There Is No Climate Tipping Point

Long before I finished my doctoral dissertation in Earth and Ocean Sciences, I tried to write a climate novel. It wasn’t much to speak of. I was 14. I fantasized that my story would so vividly depict the dangers of a warmer future that it would shock society into solving climate change.

My novel never progressed beyond a handful of chapters. In retrospect, I could never get past the blockage of figuring out how to narrate the descent into near-future catastrophe without making the conga line of disasters feel too rushed. I never doubted that some tipping point existed beyond which the planet would slide off the edge of the cliff. But how long would that take? I lacked the patience for a story structure that moved only gradually towards cataclysm, with multiple time skips that would take my protagonist from her teens to adulthood, then into her twilight years.

It turns out the future of our climate is a little more complicated anyways. Many aspects of my unfinished novel’s imagined climate future are very much a part of the research consensus on climate change—more frequent and intense wildfires, changes in the water cycle, the decimation of pine forests by invasive beetles. My underlying assumption, however—that at some specific moment in my lifetime, the Earth would cross a climate tipping point and descend into self-reinforcing madness—was entirely incorrect.

For the set of likely future scenarios we face today, the climate science literature has not identified any approaching global tipping point after which runaway climate change intensifies beyond humanity’s ability to arrest it. While tipping elements of the climate system—like Arctic permafrost thaw and loss of Amazon forest area—do influence total warming, the magnitude of this influence is substantially smaller than the societal factors that will ultimately determine the planet’s climate trajectory.

To you, the reader, the lines above may feel stiff and overly qualified. They, like countless similar sentences in IPCC reports and academic papers, rely on very careful choice of terminology to maintain their accuracy. Yet such care seems increasingly incompatible with a climate discourse that, at times, nurses a weakness for spectacle while trying to satisfy a hunger for clarity about the future that researchers cannot yet provide.

One example that holds fascination for me today, just as it did for my younger novelist self, is the topic of tipping points. More formally called “climate tipping elements,” this subject is a continuously evolving body of knowledge that has been particularly susceptible to confusion and misinterpretation.

Over the years, groups of earth scientists have offered slightly different definitions of tipping elements, and lists of proposed tipping elements have changed with various additions and removals. Tropical monsoons and abrupt changes in the El Niño cycle have fallen out of many lists, while worry over the East Antarctic ice-sheet’s stability is increasing. Meanwhile, research that presents a range of possible climate impacts after global temperatures cross some theorized tipping point often gets summarized by writers and journalists using upper-end, worst-case potential outcomes.

It is not particularly surprising that when arcane scientific detail meets simplistic reporting, it results in a muddle, and it’s a muddle the term “tipping point” itself—evoking an abruptness and immediacy not necessarily characteristic of most, let alone all, tipping elements—perhaps adds to. Climate tipping points and “runaway climate change” are now common parlance in climate conversations, and while different advocates may mean different things in practice when using these terms, they speak to a broadly shared, yet inaccurate, understanding that the climate system is on the verge of very unstable, self-reinforcing, and abruptly rapid disaster.

It isn’t. And it’s important to understand that it isn’t. Taken at rational face value, the feeling that the planet is just years away from sliding beyond a catastrophic point of no return invites unproductive fatalism. At the same time, the perception of an imminent climate cliff seemingly rules out long-term planning in favor of emergency measures, skewing discussion of climate policies in ways that can be counterproductive.

Looking ahead, the key message that the scientific community and climate advocates should reinforce is that humanity will always have chief agency over the climate. There is no tipping point beyond which Mother Earth wrestles control of the whole climate system away from human beings and proceeds to punish us for our sins.

Although the lack of an impending climate cliff may seem to dilute the impetus for climate action, the knowledge that humanity has a decisive hand on the thermostat actually imparts great responsibility upon us. It’s up to us not only to realize a more positive future for humans and nature but also to define the conditions in which we will have to build that vision.

ChatGPT HAS ENTERED THE CONVERSATION

In environmentalist discussions, “tipping points” refers to critical thresholds beyond which a particular environmental system or process is irreversibly altered, often leading to far-reaching and potentially disastrous consequences. Tipping points are often used to describe potential or actual thresholds in the Earth’s climate system, such as the melting of polar ice caps, the dieback of forests, or the acidification of oceans.

These thresholds can be thought of as points of no return, beyond which the natural system in question is altered in such a way that it cannot be restored to its previous state. For example, once a certain amount of polar ice has melted, it can no longer be regained through natural processes, leading to a permanent rise in sea levels. Similarly, once a critical threshold of carbon dioxide has been reached in the atmosphere, it can take hundreds or thousands of years for it to be absorbed by the planet’s natural carbon cycles.

