Menu

Effects & Impacts: Planetary Boundaries & Tipping Points

June 2019 the ice sheet near Qaanaaq Greenland that they would normally sled across was covered in vast meltwater lakes due to extreme surface warming (17°C). Meltwater eventually drains into the ocean, contributing to rising sea levels and disrupting oceanic currents. The darker water absorbs more heat, which in turn causes more ice to melt. – Video: Steffen M. Olsen, Danish Meteorological Institute.

Home > Climate wiki > Effects > Tipping points

Summary

The concept of planetary boundaries (Fig. 1) was proposed in 2009 to identify a safe operating space for humanity by defining proven quantitative limits for nine critical Earth system processes:
 

They are scientifically defined guardrails that ensure the Earth’s health. Stay within them, and the Earth stays our dependable home—breach them, and we risk irreversible damage to our very own life support system. Today, seven out of nine boundaries have been transgressed.  – Stockholm Resiliency Centre 2026

Planetary boundaries 2009-2026 | Licensed under CC BY-NC-ND 3.0. Credit: "Azote for Stockholm Resilience Centre, based on analysis in Sakschewski and Caesar et al. 2026".
Fig. 1: Planetary Boundaries 2009-2026; Stockholm Resilience Centre CC BY-NC-ND 3.0
Paris 2015: governments agreed that to ‘avoid a critical threshold above which the planet could experience irreversible catastrophic impacts‘, global temperatures must not exceed 1.5°C above pre-industrial levels. They acknowledged that major tipping points could be reached between 1°C – 2°C.  

It’s like someone leaning back in a chair. If they don’t tilt too far, they can easily return to having all four legs on the floor. But once they pass the tipping point, the whole system comes crashing down. And it is much harder to get up again than it was to fall. – Mathematician Niklas Boers, Carbon Brief

In 2024 average global temperatures exceeded 1.5°C. Human generated greenhouse gas emissions continued to increase while biodiversity loss had reduced Earth’s capacity to absorb CO₂, nor could Earth systems buffer the excess heat. This should have come as no surprise as ‘CO₂ concentration’ and ‘radiative forcing’ (leading to excess heat) had already exceeded the planet’s safe operating space in 2023 (Fig. 1).
 
In 2026, the Stockholm Resilience Centre revealed that another planetary boundary had been breached: ocean acidification. This is a direct result of the ocean absorbing around a third of the excess CO₂. It was clear that the planet was entering a new climate regime:

Limiting global warming to 1.5°C remains a cornerstone of the Paris Agreement, yet under current policies and alternative near-term trajectories, exceedance of 1.5°C is now widely assessed as unavoidable…There will be no going back to how things were. Some losses will be irreversible, which means returning to 1.5 doesn’t mean we return back to the same world we left. – United Nations September 2026

IPCC climate projections include the possibility of ‘briefly overshooting’ 1.5°C’ (SSP5-3.4), assuming that as-yet-to-be-invented technologies could reverse that over decades. But once certain tipping points have been crossed it’s like driving off a bridge. There is no reverse. The world is now on track to become very different place, one far more hostile to humanity. 

As we pass global warming of 1.5˚C, the most likely tipping points involve the collapse of ice sheets in Greenland or Antarctica, tropical coral reefs dying off, or abrupt thawing of Arctic permafrost. – Berkeley Earth, 2025

Increasing instability of the ocean, ice and atmosphere threatens farming, finance and society. We all need to wake up to that fact…Tipping analyses focus on huge climate changes, often globally, over decades. Weather events are fast and local. But look at the interplay between the two and it’s clear that the transition between one climate state and another is not smooth but extremely volatile…Societies are unprepared, because weather volatility related to tipping points is absent from risk assessments. – Levermann, Nature July 2026

What’s in this page:

The science behind the Planetary Boundaries framework

Tipping points

These are often non-linear and self-perpetuating. That is:

(1) They generally happen abruptly rather than gradually, and with little to no warning

(2) They are irreversible in human time-frames

(3) There is no way to control them

(4) Some will trigger massive carbon emissions from what once were natural carbon sinks, such as the Amazon rainforest, which in 2021 stopped being a carbon sink; permafrost; the loss of 28% of the Earth’s entire tropical peat stocks; and carbon in other soils (which are not accounted for in climate models) now on the move

(5) They threaten the natural world and us

Tipping points are when we push so called tipping elements across their biophysical thresholds which leads to an irreversible change. A tipping element is a biophysical system that fulfills 2 criteria:

  • Scientific evidence that it contributes to regulate the state of the climate system.
  • Scientific evidence of multiple stable states, for example, either frozen ice sheet or liquefied ice. Another example is either a rainforest or savannah.

What separates these states are the interactions and feedbacks between non-negotiable biological chemical physical properties such as the melting point of ice. For example, a healthy ice sheet with very high altitude that’s very cold. If that starts melting, it gets lower and lower altitude, so you get a self-amplifying feedback, because the lower the altitude, the warmer it gets, and the darker the surface—because it is liquefied—the albedo shifts from reflecting to absorbing yet more heat. – Rockström 2025

Summary of key tipping points mapped above by Carbon Brief

Several topics are covered in more detail in both Effects and Impacts sections
 

 

The melting cryosphere: Antarctica, Greenland, permafrost, methane clathrates

The Arctic is melting 4 times faster than the rest of the planet, and up to 7 times faster in the Berring Sea. Melting glaciers (including in Aotearoa) , Greenland, and Antarctica, and the rapid decline of sea ice formation in Antarctica and the Arctic is also well underway. This is accelerating sea level rise, changing ocean currents, more extreme weather events, loss of critical ecosystem services (biodiversity), and social and economic impacts. Millennia-old carbon storage systems once regarded as stable—permafrost and methane clathrates—are disgorging vast quantities of greenhouse gases, which means the remaining IPCC carbon budget is already overdrawn.
 
