research paper on tipping points

Global Tipping Points Report 2023

The Global Tipping Points Report, published by the University of Exeter, provides a comprehensive assessment of tipping points in the Earth system and human systems, and how they urge global change in the face of the growing threats of climate change and biodiversity loss. As the world grapples with increasing global warming and significant societal shifts, the report examines the risks and opportunities of tipping points—points where a change in a system can lead to abrupt or irreversible impacts—in the natural world and society at large. The authors aim to assess global tipping points and consider how to mobilize widespread action toward mitigation, prevention, and adaptation to urge social change that interrupts the alarming risks to the planet’s systems and promotes sustainability and justice.     

The report is divided into four main sections:

• Section 1: Earth System Tipping Points
• Section 2: Tipping Point Impacts
• Section 3: Governance of Earth System Tipping Points
• Section 4: Positive Tipping Points in Technology, Economy and Society

Key resources accompany the report, including a summary report , key messages , recommendations , and an infographic . Users can also view select case studies and multimedia videos.

Lenton TM et al. The Global Tipping Points Report 2023. University of Exeter 2023. https://global-tipping-points.org .

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Climate tipping points could lock in unstoppable changes to the planet – how close are they?

Researcher in Earth System Resilience, Stockholm University

Disclosure statement

David Armstrong McKay is a GSI Visiting Fellow at the University of Exeter and an Associated Researcher at Stockholm Resilience Centre, and is working as a freelance research consultant and science communicator on climate tipping points with the Earth Commission (hosted by non-profit research network Future Earth and is the science component of the Global Commons Alliance, a sponsored project of Rockefeller Philanthropy Advisors, with support from Oak Foundation, MAVA, Porticus, Gordon and Betty Moore Foundation, Herlin Foundation, and the Global Environment Facility) which partially funded this study. His contribution to this study was also funded by the Earth Resilience in the Anthropocene project (European Research Council grant ERC-2016-ADG-743080) and the Leverhulme Trust (RPG-2018-046).

Stockholm University provides funding as a member of The Conversation UK.

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Continued greenhouse gas emissions risk triggering climate tipping points. These are self-sustaining shifts in the climate system that would lock-in devastating changes, like sea-level rise, even if all emissions ended.

The first major assessment in 2008 identified nine parts of the climate system that are sensitive to tipping, including ice sheets, ocean currents and major forests. Since then, huge advances in climate modelling and a flood of new observations and records of ancient climate change have given scientists a far better picture of these tipping elements. Extra ones have also been proposed, like permafrost around the Arctic (permanently frozen ground that could unleash more carbon if thawed).

Estimates of the warming levels at which these elements could tip have fallen since 2008. The collapse of the west Antarctic ice sheet was once thought to be a risk when warming reached 3°C-5°C above Earth’s pre-industrial average temperature. Now it’s thought to be possible at current warming levels .

In our new assessment of the past 15 years of research, myself and colleagues found that we can’t rule out five tipping points being triggered right now when global warming stands at roughly 1.2°C. Four of these five become more likely as global warming exceeds 1.5°C.

These are sobering conclusions. Not all of the news coverage captured the nuance of our study, though. So here’s what our findings actually mean.

Uncertain thresholds

We synthesised the results of more than 200 studies to estimate warming thresholds for each tipping element. The best estimate was either one that multiple studies converged on or which a study judged to be particularly reliable reported. For example, records of when ice sheets had retreated in the past and modelling studies indicate the Greenland ice sheet is likely to collapse beyond 1.5°C. We also estimated the minimum and maximum thresholds at which collapse is possible: model estimates for Greenland range between 0.8°C and 3.0°C.

Within this range, tipping becomes more likely as warming increases. We defined tipping as possible (but not yet likely) when warming is above the minimum but below the best estimate, and likely above the best estimate. We also judged how confident we are with each estimate. For example, we are more confident in our estimates for Greenland’s ice sheet collapse than those for abrupt permafrost thaw.

This uncertainty means that we do not expect four climate tipping points to be triggered the first year global temperatures reach 1.5°C (which climate scientists suggest is possible in the next five years ), or even when temperatures averaged over several years reach 1.5°C sometime in the next couple of decades . Instead, every fraction of a degree makes tipping more likely, but we can’t be sure exactly when tipping becomes inevitable.

This is especially true for the Greenland and west Antarctic ice sheets. While our assessment suggests their collapse becomes likely beyond 1.5°C, ice sheets are so massive that they change very slowly. Collapse would take thousands of years, and the processes driving it require warming to remain beyond the threshold for several decades. If warming returned below the threshold before tipping kicked in, it may be possible for ice sheets to temporarily overshoot their thresholds without collapsing.

