Fight or Flight – a Tale of Two Disruptions

Prof. Dr. Dr. h.c. Hans Joachim Schellnhuber, Gitta Köllner, Dr. Maria Martin


To be, or not to be, that is the question:
Whether ‘tis nobler in the mind to suffer
The slings and arrows of outrageous fortune,
Or to take arms against a sea of troubles,
And by opposing, end them? To die: to sleep

William Shakespeare: The tragedy of Hamlet, Prince of Denmark (Act 3, Scene 1)


While Hamlet famously vacillates between suffering the rough sides of life and taking the courage to end it, humanity as a whole is currently facing a similar existential choice. However, what Hamlet does not actually have in mind is the third option: to take arms against a sea of troubles and fight against his outrageous fortune. There are sayings and quotes for every situation. In the case of humanity, it is time to recognise that we are architects of our own fates.

Ruling out intentional self-destruction, humanity – like Hamlet – faces a crossroads: To flee or to fight. There is imminent danger associated with anthropogenic climate change. And since we have wasted decades in analysing the situation without taking noteworthy action, we are intellectually more than well prepared to take a decision. We know the risks of both choices: On the one hand, fighting climate change will involve some serious scratches. Fleeing this fight, on the other hand, will allow more and more devastating climate impacts to catch up with us, until we will reach a state indistinguishable from intentional self-destruction.

A tale of two disruptions describes humanity’s current situation. Either we take up the proverbial arms and transform our society in an effort that is comparable in its immensity to times of war, or we will be transformed by the results of our inability or unwillingness to combat climate change.

What we see in terms of extreme events is just a foretaste of what lies ahead if we continue along the still unbroken path of carbon-based lifestyles at the expense of the world’s poor and future generations. The unprecedented dimension and frequency of extreme weather events during the last two years give a glimpse of the world to come.

A Sea of Troubles 

In the summer of 2018, heatwaves in North America, Western Europe, the Caspian Sea region and Siberia, which affected important bread-basket regions for food production, coincided with heavy rainfall in South-East Europe and Japan (Kornhuber et al. 2019). Events like these trickle into the public’s consciousness. It is but consequences for our everyday lives that make an abstract concept like climate truly manifest. One striking example of change in the highly complex atmosphere-ocean system translating directly into people’s daily routine is the meandering jet stream in the high Northern latitudes. At an altitude of eleven kilometres, this band of winds tends to form ever-bigger waves if the temperature gradient between the polar region and the temperate latitudes decreases (Figure 1). These so-called Rossby waves can overlap so the jet stops propagating for several weeks due to subtle resonance phenomena (Petoukhov et al. 2013). The longer we observe the associated wave pattern, the clearer it becomes that this phenomenon has occurred more often over recent years. In other words, extreme weather patterns last longer – so a couple of nice, warm days become a heatwave, and some refreshing rainy ones turn into a deluge (Kornhuber et al. 2019).

As the global concentration of greenhouse gas emissions is still on the rise, as air and ocean temperatures are steadily increasing, the impacts of planetary warming become more and more apparent. Heatwaves and droughts call for better planning in the agricultural sector, as well as in health systems. Weather extremes can exacerbate food insecurity, social unrest and conflict in affected regions. Tropical cyclones impact a growing number of people directly and harm economies where they make landfall (Winston and Zemyla 2019). The devastating cyclone Idai, for example, was one of the most deleterious ever in the Southern hemisphere in terms of deaths and the number of people stricken (Warren 2019). Other prominent examples are the raging bushfires in California and Australia, unprecedented in frequency and intensity, following droughts and extremely hot summers (Winston and Zemyla 2019).

But there are more examples of looming risks, particularly those associated with tipping elements in the Earth System, which may be triggered to flip irreversibly into a different state once a certain temperature threshold is crossed. Some of these elements could already be tipped within the temperature range of 1.5-2°C, i.e. within the Paris Agreement corridor (see Figure 2). Even more critical thresholds or tipping points are approached if we proceed along our current path of emissions, heading towards a largely unknown future (Schellnhuber, Rahmstorf, and Winkelmann 2016) (for more detail please see the contribution of Schellnhuber & Martin 2014 in “Sustainable Humanity, Sustainable Nature: Our Responsibility”, Pontifical Academy of Sciences, Extra Series 41, Vatican City, 2015).