In environmental discussions, tipping points are often used as a warning about the potential consequences of human activities on the environment, and to emphasize the need for rapid and decisive action to address environmental problems before they reach these critical thresholds. By highlighting the potential for irreversible environmental change, the concept of tipping points is meant to motivate individuals, communities, and governments to take action to protect the environment and ensure a sustainable future.

No tipping, no point

In many ways, the term “tipping point” in climate science was predisposed to be misunderstood. Both components of the term invite confusion.

First, the word “tipping” implies the rapidity of an unbalanced cart toppling over. Yet in practice, many climate science papers and reports suggest that rapid changes of state for tipping elements—say, systematic shifts that take just 20 years or less—are rare enough to be the exception, not the rule. Components of the climate system are sluggish on human time scales, and thus many Earth system components change over the course of decades, if not centuries or millennia. For example, future carbon release from thawing permafrost and sea-level rise from loss of the Greenland ice sheet will take place over several hundred years.

To an earth scientist thinking on geologic timescales, that does seem like a very rapid transition relative to the glacial pace at which the Earth system typically changed prior to the industrial revolution. To a layperson who thinks about a stacked pile of blocks or the leaning tower of Pisa tipping over, however, rapid means something different. This discrepancy in perspectives leads to differing expectations for how climate tipping elements behave and how quickly or slowly their impacts unfold.

Second, the word “point,” too, is bound to confuse. It implies a single, precise, known critical threshold beyond which Earth system components tip.

In some cases—and depending on the boundaries one defines for a climate system—that system may indeed behave nonlinearly after crossing an exact threshold. This is the case for a system such as the Thwaites Glacier in Antarctica, a large ice sheet the size of Florida, widely understood to be at risk of irreversible loss of mass over the course of centuries should warming push the ice sheet across a structural tipping point.

However, critical thresholds are rarely precisely known. And large continental-scale systems like Arctic permafrost landscapes or the Amazon rainforest may not possess a single overall climate tipping point, but may instead exhibit nonlinear state shifts at smaller scales in response to crossing regional and local thresholds. Rainforests degrade acre by acre, while permafrost on sunny south-facing hillsides may thaw and release carbon sooner.

If “tipping points” is such an imperfect phrase, though, how did the term become so widespread in popular discourse?

As is the case for many scientific concepts, the terminology of climate tipping points originated as a theory, which researchers have subsequently developed and explored to far greater depth. While the first colloquial occurrences of the term “tipping point” in English writing date back to around the 19th century, social and political scientists began using a tipping point framework to describe political movements and rapid socioeconomic shifts in the decades following World War II.

Following the journalist Malcolm Gladwell’s popularization of the term with his book “The Tipping Point” in the early 2000s, Earth science subsequently imported the term to help articulate the idea of Earth system components that might undergo state shifts—fast or slow—at critical thresholds. Some of the early scientific discussions revolved around a potential global-scale tipping point, and others referred imprecisely to as “tipping points.” Gradually, most scientists settled upon the term “tipping elements,” defined as “a critical threshold beyond which a system reorganizes, often abruptly and/or irreversibly,” as the latest IPCC report puts it.

But even now, there is wide variation in the extent to which the term “tipping points” is used in scientific literature to refer to a fast process, or a slow one, and whether it’s a general conceptual framework or something that can be defined mathematically or statistically.

On top of this, candidate members of the tipping elements club have shifted as scientific understanding of different Earth system components has progressed. For instance, some researchers once proposed the possibility of abrupt future decline in Arctic summertime sea ice, but this hypothesis has faded, with subsequent research reinforcing the conclusion that Arctic summer sea ice declines steadily in proportion to increasing greenhouse gas emissions. Similarly, theories that projected substantial abrupt state shifts in monsoon circulation or the El Niño cycle have largely been laid to rest. Papers from a decade ago raised alarm at the possibility that huge amounts of methane could bubble out of the ocean with apocalyptic consequences. But we now understand that frozen methane buried deep in seafloor sediments responds only slowly and gradually to warming, releasing a trickle of atmosphere-warming methane over centuries and millennia.

And so, as of this writing, Arctic summer sea ice, regional monsoons, seafloor methane hydrates, and El Niño have mostly been stricken from lists of tipping elements. In some cases, new proposed tipping elements have replaced them. A fall 2022 paper in Science, for instance, has added “collapse of the Labrador Sea subpolar ocean gyre” and “abrupt loss of Barents Sea sea-ice” as new possible tipping elements. With time, further research may validate—or eliminate—these new prospective entrants as well.