For some other tipping points, change is likely to be more dispersed. We estimate that both tropical coral reef death and abrupt permafrost thaw are possible at the current warming level. But thresholds vary between reefs and patches of permafrost. Both are already happening in some places, but in our assessment, these changes become much more widespread at a similar time beyond 1.5°C.

Elsewhere, small patches of the Amazon and northern forests might tip and transition to a savannah-like state first , bypassing a more catastrophic dieback across the whole forest. Model results that are yet to be published suggest that Amazon tipping might occur in several regions at varying warming levels rather than as one big event.

There may also be no well-defined threshold for some tipping elements. Ancient climate records suggest ocean currents in the North Atlantic can dramatically flip from being strong, as they are now, to weak as a result of both warming and melting freshwater from Greenland disrupting circulation. Recent modelling suggests that the threshold for the collapse of Atlantic circulation depends on how fast warming increases alongside other hard-to-measure factors, making it highly uncertain.

Into the danger zone

There are signs that some tipping points are already approaching. Degradation and drought have caused parts of the Amazon to become less resilient to disturbances like fire and emit more carbon than they absorb.

The front edge of some retreating west Antarctic glaciers are only kilometres away from the unstoppable retreat. Early warning signals in climate monitoring data (such as bigger and longer swings in how much glaciers melt each year) suggest that parts of the Greenland ice sheet and Atlantic circulation are also destabilising.

These signals can’t tell us exactly how close we are to tipping points, only that destabilisation is underway and a tipping point may be approaching. The most we can be sure of is that every fraction of further warming will destabilise these tipping elements more and make the initiation of self-sustaining changes more likely.

This strengthens the case for ambitious emissions cuts in line with the Paris agreement’s aim of halting warming at 1.5°C. This would reduce the chances of triggering multiple climate tipping points – even if we can’t rule out some being reached soon.

Don’t have time to read about climate change as much as you’d like? Get a weekly roundup in your inbox instead. Every Wednesday, The Conversation’s environment editor writes Imagine, a short email that goes a little deeper into just one climate issue. Join the 10,000+ readers who’ve subscribed so far.

• Climate change
• Climate modelling
• Coral reefs
• Amazon forest
• 1.5 degrees
• Greenland ice sheet
• West Antarctic ice sheet
• Thawing permafrost
• Climate tipping points

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Special issue  

• Special issue

The purpose of the special issue is to review and advance the state of the art of research on tipping points – spanning Earth system tipping points to social tipping points – and to provide underpinning content for the first "Tipping Points Status Report" for COP28 (November 2023). The special issue proposal arises from the "Tipping Points: From Climate Crisis to Positive Transformation" international conference hosted by the Global Systems Institute (GSI) and University of Exeter (12–14 September 2022), as well as the associated creation of a Tipping Points Research Alliance by GSI and the Potsdam Institute for Climate Research. It is also inspired by growing worldwide interest in tipping points.

There is a need for improved assessment of both tipping point risks and positive tipping point opportunities. Whilst the recent sixth assessment report by the Intergovernmental Panel on Climate Change (IPCC) began to consider tipping points in the climate system, there is a clear need for a more comprehensive and up-to-date assessment of tipping points across climate and social–economic systems (i.e. all three working groups of IPCC). Positive tipping point opportunities are not widely recognized but could have huge leverage.

The aim of the special issue (and associated "Tipping Points Status Report") is to produce a ground-breaking state-of-knowledge synthesis of tipping point research. We see an important niche for a special issue on the state of both "bad" and "good" tipping points in relation to climate change. The physical science element would update the status of climate and Earth system tipping points. The impacts and adaptation element would update tipping points across climate–ecological–social systems and their cascading interactions. The mitigation element would update the positive tipping points of transformative social–technological–ecological change.

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The paper examines how knowledge about climate tipping points (CTPs) influences public risk perceptions in Norway. Using an online survey, the study finds that only 13 % of Norwegians have good knowledge of climate tipping points. Communication about these tipping points had a modest effect, slightly increasing concern compared to general climate change information. The study highlights the need for further research on this topic, especially how to effectively communicate knowledge about CTPs.

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Our Positive Tipping Points are bringing change to the climate crisis.

Our research at the University of Exeter highlights the growing threat of “tipping points” that could accelerate the climate crisis.

