In persuading people of the scientific consensus on human-caused climate change, a new study shows that two factors are especially important for increasing awareness — providing numbers and soliciting estimates.

Researchers from the Yale Project on Climate Change Communication analyzed the awareness of climate change among the general American public. Results from the study’s two experiments show that American adults have varying knowledge of human-caused climate change. But providing more quantitative information, as well as first asking participants to make estimates about the extent of scientific agreement on the existence of human-caused climate change both increased the likelihood that participants would make a more accurate guess about the degree of scientific consensus.

“This study affirms that it is important to educate the public that climate scientists (the experts) are convinced that human-caused global warming is happening,” Director of the Yale Project on Climate Change Communication Anthony Leiserowitz said in an email. “Very few Americans currently understand this, and this (and other studies) demonstrate that this is one important factor (among others) that constrains public acceptance and concern about the issue.”

According to research scientist at the Yale School of Forestry and Environmental Studies Jennifer Marlon, who was not involved in the study but has worked on a similar study, understanding how sure scientists are about human-caused climate change “remains a major challenge in most parts of the country.”

The first of the two experiments involved providing the public with numerical data and with non-numerical data to gauge what type of data presentation led survey participants to say that there is a higher level of scientific agreement. The experiment concluded that providing numerical statements led to more accurate estimates of the scientific consensus.

In the second of the two experiments, survey administrators collected respondents’ estimates about the extent of scientific consensus. They found that asking for those approximations beforehand led to more accurate estimates of the scientific agreement after.

“Our studies collectively show that presenting people (just once!) with a simple message stating that, ‘97 percent of climate scientists have concluded that human-caused climate change is happening,’ can lead to substantial shifts in people’s perception of the amount of scientific agreement on the issue,” research associate and lecturer in the Department of Psychology at Princeton University Sander Van der Linden, who was not involved in the study, said in an email. “This change in people’s understanding of how many scientists agree in turn influences key attitudes and, ultimately, public support for the issue.”

Prior research involving surveys of climate scientists and empirical reviews of literature show that there is universal agreement among scientists that climate change caused by humans is a reality. However, when American adults were surveyed in 2013, only 42 percent agreed with the statement that scientists believe in the validity of global warming.

The survey also showed that 28 percent of respondents chose “do not know” in reference to their knowledge of climate scientists’ agreement.

According to Van der Linden, studies and research about climate change are not a simple matter. He said climate change is a complex issue for which not everyone has the tools or resources to learn about in the immediate moment.

Because of that confusion, Van der Linden said, climate change messaging — specifically that humans are causing climate change, and that the phenomenon is occurring now — needs to be made clearer.

According to Leiserowitz, the team plans to study how long the educational effects will last.

“Do they only last for an hour, a day, a week, a month, or does it become permanent knowledge?” he said, noting that the result depends on the source’s reliability and how often the message is reinforced.

Over the last century, temperatures have risen roughly 1.33 degrees Fahrenheit.

 

Correction, April 14

A previous version of this article contained several errors. First, it stated that Dr. Jennifer Marlon is a research assistant, when, in fact, she is a research scientist. It also stated that Sander van der Linden is a research associate and lecturer in Princeton’s Andlinger Center for Energy and the Environment and the Woodrow Wilson School of Public Affairs, when, in fact, he is a research associate and lecturer in the Department of Psychology at Princeton University.

A previous version also misstated that Dr. Sander van der Linden said scientists almost expect the general public to be confused or unsure about climate change research. When, in fact, he said that climate change is a complex issue for which not everyone has the tools or resources to learn about in the immediate moment. Finally, a previous version stated that Dr. Sander van der Linden was not involved in this study. He was involved in a study that was similar to this one on climate change and messaging.