IPCC reports are full of language that makes people doubt man-made climate change.
The United Nations’ Intergovernmental Panel on Climate Change is a big, big production. Its reports, released roughly every five years, are considered the gold standard of climate science, and are always a major media event. Thousands of scientists contribute to the reports, all of them volunteering their expertise to make the world just a little bit better.
There’s just one problem: According to a new paper out in Nature: Climate Change, the IPCC may be dramatically undermining its own work through one of its trademark tools: A system of language that the group uses to describe how certain (or uncertain) researchers are about its scientific findings. According to the new study, this system (which involves describing conclusions as “likely,” “very likely,” and so on) has the unfortunate effect of making people less sure than they ought to be of the IPCC’s most important conclusions.
Unintentionally, then, the IPCC seems to be doing just what climate skeptics and deniers are so often accused of: Sowing doubt.
The new study, by psychologist David Budescu of Fordham University and his colleagues, is actually the latest in a string of papers by these researchers showing that people systematically misunderstand what the IPCC means when it uses phrases such as “likely” and “very likely” to describe the strength of its conclusions. Take, for instance, the IPCC’s famous finding, in 2007, that “most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic [human-produced] greenhouse gas concentrations.” According to Budescu’s research, while the IPCC intends for “very likely” to mean a greater than 90 percent likelihood, that’s not necessarily the message the average person hears. Instead, when Budesco and his colleagues asked members of the public to assign a probability to the term “very likely,” the mean estimate people gave was just 62 percent.