Earth’s climate systems may be approaching a critical threshold, leading to a potential “hothouse Earth” scenario where global temperatures could remain approximately 5°C (9°F) above preindustrial levels. This alarming possibility is outlined in a recent paper published in the journal One Earth, which highlights the risk of irreversible destabilization of key Earth system components.
The study argues that uncertainties in current climate projections might mean that crucial tipping points, such as the melting of the Greenland Ice Sheet and the thawing of global permafrost, could be closer than previously thought. These tipping points, once crossed, could lead to long-term changes that are irreversible.
“As we move to higher temperatures, we enter higher risk zones,” stated Nico Wunderling, a climate scientist at the Potsdam Institute for Climate Impact Research and Goethe University Frankfurt, and coauthor of the study. Wunderling emphasized that increasing temperatures could trigger interactions between various tipping elements.
Understanding the Uncertainties
Climate models, which simulate Earth systems, are essential tools for projecting the effects of rising emissions on global temperatures, weather patterns, and other critical factors. However, these models are not perfect and contain uncertainties, particularly concerning the sensitivity of Earth systems to elevated carbon dioxide levels and the role of climate feedbacks.
One of the significant challenges in modeling is accurately predicting potential tipping points, such as the weakening of ocean circulation and the dieback of the Amazon rainforest. According to Wunderling, these uncertainties make it difficult to estimate the timing of tipping points reliably, suggesting that some components of Earth systems might be closer to these thresholds than previously believed.
Recent observations have shown that the pace of climate change has exceeded some earlier projections. In 2024, global temperatures briefly surpassed the 1.5°C (2.7°F) threshold above preindustrial levels, a key target of the Paris Agreement, indicating that this limit could be consistently breached in the future. Notably, exceptionally high temperatures in 2023, 2024, and 2025 prompted experts at Berkeley Earth to reconsider their analyses of Earth’s warming rate.
“Warming now seems to have accelerated, which is not something we expected,” said Swinda Falkena, a climate scientist at Utrecht University.
Potential Tipping Points
The paper identifies 16 Earth system components, such as ice sheets, permafrost, and rainforests, that could reach tipping points. Of these, 10 could potentially accelerate global warming if triggered. These include the collapse of major ice sheets, the loss of Arctic sea ice, and the dieback of the Amazon rainforest, among others.
The interactions between these tipping elements could create feedback loops that amplify warming. For instance, melting ice sheets reduce Earth’s ability to reflect sunlight, further increasing temperatures. Additionally, the weakening of the Atlantic Meridional Overturning Circulation (AMOC) could transform the Amazon rainforest into a dry savanna, reducing its role as a critical carbon sink.
Implications of a Hothouse Earth
If enough tipping points are breached, Earth’s climate could be pushed towards a hothouse scenario. Although there is no definitive answer about the likelihood of this trajectory, Wunderling notes that exceeding the 1.5°C (2.7°F) limit set by the Paris Agreement significantly increases the risk of triggering self-amplifying feedbacks.
“While averting the hothouse trajectory won’t be easy, it’s much more achievable than trying to backtrack once we’re on it,” said Christopher Wolf, a research scientist at Terrestrial Ecosystems Research Associates.
Despite the urgency, global efforts to reduce emissions have fallen short. Current projections suggest that Earth is on track to warm by about 2.8°C (5.04°F) by 2100. In 2025, global carbon emissions rose by 1.1% compared to 2024, with the United States seeing a 2.4% increase. The atmospheric concentration of carbon dioxide is likely higher than at any point in the last 2 million years, with average global temperatures warmer than they have been in the past 125,000 years.
The Path Forward
The combination of uncertainty regarding tipping points and rising global temperatures underscores the need for urgent action to combat climate change. The authors of the study stress the importance of achieving net-zero emissions and accelerating mitigation efforts.
“In order to avoid high-end climate risks, it is necessary to go down to net zero, to mitigate as quickly as we can,” Wunderling emphasized.
The world faces a critical juncture in its response to climate change. While the prospect of a hothouse Earth remains uncertain, the potential consequences demand immediate and concerted global action to safeguard the planet’s future.
