Key Climate Tipping Point Irreversibly Breached
A critical climate tipping point has been irreversibly crossed for the first time, according to a new report. Scientists warn that as global warming continues to rise past 1.5°C (2.7°F), warm-water coral reefs are now surpassing their thermal tipping point. This means that the reefs, which support a quarter of marine life and nearly a billion people, are at risk of being lost forever.
With Earth standing on the edge of more tipping points, scientists emphasize that climate change will continue to cause ‘catastrophic harm’ unless immediate action is taken. The second Global Tipping Points report, authored by 160 scientists from 23 countries, outlines the points at which damage caused by climate change could spiral out of control.
Although it may now be too late to save the world’s coral reefs, the authors urge immediate action to prevent additional tipping points from being breached. Co-author Dr Mike Barrett, chief scientific advisor at WWF-UK, stated, ‘The fact that warm-water coral reefs are passing their thermal tipping point is a tragedy for nature and the people who depend on them for food and income. This grim situation must serve as a wake-up call that we must act decisively now or we will also lose the Amazon rainforest, ice sheets, and vital ocean currents.’
As greenhouse gas concentrations in the atmosphere increase and the planet warms, the global climate is being pushed toward ‘tipping points.’ Professor Tim Lenton, Director of the Global Systems Institute at the University of Exeter, explained that these are ‘points where a change in the state of a system becomes self-propelling, producing accelerating and hard-to-reverse change.’ He added, ‘Crossing tipping points are among the biggest risks we face in the climate.’
Unlike most climate threats, which tend to increase gradually over time, tipping points pose the risk of rapidly escalating and widespread damage. According to the report, the first of these global tipping points is the mass die-off of warm-water coral reefs.
Coral reefs are essential to large parts of the ocean ecosystem but are extremely sensitive to the effects of climate change. When temperatures become too high, corals expel the tiny algae living in their tissues, exposing their white skeletons in a process known as bleaching. Since the 1950s, climate change and overfishing have led to the loss of more than half of the world’s coral reefs.
What Are the Climate ‘Tipping Points’?
- Coral reefs die off
- Amazon Rainforest dies back
- The West Antarctic Ice Sheet collapses
- Subpolar Gyre overturning collapses
- Mountain glaciers retreat
- Atlantic Meridional Overturning Current (AMOC) collapses
At temperatures 1.2°C (2.16°F) above the pre-industrial average, the researchers warn that repeated mass bleaching events become unavoidable. With global warming now at 1.4°C (2.52°F), this tipping point has already been passed, and there is a 99% chance that any coral reefs of meaningful scale will be lost. While some pockets of reefs may survive in certain locations, large coral reefs like the Great Barrier Reef will become a thing of the past.
However, the loss of coral reefs is only the first tipping point, and more are already very close. In particular, the report indicates that even a small increase in global temperature could trigger the widespread die-back of the Amazon rainforest. Due to deforestation and the effects of climate change, the temperature required to push the world’s largest rainforest beyond its critical threshold is now lower than previously expected. At the lowest estimate, an average temperature 1.5°C above the pre-industrial average could be enough to trigger the collapse of this vital ecosystem.
Can the Coral Reefs Be Saved?
According to Professor Tim Lenton, it is no longer possible to save the reefs as we know them today. Any reefs of considerable size will die because the planet is now too hot to sustain them. However, he suggests that some coral reefs can be ‘saved’ by identifying and protecting refuges where some coral can remain cool and reducing other pressures on reefs.
The Amazon is estimated to contain about 123 billion tons of carbon, much of which could be released into the atmosphere if this tipping point is reached. Looking further ahead, Professor Lenton says the next tipping point likely to be triggered is the ‘irreversible collapse of the West Antarctic and Greenland ice sheets.’
He states, ‘We are not on track to avoid these tipping points—we are as likely as not to cross them as the world exceeds 1.5°C global warming.’ When this collapse occurs, it will release vast quantities of fresh water into the oceans, committing the planet to multiple meters of sea level rise in the long term.
If the world’s governments continue with current policies, the planet is also likely to exceed the 2°C (3.6°F) threshold that could trigger the collapse of the Atlantic Meridional Overturning Circulation (AMOC). This vital ocean current drives the Gulf Stream and transports heat around the globe. Its collapse would lead to significantly harsher winters in north-west Europe, disrupted monsoons across West Africa and India, and the destabilization of global food systems—potentially triggering widespread famine.
Urgent Action Needed
Ahead of world leaders gathering for the COP30 climate conference, the researchers are warning that the specific nature of tipping points requires especially urgent attention. ‘Once a tipping point is passed, the resulting damages accelerate and are hard to reverse, so we have to act in advance to avoid them,’ says Professor Lenton.
The researchers stress that it is not too late to avoid breaching more tipping points in the future. Every fraction of a degree of warming and every year above 1.5°C avoided will lower the risk of passing a major tipping point. They point to a number of ‘positive tipping points,’ such as the widespread rollout of solar power, which could lead to self-propelled change towards a sustainable future.
Future positive tipping points, such as the adoption of greener steel production methods, could drive even more change. However, they warn that urgent action must be taken now to have the most benefit in the future.
Dr Manjana Milkoreit, from the University of Oslo, says current policy thinking doesn’t usually take tipping points into account. ‘Preventing tipping points requires ‘frontloaded’ mitigation pathways that minimize peak global temperature, the duration of the overshoot period above 1.5°C, and the return time below 1.5°C.’