Researchers present a new measure of carbon load on the climate system and warn: the land, sea, and air began to change as early as the 30s
Scientists are warning that the Earth may be approaching a climate tipping point, with new stress-based metrics showing that our planet's resilience has been weakening for almost a century.
New research, led by the International Institute for Applied Systems Analysis (IIASA), suggests that Earth's carbon-climate system may be more vulnerable than previously thought. The researchers have taken a broad, systemic look at how the planet responds to environmental stresses from human activity, providing a more comprehensive view than conventional climate models.
The study was published in the journal Science of the Total Environment, and involving researchers from IIASA and Lviv Polytechnic University in Ukraine. The team presented an innovative method for assessing the impact of human activity on the planet by converting carbon emissions into quantitative measures of “stress” and “strain” – terms borrowed from the physics of materials.
"Until now, the scientific community has measured the state of the Earth mainly in tons of carbon per year," explains Dr. Matthias Jonas, from the Advanced Systems Analysis Program at IIASA and lead author of the paper. "That's important, but it doesn't show how the entire Earth system responds as a physical body to the increasing load we put on it. We wanted to see how much the system stretches and deforms under this weight."
New concept: "voltage intensity"
One of the key findings of the study is the introduction of a new concept – “Stress Power”, which describes the rate of energy that human activity adds to each unit volume of the Earth system. In 2021, the stress power was estimated to be in the range of 12.8 to 15.5 Pascals per year. While such pressure is equivalent to the pressure exerted by a light wind, its cumulative effect – when applied to the Earth’s land surface, oceans and atmosphere – can shift the system from its natural equilibrium.
In a system that is not disturbed by man-made climate change, both stress and strain should remain close to zero.
A hidden turning point in Earth's response
The researchers also analyzed the system's "delay time"—the time it takes for the Earth's carbon system to respond to stresses—and identified a significant shift between 1925 and 1945. This finding suggests that the Earth's climate system began to change its response patterns as early as the first half of the 20th century, earlier than previously estimated.
“This tipping point surprised us,” says Jonas. “It suggests that continents and oceans may have stopped behaving the way they used to in the early decades of the last century. After that, these systems simply couldn’t handle the strain of human activity—and eventually stopped absorbing carbon dioxide as efficiently as they had in the past.”
Should countries act sooner than expected?
A key conclusion of the researchers is that even if countries around the world meet their emissions targets, it may not be enough. The increasing fragility of Earth's natural systems requires immediate attention – not only to the amount of emissions, but also to how the planet itself responds to them.
“Meeting future emission reduction targets is important, but we must also pay attention to the rate at which the Earth itself becomes more fragile,” Jonas emphasizes. “Even if we meet the targets, the weakening of natural systems may lead to serious disruptions sooner than expected. This change in timing – where the Earth becomes more fragile – is not yet represented in climate models, but it must be incorporated.”
The scientific team calls for further research to quantitatively examine this tipping point, and to integrate their approach into global metrics and models. They hope that moving beyond simply measuring carbon quantities to understanding how the Earth physically responds to the load will help the world better prepare for future challenges.
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