The planet has entered a “new reality” as it reaches the first of many climate tipping points: the widespread mortality of warm-water coral reefs. (Wikimedia Commons)
The planet has entered a “new reality” as it reaches the first of many climate tipping points: the widespread mortality of warm-water coral reefs, a landmark report has warned.
The second Global Tipping Points report, which was released ahead of the COP30 climate summit in Brazil next month, has found that warm-water coral reefs — on which nearly a billion people and nearly a million marine species depend — are passing their tipping point.
“Global warming will soon exceed 1.5°C, putting humanity in the danger zone where multiple climate tipping points pose catastrophic risks to billions of people,” said the report, which was produced by 160 authors from 23 countries.
“Already warm-water coral reefs are crossing their thermal tipping point and experiencing unprecedented dieback. Polar ice sheets are approaching tipping points, committing the world to several metres of irreversible sea-level rise that affect hundreds of millions of people.”
“We are rapidly approaching multiple Earth system tipping points that could transform our world, with devastating consequences for people and nature,” Tim Lenton, of the Global Systems Institute at the University of Exeter, said in a statement. “This demands immediate, unprecedented action from leaders at COP30 and policymakers worldwide.”
Every fraction of additional warming increases the risk of triggering further tipping points, the report said.
These include a collapse of the Atlantic Meridional Overturning Circulation — a system of ocean currents that circulates water within the Atlantic Ocean — that “would radically undermine global food and water security and plunge north-west Europe into prolonged severe winters”.
Climate change and deforestation put the Amazon rainforest at risk of widespread dieback below 2°C of global warming, threatening “incalculable damage” to biodiversity and affecting more than 100 million people who depend on the forest.
“These climate tipping point risks are interconnected and most of the interactions between them are destabilising, meaning tipping one system makes another more likely,” the report said.
The resulting impacts would cascade through the ecological and social systems that humanity depends on, escalating damage. “Humanity faces a potentially catastrophic irreversible outcome … How hot we let it get and for how long really matters in preventing climate tipping points.”
Dieback of warm-water coral reefs
Tropical coral reefs, which are mainly found in shallow, warm ocean waters near the equator, form significant ecosystems in regions such as the Great Barrier Reef, the Coral Triangle in Southeast Asia and the Caribbean Sea.
These vibrant reefs support roughly a quarter of all marine species and provide critical coastal protection and livelihoods for millions of people.
The report noted that, in their healthy state, coral reefs sustain rich biodiversity, fisheries and tourism economies. “However, rising ocean temperatures, acidification, overfishing and pollution can lead to coral bleaching and mortality.”
Warm-water coral reefs have experienced the worst bleaching event on record from 2023 to 2025. Crossing a tipping point could result in the widespread collapse of reef ecosystems, causing dramatic losses of marine biodiversity, diminished fish stocks and weakened coastal defences against storms and erosion.
The human and societal consequences would be severe, the report said. Regionally, hundreds of millions of people across the tropics rely on coral reefs for food security, employment and coastal protection.
A collapse would jeopardise fisheries that provide both protein and income, disrupt tourism economies and expose coastal communities to intensified storm damage, sea-level rise and groundwater salination.
“The central estimate of the thermal tipping point for warm-water coral reefs of 1.2°C global warming above pre-industrial is already exceeded and, without stringent climate mitigation, their upper thermal threshold of 1.5°C may be reached within the next 10 years, compromising reef functioning and provision of ecosystem services to millions of people,” the report said.
Even if global warming is limited to 1.5°C, without exceeding it, warm-water coral reefs are still almost certain (>99% chance) to reach their tipping point. The Paris Agreement’s goal of keeping warming well below 2°C or at 1.5°C will not be enough to prevent irreversible damage to these reefs.
“Returning global mean warming below 1.2°C with a minimal overshoot period, and eventually to 1°C above pre-industrial levels, is essential for retaining functional warm-water coral reefs at meaningful scale, beyond a few isolated refuge areas,” it said.
Strong reckoning
The magnitude and duration of global temperature overshoot above 1.5°C must be minimised, the report said. To achieve that, human-caused greenhouse gas emissions must be halved by 2030 (compared to 2010 levels) and reach net zero by 2050.
This requires an unprecedented acceleration in decarbonisation, rapid mitigation of methane emissions and other short-lived climate pollutants, and “fast-scaling of sustainable carbon removal from the atmosphere.”
“If we wait to cross tipping points before we act, it will be too late … But the window for preventing damaging tipping points is rapidly closing.”
Current national climate commitments and binding long-term or net-zero targets are not enough, the report noted. They still commit the world to ongoing global warming that will probably exceed 2°C before 2100, demanding immediate unprecedented action from leaders at COP30 and policymakers worldwide.
“The findings of this report require a strong reckoning with our current social and economic systems that have led to this moment of potentially imminent cascading crises across our planet and societies, while offering some of the transformative solutions that we need to undertake in order to enable a more just and sustainable future for all,” said Laura Pereira, a professor of sustainability transformations and futures at the Global Change Institute at Wits University.
The report’s authors are working with Brazil’s COP30 presidency on the “Action Agenda” as a platform for accelerating climate transition plans and triggering self-reinforcing change across different sectors — from agriculture to energy, from forests to cities — towards low-carbon and climate-resilient global transformation.
Action to trigger “positive tipping points” of self-propelling change — such as the rollout of green technologies — offers the only credible route to a safe, just and sustainable future.
“In the two years since the first Global Tipping Points Report, there has been a radical global acceleration in some areas, including the uptake of solar power and electric vehicles,” Lenton said.
“But we need to do more — and move faster — to seize positive tipping point opportunities. By doing so, we can drastically cut greenhouse gas emissions and tip the world away from catastrophic tipping points and towards a thriving, sustainable future.”
Every tipping point of danger can be mirrored by a tipping point of opportunity, the report said. “If coral reefs are dying back, restoration of coastal ecosystems can still drive resilience and livelihoods. If forests are at risk, their regeneration can unlock carbon removal, biodiversity recovery and sustainable prosperity.”
If energy systems remain carbon-intensive, “the exponential uptake of renewables and electrification — already led by many countries of the South — can define a new development model that cascades into positive change across other sectors.”