Welcome to Cool Words for Hot Times, an ongoing series in which we’ll unpack and break down the jargon-riddled world of climate change. You can check out previous climate change posts here. Today, we take a hard look at tipping points.

When we talk about climate change, particularly on a systemic or global level, there’s a tendency to frame it as a problem for which there is, ultimately, some definitive solution. The implication, almost invariably, is that “If we just do [insert action] by [insert time], then we can prevent [insert outcome—e.g., the worst impacts, the worst temperature increase, the most biodiversity loss, etc.].” Tragically, though, that kind of broadly optimistic approach to climate change solutions belies the increasingly apparent fact that, in certain cases, we are already too late—or almost too late—to reverse course.

These points of no return are often called “tipping points,” and they have become symbolic of the most urgent, dire aspects of the climate crisis. Dr. Tim Lenton, the director of the Global Systems Institute at the University of Exeter and an expert on tipping points describes the concept simply: “A climate tipping point, or any tipping point in any complex system, is where a small change makes a big difference and changes the state or the fate of a system.”

Put differently, climate tipping points are a bit like rafting over a waterfall. Once you see the waterfall coming, you may be able to back-paddle, at least for a while, to forestall the inevitable drop. As you near the precipice, though, there will come a point where no amount of effort will prevent your boat from going over the waterfall. You might be moving the same exact speed as before, but that last bit of forward momentum will push you too far, and you’ll end up at the bottom of the falls in mere seconds, potentially very much the worse for wear. Others have compared tipping points to a game of Jenga or the final hatchet stroke that brings a tree crashing down to the forest floor.

Lenton’s work has informed much of what we know about global tipping points, and he and his colleagues have published research on the topic for over a decade. In late 2019, they released findings in the journal Nature in which they highlighted the extreme risks of climate tipping points and the actions necessary to potentially prevent us from their irreversible, cascading effects.

So what does this all mean, and what, exactly, are the tipping points making scientists and policymakers so concerned? There are all sorts of tipping points that researchers gravitate toward, and they generally fall into one of three categories: melting, habitat shifts, or circulation changes. Tipping points related to melting include permafrost loss, Greenland ice sheet disintegration, and West Antarctic ice sheet disintegration. Habitat shift tipping points are Amazon rainforest dieback, shifts in boreal forests, and coral reef die-off. Finally, circulation change tipping points include West African monsoon shift, Indian monsoon shift, and—take a deep breath—Atlantic meridional overturning circulation breakdown. This set of examples is by no means exhaustive, and each of these tipping points comes with its own timeline and level of uncertainty.

To crystalize a few items on this dizzying list, let’s look at two tipping points that are already well underway: the disintegration of Greenland’s ice sheets and coral reef die-off. When it comes to Greenland’s melting, we have to begin with the well-documented fact that northern latitudes are warming at a faster rate than other parts of the Earth, meaning the Arctic in particular, including Greenland, is heating up and melting quicker than almost anywhere else. The complete disappearance of Greenland’s ice sheet—the only permanent ice sheet outside of Antarctica—alone could be responsible for roughly 24 feet (7.4 meters) of sea level rise, and this can happen even within the 2ºC of atmospheric warming that scientists have posited as the allowable maximum. Once melting is underway—which, again, it already is—the process is irreversible under current conditions.

Coral reef die-off, one of the major habitat-related climate tipping points, is the result of rapid ocean warming. This puts coral reefs—which are home to as much as 25 percent of all marine life and thought to be the most biodiverse habitat type on Earth—into extreme heat stress, causing them to expel the tiny algae known as zooxanthellae that they rely on for survival (yes, corals are alive). This causes a phenomenon known as “coral bleaching,” leaving behind the white, dead skeletons of once-thriving reefs. Once bleaching begins, it’s hard to slow or reverse, and as the process accelerates, it will cause the widespread collapse of fisheries, local marine economies, tourism, and a host of other social-environmental consequences. Until corals can adapt for greater heat tolerance, we’re likely to see global reef bleaching continue unabated.

Beyond the specific cascading effects of any one system’s collapse, the key takeaway here is that these tipping points will occur on a scale so large that the climate, habitats, and health of the entire globe will feel the ramifications.

As with so many climate change concepts, though, tipping points feel intractable for their sheer magnitude. Sitting in Central Oregon, it’s hard to process the tangible impacts of, say, permafrost loss. While there’s no precise way to draw a straight line from any specific tipping point to the future of the high desert right now—nor has much formal research occurred on the specific effects of global tipping points on the Pacific Northwest—let’s take a moment to consider a local tipping point.

East of the Cascades, increasingly frequent and severe wildfires could represent a tipping point for our forests and high desert habitats. Historically, our mixed pine-fir forests would burn at regular intervals, allowing the forest to naturally thin and regenerate between fires. Some fires would be high-intensity and widespread, while others might be low-severity and relatively small, but in general forests were unlikely to be completely decimated or to be fully burned multiple times in rapid succession. Now, though, we’re much more likely to see huge fires—sometimes called “stand-replacing” fires—that can wipe out a large swath of forest one year and return soon after to burn the same area again without any possibility for recovery in between. This means that some of the plants we’re used to seeing in the forest, many of which use fire to regenerate, could simply be unable to re-establish between fires. Meanwhile, other plants that are better adapted to the landscape created by a high-severity burn could take hold, fundamentally changing the make-up of our forests.

While the scale of this change is certainly smaller than the West Antarctic ice sheets disappearing, it is a type of tipping point, too. Eventually, we will cross a fire threshold after which our landscape could look and behave dramatically differently, and will not return to its historical condition. This will affect not only plants, but also wildlife, river systems, soil erosion, snowpack, recreation, and air quality.

What do we do, then, about tipping points? In some cases, the answer is: not much, because they’re already happening. Where it’s not too late, though, the way to prevent most any tipping point is the same as the necessary approach to preventing climate change: we must stop emitting greenhouse gases, which means we must stop burning fossil fuels if we don’t want to careen over the waterfall—and the drop is coming up fast.


Learn more:

• The Deschutes Land Trust's Climate Change Strategy
• Recent research on the state of tipping points and their likely cascading effects
• A more narrative overview of the above research, including perspectives from critics of the findings.
• Another primer on climate tipping points from the Environmental Defense Fund.
• Some more visual and auditory representations and explanations of tipping points from Carbon Brief.