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This post explores the tipping risk elements of the Earth system, their nature and interdependence, and how to mitigate these risks going forwards. We are now reading about the setting of new climate records and the deterioration of these tipping elements almost every week of every month. Yet we have the solutions.
“The power of human beings to affect and control and change the environment is growing, as our technology grows. And at the present time we clearly have reached the stage where we are capable, both intentionally and inadvertently, to make significant changes in the global climate and in the global ecosystem. And we’ve probably been doing on a smaller scale things like that for a very long period of time.” Carl Sagan, 1985
Tipping Elements in the Earth System
Tipping elements are large-scale components of the Earth system, important for maintaining balance in the planet’s processes and cycles. If a tipping element changes in nature, the climate on our entire planet is affected. We use the word ‘tipping’ because these system changes cannot be reversed once they occur – the system has ‘tipped over’ to another state.
Tipping elements are affected by both natural variations in the Earth and planetary system, as well as by anthropogenic (human-driven) variations.
Examples of tipping elements include the Amazon rainforest or the Arctic ice. If the Amazon rainforest is compromised, a chain of events is set in motion, culminating in dieback if global warming continues beyond the tipping point threshold (over 2 C). The rainforest could reach its tipping point in the next 100 years due to global warming. This process would be sped up, however, if we continue to cut down the rainforest. The process could then take place within one generation.
The Potsdam Institute for Climate Impact Research (PIK) has identified 16 tipping elements crucial for our climate. 9 are global tipping elements and another 7 are regional tipping elements. They are grouped into 3 categories – Ice Masses (cryosphere), Circulation Systems (marine and atmospheric elements) and Ecosystems (biosphere elements). The full list is described in the table below.
As the temperature on Earth continues to rise, these systems will be progressively compromised – we are already observing some of these effects regularly in the news. At 1.5C is it expected that multiple tipping points will be crossed.
Tipping elements are complex. Each element, once compromised, can trigger a large series of other events. And these in turn will trigger chain reactions. If the Amazon rainforest dies, it is not just the forest that is gone. Regional weather will change. Less carbon emissions will be absorbed worldwide, leading to more global warming. There will be fundamental impacts on global climate. All climate phenomena are interconnected.
Tipping Points
“Look at the world around you. It may seem like an immovable, implacable place. It is not, With the slightest push — in just the right place — it can be tipped.” – Malcolm Gladwell
Such systems are critically affected when a certain threshold temperature is reached, a threshold beyond which small changes can lead to sudden and irreversible changes in the system.
And because of the interconnectedness of the Earth’s climate system, progress towards the tipping points is not just a function of temperature or carbon concentrations.
Rather it is the cumulative effect of all negative externalities – e.g. land degradation, desertification, land clearing, fossil fuel burning, ocean acidification. And the general degradation of marine and land-based ecosystems and ecosystem services that act as sinks and counter-balances. And the interconnectedness of the tipping elements themselves, as we approach the stage of multiple tipping points and their potential interactions with each other in a domino-like chain reaction.
Positive Feedbacks
“One can see from space how the human race has changed the Earth. Nearly all of the available land has been cleared of forest and is now used for agriculture or urban development. The polar icecaps are shrinking and the desert areas are increasing. At night, the Earth is no longer dark, but large areas are lit up. All of this is evidence that human exploitation of the planet is reaching a critical limit. But human demands and expectations are ever-increasing. We cannot continue to pollute the atmosphere, poison the ocean and exhaust the land. There isn’t any more available.” – Stephen Hawking
Tipping points occur when positive feedbacks from existing global warming lead to a jump in global average temperatures. The feedbacks can occur without any additional anthropogenic emissions or other actions.
The threshold behavior is often based on self-reinforcing processes which, once tipped, can continue without further external forcing. Thus a component of the Earth system can remain ‘tipped’, even if the background climate falls back below the threshold. And the resulting transition may be either abrupt or gradual.
A number of these positive feedbacks are already occurring at a faster rate than scientists had previously predicted, increasing the risks of dangerous climate change and a shift to a less hospitable, ‘hothouse’ climate system.
If humanity fails to rapidly mitigate climate change, climate change will increase more rapidly due to these positive feedback effects. And further “tipping points”, once unleashed, will cause yet further problems. These include:
· The weakening of the natural ocean carbon sinks.
