Earth on the brink? Looking back on nearly two decades of tipping point research

Before sitting down to write the introduction to the March issue of the Bulletin of the Atomic Scientists, which is all about tipping points, I reached out to three climate scientists who have written at length about tipping points in the Earth system. I wanted to better understand the history of the term, where it had come from, how it was incorporated into climate science, how the idea evolved and changed over time, and why it remains contentious.

Tim Lenton, the founding director of the Global Systems Institute at the University of Exeter, was the lead author of the 2008 paper that formally introduced the idea of tipping points within the Earth’s climate system. We discussed the term’s origins, why the phrase caught on among scientists and non-scientists alike, how it’s changed over the years, and why Lenton has turned his attention to “positive tipping points.”

David Armstrong McKay is a lecturer and researcher at the University of Sussex and the lead author of a 2022 paper that reassessed the risk of all the tipping elements first identified by Lenton and his colleagues in 2008. We discussed the inherent uncertainty around tipping points, and why it’s a useful framework despite those uncertainties.

Thomas Stocker, a professor of Climate and Environmental Physics at the University of Bern, was the lead author of a 2024 article that argued for the necessity of a robust assessment of tipping points by the Intergovernmental Panel on Climate Change (IPCC) to establish much needed consensus on the topic. We discussed the importance of regional tipping points, how the phrase has divided the scientific community and generated vigorous debate, and why the IPCC should conduct an assessment of the likelihoods and uncertainties associated with tipping points.

Of course, after three in-depth interviews, I was only able to incorporate a fraction of their insights into my introduction (which can be found here). But the conversations were so informative and wide-ranging that I thought them worth publishing in full; they are below, lightly edited and condensed for readability.

Tim Lenton

‘The riskometer has been going up all the time’

Lenton, the founding director of the Global Systems Institute at the University of Exeter, was the lead author of the 2008 paper that formally introduced the idea of tipping points in the Earth’s climate system.

Thomas Stocker

‘Notoriously difficult to investigate and even more difficult to predict’

Thomas Stocker, a professor of Climate and Environmental Physics at the University of Bern, was the lead author of a 2024 article that argued for the necessity of a robust assessment of tipping points by the IPCC to establish much needed consensus

David Armstrong McKay

‘Metaphors can grow legs’

David Armstrong McKay is a lecturer and researcher at the University of Sussex and the lead author of a 2022 paper that reassessed the risk of all the tipping elements first identified in 2008.