tend to be tightly focused and require modest behavioural changes for individuals. According to him, social-tipping initiatives need to be convenient, and delivered by a combination of salespeople, connectors and experts. He cites a diabetes and breast cancer awareness initiative in the Black community of San Diego, led by the nurse Georgia Sadler. After an initial campaign in local churches had little impact, Sadler shifted her focus to local beauty salons. She knew they were relaxing places where people already trust the stylists, so they were trained to deliver campaign messages in conversation. This tweak in tactics led to great success – a follow-up study co-authored by Sadler found significantly higher rates of mammography among African American women exposed to the salon messaging, compared with a control group that had not (J. Natl Med. Assoc. 103 735).

youth strike for climate London 2019

The challenge with the climate crisis is that slow and steady change may no longer be good enough to avoid catastrophe. Researchers recently found that current global warming of 1.1 °C above pre-industrial levels has already shifted us into the ranges for five climate tipping points (Science 10.1126/science.abn7950). These are the collapse of both the Greenland and West Antarctic ice sheets; the thawing of permafrost regions over a short space of time releasing vast amounts of stored carbon dioxide; the complete loss of coral reefs at low latitudes; and the drastic weakening of an important ocean current in the north Atlantic.

To tackle climate challenges, world leaders are meeting now (6–18 November) at the UN Climate Change Conference in Egypt (COP 27), to negotiate key issues such as climate finance, energy pathways and adaptation to climate threats. But any agreements that are made will be of little use if promised changes are not embraced by the individuals, communities and businesses they affect. That’s why decision-makers need to understand the dynamics of social change.

One researcher who investigates the mechanisms of transitions in human–climate systems is Ilona Otto, a social scientist at the University of Graz, Austria. In a 2020 paper, Otto and her team identified six social tipping elements deemed crucial to meeting the Paris Agreement on climate change (PNAS 117 2354). They cover energy; decarbonizing cities; divesting from fossil fuels; moral implications of fossil fuels; climate education and engagement; and enhanced information on greenhouse-gas emissions. Strategies were suggested for each tipping element, based on consultations with experts from academia, industry, and civil and governmental organizations. Ideas range from novel building materials and the promotion of meat-free diets, to the formation of a global environmental court.

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For Otto, the most powerful drivers for change relate to infrastructure and social norms. Take, for example, the two Nord Stream pipelines, which were built to deliver natural gas from Russia to Europe. After Russia’s invasion of Ukraine in early 2022, the $11bn Nord Stream 2 pipeline was all but abandoned, and Russia has since switched off Nord Stream 1 in response to Western sanctions. As a result, energy and consumer prices across Europe have shot up.

Yet despite the squeeze, most European residents are not shouting for the pipelines to be turned back on – there is a collective acceptance that it would be morally abhorrent to fund Russia’s war. Otto says these recent developments are a clear sign that renewable-energy alternatives should be fast-tracked. She fears, however, that Nord Stream-scale multi-national projects only seem to happen for fossil fuels – despite all the rhetoric about green-energy transitions.

Otto is currently looking at the impact of personal choices on the climate, with provisional analyses of the UK and Germany suggesting that household heating systems are usually the largest variable in individual emissions. To understand the complex economic, social and moral issues that consumers face, Otto uses “contagion models”, which are typically used to study how epidemics spread. The results could help with campaigns to encourage people to eat less meat, use greener forms of travel or trigger changes to school curricula. “Social scientists are now working more quantitatively and are more open to quantitative models,” says Otto.

Global perspectives

Social tipping points also raise moral questions. China could be said to have demonstrated the most effective social tipping in recent history, through state-level interventions such as the one-child policy (1980–2016) and its rapid economic development. But a fixed route for social change chosen by leaders of a one-party state is very different from transitions that emerge through societal choices – whether “tipped” by government policies or not.

solar-panel installation on a house in South Africa

In fact, some countries have unique socioeconomic tipping opportunities. In South Africa, for example, almost 90% of electricity was generated by coal in 2020, yet an ageing infrastructure means the country regularly experiences blackouts. Many hope that climate targets and plummeting costs of renewable energy will enable South Africa to bypass the standard carbon-fuelled development route – instead jumping to a new regime centred on renewable energy. According to a 2022 study led by Jonathan Hanto of the Berlin Institute of Technology, this transition is slowly beginning. New wind and solar installations have been cheaper than new coal plants in South Africa since 2015, while new legislation is supporting low-carbon alternatives (Energy for Sustainable Development 69 164).

Reinette (Oonsie) Biggs, a sustainability researcher at Stellenbosch University, South Africa, says shifting the country’s energy system into a new state will be a “game-changer” because so much of the economy and society is built around energy use. But she cautions that changes will only be transformative if the economic model becomes more distributed and equitable. Biggs wants legislation that requires a certain percentage of energy to be generated by community projects, and to lower the bar for small-scale projects to sell into the grid.

With such huge challenges, a combination of local initiatives and state interventions will be needed to tip us away from the brink of climate disaster. But socioeconomic transitions need not be all doom and gloom. If the collective imagination can be activated, perhaps we can tip ourselves into a new world where natural resources are no longer the dominion of the few and prosperity is an option for all.

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