· The weakening of the natural land carbon sinks.
· The increasing release of methane from peat deposits, wetlands and thawing permafrost
· The progressive melting of reflective sea ice
· The disintegration of the Greenland and West Antarctica Ice Sheets.
Earth System Dynamics
“It’s not that the world hasn’t had more carbon dioxide, it’s not that the world hasn’t been warmer. The problem is the speed at which things are changing. We are inducing a sixth mass extinction event kind of by accident and we don’t want to be the ‘extinctee.’” – Bill Nye
The schematic below summarises the complex mix of causal interactions, impacts and feedbacks observed between humans and the wider Earth system.
At the top level, we have an ever-growing population, driving ever-growing global demand for energy, land and land-use changes, natural resources, products and services and so on. Over the past 100+ years we have also evolved a petroleum-driven global economy with very strong momentum, one that will take decades to change.
Further down, we see the effects on the natural world of mankind’s activity, and how these interact with and impact upon the global biogeochemical cycles and the global commons. As set out in an earlier post and in the paper Syndromes of Global Change, our collective development has been described by some 16 identified syndromes of unsustainable global environmental and social change. Such syndromes have led to the current status quo and the imbalances in carbon, water and other budgets, and the continuing feedback effects.
Conclusion
The existing Earth system problems are interconnected problem sets.
The solution sets will be similarly interconnected, through investing in, supporting and replenishing Mother Nature on a mass scale and reversing the long-term declines in natural capital.
As we well know, much greater problems are around the corner, if we fail to mitigate and reverse these problems.
The current system was built with the support of the highest calorifically-dense source of energy the world has ever known (oil), in cheap abundant quantities, with easy credit and seemingly unlimited mineral resources.
Its replacement is hoped to be done at a time when there is expensive energy, a more fragile finance system, not enough resources, and an unprecedented world population, embedded in a deteriorating natural environment.
And this has to be done within a few decades, if not sooner…
“We are the first generation to feel the effect of climate change and the last generation who can do something about it.” – Barack Obama
The solutions are well known.
• For the first time we are obliged to attempt restoration projects on a massive scale.
• We must also accelerate the progress made towards new energy sources that harness nature (and physics), and build out technologies to bridge the emissions gap to avoid ‘overshoot’.
• Augment and replace over time the current energy system and reduce emissions to net zero
• Remove industry waste streams and existing wastes from land and oceans
• Build out a global zero waste circular economy – produce in the same way nature does (closed loops, no waste, no toxicity)
• Restore arable land by re-establishing the soil food web in whole regions
• Reforest and revegetate large regions, and re-establish the natural biodiversity of flora and fauna
• Investment in and protection of natural capital assets (assets that rely on ecological systems)
• Build out a global Common Wealth entities industry
“Our true nationality is mankind”. “Adapt or perish, now as ever, is Nature’s inexorable imperative”. H.G. Wells
Appendix – Table of Tipping Elements and Commentary
Source: Potsdam Institute for Climate Impact Research (PIK). All temperature thresholds refer to warming with respect to pre-industrial levels. Temperature thresholds represent the global mean temperature rise (or range) at which the tipping element is likely to be tipped.
Section 1 – Ice Masses (cryosphere elements)
When ice melts it exposes the underlying surface, such as the sea or rock. Such surfaces absorb more solar radiation, in turn accelerating the remaining ice melt. This is the ice-albedo feedback mechanism, a self-reinforcing process where ice loss is both the driver and the result of temperature increases. But the mechanism is not unique in making tipping elements of the Earth’s large ice masses.
- Greenland Ice Sheet – Greenland is covered by an ice sheet up to 3km thick. Due to global warming, ice loss occurs as a result of glacier melt flow into the sea and enhanced summer melt. This ice loss is currently estimated at 270 billion tonnes per annum. As a consequence, the ice sheet is becoming thinner and losing height. Its surface is increasingly exposed to warmer layers of air, which accelerate the melting process. The Greenland tipping point, leading to complete ice loss, is likely reached at global warming of around 1.5°C. The more that threshold is exceeded, the faster the tipping process. Complete ice loss may take at least 1000 years, with a sea-level rise of up to seven meters. Other tipping points would be triggered during the process, such as the AMOC (Atlantic Meridional Overturning Circulation).