Exeter researchers are also identifying sources of hope: Positive Tipping Points. We have identified Positive Tipping Points in a range of areas – from agriculture and ecosystem regeneration to politics and public opinion. Some Positive Tipping Points are already in progress. Others are yet to be triggered. Understanding these areas and working to identify the opportunities could allow us to activate Tipping Points that could combine into cascades of positive change.

Our Tipping Points are creating positive change.

Discover how our vital research is helping combat the climate crisis.

Hope in the fight against climate change

We have left it too late to tackle climate change incrementally. It now requires transformational change, and a dramatic acceleration of progress.

“Just as Tipping Points are part of the greatest threat we face – the same logic may also provide the solution. At the University of Exeter, we have identified a variety of Positive Tipping Points in human societies that can propel rapid decarbonisation. This concept could unlock the stalemate – the sense that there's nothing we can do about climate change.”

Professor Tim Lenton Director of the Global Systems Institute

Triggering Positive Tipping Points in power generation

In the UK, power generation from coal has dropped to almost nothing within the last five years.

Triggering Positive Tipping Points to regenerate ecosystems

Antifungal resistance is less recognised amid the AMR challenge, yet fungal diseases affect billions of people each year and are responsible for approximately 1.5 million deaths per year worldwide.

Positive Tipping Points accelerate electric vehicle revolution

Electric vehicles (EVs) are better for the environment than petrol or diesel cars.

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Professor Tim Lenton

Director of the Global Systems Institute

  [email protected]

My research focuses on understanding the behaviour of the Earth as a whole system, the complex web of biological, geochemical and physical processes that shape the chemical composition of the atmosphere and oceans, as well as the climate of the Earth. I am particularly interested in how life has reshaped the planet in the past and what lessons we can draw from this as we proceed to reshape the planet now. My work identifying tipping points in the climate system has led me on to examine positive tipping points within our social systems which could help accelerate progress towards a sustainable future.

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A socio-technical transition perspective on positive tipping points in climate change mitigation: Analysing seven interacting feedback loops in offshore wind and electric vehicles acceleration

• IMP Innovation, Strategy and Sustainability

Research output : Contribution to journal › Article › peer-review

• Accelerated low-carbon transitions
• Tipping point dynamics
• Multi-Level Perspective
• Feedback effects

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• Climate Change Social Sciences 100%
• Electric Vehicles Social Sciences 100%
• Case Study Social Sciences 100%
• Electric Vehicle Earth and Planetary Sciences 100%
• Climate Change Mitigation Earth and Planetary Sciences 100%
• Offshore Wind Earth and Planetary Sciences 100%
• Feedback Loop Engineering 100%
• Consumption Theory Economics, Econometrics and Finance 100%

T1 - A socio-technical transition perspective on positive tipping points in climate change mitigation:

T2 - Analysing seven interacting feedback loops in offshore wind and electric vehicles acceleration

AU - Geels, Frank

AU - Ayoub, Martina

PY - 2023/8

Y1 - 2023/8

N2 - This paper engages with climate mitigation debates on positive tipping points, which attract increasing attention but remain divided between technological and social tipping point approaches. Building on recent attempts to overcome this dichotomy, the paper develops a socio-technical transitions perspective which shows how co-evolutionary interactions between techno-economic improvements and actor reorientations can significantly accelerate diffusion. Mobilising insights from political science, discourse theory, business studies, consumption theory, and innovation studies, we elaborate the Multi-Level Perspective to articulate seven feedback loops in tipping point dynamics. We illustrate and test our co-evolutionary perspective with two case studies, UK offshore wind and electric vehicles. These case studies not only demonstrate the importance of interacting feedback loops, but also show a contrasting sequence in tipping point dynamics, with substantial techno-economic deployment preceding major actor reorientations in offshore wind, while following them in the EV case. The cases also indicate the crucial roles of policymakers in low-carbon tipping point dynamics as well as the importance of policy learning and social, political, and business feedbacks in strengthening and reorienting policy support.

AB - This paper engages with climate mitigation debates on positive tipping points, which attract increasing attention but remain divided between technological and social tipping point approaches. Building on recent attempts to overcome this dichotomy, the paper develops a socio-technical transitions perspective which shows how co-evolutionary interactions between techno-economic improvements and actor reorientations can significantly accelerate diffusion. Mobilising insights from political science, discourse theory, business studies, consumption theory, and innovation studies, we elaborate the Multi-Level Perspective to articulate seven feedback loops in tipping point dynamics. We illustrate and test our co-evolutionary perspective with two case studies, UK offshore wind and electric vehicles. These case studies not only demonstrate the importance of interacting feedback loops, but also show a contrasting sequence in tipping point dynamics, with substantial techno-economic deployment preceding major actor reorientations in offshore wind, while following them in the EV case. The cases also indicate the crucial roles of policymakers in low-carbon tipping point dynamics as well as the importance of policy learning and social, political, and business feedbacks in strengthening and reorienting policy support.

