A detailed summary of the 2022 study on climate tipping points, highlighting risks of surpassing 1.5°C warming and its global impacts.
A 2022 study by David I. Armstrong McKay and co-authors offers a comprehensive re-evaluation of the Earth's climate tipping points and provides strong evidence that exceeding 1.5°C of global warming could trigger multiple irreversible shifts in the climate system.
Building on previous research, this report expands the list of potential tipping points and introduces new insights into the cascading effects that these events may cause.
Understanding Climate Tipping Points: What Are Climate Tipping Points?
A climate tipping point occurs when a critical threshold is crossed, leading to significant, self-sustaining changes in the state of a system. Unlike gradual climate changes, tipping points cause rapid, often irreversible shifts in large parts of the Earth’s climate. Once triggered, these changes continue, even if the factors that caused them are reduced or removed. Tipping elements are key climate subsystems—like ice sheets, rainforests, or ocean currents—whose collapse or shift can cause significant regional and global impacts. Crossing tipping points can trigger catastrophic outcomes, including sea level rise, biodiversity loss, and ecosystem disruptions, all of which pose serious threats to human welfare.
Revisiting and Expanding the List of Tipping Elements
In 2008, Timothy Lenton and colleagues first identified nine key tipping elements, such as Arctic sea ice, the Amazon rainforest, and major ice sheets, whose collapse could trigger widespread impacts.
Since then, substantial advancements in paleoclimate data, model simulations, and observations have revealed that many of these systems are closer to tipping than previously thought.
The 2022 report reassesses these original tipping points and introduces new candidates, including the East Antarctic Ice Sheet and coral reefs. With current global warming at ~1.1°C above preindustrial levels, several of these tipping elements are now at risk of crossing critical thresholds.
In this study, the authors reassess 16 climate tipping elements, now categorized as either global "core" tipping elements or regional "impact" tipping elements:
Global core tipping elements are systems that contribute significantly to the overall functioning of the Earth’s climate. Their tipping would have large-scale impacts, such as changes in atmospheric or oceanic circulation.
Regional impact tipping elements are systems whose tipping points would significantly affect human welfare or the environment at a regional level, though with more localized consequences compared to global core elements.
Tipping Points Within the Paris Agreement Range
The study confirms that several tipping elements are likely to be triggered between 1.5°C and 2°C of global warming, the range targeted by the Paris Agreement. Notably:
Greenland Ice Sheet: The Greenland Ice Sheet is highly vulnerable to warming. If temperatures rise by 1.5°C to 2°C, it could reach a tipping point where the melt-elevation feedback becomes self-sustaining. As the ice melts, the surface lowers, exposing it to warmer air and accelerating melt. This process could lead to the irreversible loss of much of the ice sheet over centuries, contributing up to 7 meters of sea-level rise.
West Antarctic Ice Sheet (WAIS): Similarly, parts of the WAIS are grounded below sea level, making them susceptible to collapse through a process known as marine ice sheet instability. As the grounding line retreats, ice flow accelerates, leading to further retreat in a self-reinforcing cycle. The collapse of the WAIS could add up to 3 meters to global sea levels. The study suggests this tipping point may already be close at current warming levels (~1.1°C), with greater risks at 1.5°C.
Low-Latitude Coral Reefs: Coral reefs are extremely sensitive to even small increases in ocean temperatures. The study indicates that widespread coral die-off is almost certain at 1.5°C, as these ecosystems are vulnerable to bleaching events caused by heat stress. Coral reefs are essential for marine biodiversity and coastal protection, and their collapse would have cascading effects on fisheries, tourism, and ocean ecosystems.
Amazon Rainforest: The Amazon plays a critical role in regulating global carbon levels by absorbing CO2 from the atmosphere. However, rising temperatures and deforestation are pushing the Amazon closer to a tipping point where it could transition from a rainforest to a savanna-like ecosystem. This would not only release vast amounts of stored carbon but also disrupt regional rainfall patterns, potentially affecting agriculture across South America. The study suggests that this tipping point could occur between 3.5°C and 4°C, though regional deforestation might lower this threshold.
Cascading Tipping Points: The Domino Effect
One of the most alarming aspects of climate tipping points is their interconnectedness. The study highlights the risk of tipping cascades, where the triggering of one tipping point increases the likelihood of others being triggered. For instance, the loss of the Greenland Ice Sheet would disrupt ocean circulation patterns, which could, in turn, destabilize the Atlantic Meridional Overturning Circulation (AMOC). AMOC slowdown or collapse would lead to significant cooling in the North Atlantic and changes in weather patterns across Europe and North America. These interconnected systems mean that the collapse of one could amplify the collapse of others, creating a domino effect.
The study identifies that up to five tipping points could be triggered within the Paris Agreement’s target range of 1.5°C to 2°C of warming, with even more likely at the 2°C to 3°C range expected under current policies. This makes it clear that keeping global warming below 1.5°C is critical to avoid these dangerous cascading effects.
The Cost of Inaction: Current Policies Lead to Unsafe Levels of Warming
Even with current climate pledges and net-zero targets, the world is on track to exceed 1.5°C by the early 2030s. The study notes that without more ambitious efforts, global warming is likely to reach 2°C to 3°C by the end of the century, which would almost certainly trigger multiple tipping points. For instance, the West Antarctic and Greenland ice sheets could begin irreversible collapse, low-latitude coral reefs would face near-total die-off, and the Amazon could experience widespread dieback.
While limiting warming to 1.5°C or just below 2°C would reduce the risk of some tipping points, it does not eliminate the danger entirely. The authors argue that even the Paris Agreement's "well below 2°C" target is not sufficient to avoid serious impacts and that immediate, aggressive mitigation strategies are needed to minimize the risk of crossing these thresholds.
Early Warning Systems and the Need for Action
The study also emphasizes the importance of developing early warning systems that can detect when tipping points are approaching. Using satellite data, machine learning, and improved climate models, scientists can monitor changes in critical systems such as ice sheets, permafrost, and ocean circulation. This would provide policymakers with the information needed to act before tipping points are crossed.
Conclusion: 1.5°C is a Critical Threshold
The 2022 report by Armstrong McKay and colleagues provides a stark warning: the 1.5°C threshold is not a "safe" limit. Exceeding it could trigger multiple tipping points that would drastically alter the Earth's climate and ecosystems. While there is still time to prevent the worst outcomes, the window for action is closing fast. The report underscores the urgent need for more ambitious climate policies and global cooperation to mitigate emissions and avoid crossing these dangerous thresholds.
Sign up for our newsletter or connect with us on social media to stay up-to-date with our latest posts and permaculture inspiration.
Explore our inspiring series and posts:
Love the post? Share it with your circle, inspire your people: