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1.5C of global warming is a physical limit

According to the World Meteorological Organization (WMO), 2023 is by far the warmest year on record, and 2024 may become even warmer. After eight months of record warmth, the last 12 months were officially 1.5°C above pre-industrial levels.

The world is already at 1.2°C of warming (10-year average), and emissions have not fallen yet, meaning that the 1.5°C threshold, as set in the Paris Agreement, is approaching quickly. Beyond that threshold, scientists predict that the impacts of climate change will rapidly escalate. There is even the risk that we permanently shift away from the Earth’s current climate, which would have a catastrophic impact on people and ecosystems.

According to Johan Rockström, director of the Potsdam Institute for Climate Impact Research, Earth’s powerful biophysical processes could get the temperature down to a safe state if we quickly stop emitting fossil fuels and drastically change how we use land and resources. But only so if we do not cross the tipping points of these processes.

Current climate models assume that we can keep relying on these processes, but research has repeatably shown that we can’t if we continue heating up the planet. And, at 1.2°C, we’re already pushing some of them to their limits.

So far, climate scientists have identified 16 tipping elements elements that regulate Earth’s climate, and 5 of them are likely to collapse at 1.5°C of warming. Each tipping element has multiple stable states (think frozen or liquified ice sheets), and at a specific point, they change from self-cooling to self-warming or from carbon sink to carbon emitter. This change won’t happen overnight, but it would be unstoppable, and the result could be irreversible. Limiting global warming to 1.5°C won’t be enough to protect these systems. In fact, we’ll likely cross the threshold of 5 of them.

List of tipping elements

There is also the risk that interacting positive feedback loops, which are the self-amplifying physical and biochemical properties of these processes, amplify each other and further accelerate climate change. In climate change science, a feedback loop is a physical or biochemical mechanism that accelerates or slows down global warming. In a recent study, scientists have managed to identify 41 different feedback loops, the majority of which are driving up global warming. They can interact and amplify each other, effectively accelerating global warming even faster than they do on their own.

Tipping elements and feedback loops are well understood on their own, but their cumulative effects are not. When interacting feedback loops amplify each other and push one tipping element past its threshold, this could initiate a cascade (a domino-like chain reaction), where one point is crossed after another. And it is precisely these risky interactions that are not yet implemented in IPCC climate models.

Scientists are calling for urgent action because these findings could mean that we have underestimated the impacts of climate change and that the proposed mitigation pathways are inadequate.

The truth is that we have already left the safe and just threshold of 1°C warming behind us and that every additional 0.1°C of warming will cause more damage and suffering than the previous one. As the severe impacts of climate change are already being felt, it’s too late to prevent it from happening, but there is still time to limit the harm. So, let’s get to work, and make sure that social tipping points are the only ones we cross.

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