KW - Accelerated low-carbon transitions

KW - Tipping point dynamics

KW - Multi-Level Perspective

KW - Feedback effects

UR - http://www.scopus.com/inward/record.url?scp=85159356529&partnerID=8YFLogxK

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U2 - 10.1016/j.techfore.2023.122639

DO - 10.1016/j.techfore.2023.122639

M3 - Article

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JF - Technological Forecasting and Social Change

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• Review Article
• Published: 19 June 2011

Early warning of climate tipping points

• Timothy M. Lenton 1 , 2  

Nature Climate Change volume  1 ,  pages 201–209 ( 2011 ) Cite this article

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A climate 'tipping point' occurs when a small change in forcing triggers a strongly nonlinear response in the internal dynamics of part of the climate system, qualitatively changing its future state. Human-induced climate change could push several large-scale 'tipping elements' past a tipping point. Candidates include irreversible melt of the Greenland ice sheet, dieback of the Amazon rainforest and shift of the West African monsoon. Recent assessments give an increased probability of future tipping events, and the corresponding impacts are estimated to be large, making them significant risks. Recent work shows that early warning of an approaching climate tipping point is possible in principle, and could have considerable value in reducing the risk that they pose.

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Acknowledgements

V. Livina and V. Dakos performed the analysis in, and helped produce, Figs 3 and 4 . E. Shuckburgh encouraged the author to produce Fig. 5 . This research was supported by the Natural Environment Research Council (NE/F005474/1) project 'Detecting and classifying bifurcations in the climate system' and was partly conducted at the Isaac Newton Institute for Mathematical Sciences, Cambridge University, on the programme 'Mathematical and Statistical Approcahes to Climate Modelling and Prediction'.

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Lenton, T. Early warning of climate tipping points. Nature Clim Change 1 , 201–209 (2011). https://doi.org/10.1038/nclimate1143

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Published : 19 June 2011

Issue Date : July 2011

DOI : https://doi.org/10.1038/nclimate1143

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Tipping Points for the Planet

Complex environmental systems are undergoing profound upheavals as a result of human activity.

By David Gelles and Manuela Andreoni

A drumbeat of recent reports has driven home the fact that our planet’s complex environmental systems are undergoing profound upheavals as a result of human activity.

Glaciers around the world, from Greenland to Switzerland to Antarctica , are melting faster than expected as atmospheric and ocean heat hit new highs.

New research suggests that up to half of the Amazon rainforest could rapidly transform into grasslands or weakened ecosystems in the coming decades as a result of deforestation, climate change and drought. Those stresses could eventually drive the entire forest ecosystem, home to a tenth of the planet’s land species, past a tipping point that would trigger a forest-wide collapse.

And a new study suggests that a crucial network of ocean currents that carries warm water into the North Atlantic is showing early signs of collapse because of an influx of fresh water from melting glaciers.

All of these developments appear worrisome on the surface. But, most concerning of all, they raise the specter that the planet may be approaching some of the so-called tipping points that could trigger severe and irreversible changes.

Tim Lenton, a professor who studies climate and Earth systems at the University of Exeter, said tipping points were characterized by “amplifying feedback within a system that’s getting strong enough that it can cause a self-propelling change.”

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Tipping Elements – big risks in the Earth System

Climate tipping elements are critical, large-scale components of the Earth system, which are characterized by a threshold behaviour. These systems appear to remain stable with increasing global temperature, but starting at a particular global temperature threshold, very small additional disturbances can 'tip' them into a qualitatively new state. If you imagine a valuable vase that initially remains standing while the table is being tilted. At first nothing happens; then the slightest vibration is enough for it to tip over.

The geographical distribution of global and regional tipping elements, color-coded according to the best estimate for their temperature thresholds, beyond which the element would likely be 'tipped'. Figure designed at PIK (under cc-by licence), based on Armstrong McKay et al., Science (2022).

The threshold behavior is often based on self-reinforcing processes which, once tipped, can continue without further external forcing. It is thus possible that a component of the Earth system remains ‘tipped’, even if the background climate falls back below the threshold. The transition resulting from the exceedance of a system-specific tipping point can be either abrupt or gradual. Crossing single tipping points has severe impacts on the environment and threatens the livelihood of many people 1 . There is also the risk that, through feedback loops, further tipping points in the Earth System are reached and a domino-like chain reaction is initiated 2 , 3 .

