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Assessment of how climate scientists communicate risk shows imperfections, improvements

The hardest part, experts find, is communicating ‘unquantifiable’ uncertainty

For Immediate Release Jun 20, 2023

BLOOMINGTON, Ind. — Scientists are finding new ways to present crucial facts about the complex science of future sea-level rise, according to research led by an Indiana University professor and an international group of climate scientists.

Jessica O'Reilly Jessica O'ReillyTheir analysis, published in Nature Climate Change, reveals that the consequences of improving communications are enormous, as civic leaders actively incorporate climate scientists’ risk assessments into major planning efforts to counter some of the effects of rising seas.

To conduct their analysis, scientists reviewed the language and graphics used in climate assessment reports from 1990 to 2021 by members of the United Nations’ Intergovernmental Panel on Climate Change. One area those reports focused on was the process for assessing risk of sea-level rise from the disintegration of the West Antarctic Ice Sheet.

Cultural anthropologist Jessica O’Reilly, an associate professor in the IU Hamilton Lugar School of Global and International Studies, studies scientists and the impact of their research on environmental policy and governance. She is also an expert on Antarctic science and policy.

“Decision-makers need information about the timing of this ice sheet disintegration and how it will affect their local communities; scientists, though, still have some uncertainties around their projections,” O’Reilly said. “Uncertainties cannot be reduced to zero when we’re talking about climate models, but they can be quantified and narrowed down.”

According to O’Reilly and her co-authors, statistically speaking, future sea-level change is characterized by two types of uncertainty. The first is quantifiable uncertainty, which can be measured and presented with a degree of confidence. The second, ambiguity, cannot be measured quantitatively.

As the only social scientist on the research team, O’Reilly contributed analysis around this notion of ambiguity.

“IPCC authors have become increasingly adept at describing and communicating uncertainties in a way that is useful for decision-makers,” O’Reilly said. “Our article takes this a further step by exploring concrete techniques to express ambiguity. ‘Ambiguity,’ or deep, unquantifiable uncertainty, is about navigating complex science when parts of processes aren’t well understood, or experts have deep disagreements about the information at hand.”

The analysis shows that aspects of sea-level rise where the risk level could be quantified have been presented accurately, informing public bodies effectively.

But when conveying sea-level uncertainties that have been and remain difficult to quantify, the language in the reports often has fallen short — either oversimplifying projections or conveying the information in a confusing manner, according to the analysis. Such language could lead policymakers to neglect the risks associated with possible high-end sea-level outcomes.

To identify such consequential mistranslations of scientific projections, O’Reilly said her research analyzed the IPCC assessment through the notion of “boundary chains.”

“Boundary chains are specific tracks that science and policy information travel, requiring translation between fields of expertise, governments and the general public,” O’Reilly said. “This builds upon IU Sociology Professor Emeritus Thomas Gieryn’s pioneering concept of ‘boundary work’ that demarcates scientific knowledge from other kinds of knowledge, like policy.”

The study contrasts the language used to convey ambiguities in the risk of late-century sea-level rise in the IPCC reports in 1990, 1995, 2001, 2007, 2013 and 2021, along with the IPCC’s Special Report on the Ocean and Cryosphere in a Changing Climate issued in 2019.

In the First Assessment Report, released in 1990, the authors characterized a rapid disintegration of the West Antarctic Ice Sheet because of global warming as “unlikely in the next century.”

In contrast, in the Sixth Assessment Report, published in 2021, scientists warn that higher rates of sea-level rise before 2100 could be “caused by earlier-than-projected disintegration of marine ice shelves, the abrupt, widespread onset of marine ice sheet instability and marine ice cliff instability around Antarctica.”

The report goes on to explain that the processes are characterized by “deep uncertainty.” It concludes: “In a low-likelihood, high-impact storyline, under high emissions such processes could in combination contribute more than one additional meter of sea-level rise by 2100.”

Communicating complex future scenarios to the public in an effective manner is an ongoing process. If the approach taken in the most recent climate report in 2021 is successful, it will be accurately reflected in future regional assessments and will ultimately be judged by policymakers, along with climate and social scientists.

It matters that scientists get it right, the study concludes.

“We are at a critical decade for making decisions that can exacerbate or solve the climate problem,” O’Reilly said. “Our article contributes to facilitating informed decision-making.”

O’Reilly led the study with Robert Kopp, professor in the Department of Earth and Planetary Sciences at the Rutgers School of Arts and Sciences, and Michael Oppenheimer, a Princeton University climate scientist who has served with the IPCC since the First Assessment Report.

The other authors in the study, all of whom were involved with the Sixth Assessment Report, include those from Brown University and the University of Buffalo in the U.S., as well as others in China, France, Germany, Great Britain, the Netherlands, New Zealand and Singapore.

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Hamilton Lugar School of Global and International Studies

Sarah DeWeese

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