Temperatures alone cover only one dimension of tipping dynamics. For instance, the Amazon rainforest is of global climate relevance and a very sensitive ecosystem. Its life-supporting hydrological cycle is prone to disruption with increasing temperatures and forest-cover loss, which could lead to a shift to savanna vegetation and a decrease in precipitation followed by prolonged dry-seasons. Synergies between warming temperatures, deforestation and clearance fires could lower that threshold of tipping to mere 20-25% forest cover loss (Lovejoy and Nobre 2018). In such complex systems, multi-layered interactions can bring us faster to exceed the thresholds and, in some cases, to a point of no return. Acting in a precautionary manner becomes imperative, especially when uncertainties are involved.

Figure 2: Tipping elements in the context of global mean temperature change (West Antarctic Ice Sheet (WAIS); thermohaline circulation (THC); El Niño–Southern Oscillation (ENSO); East Antarctic Ice Sheet (EAIS). Shown is the global-mean surface temperature development from the Last Glacial Maximum through the Holocene, based on palaeoclimatic proxy data as the grey and light blue lines, with the blue shading showing one standard deviation), instrumental measurements since 1750 ad (HadCRUT data, black line) and different global warming scenarios for the future. Threshold ranges for crossing various tipping points, where major subsystems of the climate system are destabilized, are indicated by gradient from yellow to red bars for each tipping element. Coral reefs are likely to reach tipping point within the range of the Paris Agreement (Source: Schellnhuber et al., 2016, Nature Climate Change).

Standing at a crossroads, one needs to take a decision. But how? In the end, it comes down to weighing the trade-offs between anticipated benefits and damages in the broadest sense. However, our evolutionary heritage has not endowed us with a particular talent to factor in long-term risks – this is challenge number one. Challenge number two is further complicating the decision process: Climate-related risks are usually not distributed in the typical bell-shaped Gaussian (normal) distribution, but are characterized by “fat tails” (Weitzman 2014). This means that statistical “outliers”, extremes that are very different from the norm, are more likely than usually expected. We, however, intuitively perceive them as less likely to happen, due to our everyday experience with normal distributions (like the outcome of a lottery game). This partial blindness of humanity is particularly dangerous.

Projections of global warming are prominent illustrations of a fat-tailed distribution. Accelerated and runaway warming is not the most likely event, but it would have impacts beyond imagination. Since we define risk as the product of likelihood multiplied by impact, impactful outliers at the fringe of the probability distribution pose an existential risk to civilization. Although it appears counterintuitive, we have to factor them into the decision process on which path to take and act accordingly. On a global scale, warming around 4°C would not allow us to preserve our societal structures of today. Ecosystems would cascade into decay and no longer support human societies adequately, and violent conflicts are likely to arise more frequently (Spratt, Dunlop, and Barrie 2019).

Going down the business-as-usual path, we will reach tipping points in the Earth System, even some irreversible ones. Leading the way to self-reinforcing biogeophysical feedbacks, tipping cascades across elements of the cryosphere, the biosphere and global circulation patterns could very well change the face of the planet – transforming it to a Hothouse Earth without the possibility for return (Steffen et al. 2018).

Tipping cascades strung around the planet threaten the conditions we live in. For example, the decrease of Arctic sea ice further warms the region due to albedo feedbacks and thus causes accelerated melting of the Greenland ice sheet. This inserts freshwater into the North Atlantic Ocean, potentially slowing down the Atlantic Meridional Overturning Circulation (Lenton et al. 2019). Observations suggest that a slowdown of 15% since the 1950s has already happened (Caesar et al. 2018). The global heat transport through the ocean by the Gulf Stream might affect the West African monsoon negatively and generate severe droughts in the Sahel region. Another consequence could be the drying of the Amazon rainforest, which could trigger a shift to savanna vegetation. As a consequence, heat building up in the Southern Ocean might reinforce the pace of Antarctic ice loss (Lenton et al. 2019).

The urgency of the situation into which humanity has navigated itself calls for rapid action and behavioural change. Unfortunately, it is not that simple, since humans are creatures of habit. For example, the perception of the link between extreme weather events and human interference with the climate system is highly dependent on the individual attribution of those extremes. It varies greatly due to political beliefs, loyalties and social norms (Ogunbode et al. 2019). Heterogeneity of societies and individuals can be seen as a hurdle, which needs to be overcome for behavioural change. Simultaneously, diversity can offer opportunities for innovation and cooperation in tackling the climate crisis, especially in adapting and scaling solutions down to a regional context. Tackling the challenge from all possible angles, politically, economically, institutionally and socially, might yield the highest success rate. Perhaps one such focus in this context is on socioeconomic “tipping” points and processes, as discussed in a recent study (Otto et al. 2020).

