It is almost certain that 2023 will go down in history as the warmest year ever recorded by humans, quite possibly surpassing the highest temperatures seen in at least 125,000 years. Numerous temperature records have been shattered, with global average temperatures during certain periods significantly exceeding the 1.5°C mark. Alarming rates of Antarctic sea ice loss, alongside various indicators pointing to rapid climate change, prompt the question: does 2023 mark the onset of a more perilous phase for the climate?
While many anticipate that stressed systems—whether it be the human body, an ecosystem, or a part of the climate system—will respond predictably to increased pressure, this expectation is not always accurate. Some systems exhibit linear changes up to a certain point under stress, beyond which substantial or abrupt alterations become inevitable.
This phenomenon of “nonlinear” changes includes the concept of “tipping points,” where a system, once pushed past a critical threshold, undergoes self-sustaining change. Comparable to rolling a boulder up a hill, reaching the summit creates a precarious balance, and even a minor push, like a gust of wind, can set the boulder on a irreversible descent down the other side.
The climate system encompasses various potential tipping points, such as the disappearance of ice sheets or the transformation of dense rainforests into significantly drier and more open landscapes. Once these tipping points are crossed, recovery becomes exceedingly challenging, if not impossible.
A group of 200 scientists, including ourselves, recently unveiled the Global Tipping Points Report during the COP28 UN climate talks in Dubai. The report delves into the science behind the “negative” tipping points in the Earth system that pose threats to both nature and humanity, as well as potential “positive” societal tipping points that could expedite sustainability measures.
The report identifies over 25 tipping points in the Earth system, spanning air, land, and sea. Six are situated in the cryosphere, including the collapse of massive ice sheets, while sixteen are within the biosphere, encompassing issues like widespread tree deaths in the Amazon and degradation of savannas. Additionally, four potential tipping points are identified in the circulation of oceans and atmosphere.
Human activities are pushing some of these tipping points closer to reality, with uncertainty surrounding the exact thresholds. At the current global warming of 1.2°C, the loss of warm water coral reefs is becoming likely, and tipping in four vital climate systems is possible. Beyond 1.5°C, several of these become likely, and other systems start to become vulnerable.
The consequences of crossing these tipping points are profound, ranging from the loss of biodiversity to economic impacts and exposure of millions to extreme heat. Despite the monumental risks associated with tipping points, most economic assessments of climate change tend to overlook them, a disconcerting finding highlighted in the report.
Beyond the environmental impacts, there is also the potential for negative tipping in human societies, leading to financial instability, displacement, conflict, or polarization. These societal challenges could hinder efforts to limit further Earth system tipping points and potentially shift towards a more authoritarian and hostile social system.
The interconnectedness of Earth’s tipping systems raises the specter of a “tipping cascade,” where triggering one system makes others more likely to tip as well. The report emphasizes that urgent measures, including reducing greenhouse gas emissions to zero, are crucial to mitigate the risks associated with tipping points. Additionally, addressing habitat loss, pollution, and supporting ecological restoration and sustainable livelihoods are vital to prevent tipping points in the biosphere.
The report calls for ambitious governance approaches, urging international bodies such as the UN’s climate talks to incorporate tipping points into their considerations. An update to the understanding of dangerous climate change is deemed imperative.
