The death of coral reefs marks the first catastrophic climate tipping point linked to greenhouse gas emissions. “Unless global heating is reduced to 1.2 degrees Celsius ‘as fast as possible’, warm water coral reefs will not remain ‘at any meaningful scale’,” the Global Tipping Points Report by 160 scientists across 87 institutions from 23 countries warns. The report is a wake-up call: we have likely crossed the first climate tipping point – in coral reefs – and we are perilously close to others. The window to avoid further irreversible changes is shrinking rapidly.
The warning in the report, which synthesizes groundbreaking science to estimate points of no return, is strategically timed ahead of the COP30 climate summit to press world leaders to limit temperature overshoot and take stronger steps. The summit will be held at the edge of the Amazon rainforest in Brazil.
‘Points of no return’
Climate scientists warn that other irreversible tipping points will be reached in the near future. “Change is happening fast now, tragically, in parts of the climate, the biosphere,” said environmental scientist Tim Lenton at the University of Exeter, who is the lead author of the report. The key message of the report is that every fraction of a degree and each year spent above 1.5 degrees Celsius matters for avoiding the triggering of additional tipping points.
Climate scientists have been conducting research for years on so-called “tipping points.” Those tipping points are specific points that, once reached, cannot be reversed. With global warming currently at approximately 1.4 degrees Celsius, scientists believe the tipping point for coral reefs – the most vulnerable systems to global heating – has been reached.
Even if warming can be limited to 1.5 degrees Celsius, the chances of coral reefs surviving are virtually nonexistent. This means that the reefs that support the livelihoods of around a billion people and a quarter of all marine life will disappear irreversibly. The report points to reefs in the Caribbean, where marine heatwaves, low diversity, and disease outbreaks have pushed reefs “toward collapse”.
Amazon rainforest
Scientists have been surprised by how quickly changes are unfolding in nature, with average global temperatures already 1.3-1.4 degrees Celsius above the preindustrial average. The last two years were Earth’s warmest on record, with marine heatwaves that stressed 84% of the world’s reefs to the point of bleaching and, in some cases, death.
At the same time, the study’s authors warn of other important tipping points. For example, the Amazon rainforest is flagged as being near a critical threshold of dieback under continued deforestation and warming.
Atlantic Meridional Overturning Circulation
The Atlantic Meridional Overturning Circulation (AMOC), an ocean current that supplies warm water to our regions, could also come to a complete standstill if temperatures drop below 2 degrees Celsius. This would result in colder winters in northwestern Europe and the cessation of monsoon rains in India and West Africa, severely impacting agricultural yields in large parts of the world.
Ice sheets – especially in Antarctica – are under scrutiny: recent studies suggest that rapid Antarctic ice loss may be a tipping risk.
Key message
“The new report makes clear that each year, there is an increase in the scope and magnitude of the negative impacts of climate change,” said Pep Canadell, a senior scientist at Australia’s CSIRO Climate Science Center. The world is currently on track for about 3.1 degrees C of warming in this century, based on national policies. The key message of the report is that every fraction of a degree and each year spent above 1.5 degrees Celsius matters for avoiding the triggering of additional tipping points.
To prevent these tipping points, there is only one remedy, the scientists conclude: the rollout of renewable energy and accelerated reductions in CO2 emissions. The report does offer some hope, saying there are likely “positive tipping points” in society – such as electric vehicle adoption – that could also have runaway effects, rapidly reducing greenhouse gas emissions.
