Hothouse Earth risk could rise as warming accelerates, scientists say

A paper in the journal One Earth reports that warming is accelerating and that the average global temperature over the last three years exceeded 1.5°C; the authors say key planetary tipping points such as Greenland ice-sheet melt and Amazon dieback are at heightened risk of triggering cascading changes.

A paper published in the journal One Earth reports that global warming is accelerating and raises the risk of crossing planetary tipping points. The authors note the recent three-year global temperature average exceeded 1.5 degrees Celsius, while the Paris threshold is judged over a 20-year average. They cite signs of destabilization in major systems including the Greenland and West Antarctic ice sheets and warn that some natural carbon sinks are weakening. The paper characterizes the prospect of linked tipping points as a growing concern, while saying the most extreme outcome is not yet realized. Key reported observations: - The One Earth paper reports that recent warming has accelerated and that the last three-year average temperature exceeded 1.5°C, though the 20-year average used for official Paris Agreement assessments has not yet been surpassed. - The authors report carbon dioxide levels are at their highest in at least 2 million years and that the planet is likely as warm as or warmer than any time in the last 125,000 years. - The paper notes signs of destabilization in major systems, including the Greenland and West Antarctic ice sheets, and increasing stress on forests and ocean carbon uptake. - Scientists in the paper describe a risk that crossing one tipping point (for example ice-sheet melt) could increase the likelihood of others (for example rainforest dieback), potentially producing cascading changes. Summary: The authors conclude the world is approaching thresholds where interconnected tipping points could accelerate climate change, with several major systems already showing concerning signs. They state the most severe "hothouse Earth" outcome is not observed now but that the risk is higher than previously assessed. Undetermined at this time.