Climate Tipping Points Could Pose 'Existential Threat'

With this year’s United Nations climate conference set to kick off in Madrid Monday morning, the Earth is in danger of crossing as many as nine crucial climate “tipping points” that represent an “existential threat to civilization”, scientists warn in a commentary published Wednesday in the journal Nature.

“These climate thresholds, such as the decline of ice sheets and loss of biodiverse habitats, could cumulatively trigger a global tipping point,” VICE News reports, citing the article.

“Evidence is mounting that these events could be more likely than was thought, have high impacts, and are interconnected across different biophysical systems, potentially committing the world to long-term, irreversible changes,” corresponding author Tim Lenton, director of the University of Exeter’s Global Systems Institute, told VICE in an email.

The Guardian explains that climate tipping points “are reached when particular impacts of global heating become unstoppable, such as the runaway loss of ice sheets or forests. In the past, extreme heating of 5.0°C was thought necessary to pass tipping points, but the latest evidence suggests this could happen between 1.0 and 2.0°C.” The paper notes that average global warming has already hit 1.0°C, and is sure to go higher due to greenhouse gas emissions that are still increasing at an accelerating rate.

“A saving grace is that the rate at which damage accumulates from tipping could still be under our control to some extent,” they write. But “the stability and resilience of our planet is in peril. International action—not just words—must reflect this.”

Lenton and his colleagues “acknowledge there is a high degree of uncertainty about the activation and effects of climate tipping points,” VICE states. But “they stress that even the speculative implications demand urgent action.”

“It is our position that, given its huge impact and irreversible nature, any serious risk assessment must consider the evidence, however limited our understanding might still be,” the scientists write. “To err on the side of danger is not a responsible option.”

“As a scientist, I just want to tell it how it is,” Lenton added. “It is not trying to be alarmist, but trying to treat the whole climate change problem as a risk management problem. It is what I consider the common sense way.”

VICE says the commentary divides the nine tipping points into two main categories: loss of the planet’s icy cryosphere through the melting of Arctic, Antarctic, and Greenlandic ice sheets, and biosphere impacts like boreal and Amazon deforestation, loss of coral reefs, and thawing permafrost.

Lenton cites the potential collapse of the Atlantic Meridional Overturning Circulation (AMOC) as the most dangerous tipping point, what VICE calls “its own category of catastrophe”.

The AMOC is a critical flow of ocean currents that “has large, direct effects on climate in heavily-populated regions like western Europe, and also it couples together lots of other tipping points,” Lenton said. “For example, weakening of the AMOC in the past was linked to serious disruption of the West African monsoon and the monsoons in India and South America.”

VICE says the Intergovernmental Panel on Climate Change first began identifying some of the tipping points in its 2001 report. Severn years later, Lenton led a project team that expanded the list in a study for the Proceedings of the National Academy of Scientists.

University of East Anglia environmental scientist Phil Williamson, who was not involved in producing the article, said the latest prognosis “is, unfortunately, fully plausible: that we might have already lost control of the Earth’s climate.”