Current warming rates will put the Earth at risk of passing through six “dangerous” climatic tipping points, according to a new analysis.
Exceeding these thresholds would disrupt terrestrial systems causing the collapse of ice sheets and the loss of coral reefs.
Scientific commentators have previously argued that reaching such a point would be a “climate emergency”.
The researchers analyzed evidence of turning points from 200 recent articles.
At what temperature the tipping points would be reached
What impacts there would be for other systems on Earth
In what times would the impacts be felt.
The research, based on data published since 2008, found that at current levels of global warming the world is already at risk of triggering six dangerous climatic tipping points, and the risks increase with every tenth of a degree of warming.
The Climate Action Tracker estimates that, even under an optimistic scenario, if the current global climate targets are met, the world will see an average warming of 1.8 ° C.
The idea of ”climate turning points” was first introduced by the United Nations climate science group, the Intergovernmental Panel on Climate Change (IPCC), two decades ago.
If crossed they could trigger a significant change in the way terrestrial systems operate, affecting oceans, weather conditions and chemical processes, which could be “irreversible,” according to the UN.
Once a critical point is crossed – or “reversed” – the system failure is self-sustaining, so it will continue even if there is no further warming.
This is self-perpetuating: kind of like a ball goes over the top of a hill and starts rolling down and can’t stop.
At the time, it was thought that tipping points would only be exceeded if global average temperatures rose to more than 5 ° C.
But there has been growing evidence since then that these thresholds could be crossed much sooner.
The six “probably” turning points to cross, according to the research, published in ScienceI am:
Collapse of the Greenland ice sheet
Collapse of the West Antarctic ice sheet
Collapse of ocean circulation in the polar region of the North Atlantic
The reef dies in low latitudes
Sudden thawing of permafrost in the northern regions
Abrupt loss of sea ice in the Barents Sea.
Lead author David Armstrong McKay, of the Stockholm Resilience Center, University of Exeter and the Earth Commission, said some destabilization that precedes a system failure is already starting to be seen in the polar regions.
Greenland and Antarctica are currently losing ice six times faster than 30 years ago, and Greenland’s ice sheet has been shrinking continuously over the past 25 years due to climate change, according to the United Nations.
While some of the other “hotspots” such as degradation in the Amazon rainforest are not expected to activate unless global temperatures rise by 3.5 ° C, all of these systems are linked. So, once one system starts to fail, it could increase the likelihood that others will collapse.
Multiple points of no return
Co-author Ricada Winkelmann, a researcher at the Potsdam Institute for Climate Impact Research and a member of the Earth Commission, said: “Importantly, many tipping elements in the Earth system are interconnected, which makes the points cascade tipping is a serious additional concern. “
For example, if there are smaller or fewer ice sheets and sea ice, less solar energy is reflected leading to further global warming.
In addition to identifying these major risks, the team also suggested that the list of potential pain points could be increased from nine to sixteen.
The team worked with paleoclimatic data (climatic conditions from thousands of years ago), current observations and the results of climate models to make these new identifications.
But some previously considered critical points, for example, El Niño Southern Oscillation (ENSO) have been removed for lack of evidence.
Listen to The Climate Tipping Points on BBC Sounds.