The massive transformation enacted by humanity is also why our geological era, which is akin to the operating system on which the living world depends, recently had its name updated to the anthropocene – the age of humanity. So what is the path forward? The necessary solutions for ensuring that our children enjoy healthy and abundant natural habitats are not simple. But one thing is certain. For humanity to head in the right direction, we must take a closer look at what is around us. We cannot count on the blind leading the blind.
The Anthropocene represents the beginning of a very rapid human-driven trajectory of the Earth System away from the glacial– interglacial limit cycle toward new, hotter climatic conditions and a profoundly different biosphere. The current position, at over 1 °C above a preindustrial baseline, is nearing the upper envelope of interglacial conditions over the past 1.2 million years. More importantly, the rapid trajectory of the climate system over the past half century along with technological lock in and socioeconomic inertia in human systems commit the climate system to conditions beyond the envelope of past interglacial conditions. Therefore, it is possible the Earth System may already have passed one ‘fork in the road’, a bifurcation with potentially many trajectories , often represented by the large range of global temperature rises simulated by climate models.
In most analyses, these trajectories are largely driven by the amount of greenhouse gases that human activities have already emitted and will continue to emit into the atmosphere over the rest of this century and beyond—with a presumed quasilinear relationship between cumulative carbon dioxide emissions and global temperature rise. However, biogeophysical feedback processes within the Earth System coupled with direct human degradation of the biosphere, may play a more important role than normally assumed, limiting the range of potential future trajectories and potentially eliminating the possibility of the intermediate trajectories. There is a significant risk that these internal dynamics, especially strong nonlinearities in feedback processes, could become an important or perhaps, even dominant factor in steering the trajectory that the Earth System actually follows over coming centuries.
The trajectory of the Earth System is influenced by biogeophysical feedbacks within the system that can maintain it in a given state (negative feedbacks) and those that can amplify a perturbation and drive a transition to a different state (positive feedbacks). Some of the key negative feedbacks that could maintain the Earth System in Holocene-like conditions— notably, carbon uptake by land and ocean systems—are weakening relative to human forcing, increasing the risk that positive feedbacks could play an important role in determining the Earth System’s trajectory.
Beyond the threshold of 2 °C above preindustrial temperature this intrinsic biogeophysical feedbacks in the Earth System could become the dominant processes controlling the system’s trajectory. Precisely where a potential planetary threshold might be is uncertain. The 2 °C warming could activate important tipping elements, raising the temperature further to activate other tipping elements in a domino-like cascade that could take the Earth System to even higher temperatures (Tipping Cascades). Such cascades comprise, in essence, the dynamical process that leads to thresholds in complex systems. This analysis implies that, even if the Paris Accord target of a 1.5 °C to 2.0 °C rise in temperature is met, we cannot exclude the risk that a cascade of feedbacks could push the Earth System irreversibly onto a ‘Hothouse Earth’ pathway.
A critical issue is that, if a planetary threshold is crossed toward the Hothouse Earth pathway, accessing the Stabilized Earth pathway would become very difficult no matter what actions human societies might take. Beyond the threshold, positive (reinforcing) feedbacks within the Earth System —outside of human influence or control— could become the dominant driver of the system’s pathway, as individual tipping elements create linked cascades through time and with rising temperature.
It is bad enough as it is, but are we not just treating the symptoms …
The discourse around climate change, is about the metric buzzwords – carbon, greenhouse, emissions, temperature, alternative energy etc. Is it possible that in the debate around measuring what’s happening and how badly it’s happening, we have been distracted from a true root cause of ecological crisis?
What is typically measured is that which serves the economic and political interests, and unconscious biases, of those who commission the measurements. The conventional climate discourse is heavily influenced by a geo-mechanical view of the world. From that view, fixing the planet becomes a matter of tweaking the atmospheric gas composition. When we focus on quantifiable metrics of the climate problem, we may be led to believe that the control of these metrics brings us closer to planetary safety or even healing, when in fact, the root cause drivers of ecological destruction remain active.
