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How Does the Public Perceive Climate Change?



David Budescu, Ph.D., the Anne Anastasi Chair in Psychometrics and Quantitative Psychology.
Photo by Chris Taggart

Scientists describing phenomena such as global warming would be better served by using both numbers and verbal terms to communicate their findings, according to a new study by a group of researchers led by a Fordham University professor.

David Budescu, Ph.D., the Anne Anastasi Chair in Psychometrics and Quantitative Psychology, teamed up with researchers in 24 countries to measure how well the public understands phrases such as very likely, likely,unlikely and very unlikely when reading the findings of climate change research. These terms are among seven simple qualifiers used by the Intergovernmental Panel on Climate Change (IPCC) to describe scientists’ research findings to policymakers and the public.

In the context of the reports, each term is meant to correspond to a range of numerical probabilities (e.g., very likely refers to 90 percent or higher probability, and unlikelymeans 33 percent or lower  probability).

But Budescu’s research revealed that the public usually interprets the verbal terms in a conservative fashion – meaning less extreme, and closer to 50 percent than the scientists had intended.

The study asked over 11,000 volunteers in 24 countries (and in 17 different languages) to provide their interpretations of a the intended meaning and possible range of 8 sentences form the IPCC report that included the various phrases. For example, one sentence read: “It is very likely that hot extremes, heat waves, and heavy precipitation events will continue to become more frequent.” Only a small minority of the participants interpreted the probability of that statement consistent with IPCC guidelines (over 90 percent), and the vast majority interpreted the term to convey a probability in around 70 percent.

However, supplementing the verbal phrases with numbers considerably improved communication, the report said. The benefits of the dual presentation (words + numbers) were especially large for the most extreme words where it doubled the rate of interpretations consistent with the IPCC guidelines

These findings replicate previous results of Budescu and colleagues in US samples. Climate change is a global problem and the IPCC is an international body that seeks to reach people in all countries, and cultures. The new study shows that the problem – systematic misinterpretation of the communication –  is also universal, and the proposed solution – combining numbers and verbal terms – also works in every country. In fact, one of the most encouraging results of the study was the finding that the revised presentation format increased the agreement between the interpretation of the various sentences across countries and languages and is likely to facilitate communication of experts and policy makers.

The researchers recommended that the IPCC use both words and numbers to communicate uncertainty and probability in all its future reports.  This alternative communication format is more flexible, it appeals to all — people who prefer numerical presentations and those who favor natural language – and would improve greatly the public’s understanding of the IPCC reports’ findings. The results of the study have been published in the April 20 edition of Nature Climate Change.


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