A key climate tipping point has been irreversibly breached for the first time, a new report has warned.
With global warming on track to climb past 1.5°C (2.7°F), scientists say that warm-water coral reefs are now passing their thermal tipping point.
That means the reefs on which a quarter of marine life and nearly a billion people rely will almost certainly be lost.
With Earth now poised on the brink of more tipping points, scientists warn that climate change will continue to cause ‘catastrophic harm’ unless urgent action is taken.
The second Global Tipping Points report, written by 160 scientists from 23 countries, lays out the points at which the damage caused by climate change may spiral out of control.
Although it may now be too late to save the world’s coral reefs, the authors are calling for immediate action to prevent more tipping points from being breached.
Co-author Dr Mike Barrett, chief scientific advisor at WWF-UK, says: ‘That warm-water coral reefs are passing their thermal tipping point is a tragedy for nature and the people that rely on them for food and income.
‘This grim situation must be a wake-up call that unless we act decisively now, we will also lose the Amazon rainforest, the ice sheets and vital ocean currents.’
The first key climate tipping point has now been breached, according to a new report. Global temperatures are now so warm that a mass die-off of the world’s warm-water coral reefs is 99 per cent certain and likely irreversible. Pictured: Turtles swim over a bleached section of the Great Barrier Reef
The second Global Tipping Points report, written by 160 scientists from 23 countries, identifies the key points beyond which damage to the environment will become self-propelling and hard to reverse
As the concentration of greenhouse gases in the atmosphere increases and the planet becomes warmer, the global climate is being pushed towards ‘tipping points’.
Professor Tim Lenton, Director of the Global Systems Institute at the University of Exeter, told Daily Mail that these are ‘The point where a change in the state of a system becomes self-propelling, producing accelerating and hard-to-reverse change.’
He adds: ‘In the climate, crossing tipping points are among the biggest risks we face.’
Unlike most climate threats, which are increasing steadily over time, tipping points risk causing 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.
While coral is vital to huge parts of the ocean ecosystem, it is also extremely sensitive to the effects of climate change.
If temperatures become too hot, the coral will expel the tiny algae that live in their tissues, exposing their white skeletons in a process known as bleaching.
Since the 1950s, climate change and overfishing have led to more than half of the world’s coral reefs vanishing.
Beyond temperatures of 1.2°C (2.16°F) above the pre-industrial average, mass bleaching events and large-scale coral die-backs become inevitable. With the world now 1.4°C (2.52°F) above the pre-industrial average, it is likely too late to save most large reefs
However, 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 now been passed, and there is a 99 per cent chance that any coral reefs of meaningful scale will be lost.
Pockets or reefs may survive in a few locations, but large coral reefs like the Great Barrier Reef will become a thing of the past.
However, the loss of the world’s coral reefs is only the first tipping point, and more are already very close.
In particular, the report finds that even a small increase in global temperature could now trigger the widespread die-back of the Amazon rainforest.
Due to a combination of deforestation and the other effects of climate change, the temperature required to push the world’s largest rainforest beyond this 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.
If this occurs, the effects would be devastating on both a local and global scale.
The next major tipping point will be the mass die-back of the Amazon rainforest, which might begin at temperatures 1.5°C above the pre-industrial average
The warmer the climate becomes and the further above 1.5°C the temperature reaches, the greater the risks will become. If nothing is done, the report predicts that ‘catastrophic’ damage is likely
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 forward, Professor Lenton says that the next tipping point that will likely be triggered is the ‘irreversible collapse of the West Antarctic and Greenland ice sheets’.
Professor Lenton says: ‘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 that collapse occurs, it will release vast quantities of fresh water into the world’s oceans, committing the planet to multiple metres of sea level rise in the long term.
If the world’s governments continue with their current polices, 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 is responsible for driving the Gulf Stream and transporting 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 destabilisation of global food systems – potentially triggering widespread famine.
Ahead of world leaders gathering for the COP30 climate conference, the researchers are warning that the specific nature of tipping points means they need especially urgent attention.
From 2°C (3.6°F) above the pre-industrial average, there is a serious risk that the Atlantic Meridional Overturning Circulation (AMOC) will collapse. This key current drives the Gulf Stream (pictured), which keeps northern Europe warm
‘Once a tipping point is passed, the resulting damages accelerate and are hard to reverse, so we have to act in advance to avoid tipping points, 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.
The researchers 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 minimise peak global temperature, the duration of the overshoot period above 1.5°C, and the return time below 1.5°C.’
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