Fight or Flight

Which path are we going to take at this crossroads? The evolutionary options for individuals and collectives, when confronted with a life-threatening situation, are to fight, to flee or to freeze. Inaction of governments and lack of political will, especially in the developed countries in the global North, has actually procrastinated adequate action on climate change mitigation and adaptation for more than 30 years. We need to switch to fighting mode now. It requires courage and resolve to embark on a deliberate transformation. However, it is the only sensible option in order to avoid the by far more devastating uncontrolled transformation imposed upon us by a disruptively changing climate.

The degree of bravery needed, however, has increased over time through our unwillingness to take action, and is quickly approaching the border to bravado. Thorough assessments of our remaining options to hold the 1.5°C line reveal them crumbling to almost nothing when unrealistic pathways are one by one excluded. There simply is no good answer to the 1.5°C question! In most models, emission pathways include massive carbon dioxide removal (CDR) from the atmosphere to achieve climate stabilization. Yet in reality, the technologies available for capturing and storing carbon, either geologically or on managed land, have not evolved to a level that meets the performance targets of the models so far. Efficiency and scale lag far behind the projected timeline of decarbonisation pathways.

The question remains: What does the necessary action look like, from the political, economic, and individual perspective? Everything that is not physically or ethically impossible is a moral imperative. Fortunately, there are numerous studies and a vast variety of science-based suggestions. One of the biggest efforts will be the decarbonisation of the global economies. This appears to be a tremendously vague undertaking, but bright minds have broken theoretical concepts down to feasible, step-by-step programs. Roadmaps for countries and sectors can be particularly useful tools, since they act as planning instruments bridging short-term goals with long-term strategies. Rockström et al. (2017) highlight the decade from 2020 to 2030 as the base from which to launch rapid decarbonisation. In their scenario, carbon dioxide emissions should peak no later than 2020 in view of the Paris Agreement. Options for kicking off the transformational processes are manifold: carbon tax schemes, cap-and-trade systems, feed-in tariffs or polycentric power grids are viable schemes. Certainly, human behaviour plays an enormous role. Behavioural change has the reputation of evolving slowly and not being predictable. Nevertheless, disruptive, innovative change provoked by collective human behaviour has happened throughout history and bears the potential to achieve ambitious goals in the near future. We should channel this capacity into bold action for building a resilient future (Rockström et al. 2017). The defining decade for serious climate action has begun.

Planetary Emergency

The probability that - even if all national pledges in the context of the Paris Agreement were implemented completely - global warming could reach 3°C (or more) at the end of this century is unfortunately very high. Pledges are not on track to achieve the emission reductions they are supposed to. In order to avoid catastrophic impacts, the slow-down of heating should start as soon as possible. It is a simple rule: the lower the warming, the better.

The goal of staying well below 2°C, preferably not exceeding 1.5°C of warming compared to pre-industrial levels (IPCC 2018), actually places us in an emergency situation. The status of emergency mirrors the high risk of severe consequences of inaction and the urgency of a timely solution. The factors setting the stage are the intervention time and the reaction time – or, more precisely, their relationship: If the reaction time of tackling climate change is longer than the intervention time, there is no time left to manoeuver – we have lost control (see Box: Lenton et al. 2019).

Moreover, it has to be stated repeatedly that the challenge is immense: The tipping of one element in the Earth system can increase the probability of tipping another element significantly – tipping cascades of biogeophysical elements can be triggered. Such an existential threat to societies worldwide clearly defines an emergency situation, which requires an emergency response. We need to consider where future tipping points may lie and what other tipping elements will possibly emerge. Further monitoring, quantification and modelling is vital for fostering our understanding of the hyper-complex situation we live in (Lenton et al. 2019).

Continuing on the path of ‘business as usual’ means risking chaotic and disruptive changes accompanied by conflict and violence on a global scale. Proactive measures are the way to choose, instead of a sheer responsive reaction to an emergency: Fight and not flee. It is time to seize the opportunity of momentum provoked by the fierce and persistent protests by young people around the world. The question Hamlet poses only leaves one conclusive and coherent answer when considering the current global situation, namely to behave like a connected global society, taking arms against a sea of troubles (and literally against rising sea levels). A happy ending of this tale of two disruptions is still possible.


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