Scientists question the use of “tipping point” metaphor in climate change discussions

A group of scientists, including researchers from Rutgers University-New Brunswick, Princeton University and Carleton University, has questioned the accuracy and utility of the metaphor “tipping point” in calling attention to the threat of climate change.

The phrase, while perhaps initially useful as a clarion call that warns about sudden, drastic changes, may now be confusing the public and impeding action, researchers said.

Writing a perspective in Nature Climate Change, the scientists, from the Rutgers Climate and Energy Institute, Princeton’s Center for Policy Research on Energy and the Environment, and Climate Resilient Societies through Equitable Transformations (ReSET) Lab at Carleton University as well as six other academic institutions, argue that the notion of tipping points, when referencing physical and human aspects of the Earth’s changing climate, is not well-defined and often applied inappropriately. There also is no evidence, they said, that the apocalyptic tone of the phrasing is driving action.

The researchers said the public is more likely to respond to threats that are perceived as relatively certain, near-term and nearby than to what are viewed as abstract dangers, the timing of which are either highly uncertain or unpredictable.

“While many of the physical phenomena bundled under the ‘tipping points’ label are systemically important and well worth studying, the tipping-points framing does not necessarily highlight – and may obscure – their most critical or consequential aspects,” said Robert Kopp, the paper’s first author, a Distinguished Professor in the Department of Earth and Planetary Sciences at the Rutgers School of Arts and Sciences, and a Visiting Fellow at the Princeton School of Public and International Affairs.

Social science research, the authors said, indicates that constructive collective action is more likely to be inspired by identifiable “focusing events” tied to climate change – such as widespread wildfires, protracted drought and intense heat waves and flooding – than by the more abstract and loosely applied notion of climate tipping points.

The phrase "tipping point" is a metaphor that describes a critical point in any system when a small change leads to a significant and often irreversible larger-scale change. An event occurs, a threshold is crossed and a system reorganizes and doesn’t return to its original state. In climate science, the United Nations Intergovernmental Panel on Climate Change uses the term to refer to “critical threshold[s] beyond which a system reorganises, often abruptly and/or irreversibly.”

The expression, Kopp said, entered widespread use in popular culture in the early 2000s with the popularity of Malcolm Gladwell’s bestselling The Tipping Point: How Little Things Can Make a Big Difference. Gladwell, a New Yorker writer, defined a tipping point as "the moment of critical mass, the threshold, the boiling point” and applied it as a principle underlying several sociological trends, from the rise in popularity of Hush Puppies shoes to steep declines in crime rates.  

In subsequent years, climate scientists adapted the term to apply to phenomena such as the potential collapse of the Atlantic Meridional Overturning Circulation, the West Antarctic Ice Sheet and coral reef ecosystems.

“Tipping points” and their multiple uses in science and beyond aren’t well defined and provide an illusion of precise scientific understanding, the authors said.

“Attempts to subsume so many issues and behaviors under the same label and common interpretive framework do not advance science,” said co-author Michael Oppenheimer, the Albert G. Milbank Professor of Geosciences at Princeton University.

As the use of “tipping points” has expanded to describe not only climatic events but social ones – ranging from social cohesion to food prices – its all-encompassing use has rendered it necessarily vague. This is not helpful toward inspiring action, the authors said.

“Democracies are more likely to act after collective recognition of an identifiable focusing event – like a destructive wildfire or disruptive energy fuel shortage –

that provide political openings for existing policy communities  to advance recognized remedies,” said co-author Rachael Shwom, a professor in the Department of Human Ecology at the Rutgers School of Environmental and Biological Sciences.

Confusion may arise when discussions erroneously conflate temperature-based policy targets, such as the goal of not exceeding a global average temperature increase, with climate tipping points, the authors wrote. It would be a mistake to allow science to be wrongly perceived as identifying precise thresholds for catastrophic outcomes when the timing of such thresholds is deeply uncertain. This could lead to a “false alarm” effect that may reduce the credibility of future claims should those catastrophic outcomes fail to occur when the anticipated thresholds are crossed, they said.    

“Every fraction of a degree matters: 1.45°C is bad, and 1.55°C is worse,” said co-author Elisabeth Gilmore, an associate professor of environmental engineering at Carleton University, a visiting professor at the Rutgers Bloustein School of Planning & Public Policy and corresponding author on this manuscript. “Yet many in the media and the public appear to think that 1.50°C is of special physical significance or a threshold after which climate mitigation is not worth undertaking. Quite the opposite is the case: the warmer Earth becomes, the greater the need to promptly reduce emissions and expand efforts to build resilience and adapt to a hotter planet.”

The scientists said they aren’t the first to raise concerns about employing “tipping point” in public discourse about climate change. In 2006, in the midst of an initial surge of popularity surrounding the phrase, editorial writers at Nature critiqued the phrase in an essay for its overemphasis on deeply uncertain science and the risk that such a focus could lead to fatalism.

“Scientific framings that are intended to be policy-relevant ought to be subject to scientific scrutiny,” Gilmore said. “To the extent scientists continue to talk about tipping points, the communicative effects of that framing should be a topic of research.”

Regardless of the threat of tipping points, climate change is already causing demonstrable and obvious harm around the world, said Kopp, who also is director of the Megalopolitan Coastal Transformation Hub, a 13-institution National Science Foundation-funded consortium that includes Rutgers, Princeton, and Carleton. “The obvious cost in lives and property damage is enough to justify much more aggressive action by countries worldwide,” Kopp said.