 
Antarctica
Thwaites Glacier is close to collapsing. Modelling and recent research indicates that the loss of the West Antarctic Ice Shelf (WAIS) is now unavoidable, even if emissions are stabilised. In Video 4 Prof. Tim Naish from Wellington University explains what Antarctic climate scientists are finding out and why they are so concerned. Not only will sea levels rise faster this century, if the West Antarctic Ice Sheet is destabilized, the melting process could be continuous and irreversible for centuries.
 

Atlantic Meridional Overturning Circulation (AMOC) breakdown | West African & Indian monsoon shift

The AMOC is literally a conveyor belt for exchanging heat and nutrients across four of the five world’s major oceans. The current, which moves nearly 20 million cubic metres of water per second, is driven in part by the formation of Arctic sea ice each year. When ocean water freezes, it leaves salt behind, making the surrounding water denser and heavier, so it sinks. The scale of sea ice formation was so large that until recently, the sinking salty water is one of the the world’s largest waterfalls (the largest is around Antarctica). Recent research indicates the AMOC will shut down this century, with global implications. Amongst other impacts, it would send Europe into a a deep freeze, cause havoc to Monsoon rains across India and West Africa, and accelerate warming in the Southern Hemisphere including Aotearoa. In Video 5, Stefan Rahmstorf, Professor of Physics of the Oceans, presents the situation to the Arctic Circle Assembly in Reykjavik, Iceland October 2024. In 2025 Iceland officially designated a potential collapse of AMOC as an existential threat and a national security risk.

A full AMOC collapse would be a massive, planetary-scale disaster. We really want to prevent this from happening. In other words: we are talking about risk analysis and disaster prevention. This is not about being 100% or even just 50% sure that the AMOC will pass its tipping point this century; the issue is that we’d like to be 100% sure that it won’t. That the IPCC only has “medium confidence” that it will not happen this century is anything but reassuring, and the studies discussed here, which came after the 2021 IPCC report, point to a much larger risk than previously thought. – Rhamstorf, April 2025

Losing biodiversity coupled with current warming has already ‘tipped’ heavily forested regions from being carbon sinks into carbon sources. 

Biome shift: Amazon rainforest dieback

The south-east Amazonian rainforest, which now appears to have reached a point where plants return more CO2 into the atmosphere than they absorb (Fig. 3 & Video 3).

Observations from across the Amazon suggest that CO2-driven accelerations of tree growth may have contributed to increasing tree mortality rates (trees grow faster but also die earlier), which could eventually neutralize the forest carbon sink in the coming decades. – Flores et al, 2024

Biome shift: Africa

The same has occurred in African broadleaf forests and the South American monsoon is at risk of collapsing. If temperatures continue to rise over the next few years, it may not be possible for forests to recover because they will have tipped into a new state, one that does not support their future existence. For example, in 2023 widespread wildfires in Canada and Australia were so extreme that new forests are now unlikely to regrow.

We may be able to prevent some tipping points if we can reverse rising temperatures by drawing down excessive carbon from the atmosphere. The fastest and most cost-effective way to achieve this is by restoring natural ecosystems, which will bring the collateral benefits of healthy ecosystem services as well as a livable climate.

Biome loss: Aotearoa

Not all tipping points have global ramifications. Threats are from introduced pest plants and animals that thrive in a changing climate, ongoing agricultural expansion, pollutants entering waterways, demands for reliable water for irrigation, bulldozing marine ecosystems through bottom trawling, and an Emissions Trading Scheme that financially incentivise monoculture radiata pine plantations over the protection and restoration of biodiverse native ecosystems. Once tipping points for some native ecosystems and species are reached, the ecosystem services they provided (including flood mitigation, coastal defenses against rising sea levels, and long term carbon sequestration) are, along with many endangered species, gone forever.
 
Since 2012…over a hundred thousand hectares of true land-use change [has been] going on around wetlands, scrub being cleared, and dairy land-use intensification. – Landcare Research, 2020
Even the most egregious offences—including a dam built on a wetland, clearance of a nationally endangered form of kānuka, and aerial poisoning of swathes of regenerating native bush—often prompted little more than a warning from authorities. – Charlie Mitchell, Stuff, 2020

Stratocumulus clouds

One of the characteristics of tipping points is that when a complex system has been tipped into a new state, it can’t be returned to its original state simply by undoing or reversing the tipping event. A good example of this are stratocumulus clouds. Found over 20% of Earth, they reflect 30–60% of the solar radiation back into space before it reaches the ground. So they are a vital climate-controlling mechanism, acting as a natural sunshade. But as greenhouse gases increase, modelling shows that a tipping point is reached once atmospheric CO2 passes 1,200ppm a tipping point is crossed. In order for stratocumulus clouds to begin forming again, greenhouse gas concentrations in the atmosphere would need to drop below 300ppm. While 1,200ppm is much higher than today’s 430ppm, other tipping points now being crossed is accelerating this increase. See  the NASA explanation of the research paper: Clouds, Arctic Crocodiles and a New Climate Model and the 2019 research: Schneider et al: Possible climate transitions from breakup of stratocumulus decks under greenhouse warming. Nature Geoscience 12 pp163-167

More information

Home > Climate wiki > Effects > Tipping points