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Tipping points in the climate system | HearLore
— Ch. 1 · Defining Climate Tipping Points —
Tipping points in the climate system.
~5 min read · Ch. 1 of 7
In climate science, a tipping point is a critical threshold that, when crossed, leads to large, accelerating and often irreversible changes in the climate system. The Intergovernmental Panel on Climate Change defines this as a level of change beyond which a system reorganizes, often abruptly or irreversibly. A small disturbance can cause a disproportionately large change in the system state. This process may be associated with self-reinforcing feedbacks that lead to changes irreversible on a human timescale. For any particular climate component, the shift from one stable state to another may take many decades or centuries. Scientists have identified nine global core tipping elements and seven regional impact tipping elements as of September 2022. Some of these thresholds are estimated to be close to being crossed today.
Cryosphere Ice Sheet Collapse
The Greenland ice sheet is the second largest ice sheet in the world, holding enough water to raise sea levels globally by 7.2 metres if completely melted. Surface melting reduces the height of the ice sheet, exposing it to warmer air at lower altitudes and accelerating its melt further. Around half of the ice loss occurs via surface melting, while the remainder happens at the base where the ice touches the sea through calving. A 2021 analysis of sub-glacial sediment found that the Greenland ice sheet melted away at least once during the last million years. The West Antarctic Ice Sheet sits on bedrock mostly below sea level, making it vulnerable to fast and irreversible ice loss. Thinning and collapse of its ice shelves help accelerate grounding line retreat into deeper basins. If completely melted, this sheet would contribute around 3.3 meters of sea level rise over thousands of years.
Ocean Current Disruption Risks
The Atlantic meridional overturning circulation acts as a conveyor belt sending warm surface water from the tropics northward while carrying cold fresh water back south. Increased rainfall and melting ice dilute salty surface water, decreasing its density and ability to sink, which slows down the entire circulation. Theory suggests freshwater input from melting glaciers could cause a collapse into a state of reduced flow even after melting stops. An October 2024 open letter signed by 44 climate scientists claimed the risk of AMOC collapse has been greatly underestimated and could occur in the next few decades. An August 2025 study concluded that the collapse of AMOC could start as early as the 2060s. A weakening of 24% to 39% is expected depending on greenhouse emissions, even without full tipping behavior. If the AMOC does shut down, a new stable state could emerge that lasts for thousands of years.
Terrestrial Ecosystem Shifts
The Amazon rainforest produces around half of its own rainfall by recycling moisture through evaporation and transpiration as air moves across the forest. When forest is lost via droughts or deforestation, there will be less rain in downwind regions, increasing tree stress and mortality. In 2022, a study reported that the rainforest has been losing resilience since the early 2000s. Perennially frozen ground covers large fractions of land mainly in Siberia, Alaska, northern Canada and the Tibetan plateau. Subsea permafrost up to 100 metres thick also occurs on the sea floor under part of the Arctic Ocean. Scientists believe there is nearly twice as much carbon in permafrost than is present in Earth's atmosphere. As the climate warms, microbes become active and decompose biological material, releasing carbon dioxide and methane into the atmosphere.
Cascading Systemic Failures
Crossing a threshold in one part of the climate system may trigger another tipping element to tip into a new state. Such sequences are called cascading tipping points, representing a domino effect. Ice loss in West Antarctica and Greenland will significantly alter ocean circulation. Sustained warming of the northern high latitudes could activate tipping elements such as permafrost degradation and boreal forest dieback. A 2021 study with three million computer simulations showed that nearly one-third resulted in domino effects even when temperature increases were limited to 2 degrees Celsius. The authors argued that the possibility of cascading tipping points represents an existential threat to civilization. Network model analysis suggested temporary overshoots of climate change can substantially increase risks of climate tipping cascades by up to 72% compared with non-overshoot scenarios.
Mathematical Theory And Detection
Tipping point behavior in the climate can be described using mathematical terms identifying three types: bifurcation, noise-induced, and rate-dependent. Bifurcation-induced tipping happens when a parameter passes a critical level where a stable state loses its stability or disappears. Systems display critical slowing down with increased memory and variance as they approach a tipping threshold. These early warning signals are often developed and tested using time series from paleo records like sediments, ice caps, and tree rings. Abrupt change is not always an early warning signal since it can occur if changes are reversible to the control parameter. Noise-induced transitions do not show any early warning signals which occur with bifurcations because the underlying potential does not change. Rate-induced tipping occurs when environmental change is faster than the force restoring the system to its stable state.
Historical Geological Evidence
The geological record shows many abrupt changes on geologic time scales that suggest tipping points may have been crossed in pre-historic times. Dansgaard-Oeschger events during the last ice age were periods of abrupt warming within decades in Greenland and Europe. During deglaciation in the early Holocene, sea level rise rose abruptly during meltwater pulses rather than smoothly. The monsoon in North Africa saw abrupt changes on decadal timescales during the African humid period spanning 15,000 to 5,000 years ago. This period ended suddenly in a drier state leading to desertification and regime shifts. A review of abrupt changes over the last 30,000 years showed that tipping points can lead to large sets of cascading impacts in climate, ecological and social systems. For instance, the abrupt termination of the African humid period led to the retreat of pastoral societies in North Africa and a change of dynasty in Egypt.
What is a tipping point in the climate system according to the Intergovernmental Panel on Climate Change?
A tipping point is a critical threshold that, when crossed, leads to large, accelerating and often irreversible changes in the climate system. The Intergovernmental Panel on Climate Change defines this as a level of change beyond which a system reorganizes, often abruptly or irreversibly.
When did scientists identify nine global core tipping elements and seven regional impact tipping elements?
Scientists identified nine global core tipping elements and seven regional impact tipping elements as of September 2022. Some of these thresholds are estimated to be close to being crossed today.
How much sea level rise would occur if the Greenland ice sheet completely melted?
The Greenland ice sheet holds enough water to raise sea levels globally by 7.2 metres if completely melted. Surface melting reduces the height of the ice sheet, exposing it to warmer air at lower altitudes and accelerating its melt further.
When could the collapse of the Atlantic meridional overturning circulation start based on an August 2025 study?
An August 2025 study concluded that the collapse of AMOC could start as early as the 2060s. If the AMOC does shut down, a new stable state could emerge that lasts for thousands of years.
What percentage of carbon in permafrost exists compared to Earth's atmosphere according to scientific belief?
Scientists believe there is nearly twice as much carbon in permafrost than is present in Earth's atmosphere. As the climate warms, microbes become active and decompose biological material, releasing carbon dioxide and methane into the atmosphere.
During which period did the monsoon in North Africa see abrupt changes on decadal timescales?
The monsoon in North Africa saw abrupt changes on decadal timescales during the African humid period spanning 15,000 to 5,000 years ago. This period ended suddenly in a drier state leading to desertification and regime shifts.