Six tipping points “likely” to be overcome

Current rates of warming will put Earth at risk of crossing six “dangerous” climate tipping points, according to a new analysis.

Exceeding these limits will disrupt Earth’s systems by causing the collapse of ice sheets and the loss of coral reefs.

Scientific commentators have previously said that reaching such a point would be a “climate emergency”.

The researchers analyzed data for cutting edge points from 200 recent papers.

They considered:

  • At what temperature will the tipping points be reached?

  • What implications will there be for other Earth systems?

  • At what time intervals will the effects 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 climate 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 current climate targets are met, the world will see an average warming of 1.8C.

The concept of “climate tipping points” was first introduced by the UN’s climate science group, the Intergovernmental Panel on Climate Change (IPCC), two decades ago.

If they intersect they could cause a major change in the way Earth’s systems work, affecting the oceans, weather and chemical processes, which could be “irreversible”, according to the UN.

Once a critical point is passed – or “turned over” – the damage to the system is self-sustaining, so it will continue even if there is no further heating.

This is self-perpetuating: a bit like when a ball tops a hill and starts rolling down and can’t stop.

Irreversible cataract

At the time it was thought that tipping points would only be crossed if global average temperatures rose by more than 5 degrees Celsius.

But since then there are growing signs that those limits may be crossed much sooner.

Six tipping points “likely” to be overcome, according to research published in the Scienceis:

  • 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

  • Coral reefs die in low latitudes

  • Sudden thawing of the permafrost in the northern regions

  • Precipitous loss of sea ice in the Barents Sea.

Lead author David Armstrong McKay, from the Stockholm Resilience Centre, the University of Exeter and the Earth Commission, said some destabilization that precedes a system collapse is already beginning to be seen in the polar regions.

Greenland and Antarctica are losing ice six times faster than 30 years ago, and the Greenland ice sheet has been shrinking steadily for the past 25 years due to climate change, according to the UN.

Although some of the other “tipping points,” such as the decline in the Amazon rainforest, are not expected to be triggered unless global temperatures rise by 3.5 degrees Celsius, all of these systems are linked. Thus, once one system begins to fail, it could increase the likelihood of others collapsing.

Multiple tipping points

Co-author Ricarda Winkelmann, a researcher at the Potsdam Institute for Climate Impact Research and a member of the Earth Commission, said: “Importantly, many tipping points in the Earth system are interconnected, making cascading tipping points a serious additional concern.”

For example, if there are smaller or fewer ice sheets and sea ice, then less energy from the sun is reflected leading to further global warming.

In addition to identifying these higher risks, the team also suggested that the list of potential tipping points could be increased from nine to sixteen.

The team worked with paleoclimate data (climate conditions thousands of years ago), current observations and results from climate models to make these new identifications.

However, some previously considered inflection points, for example the El Niño Southern Oscillation (ENSO), have been removed due to lack of evidence.

Listen to The Climate Tipping Points on BBC Sounds.

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