All of this illustrates how the current understanding of climate tipping elements remains uncertain. Climate skeptics might seize upon such uncertainty to question climate change itself. But make no mistake—the uncertainty of tipping elements revolves around the degree of future impacts. That climate change is affecting these systems is not remotely in question. At the same time, our projections for future climate are unmistakably less certain than we might like. The best scientific efforts and latest research typically yield a range of potential answers—zones of risk within which critical thresholds may lie.

Given such grim ambiguity, media headlines often seize on the worst-case, high-end impacts as the likeliest outcome. For instance, science headlines have popularly termed greenhouse gases released from thawed Arctic soils as a “carbon bomb,” even as permafrost experts wearily stress that overall carbon release will be gradual. Writers and reporters have likewise described the threat of seafloor methane bubbling out of the oceans as a “bomb” or “gun,” selectively invoking a diminishing number of studies advancing an increasingly discredited hypothesis of abrupt and dangerous ocean methane release.

This state of affairs, at its root, may not be anybody’s fault. Even low-stakes science communication is rife with difficulties, as the pervasive myth that humans only use 10% of their brains attests. More recently, the COVID-19 pandemic has vividly illustrated the limits to public understanding and acceptance of messaging from researchers and experts. Add in the long-running game of telephone between earth scientists, the media, and the general public—along with changing scientific understandings—and misconceptions are hardly surprising.

How confusion about tipping points influences climate discourse

But a misunderstanding being common doesn’t make it excusable. Given the frequency with which tipping elements feature in climate conversations, it is worth unpacking how skewed perceptions of this topic have affected the broader climate effort.

An experience that earth scientists can increasingly relate to is when a conversation turns to the subject of their work, and a friend or new acquaintance chuckles nervously and jokes, “So, just how screwed are we, exactly?” Or perhaps a relative forwards them an article on the threat of sudden, massive carbon releases from northern permafrost or seafloor methane, asking: “Have you seen this? Is this true?” Such everyday interactions speak to a larger, popular sense of inevitable, disastrous consequences—but also of an unspoken need for answers and reassurance that things are not as bad as they seem.

In fact, they are not irrevocably bad. The consequences of climate change are still within the power of human beings to mitigate, nor will humans ever be powerless to reduce or cushion the impacts of a warmer world through adaptation. The research literature shows that even middle-of-the-road climate mitigation pathways can dramatically reduce the rate and extent of permafrost thaw and limit the long-term loss of ice sheets. Limiting end-of-century warming to 2-3°C will essentially eliminate any risk of significant climate feedbacks from seafloor-frozen methane hydrates. And a combination of budding progress toward decarbonization and more recent climate research has already greatly reduced the likelihood of the worst-case future climate scenarios.

Certainly, this is no reason for complacency. The sensitivity of some systems like the Atlantic Meridional Overturning Circulation—a major global ocean circulation pattern—to low or moderate long-term warming remains uncertain. And shallow tropical coral reef ecosystems may suffer grievous biodiversity loss under even 1.5°C of warming. Besides, parts of the Amazon rainforest are already severely threatened by further warming and deforestation.

Yet climate conversations persistently characterize the present day as a do-or-die, tip-or-not moment, with perfect climate action or annihilation as the only two possible outcomes. In opening the 2019 UN climate summit in Madrid, UN Secretary-General António Guterres ominously warned: “The point of no return is no longer over the horizon. It is in sight and hurtling toward us.” In July of last year, Guterres declared: “We have a choice. Collective action or collective suicide.” Such a framing contributes to a growing air of nihilism and defeatism.

For environmental activists, climate tipping points are certainly useful for advocacy. Journalists, coordinators, and my younger aspiring novelist self yearn for narratives that can advance a cause, as opposed to endless qualifications, hypotheticals, and uncertainties. Politicians have their own fondness for Hollywood-esque melodrama at the speaking podium. The idea that a hubristic humankind might blunder pridefully across a point of no return only to find itself committed to damnation carries powerful romantic appeal, second only to the distinction of standing on the right side of history as it all unfolds. To a crusader, the pending end of humanity is a thrilling call to action.

But no matter the age or the cause, crusaders have always represented just a sliver of society at large. An ordinary person looks at the immensely difficult slope of climate action that activists demand and reasonably concludes that it will be impossible to reduce emissions as quickly as many advocates and scientists seem to say is necessary. Having established their powerlessness in the face of humanity’s future fate, they resign themselves to uneasily continuing their normal lives. This false sense of futility is undoubtedly detrimental to climate efforts, and a more nuanced understanding of climate tipping elements could help combat such hopelessness.

