Riccardo Liguori According to the Global Tipping Points Report 2025, warm-water coral reefs have crossed the critical threshold of 2.2°F (1.2°C) of global warming, entering the first catastrophic tipping point due to greenhouse gas emissions. With current warming at about 2.5°F (1.4°C), corals face widespread decline
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In the silence of the oceans, a crisis is unfolding that marks a boundary in the Planet’s climate history. According to the Global Tipping Points Report 2025, warm-water coral reefs have exceeded their survival threshold: with global warming now approaching 2.5°F (1.4°C) above pre-industrial levels, Earth has reached its first climate tipping point.
The study, the result of work by 160 scientists from 87 institutions in 23 countries, confirms that coral ecosystems can no longer withstand the current level of thermal stress. Only a “rapid and sustained” reduction in average global temperature to 2.2°F (1.2°C) — or, ideally, to 1.8°F (1°C) — could allow the survival of a portion of the reefs on a significant scale.
When the threshold breaks
In scientific terms, a tipping point is the moment when a natural system crosses a limit beyond which change becomes rapid, widespread and irreversible. Coral reefs, which host about a quarter of all marine species, are among the most heat-sensitive habitats: the loss of symbiotic algae causes the so-called bleaching and, over time, the death of corals.
The current fourth global bleaching event (GBE4), which began in 2023, is the most severe ever recorded. More than 80% of reefs in over 80 countries have experienced extreme heat waves, with entire areas reduced to white, lifeless expanses.
“The widespread decline of coral reefs is already underway,” explained Tim Lenton, director of the Global Systems Institute at the University of Exeter, to The Guardian. “If emissions are not addressed quickly, the 2.7°F (1.5°C) threshold will be exceeded within ten years, with irreversible effects.”
From the Caribbean to the Amazon: the chain of tipping points
Caribbean coral reefs clearly show the advancing collapse: heat waves, diseases and loss of biodiversity are undermining their resilience. But the report outlines a broader picture: the Planet is entering a “danger zone,” in which other crucial natural systems risk crossing their own critical threshold.
Among the main ones:
- The ice sheets of Greenland and West Antarctica, already in accelerated melting, with potential sea level rise of several meters.
- The Atlantic ocean circulation (AMOC), whose destabilization would radically alter European climate and global food security.
- The Amazon rainforest, close to the point of collapse due to deforestation and warming, with an estimated threshold between 2.7 and 3.6°F (1.5 and 2°C).
Every tenth of a degree more, scientists warn, increases the risk of triggering chain reactions in Earth’s climate system.
Governing the crisis
The Global Tipping Points Report 2025 indicates that the window for intervention remains open, but is rapidly closing. Accelerated decarbonization is needed, along with targeted protection policies: reducing deforestation, combating pollution and protecting so-called “climate refuges”, areas where ocean conditions remain more stable and corals can regenerate.
As Mike Barrett, scientific advisor to WWF-UK and co-author of the report, emphasizes, “conservation of refuges is essential to maintain the seeds of recovery, while waiting for a stabilized climate.”
Beyond the risks, the document also highlights the possibility of positive tipping points: virtuous transformations already underway, such as the spread of renewable energy, electric mobility and more sustainable agricultural practices. These are processes capable of generating self-sustained changes and pushing society toward faster emissions reduction. “The race has begun to activate these positive tipping points before the negative ones become unmanageable,” Lenton concludes.
A threshold that marks a before and after
Crossing the thermal limit of coral reefs represents a historic passage in the global climate crisis. It is not just a biological signal, but measurable proof of the irreversible change that the Earth system is undergoing. After millions of years of equilibrium, the oceans have begun to respond to heat in a non-linear way: the warmer they get, the more they lose the ability to absorb it and sustain life.
Source: Global Tipping Points
