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For decades, climate researchers have cautioned that Earth’s complex systems are not infinitely resilient. Now, a new synthesis published in One Earth suggests that humanity may be far closer to triggering irreversible planetary changes than previously believed. The authors—including renowned climate scientists Hans Joachim Schellnhuber of the International Institute for Applied Systems Analysis (IIASA) and Johan Rockström of the Potsdam Institute for Climate Impact Research (PIK)—warn that the world is approaching a threshold beyond which a self‑reinforcing “Hothouse Earth” state could emerge.
Their message is stark: the stability that has allowed human civilization to flourish for more than 11,000 years is under acute threat.
A Planet Approaching Its Limits
Earth’s climate has always fluctuated, but since the end of the last Ice Age it has remained within a remarkably stable temperature band. This stability enabled agriculture, cities, and complex societies to develop. But the rapid combustion of fossil fuels since the Industrial Revolution has pushed the planet out of this equilibrium with unprecedented speed.
The new analysis highlights a troubling possibility: several major climate “tipping elements”—systems that, once pushed beyond a critical threshold, begin to change irreversibly—may be closer to collapse than previously assumed.
Among the most concerning:
Melting Ice Sheets
The Greenland and Antarctic ice sheets are losing mass at accelerating rates. Their collapse would lock in several meters of sea‑level rise, reshaping coastlines and displacing millions.
Thawing Permafrost
Vast stores of carbon and methane lie frozen in Arctic soils. As permafrost thaws, these potent greenhouse gases escape, amplifying warming in a dangerous feedback loop.
Shrinking Rainforests
The Amazon and other tropical forests are approaching a point where drought, deforestation, and fire could transform them from carbon sinks into carbon sources.
Weakening Ocean Circulation
The Atlantic Meridional Overturning Circulation (AMOC)—the system that includes the Gulf Stream—has shown signs of weakening. A collapse would dramatically alter weather patterns, particularly in Europe, and disrupt marine ecosystems.
Rockström describes these developments as evidence of “a loss of planetary resilience,” with feedbacks pushing the climate system toward instability.
The 1.5°C Threshold: Already Behind Us?
For the first time, global temperatures have remained at or above 1.5°C above pre‑industrial levels for twelve consecutive months. While the Paris Agreement evaluates such thresholds using 20‑year averages, the sustained spike suggests that the long‑term trend may already be brushing against the 1.5°C limit.
The consequences are increasingly visible: more intense heatwaves, prolonged droughts, destructive floods, severe cold snaps, and record‑breaking wildfires. Rising greenhouse gas concentrations remain the primary driver, but the recent decline in atmospheric aerosols—tiny particles that reflect sunlight—may also be contributing to short‑term warming.
“It is likely that global temperatures are now as warm, or warmer, than at any time in the past 125,000 years,” says co‑author Christopher Wolf. The pace of change, he adds, is outstripping many scientific projections.
A Systemic Risk, Not a Distant Threat
Schellnhuber argues that climate change has shifted from a long‑term environmental issue to a “profound systemic danger.” The risk is not merely higher temperatures, but the potential for cascading failures across interconnected Earth systems.
The authors call for:
- Rapid and coordinated global emissions reductions
- Enhanced monitoring of tipping elements
- Stronger international climate commitments
- Investment in resilience and adaptation strategies
Current national pledges would put the world on a trajectory toward roughly 2.8°C of warming by 2100—far beyond what scientists consider safe.
Even if the exact tipping thresholds remain uncertain, the researchers emphasize that uncertainty is not an excuse for inaction. On the contrary, it heightens the urgency.
A Narrow Window of Opportunity
Despite the alarming findings, the authors stress that humanity has not yet crossed into an unavoidable “Hothouse Earth” pathway. But the margin for error is shrinking rapidly.
“Our work shows that we are not there yet—but very close,” Rockström warns.
The coming years will determine whether the world stabilizes the climate system or triggers changes that unfold over centuries and reshape the planet for millennia.
The choice, the scientists argue, is still ours to make.
- Hector Pascua with reports from vienna.at/picture: pixabay.com
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