Coral reefs have crossed their thermal tipping point, triggering irreversible dieback
Over 84% of reefs across 82 countries affected by record heat
One billion people depend on coral reefs for food and livelihoods
Other ecosystems, from Amazon forests to polar ice sheets, are nearing collapse
Scientists warn the world is entering a “new reality” unless drastic action is taken
Warm-water coral reefs have crossed their thermal tipping point and are facing unprecedented dieback, according to the Global Tipping Points report released by a team of 160 scientists from 23 countries. These reefs are often described as the rainforests of the oceans.
The report warned that the world has entered a dangerous “new reality” as global heating, driven by greenhouse gas emissions, nears the critical 1.5°C threshold. This rise in temperature, it cautions, is not only destroying coral ecosystems but also pushing several other planetary systems toward collapse.
Since January 2023, coral reefs across the world have been under extreme thermal stress, undergoing the fourth global mass bleaching event in history. The report, compiled by 160 scientists from 23 countries, noted that 84.4 per cent of coral reefs across 82 countries have been affected by record ocean temperatures, the worst bleaching on record.
Coral reefs are vital for both biodiversity and human livelihoods. A quarter of all marine species and nearly one billion people worldwide depend on them for food, income, and coastal protection. Yet, with the thermal threshold for warm-water corals already exceeding 1.2°C, irreversible dieback has begun.
“Already warm-water coral reefs are crossing their thermal tipping point and experiencing unprecedented dieback, threatening the livelihoods of hundreds of millions who depend on them,” the report said. Global warming is projected to cross 1.5 degrees Celsius by 2030 as per the World Meteorological Organization.
The study also warns that other critical tipping points, including the dieback of Amazon forest, collapse of the Atlantic Meridional Overturning Circulation (AMOC) and melting of ice sheets including land permafrost and the sub-polar gyre (SPG), mountain glaciers and boreal forests, are also approaching.
The AMOC, a key system of ocean currents that redistributes heat from the tropics to higher latitudes, could collapse below 2 degrees Celsius of global warming, the report noted. Such a collapse would radically alter global food and water security and plunge northwest Europe into prolonged severe winters.
The SPG in the North Atlantic, another heat-transporting ocean system, along with land permafrost, is also likely to reach tipping points around 1.5°C. Other ecosystems, such as mountain glaciers and boreal forests, face irreversible risks as temperatures approach 2°C, the report said.
The Amazon rainforest, which plays a crucial role in regulating global carbon and water cycles, could face widespread dieback below 2°C of warming. Its loss would cause “catastrophic and incalculable” damage to biodiversity and directly affect more than 100 million people who rely on its resources.
These systems are not isolated, but are interconnected tipping networks instead, meaning that crossing one threshold could accelerate the collapse of others. This cascading effect poses an existential risk to planetary stability.
The report delivers a stark warning: current Nationally Determined Contributions under the Paris Agreement, along with long-term net-zero targets, are insufficient to limit global warming below 2°C by 2100.
“The window for preventing some damaging, irreversible tipping points is rapidly closing. If we wait for certainty that tipping points have been crossed before we act, it will be too late.”
It underlined that unprecedented action is needed from leaders and policymakers worldwide meeting at 30th Conference of Parties (COP30) to the United Nations Framework Convention on Climate Change later in November in Brazil to prevent damaging tipping points.
Polar ice sheets, they warn, are also nearing tipping points that could commit the world to several metres of irreversible sea-level rise, threatening hundreds of millions of people in coastal and low-lying regions.