Even if climate protection has fallen out of focus in many countries, climate change is not waiting. Now climate researchers are sounding the alarm again. Accordingly, several components of the earth’s climate system could be closer to their tipping point than expected. The researchers warn that increasing warming and increasing greenhouse gas levels in the atmosphere have further increased the risk of developing into a new “hot period”. This is reinforced by positive feedback in the climate system, which even affects continents. They can cause important stabilizers in the climate system to unbalance each other. Precisely because it is not clear at what temperature for many of these elements they tip over, the danger is acute, according to the team.
Human civilization also owes its current level of development to the climate: after the end of the last ice age around 12,000 years ago, the previously common climate changes calmed down and since then we have lived in an unusually stable, mild climate. “It was this stable phase that allowed agriculture, complex societies and ecosystems to develop and thrive,” explain William Ripple of Oregon State University and his colleagues. But this stable climate is now in acute danger. “Today, temperatures are higher than at any time in the last 125,000 years and atmospheric carbon dioxide concentrations are higher than at any time in the last two million years,” said climate researchers. Global warming has now exceeded 1.5 degrees compared to pre-industrial times for twelve months in a row – the threshold that, according to the Paris Climate Agreement, should actually not be exceeded as the maximum value of warming.
Of tilting elements and feedback
Ripple and his team are now once again clearly showing us what this means for the future of the climate. They have once again examined the current findings on the state of the known feedback loops and tipping points in the climate system and come to the conclusion: Several “adjusting screws” of the earth’s climate system are closer to destabilization than previously assumed. Of the 16 known tipping elements in the climate system – subsystems that tip over the long term and sometimes irreversibly into a new equilibrium at a certain temperature – several are on the verge of tipping over or have already exceeded it. “This is the case for the ice sheets of Greenland and West Antarctica, for the boreal permafrost and the mountain glaciers,” report the researchers. The Amazon rainforest is also on the verge of tipping over.
This is promoted by positive feedback in the climate system – interactions that further intensify climate change. “Such reinforcing feedbacks increase the risk of accelerated warming,” explains Ripple. “For example, melting ice and snow, thawing of permafrost, forest dieback and loss of soil carbon can increase warming – and in turn influence the climate system’s sensitivity to greenhouse gases.” Such feedback also poses a risk that the tipping of one climate element will result in a whole cascade of destabilization: “When an element tips over, it also pushes other systems over their thresholds and thus triggers the cascade,” explain Rippel and his team.
The danger is that such a cascade of tipping processes will further fuel climate change and put the Earth system on an almost irreversible path towards a “greenhouse” Earth. “This would be a development path in which mutually reinforcing feedbacks bring the climate system past a point of no return,” explain the climate researchers. “This pushes the planet into a regime with substantially higher long-term temperatures.” This could then no longer be reversed by later emission reductions – at least not over the course of human timescales.
The danger is still underestimated
According to climate researchers, the risk of such a new “hot period” is still underestimated by politicians and the public. It is often stated that the specific threshold values for many tilting elements have not yet been precisely defined. But it is precisely these uncertainties in the climate forecasts that do not reduce the danger, they actually increase it: “The risks we describe are worrying not only because of their magnitude, but also because of their uncertainty,” emphasize Ripple and his team. Precisely because the exact thresholds for some tilting elements are still unclear, there is a risk that warming in the immediate future will be enough to destabilize them.
Despite the existing uncertainties, there is an increasing number of models and analyzes that predict a tipping point for some elements if the warming exceeds 1.5 degrees. “The model results indicate that even temporarily exceeding this value increases the risk of tipping by up to 72 percent compared to adhering to this limit,” said Ripple and his colleagues.
According to the researchers, the inherent uncertainties of climate forecasts should be seen as a signal that efforts to contain and adapt to climate change urgently need to gain momentum. “Existing approaches to climate protection, including the expansion of renewable energies and the protection of carbon-storing ecosystems, are crucial to limiting the rise in global temperatures,” said Ripple. Politicians and the public are inadequately informed about the risks that could lead to a new hot period. “We must act quickly to take advantage of rapidly diminishing opportunities and prevent dangerous and uncontrollable climate impacts,” the team said.
Source: William Ripple (Oregon State University, Corvallis) et al., One Earth, doi: 10.1016/j.oneear.2025.101565