In the dominant climate change narrative, humans are an external force driving change to the Earth System in a largely linear, deterministic way; the higher the forcing in terms of anthropogenic greenhouse gas emissions, the higher the global average temperature. Human societies and our activities need to be recast as an integral, interacting component of a complex, adaptive Earth System. This framing puts the focus not only on human system dynamics that reduce greenhouse gas emissions but also on those that create or enhance negative feedbacks that reduce the risk that the Earth System will cross a planetary threshold and lock into a Hothouse Earth pathway.
Humanity’s challenge then is to influence the dynamical properties of the Earth System in such a way that the emerging unstable conditions in the zone between the Holocene and a very hot state become a de facto stable intermediate state.
This requires that humans take deliberate, integral, and adaptive steps to reduce dangerous impacts on the Earth System, effectively monitoring and changing behavior to form feedback loops that stabilize this intermediate state. There is much uncertainty and debate about how this can be done—technically, ethically, equitably, and economically—and there is no doubt that the normative, policy, and institutional aspects are highly challenging. Societies could take a wide range of actions that constitute negative feedbacks, to steer the Earth System toward Stabilized Earth.
While reducing emissions is a priority, much more must be done to reduce direct human pressures on critical biomes that contribute to the regulation of the state of the Earth System through carbon sinks and moisture feedbacks, such as the Amazon and boreal forests, and to build much more effective stewardship of the marine and terrestrial biospheres in general. The present dominant socioeconomic system, however, is based on high-carbon economic growth and exploitative resource use. Attempts to modify this system have met with some success locally but little success globally in reducing greenhouse gas emissions or building more effective stewardship of the biosphere.
Incremental linear changes to the present socioeconomic system are not enough to stabilize the Earth System. Widespread, rapid, and fundamental transformations will likely be required to reduce the risk of crossing the threshold and locking in the Hothouse Earth pathway; these include changes in behavior, technology and innovation, governance, and values.
In addition to institutional and social innovation at the global governance level, changes in demographics, consumption, behavior, attitudes, education, institutions, and socially embedded technologies are all important to maximize the chances of achieving a Stabilized Earth pathway.
Ultimately, the transformations necessary to achieve the Stabilized Earth pathway require a fundamental reorientation and restructuring of national and international institutions toward more effective governance at the Earth System level, with a much stronger emphasis on planetary concerns in economic governance, global trade, investments and finance, and technological development. And even if world leaders somehow got their act together, significant and dangerous levels of warming are still inevitable, baked into the system from all the carbon dioxide that has already been dumped. There’s a time lag between carbon dioxide increase and subsequent effects, between the wind we sow and the whirlwind we reap. Barring a miracle, the next 20 years are going to see increasingly chaotic systemic transformation in global climate patterns, unpredictable biological adaptation and a wild spectrum of human political and economic responses, including scapegoating and war. The middle and later decades of the 21st century — my grandchildren’s adult life’s — promise as it looks like at the moment a global catastrophe whose full implications any reasonable person must turn away from in horror. Society is not simply an aggregate of millions or billions of individual choices but a complex, recursive dynamic in which choices are made within institutions and ideologies that change over time as these choices feed back into the structures that frame what we consider possible. All the while, those structures are being disrupted and nudged and warped and shaken by countless internal and external drivers, including environmental factors such as global warming, material and social innovation, and the occasional widespread panic. We choose from possible options, not ex nihilo.
Our (grand)children will not face the choices we face. They won’t have the opportunities we now have for action. They’ll confront a range of outcomes whose limits were determined by the choices we made. Yet while some degree of warming now appears inevitable, the range of possible outcomes over the next century is wide enough and the worst outcomes extreme enough that there is some narrow hope that revolutionary socio-economic transformation today might save billions of human lives and preserve global civilization as we know it in more or less recognizable form
This requires a fundamental change in the role of humans on the planet: a deliberate and sustained action to become an integral, adaptive part of Earth System dynamics, creating feedbacks that keep the system on a Stabilized Earth.