A grim climate reality

From polar ice sheets to coral reefs, Earth's natural systems are either nearing or already crossing dangerous thresholds, warns a new climate report published in October. 

The Global Tipping Points Report 2025 (bit.ly/global-tipping) is the second report led by the University of Exeter in the U.K. on the latest scientific understanding of the potential impacts of rising temperatures. The first report, published in 2023, coincided with the COP28 conference. COP (Conference of the Parties) is a decision-making body that meets annually at the United Nations Climate Change Conference, commonly called COP. The 2025 report was launched ahead of COP30 being held from November 10 in Brazil. 

"In those two years since we published the original report, there's been a lot of change," says Steven R. Smith of the University of Exeter, a lead author of the reports. "We consider ourselves in a new climate reality because before we could say that tipping points may be close, but we are confident now to say that we've passed the first major climate tipping point." 

A tipping point, Smith explains, is a threshold beyond which there is self-propelling change — and that change is often abrupt and irreversible. Tipping points can be negative (dangerous) or positive (beneficial). The crossing of the thermal threshold for tropical and sub-tropical coral reefs is the first negative climate tipping. "Warm-water coral reefs have experienced the worst bleaching event on record over 2023-2025 and the central estimate of their thermal tipping point of 1.2°C global warming has been crossed," according to the report. Coral reefs are highly sensitive, says Smith, and global warming has to go down to one degree for them to be safe again. 

On an average, the global temperature rise over a long term (30 years) is now around 1.4°C above pre-industrial levels. By 2030, the planet is set to cross the 1.5°C long-term average, experts warn. Already in 2024, the warmest year on record, global warming had exceeded 1.5°C. "For every day that we're overshooting 1.5, this puts us in the danger zone of escalating risks of even more tipping points being crossed," adds Smith. 

The report notes that "parts of the polar ice sheets may also have crossed tipping points that would eventually commit the world to several metres of irreversible sea-level rise affecting hundreds of millions." 

Negative tipping points aren't limited to dying coral reefs and shrinking Greenland and West Antarctic ice sheets. 

"One is the Amazon forest dieback which is being driven not only from warming in the region, which is drying out those forests, but also exacerbated by deforestation for local activities such as agricultural production," says Ajay Gambhir, Director of Systemic Risk Assessment at the Accelerator for Systemic Risk Assessment (ASRA) and a contributing author. The Amazon is a huge carbon sink but it may become a carbon source with the drying out of biomass in its forests, Gambhir says. "This is of particular concern." Preventing, slowing down and reversing the deforestation activities would build resilience in the Amazon, he says.

Though the report uses the Amazon as a case study, Smith says that the world's rainforests are at risk above 1.5°C. "It also applies to other rainforests." Rainforests have massive biodiversity and are important for natural carbon removals, he says. Another negative tipping point highlighted in the report is the collapse of the Atlantic Meridional Overturning Circulation (AMOC), a key ocean circulation system that regulates the climate system. AMOC, the report states, "is also at risk of collapse below 2°C, which would radically undermine global food and water security and plunge northwest Europe into severe winters."