Since the first publications in 2007/2008 4 , 5 , scientific knowledge about tipping elements has greatly improved – and it is still a highly-active field of research. For example, the University of Exeter and the Potsdam Institute for Climate Impact Research (PIK) have signed an agreement to jointly investigate climate change tipping points - a first output is there: the Global Tipping Points Report . Also, a project is being prepared to compare computer-model output with respect to tipping points : TipMIP, a „TIPping point Model Intercomparison Project “. A general note: In research, new studies complement older ones. The exact number of tipping elements reported, for example, often simply depends on details in the definition of a tipping element, or on the focus of a study (see also Developments in tipping elements science ). PIK News and Publications about Tipping Elements

The most recent science

Below each tipping element is briefly profiled and the most recent research summarised – based on a 2022 updated tipping element review by an international group of scientists (from Exeter University, Stockholm Resilience Center, Future Earth and the Potsdam Institute for Climate Impact Research) 6 .

Click to expand the grey bars and learn more about individual tipping elements (for instance about the tipping process, timescales and impacts of tipping). All stated temperatures refer to warming with respect to preindustrial levels. The temperature threshold is the global mean temperature increase at which the tipping element is likely to be tipped. In brackets we provide the range of global mean temperature increase at which it is possible for the tipping element to be tipped, e.g. 3°C (2°-4°C).

The meaning of the symbols

Ice Masses (cryosphere entities)

When ice melts it exposes a generally darker underlying surface, whether the rocky bed of a glacier or the sea. This darker surface absorbs more radiation from the sun, in turn accelerating the melting of the remaining ice. This mechanism, known as the ice-albedo feedback, is a classic example of a self-reinforcing process where the same phenomenon, namely ice loss, is both the driver and the result of temperature rise. However, this is not the only mechanism (described below) that makes the Earth's large ice masses a tipping element.

Greenland Ice Sheet

What and Where? Greenland is covered by an up to three kilometer thick ice sheet – all year around.

Tipping Point & Tipping Process Loss: The Greenland ice loss due to glacier flow into the sea and enhanced melting during summer has considerably increased in recent years due to global warming. As a consequence, the ice sheet is becoming thinner and thereby losing height. This means that its surface, which today still reaches into high, cold air layers, is increasingly exposed to lower and warmer layers of air, which accelerates the melting process.

Temperature Threshold & Timescales There are indications that the tipping point, leading to a long-term (10 000 years) complete ice loss, is likely reached at global warming levels of 1.5°C (possibly between 0.8°C and 3°C). The more that threshold is transgressed, the faster the tipping process can unfold (but at least 1000 years; the maximum estimate is 15 000 years).

Impacts of Tipping Complete loss of the ice sheet would lead to world-wide sea-level rise of up to seven meters, and other tipping elements (particularly the Atlantic Meridional Overturning Circulation) would be affected.

Arctic Winter Sea Ice

What and Where? The Arctic ocean is – to a large extent – covered by a floating cover of frozen ocean water, called sea ice. The extent of the ice cover depends on the season. This tipping element is the winter sea-ice cover, which never exceeds a thickness of a few meters. [Sea ice is not to be confused with table icebergs, which can be several hundreds of meters thick. They are pieces of former ice shelves, which are the floating end of land-based glaciers. It should also not be confused with the summer sea-ice cover, which has already been diminished to such an extent that the North Pole is likely to be ice free in summer within this century.]

Tipping Point & Tipping Process Collapse : Several computer model simulations show that shifts in the timing of sea-ice growth and melt causes exhibit threshold behaviour.

Temperature Thresholds & Timescales The threshold that can be identified from the models lies at approximately 6.3°C (4.5-8.7°C), and the duration of the tipping process is estimated at 20 years (10-100 years).

Impacts of Tipping The sea ice cover in winter and summer are strongly dependent on one another. An uncovered ocean surface contributes through several processes to warming in the northern latitudes that is twice as large as the global average. Overall, this feedback could lead to an increase in global warming of 0.6°C.

Barents Sea Ice

What and Where? The winter sea ice in the Barents Sea (between Scandinavia, the island of Svalbard and Nowaja Semlja) is a special case in comparison with the rest of the Arctic Sea ice.

Tipping Point & Tipping Process Abrupt loss: Loss of Barents sea ice is self reinforced due to increased inflow of warm water from the Atlantic.

Temperature Thresholds & Timescales Two models show an abrupt loss at 1.6°C (1.5-1.7°C), with a potential timescale of about 25 years.