- Arctic Winter Sea Ice – The Arctic ocean largely covered by a floating cover of sea ice. The extent of which depends on the season. The winter sea-ice cover has a thickness of a few meters on average. Summer sea-ice cover has already been diminished to such an extent, that the North Pole is likely to be ice free in summer within this century. The Arctic tipping point threshold identified from models lies in the range 4.5-8.7°C, with a tipping process duration of 10-100 years. Complete loss of the Arctic sea ice is estimated to contribute, through several processes, 0.6°C to global warming.
- Barents Sea Ice – 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. Loss of the Barents winter sea ice is self-reinforced due to increased inflow of warm water from the Atlantic. Two models show an abrupt loss at 1.5-1.7°C, with a tipping process timescale of about 25 years. Complete Barents sea-ice loss will have a significant impact on atmospheric circulation, the climate in Europe as well as potential impacts on the AMOC.
- Boreal Permafrost (abrupt thaw) – Permafrost is composed of sand, soil and rocks, bound together by ice, in formations up to 600 meters deep. Near the surface, permafrost-rich, boreal landscapes contain large quantities of organic carbon from dead plants that couldn’t decompose due to the cold temperatures. Permafrost occurs as far north as 84°N in northern Greenland, and as far south as 26°N in the Himalayas. Most permafrost in the Northern Hemisphere occurs north of 60°N in Russia, Canada and northern Alaska. Around 1000 billion tons of carbon are estimated to be stored in the upper 3 meters of the frozen soil. Thawing of the permafrost layer exposes further soil layers and the ice melt leads to infrastructure damage and erosion, with potential relocation of communities. Additionally, thawed organic matter decomposes, leading to further methane and carbon dioxide emissions. The temperature threshold for this kind of tipping is estimated to be 1-2.3°C, with a timescale of 100-300 years. Abrupt thaw could increase carbon emissions from permafrost soils by 50-100%, potentially triggering large-scale boreal permafrost collapse.
- Boreal Permafrost (collapse) – The Arctic permafrost 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. The amount of carbon trapped in this type of permafrost is much more prevalent than originally thought and may be about 210-500 Gt, a multiple of the amount released each year from the burning of fossil fuels. Thawing yedoma is a significant source of atmospheric methane (about 4 million tonnes of CH4 p.a.) originating from organic material stored during the last Ice Age. The heat caused by microbial decomposition of the carbon compound accelerates thawing and soil degradation. The tipping point threshold is not well-studied, but estimated to be around 3-6°C with a timescale for tipping of 10-300 years, and a global warming impact of 0.2-0.4°C.
- Extrapolar Glaciers – Extrapolar glaciers are all glaciers not located in Greenland or Antarctica, often referred to as ‘alpine glaciers’. The European glaciers are the most sensitive to loss, with the high alpine regions of Asia more robust. The tipping point threshold estimate is 1.5-3°C, with a tipping process duration of 50-1000 years. Loss of the glaciers will lead to loss of freshwater supply and water shortages.
- West Antarctic Ice Sheet – 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 2.5 km below sea level. Due to this topography, the ice sheet is subject to ice melt caused by both warming air above and warming water below, with acceleration and destabilisation from flow dynamics. The threshold for tipping is estimated at 1-3°C. The timescale for a collapse is estimated to be at least 500 years. If the WAIS were to break up, sea level would rise by around 3 meters.
- East Antarctica: Subglacial Basins – 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 and Recovery basins. The temperature threshold for collapse is estimated at 2-6°C with a similar timeline of at least 500 years.
- East Antarctic Ice Sheet – The East Antarctic ice sheet contains the largest part of Earth’s frozen reservoir of freshwater. While it appears to be stable today, the loss of the WAIS and self-perpetuating feedbacks could kick in here as well, at very high temperatures. The tipping point threshold is estimated at 5-10°C, leading to a complete loss of the East Antarctic ice sheet, with a duration of at least 10,000 years. The complete loss of ice in East Antarctica corresponds to around 52 meters of sea-level rise.
Section 2 – Circulation Systems (marine and atmospheric elements)
Throughout our planet’s climate record, there have been multiple phases of disruption and re-organization of its circulation systems.
