An international group of climatologists, including a renowned Rutgers specialist, say scientists are improving their ability to communicate more effectively despite the fact that they have long struggled to find the best way to convey important data about future sea level rise.
The implications of improving communication are huge, the researchers said, as civic leaders actively incorporate climate scientists’ risk assessments into major planning efforts to counter some of the effects of rising seas.
Writing in Nature Climate Change, scientists examine the language and graphics used in climate “assessment” reports from 1990 to 2021 by members of the UN’s Intergovernmental Panel on Climate Change (IPCC).
“Future sea-level rise results from many different processes,” said Robert Kopp, lead author of the study and professor in the Department of Earth and Planetary Sciences at Rutgers School of Arts and Sciences. “The challenge is that we understand the physics of some of these processes quite well—for example, how the ocean receives heat and expands in response so we can quantify and mediate these risks. But other processes, particularly some of those acting on ice sheets, involve factors that are not so well understood and difficult to quantify, but could nevertheless cause rapid sea-level rise.
That means, statistically speaking, future sea level change is characterized by two different types of uncertainty, said Kopp, who is director of the Megalopolitan Coastal Transformation Hub, a 13-institution, National Science Foundation-funded partnership led by Rutgers et al. -Director of the Rutgers Office of Climate Action.
“There is quantifiable uncertainty that can be measured and presented with some degree of confidence,” he said, “and then there is ambiguity, a form of deep uncertainty that cannot be quantified well.”
The analysis shows aspects of sea level rise where the level of risk could be quantified, presented accurately and communicated effectively to public authorities.
But the language in the reports often failed to convey uncertainties about sea level, which were and remain difficult to quantify, either oversimplifying projections or conveying information in confusing ways, according to the analysis. Such language could lead policymakers to overlook the risks associated with possible peak sea-level outcomes.
Ambiguity arises in situations where analysts can interpret a common set of facts in very different ways or cannot interpret them at all, Kopp said.
“Sea level projections only a few decades into the future and under lower emissions scenarios show less ambiguity than projections over the long term and under higher emissions scenarios,” he said.
The study contrasts the language used to express ambiguities about the risk of end-of-century sea-level rise in the IPCC’s 1990, 1995, 2001, 2007, 2013 and 2021 reports, along with the 2019 UN Special Report on Oceans and the Cryosphere in a Changing Climate.
In the First Assessment Report, published in 1990, the authors characterized rapid disintegration of the West Antarctic Ice Sheet due to global warming as “unlikely within 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-expected breakup of sea ice shelves, a sudden, widespread onset of sea ice sheet instability. and the instability of sea ice reefs around Antarctica.’
The report goes on to explain that the processes are characterized by “deep uncertainty”. It concludes: “In an unlikely high-impact story, such processes at high emissions could combine to contribute more than one additional meter of sea-level rise by 2100.”
