Stephen B. Broomell

Effective communication of uncertainty in the IPCC reports

The Intergovernmental Panel on Climate Change (IPCC) publishes periodical assessment reports informing policymakers and the public on issues relevant to the understanding of human induced climate change. The IPCC uses a set of 7 verbal descriptions of uncertainty, such as unlikely and very likely to convey the underlying imprecision of its forecasts and conclusions. We report results of an experiment comparing the effectiveness of communication using these words and their numerical counterparts. We show that the public consistently misinterprets the probabilistic statements in the IPCC report in a regressive fashion, and that there are large individual differences in the interpretation of these statements, which are associated with the respondents’ ideology and their views and beliefs about climate change issues. Most importantly our results suggest that using a dual (verbal—numerical) scale would be superior to the current mode of communication as it (a) increases the level of differentiation between the various terms, (b) increases the consistency of interpretation of these terms, and (c) increases the level of consistency with the IPCC guidelines. Most importantly, these positive effects are independent of the respondents’ ideological and environmental views.

The Composition of Optimally Wise Crowds

We investigate optimal group member configurations for producing a maximally accurate group forecast. Our approach accounts for group members that may be biased in their forecasts and/or have errors that correlate with the criterion values being forecast. We show that for large forecasting groups, the diversity of individual forecasts linearly trades off with forecaster accuracy when determining optimal group composition.

Anchoring climate change communications

Verbal probability expressions (VPEs) are frequently used to communicate risk and uncertainty. The Intergovernmental Panel on Climate Change attempts to standardise the use and interpretation of these expressions through a translation scale of numerical ranges to VPEs. A common issue in interpreting VPEs is the tendency for individuals to interpret VPEs around the midpoint of the scale (i.e. around 50%). Previous research has shown that compliance with the IPCC’s standards can be improved if the numerical translation is presented simultaneously with the VPE, reducing the regressiveness of interpretations. We show that an explicit statement of the lower or upper bound implied by the expression (e.g. 0–33%; 66–100%) leads to better differentiated estimates of the probability implied by ‘likely’ and ‘unlikely’ than when the bound is not explicitly identified (e.g. less than 33%; greater than 66%).

Eliciting risk perceptions with an online game: preliminary results

We describe a scientific casual browser game called LinkIT for eliciting societal risk perceptions in the form of mental models represented as influence diagrams. Given this knowledge, we can highlight similarities and differences across demographic groups as well as compare individual responses with expert models. These comparisons inform how risk should be best communicated to resolve knowledge gaps and misperceptions. Here we introduce the LinkIT concept, present preliminary results and propose future work.