Using Specific Language to Describe Risk and Probability

Good assessment of environmental issues, such as climate change, requires effective communication of the degree of uncertainty associated with numerous possible outcomes. One strategy that accomplishes this, while responding to people’s difficulty understanding numeric probability estimates, is the use of specific language to describe probability ranges. This is the strategy adopted by the Intergovernmental Panel on Climate Change in their Third Assessment Report. There is a problem with this strategy, however, in that it uses words differently from the way lay readers of the assessment typically do. An experiment conducted with undergraduate science students confirms this. The IPCC strategy could result in miscommunication, leading readers to under-estimate the probability of high-magnitude possible outcomes.