While some tipping points may have been crossed or are close to being crossed, more would be crossed as the planet warms, says study
There are certain large-scale systems on Earth which are essential for its sustenance. Scientists call them ‘climate tipping elements’. There are certain thresholds of these elements known as ‘tipping points’, beyond which even a slight change in them can become unstoppable, leading to catastrophic consequences.
Scientists who first identified and assessed climate tipping elements and their tipping points in 2008, have reassessed them.
They found that while some of the tipping points may have been crossed or are close to being crossed at 1.1 degrees Celsius of warming since pre-industrial times, more of them would be crossed as the planet warmed further.
In fact, the paper says that the West Antarctic Ice sheet may have already crossed its tipping point.
The researchers, who published their findings in a research paper published in the journal Science on September 8, 2022, also increased the probable number of climate tipping elements from nine to 16.
They pored through 200 research papers, paleo-climatic data, current observations and outputs from latest climate models to arrive at their conclusions.
Of the 16, the research team categorised nine as ‘core tipping elements’ affecting the climate of the Earth in general. The remaining seven were categorized as ‘regional tipping elements’ that had an impact on the climate of various regions but could also interact with climate elements from other regions, creating cascading impacts and crossing of tipping points.
The Amazon rainforest is an example of a core tipping element while the west African monsoon is considered to be a regional tipping element.
Current levels of warming may trigger the melting and collapse of the West Antarctic Ice Sheet, a similar event for the Greenland Ice Sheet, thawing of the permafrost, collapse of the Labrador Sea convection and massive die-off of tropical coral reefs.
Once a climate tipping element passes a tipping point, even if temperature rise is arrested then and there, the system would further collapse into oblivion. This may take decades to thousands of years in the case of ice sheets, raising sea levels by many metres gradually.
The change may be rather abrupt in the case of ecosystems and atmospheric phenomena, creating wide scale cascading changes in weather systems, impacting human lives along with animal and plant species.
The collapse of the ice sheets can lead to sea level rise, in turn, leading to gradual subsidence and submergence of many small island countries. The die back of large and complex ecosystems such as coral reefs could lead to unfathomable losses to biodiversity.
“An estimated 25 per cent of all marine life, including over 4,000 species of fish, are dependent on coral reefs at some point in their life cycle,” according the United States Environmental Protection Agency (US EPA). The thawing of permafrost leads to release of carbon into the atmosphere, mainly in the form of methane gas.
Countries of the world have to bring down their greenhouse gas emissions and limit warming to less than 1.5°C as agreed under the Paris Agreement of the United Nations Framework Convention on Climate Change.
If they are not able to do, four of the five tipping points of the elements move from the realm of possibility to becoming likely events and five others become possible, increasing risks for populations around the world.
The risks of crossing the tipping points steadily increases after this point, with it being highest beyond 2°C of warming.
As it is, “the world is heading towards 2-3°C of global warming,” Johan Rockström, director of the Potsdam Institute of Climate Impact Research (PIK) in Germany and co-chair of the Earth Commission, said.
If all the current climate pledges are met, the temperature rise could be kept below 2°C but even then, there is a risk of at least 10 climate elements tipping over. Six of these are likely and four are possible.
“Importantly, many tipping elements in the Earth system are interlinked, making cascading tipping points a serious additional concern. In fact, interactions can lower the critical temperature thresholds beyond which individual tipping elements begin destabilising in the long-run,” Ricarda Winkelmann, co-author of the study and researcher at PIK, said.
“To maintain liveable conditions on Earth, protect people from rising extremes and enable stable societies, we must do everything possible to prevent crossing tipping points. Every tenth of a degree counts,” Rockström said.
“We can see signs of destabilisation already in parts of the West Antarctic and Greenland ice sheets, in permafrost regions, the Amazon rainforest, and potentially the Atlantic overturning circulation as well,” David Armstrong McKay, lead author of the study and part of the Stockholm Resilience Centre, University of Exeter and the Earth Commission, said.
“Our new work provides compelling evidence that the world must radically accelerate decarbonising the economy to limit the risk of crossing climate tipping points,” Timothy Lenton, co-author of the study and director of the Global Systems Institute at the University of Exeter, said.
“To achieve that, we now need to trigger positive social tipping points that accelerate the transformation to a clean energy future. We may also have to adapt to cope with climate tipping points that we fail to avoid and support those who could suffer uninsurable losses and damages,” Lenton added.
“We have made a first step towards updating the world on tipping point risks,” said McKay.
There is an urgent need for a deeper international analysis, especially on tipping element interactions, towards which the Earth Commission is starting a Tipping Points Model Intercomparison Project, he added.
Summary table showing the Climate Tipping Points possible or likely at selected warming levels (current warming, Paris Agreement and current policies), defining "possible" as at or above the study’s minimum threshold estimate and "likely" as at or above the study’s central threshold estimate.
|Warming level||Tipping Points possible/likely at this level|
|Current (2022) (1.1-1.2°C)||0 likely 5 possible (Greenland Ice Sheet [GrIS] from 0.8°C, West Antarctic Ice Sheet [WAIS] from 1.0C, Labrador-Irminger Sea Convection [LABC] from 1.1°C, Low-latitude coral reefs [REEF] from 1.0°C, Boreal permafrost abrupt thaw [PFAT] from 1.0°°C)|
|Paris Agreement, full ambition (1.5°C)||4 likely (GrIS from 1.5°C, WAIS from 1.5°C, REEF from 1.5°C, PFAT from 1.5°C) 6 possible (LABC from 1.1°C, Atlantic Meridional Overturning Circulation [AMOC] from 1.4°C, Barents sea ice [BARI] from 1.5°C, Mountain glaciers [GLCR] from 1.5°C, Boreal forest (southern dieback) [BORF] from 1.4°C, Boreal forest (northern expansion) [TUND] from 1.5°C)|
full range (1.5-<2°C)
|6 likely (GrIS from 1.5°C, WAIS from 1.5°C, REEF from 1.5°C, PFAT from 1.5°C, BARI from 1.6°C, LABC from 1.8°C) 4 possible (AMOC from 1.4°C, GLCR from 1.5°C, BORF from 1.4°C, TUND from 1.5°C)|
|Current policies, best estimate (~2.6°C, based on Meinshausen et al., 2022)||7 likely (GrIS from 1.5°C, WAIS from 1.5°C, REEF from 1.5°C, PFAT from 1.5°C, BARI from 1.6°C, LABC from 1.8°C, GLCR from 2°C) 6 possible (AMOC from 1.4°C, BORF from 1.4°C, TUND from 1.5°C, East Antarctic subglacial basins [EASB] from 2°C, Amazon rainforest [AMAZ] from 2°C, Sahel vegetation & West African Monsoon [SAHL] from 2°C)|
|Current policies, full range (1.9-3.7°C, based on Meinshausen et al., 2022)||10 likely (GrIS from 1.5°C, WAIS from 1.5°C, REEF from 1.5°C, PFAT from 1.5°C, BARI from 1.6°C, LABC from 1.8°C, GLCR from 2°C, EASB from 3°C, AMAZ from 3.5°C, SAHL from 2.8°C) 4 possible (AMOC from 1.4°C, BORF from 1.4°C, TUND from 1.5°C, Boreal permafrost (collapse) [PFTP] from 3°C)|
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