Impacts of Tipping Among the consequences of sea-ice loss in the Barents Sea are a significant impact on atmospheric circulation, the climate in Europe as well as potential impacts on the Atlantic Meridional Overturning Circulation.

Boreal Permafrost (abrupt thaw)

What and Where? Around a thousand billion tons of carbon are estimated to be stored in the upper three meters of the frozen soil.

Tipping Point & Tipping Process Abrupt Thaw: Degradation of the surface layer exposes deeper soil layers to thawing and decomposition and therefore accelerates thermokarst formation. Although this is a local process, it could be triggered almost synchronously at sub-continental scale.

Temperature Thresholds & Timescales The temperature threshold for this kind of tipping is estimated to be 1.5°C (1-2.3°C), with a timescale of 200 years (100-300 years).

Impacts of Tipping Abrupt thaw could, in comparison to gradual thaw, increase carbon emissions from permafrost soils by 50-100%, and could potentially trigger large-scale boreal permafrost collapse (see below). In any case, thawing permafrost would contribute considerably to global warming and therefore to the associated risks, from extreme weather to sea-level rise.

Boreal Permafrost (collapse)

  What and Where? The arctic permafrost, which has been frozen for centuries or even millennia, is located in Siberia and North America. These 'Yedoma soils' lie over three meters beneath the surface and are thought to contain many additional billions of tonnes of carbon. If it were to thaw, it would potentially release large amounts of the greenhouse gases carbon dioxide and methane.

Tipping Point & Tipping Process Collapse : These gas compounds originate from organic material which was stored during the last Ice Age. The heat caused by microbial decomposition of the carbon compound accelerates thawing and degradation of the soil.

Temperature Thresholds & Timescales A threshold could be reached at about 4°C (3-6°C) according to the (relatively few) estimates. The timescale for tipping is 50 years (10-300 years).

Impacts of Tipping The released carbon compounds could lead to additional global warming of 0.2-0.4°C.

Extrapolar Glaciers

  What and Where? Extrapolar glaciers are all glaciers are not located in Greenland or Antarctica. Often referred to as 'alpine glaciers', they usually have specific local properties.

Tipping Point & Tipping Process Loss: However, there are signs that certain temperature thresholds can mark simultaneous glacier loss across large areas. The European glaciers are the most sensitive ones, and the relatively more robust are those in high alpine regions of Asia.

Temperature Thresholds & Timescales A global estimate for the temperature threshold is 2°C (1.5-3°C), and for the duration of the process 200 years (50-1 000 years).

Impacts of Tipping Freshwater supply strongly depends on reliable and continuous meltwater from glaciers in many regions of the world. If the glaciers disappear, many communities will be subject to water shortages.

West Antarctic Ice Sheet

What and Where? Large parts of the base of the towering West Antarctic ice sheet rest on the continental bedrock below sea level. Moving inland, this bedrock falls away, reaching a depth of 2.5km below sea level - the ice sheet, however, is high enough to still reach above sea level.

Tipping Point & Tipping Process Loss: Due to this topography, the West Antarctic ice sheet can be destabilized by particular flow dynamics. The destabilisation is triggered when the ice retreats beyond a certain point, for example as a result of warming ocean temperatures. A self-perpetuating feedback kicks in, causing accelerated ice loss.

Temperature Thresholds & Timescales The threshold for tipping is estimated at 1.5°C (1-3°C) global mean temperature rise. The timescale for a collapse is estimated at 2 000 years (500 years if the threshold is strongly exceeded, with a maximum of 13 000 years).

Impacts of Tipping If the ice sheet were to break up, sea level would rise worldwide by about three meters.

East Antarctica: Subglacial Basins

  What and Where? There are some sub-glacial basins in East Antarctica that, like the West Antarctic ice sheet, are grounded below sea level. These include the Wilkes, Aurora und Recovery basins.

Tipping Point & Tipping Process Loss: A self-perpetuating feedback can arise here as well.

Temperature Thresholds & Timescales The temperature threshold for collapse is estimated at 3°C (2-6°C) and the process could happen within 2 000 years (500-10 000 years).

Impacts of Tipping Another contribution to sea-level rise.

East Antarctic Ice Sheet

 What and Where? The East Antarctic ice sheet stores the biggest part of Earth’s frozen reservoir of freshwater.

Tipping Point & Tipping Process Loss: While the East Antarctic ice sheet seems stable today, self-perpetuating feedbacks could kick in here as well, at very high temperatures.

Temperature Thresholds & Timescales At warming of around 7.5°C (5-10°C) a tipping process could start leading to a complete loss of the East Antarctic ice sheet over more than 10 000 years.