10. Atlantic Meridional Overturning Circulation (AMOC) – 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, as it is driven by differences in both temperature and salinity. The Gulf Stream, which is responsible for the mild climate of northwestern Europe, is part of this large-scale system. One of the main AMOC motors is the cold, dense salt water which sinks near Greenland and the Labrador coast. As the amount of freshwater from ice melt increases, this deep water formation is affected, slowing down the AMOC circulation motor. The tipping point threshold is estimated at 1.4-8°C, with a timescale of 15-300 years. Tipping impacts include changes in temperature and precipitation patterns; warming of the southern hemisphere; monsoon weakening in Africa and Asia; 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.
11. Labrador-Irminger Seas Convection – As part of the subpolar gyre in the North Atlantic, there is an overturning circulation in the Labrador-Irminger sea, similar to the AMOC. The Labrador Sea is directly to the west of Greenland, with the Irminger Sea directly to the east of Greenland, extending to the Reykjanes Ridge (a northern part of the Mid-Atlantic Ridge). Several models show a collapse of the overturning circulation at a threshold of 1.1-3.8°C, with a duration of 5-50 years. Tipping would result in regional cooling in the North Atlantic of around 2-3°C and potentially global cooling of 0.5°C. A northern shift of the jet stream is expected, as are weather extremes in Europe.
Section 3 – Ecosystems (biosphere elements)
The living part of the Earth system, called the biosphere, plays a decisive role for the climate, both locally and via feedback mechanisms. 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, fuelling further warming.
12. Northern Forests (southern dieback) – The coniferous forests of the northern regions (taiga, or ‘boreal forests’) represent almost a third of global forest area. They are located circularly around the Arctic. 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. The best estimate of a threshold is 1.4-5°C, with a timescale of at least 50 years. Tipping would lead to the replacement of the forests by grass-dominated steppe/prairie. The released carbon and the altered environment could contribute to an additional global warming of about 0.2 °C.
13. Northern Forests (northern expansion) – With warming, the Northern Forests can expand abruptly further North, thereby covering usually very bright and reflecting (high albedo) snow surfaces – accelerating Arctic warming. A precise threshold is not available as yet, but the best estimate is 1.5-7.2°C, with a timescale of at least 40 years.
14. Low-latitude Coral Reefs – Tropical and subtropical coral reefs are among the highest biodiversity ecosystems, with strong positive benefits for the marine food web, nutrient and carbon cycles. They are threatened by a multitude of human impacts – ocean acidification, overfishing, direct damages and sedimentation. When water temperatures cross a certain threshold, corals repel their symbiotic algae, leading to bleaching and then to die-off. The threshold for widespread die-off is estimated at 1-2°C, with a timescale of one decade.
15. Sahel Vegetation & West African Monsoon – The West African monsoon and the vegetation in Sahel are closely connected, allowing for greening of the Sahel. Self-reinforcing processes include the effect of dust and aerosols on rainfall patterns. Increasing rainfall leads to increased vegetation and vice versa. Tipping is not a certainty, but there have been abrupt changes in the past (Armstrong McKay et al). Threshold estimates are 2-3.5°C leading to a fundamental change in regional vegetation, over a timescale of 10-500 years.
16. Amazon Rainforest – The Amazon rainforest has a major impact on the global water and carbon cycles and thus plays an important role in the entire Earth System. A large part of the Amazon basin rainfall originates from evapotranspiration over the rainforest. A warmer global climate with declining regional precipitation in combination with deforestation and forest fires, could push the rainforest towards a critical threshold. Threshold estimates are 2-6°C without the influence of deforestation, with a duration of 50-200 years. If deforestation continues and fires spread, it can quickly reach the tipping point could be triggered earlier and the forest could die. The resulting transition into a drier seasonal forest and grassland, would have fundamental impacts on global climate, as the region is responsible for around 25% of the global atmosphere-biosphere carbon-exchange.
Section 4 – Former Tipping Elements
Some proposed tipping elements, depending on not always consistent definitions, have now been rejected – 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 Tibetan snowfields;
– Global anoxia in the ocean.
2. Rejected:
– Abrupt expansion of the Arctic ozone hole;
– Permanent/extreme El Niño;
– Instability of the northern polar jetstream.
3. Other
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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