Beyond defeatism, tipping point anxiety may inhibit precisely the kind of sustained, long-term work needed for decarbonization by focusing all attention on immediately actionable solutions and policies.

For example, if the planet has “only seven years” left to avoid 1.5°C of global warming by 2100, as a popular mantra asserts, any policies, technologies, or solutions that would take longer than a few years to implement are, by definition, pointless. That includes the expansion of nuclear power, or efforts to spur innovation in areas like low-carbon aviation, direct air carbon capture, and advanced geothermal energy. As one IPCC reviewer worried, “In the timeframe of the exhaustion of the carbon budget of 1.5°C, there may be not enough time for totally new technologies to ramp up market penetration in a way that makes the difference.” Yet even many widely hailed climate solutions, such as offshore wind energy or utility-scale battery storage, may not reach their full maturity until the 2030s.

In practice, even aggressive global decarbonization efforts are likely to take several decades, and multi-decadal timescales for climate action are entirely consistent with ambitious decarbonization scenarios. Longer-term solutions that come to fruition in the 2030s or 2040s will absolutely be able to contribute to emissions reductions. A measure that eliminates some of the last, hardest millions of tons of CO2 emissions in the year 2050 is no less valuable than a measure that resolves easier-to-eliminate greenhouse gas emissions today.

From tipping point to action

The Sixth Assessment Report from the IPCC’s Working Group I bluntly states that the current literature shows “no evidence of abrupt change in climate projections of global temperature for the next century” and expressed “low confidence” as to whether such behavior could possibly occur to begin with. It adds, “possible abrupt changes and tipping points in biogeochemical cycles lead to additional uncertainty in 21st century greenhouse gas concentrations, but these are very likely to be smaller than the uncertainty associated with future anthropogenic emissions.”

Climate change remains a serious global challenge that motivates major global efforts to reduce emissions. But instead of an imminent cliff, we face a slope—or perhaps a sliding scale is a better metaphor—of increasing future climate impacts with further warming. While many climate impacts will be irreversible on the timescale of human life spans, humans have, and will continue to have, chief agency over how much the planet ultimately warms.

Some discomfort should come with the knowledge that there is no rapidly approaching planetary cliff. If there is no imminent tipping point beyond which the world is doomed, then there is also no point at which all humans are saved. No point of mutually assured, universal destruction means less motivation for everyone to pursue collective salvation. Since it is increasingly clear that the gun of climate change is pointed first and foremost at the world’s poorest and most vulnerable, then the climate movement must prioritize grappling with inequality.

Another pang of discomfort is that human beings will need to make key decisions on climate, energy, food, and economic and other policies in the face of persistent remaining scientific uncertainty. Brazil will need to implement measures to limit deforestation without knowing where exactly the critical thresholds for the Amazon rainforest lie. Europe will have to execute clean energy policies in the absence of complete certainty regarding how sensitive the Atlantic Meridional Overturning Circulation is to ocean warming and salinity changes. And given remaining unknowns regarding climate sensitivity—how much the climate warms based on how much we emit—we are not able to guarantee an exact climate outcome based on societal greenhouse gas limits.

Many argue compellingly that this strengthens the case for more stringent climate targets to minimize risks associated with such uncertainties. But that is different from saying that future climate risks from tipping elements are precisely known, occur at exact thresholds, and present us with an extreme binary choice between either a bad or a civilization-ending future.

In my draft novel from over a decade ago, I had imagined a moment of melancholic retrospection when my protagonist would realize with full certainty that humanity, for all of its historical progress and achievements, was condemned to extinction. In a similar vein, the already-forgotten but momentarily acclaimed climate film “Don’t Look Up” depicted climate change as an asteroid—a global threat that would deliver the end-times nearly instantaneously, while allowing for one poetic moment of penance in which humanity realized that the giant space rock was unavoidable, that the critical threshold was already past.

As I now see it today, the fight against climate change will be a long-term, multi-generational struggle without any such cathartic moment of clarity. It will involve efforts not just to build solar farms and nuclear reactors but also to deploy affordable cooling systems in apartments across Lagos and Bangalore and distribute drought-resistant crop varieties in Ethiopia and Afghanistan. Humans will continuously dictate and revise Earth’s climate conditions, and humans must continuously strive to build a more free, just, and sustainable present and future within those conditions.

In the popular imagination, climate tipping elements offer a fast, clear, external, global judgment of climate success or failure. A more correct understanding of tipping elements leaves human and environmental well-being primarily for us to define in the face of an uncertain future. And so humanity will remain the plaintiff, defendant, and judge all at once, with as many verdicts rendered as there are human beings, for as long as the seasons change and the tides rise and fall.