Impacts of Tipping Ice in East Antarctica corresponds to around 50 meters of sea-level rise.

Circulation Systems

There are some prominent examples of atmospheric and ocean circulation with marked (but variable) annual or seasonal patterns – but these can change. Throughout the history of our planet’s climate, there have been multiple phases of disruption and re-organization. This section gives a brief outline of potentially abrupt changes in circulation systems which could occur in the future.

Atlantic Meridional Overturning Circulation

What and Where? The overturning circulation of the Atlantic is like a huge conveyor belt, transporting warm surface water northwards and, after cooling and sinking in high latitudes, cold deep water southwards. It is called a 'thermohaline' circulation because it is driven by temperature differences and differences in salinity. The Gulf Stream, which is responsible for the mild climate of northwestern Europe, is part of this large-scale system of Atlantic currents.

Tipping Point & Tipping Process Cessation: One of its main motors is the cold, dense (and therefore heavy) salt water which sinks near Greenland and the Labrador coast. If the amount of freshwater from melting ice in the northern latitudes increases, this deep water formation could cease, slowing down the circulation motor.

Temperature Thresholds & Timescales Scientific evidence points to a temperature threshold of 4°C (1.4-8°C) with a timescale of 50 years (15-300 years).

Impacts of Tipping There are severe impacts on temperature and precipitation patterns: warming of the southern hemisphere, a southward shift of the intertropical convergence zone, monsoon weakening in Africa and Asia, strengthening in the southern hemisphere leading to drying in the Sahel and in parts of the Amazon, and reduced natural carbon sinks. It can also lead to cooling in the North Atlantic - however, this does not result in a substantial reduction in global warming since the different processes interact in such a way that the resulting warming and cooling effects cannot simply be added together.

Labrador-Irminger Seas Convection

What and Where? As part of the subpolar gyre in the North Atlantic, there is an overturning circulation in the Labrador-Irminger sea.

Tipping Point & Tipping Process Collapse: Several models show a collapse of that overturning circulation as a consequence of global warming.

Temperature Thresholds & Timescales The temperature threshold is estimated to lie at around 1.8°C (1.1-3.8°C), and the process could take place within 10 years (5- 50 years).

Impacts of Tipping The consequences of tipping are a regional cooling in the North Atlantic of around 2-3°C and potentially a global cooling of 0.5°C (however, this should not be understood as a potential mechanism for combatting global warming). Furthermore, a northern shift of the jet stream is expected, as are weather extremes in Europe and a southward shift of the intertropical convergence zone.

Ecosystems (biosphere components)

The living part of the Earth system, called the biosphere, plays a decisive role for the climate, both locally and via difference feedback mechanisms also for the global climate. For example, drier, warmer climate conditions can lead to vegetation die back, which releases additional carbon back into the atmosphere, resulting in increased carbon dioxide in the atmosphere and thus further fuelling climate change. When global warming crosses a temperature threshold, a tipping point, ecosystems can experience irreversible change.

Northern Forests (southern dieback)

What and Where? The coniferous forests of the northern regions (taiga) - experts often call them 'boreal' forests - represent almost a third of the global forest area. They are located circularly around the Arctic. This tipping element exhibits two tipping processes: southern dieback and northern expansion (see below).

Tipping Point & Tipping Process Southern dieback: Boreal forests can be destabilized over larger areas (~100km) at their southern periphery, as a consequence of warming-induced hydrological changes, more frequent fires and bark beetle outbreaks.

Temperature Thresholds & Timescales The best estimate of a threshold is 4°C (1.4-5°C) with timescales of 100 years (at least 50 years).

Impacts of Tipping The forests are replaced by grass-dominated steppe/prairie. The released carbon and the altered environment could contribute to an additional global warming of about 0.2 °C.

Northern Forests (northern expansion)

  What and Where? The coniferous forests of the northernregions (taiga) - referred to by scientists as 'boreal forests' - represent almost a third of the global forest area. They are located circularly around the Arctic. This tipping element exhibits two tipping processes: southern dieback (see above) and northern expansion.

Tipping Point & Tipping Process Northern expansion: The forests can, due to warming, expand abruptly at their northern periphery, and thereby cover usually very bright and reflecting snow surfaces – accelerating arctic warming. Dark surfaces absorb more energy, light surfaces reflect more sunlight.

Temperature Thresholds & Timescales A precise threshold is not reliably constrained yet. The best estimate is 4°C (1.5-7.2°C), with a timescale of 100 years (at least 40 years).

Impacts of Tipping On the one hand, more CO2 is taken up by an increase of vegetation. On the other hand, the surface darkens, such that all in all global warming would be enhanced.

Low-latitude Coral Reefs

  What and Where? Tropical and subtropical coral reefs are among the ecosystems with the highest biodiversity worldwide. They have an enormous influence on the marine food web, nutrient an carbon cycles in the ocean and are essential for the well-being of millions of people worldwide. For example, they provide coastal protection and are important for tourism.

Tipping Point & Tipping Process Die-off: Coral reefs are threatened by a multitude of human impacts, among them overfishing, direct damages, sedimentation and ocean acidification. However, when water temperatures cross a certain threshold, corals repel their symbiotic algea, leading to bleaching and then to dieoff of the corals.

Temperature Thresholds & Timescales The threshold for widespread die-off is estimated at 1.5°C (1-2°C). The process could happen over the course of a decade.

Impacts of Tipping All of the above mentioned ecosystem services of coral reefs vanish with die-off.

Sahel Vegetation & West African Monsoon

What and Where?

The West African monsoon and the vegetation in Sahel are closely connected, allowing for greening of the Sahel.

Tipping Point & Tipping Process Greening: There are many known self-reinforcing processes. In particular, dust and aerosols influence rainfall patterns. Increasing rainfall leads to increased vegetation and vice versa.

Temperature Thresholds & Timescales It is not entirely clear if indeed tipping will take place, but there are hints pointing towards several abrupt changes in the past, known weaknesses in models that fail to reproduce expected tipping behavior and enormous regional consequences. Therefore, the authors of Armstrong McKay et al., define this process as tipping point, with a threshold of 2.8°C (2-3.5°C), and a timescale of 50 years (10-500 years).

Impacts of Tipping A fundamental change in regional vegetation.

Amazon Rainforest

  What and Where? The Amazon rainforest in South America is an element of the biosphere, which due to the water and carbon cycles plays an important role in the entire Earth System.

Tipping Point & Tipping Process Dieback: A large part of the rainfall in the Amazon basin originates from water evaporating over the rainforest. A warmer global climate with declining regional precipitation in combination with deforestation and forest fire could push the rainforest towards a critical threshold.

Temperature Thresholds & Timescales The best estimate currently available from partially unclear scientific consensus is around 3.5°C (2-6°C) – but without the influence of deforestation. The timescale for die-back could lie around 100 years (50-200 years).

Impacts of Tipping A transformation of the Amazon rainforest into a seasonal forest, adapted to drier conditions, or to grassland, would have fundamental impacts on global climate, since around 25% of the global atmosphere-biosphere carbon-exchange takes place here.

Developments in tipping elements science

Tipping element research has made enormous advances since its beginnings in the 2000s. Some proposed tipping elements, depending on not always consistent definitions, have been rejected in the meantime – or are so uncertain that they no longer appear in the list above.

Uncertain: Shift of Indian summer monsoon; Increase or loss of sea ice in the southern Ocean; Break-up of stratocumulus clouds near in equatorial latitudes; Collapse of Antarctic Bottom Water formation, Increase of Indian Ocean upwelling; Loss of tibetean snowfields; Global anoxia in the ocean.

Rejected : Abrupt expansion of the Arctic ozone hole; Permanent/extreme El Niño; Instability of the northern polar jetstream.

There are other possible tipping elements showing self-perpetuating processes, but they either have no threshold behavior or show only local, but no large-scale synchronized tipping. Among these are the gradual thaw of boreal permafrost, loss of Arctic summer sea ice, the weakening of the global carbon sink on land and in the ocean, the weakening of the biological ocean carbon pump and the dissolution of marine methane hydrates.

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Tipping Points

Pj lamberson, scott page.

Paper #: 12-02-002

This paper formally defines tipping points as a discontinuity between current and future states of a system and introduces candidate measures of when a system tips based on changes in the probability distribution over future states. We make two categorical distinctions between types of tips relevant in social contexts: The first differentiates between direct tips and contextual tips. A direct tip occurs when a gradual change in the value of a variable leads to a large, i.e. discontinuous, jump in that same variable in the future. A contextual tip occurs when a gradual change in the value of one variable leads to a discontinuous jump in some other variable of interest. We argue that while scholars and writers often focus on direct tips, contextual tips often make direct tips possible, such as when human rights conditions in a state deteriorate creating the potential for an uprising. The second differentiates tips between outcomes that belong to the same class--such as tips from one equilibrium to another--from tips that result in a change in the outcome class, such as tips that occur when an equilibrium system becomes chaotic or complex.

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