Research Article: Carbon innumeracy

Date Published: May 3, 2018

Publisher: Public Library of Science

Author(s): Amir Grinstein, Evan Kodra, Stone Chen, Seth Sheldon, Ory Zik, Juan J. Loor.


Individuals must have a quantitative understanding of the carbon footprint tied to their everyday decisions to make efficient sustainable decisions. We report research of the innumeracy of individuals as it relates to their carbon footprint. In three studies that varied in terms of scale and sample, respondents estimate the quantity of CO2 released when combusting a gallon of gasoline in comparison to several well-known metrics including food calories and travel distance. Consistently, respondents estimated the quantity of CO2 from gasoline compared to other metrics with significantly less accuracy while exhibiting a tendency to underestimate CO2. Such relative absence of carbon numeracy of even a basic consumption habit may limit the effectiveness of environmental policies and campaigns aimed at changing individual behavior. We discuss several caveats as well as opportunities for policy design that could aid the improvement of people’s quantitative understanding of their carbon footprint.

Partial Text

While political action is already underway in multiple countries in response to urgent calls for reductions in greenhouse gas emissions such as the widely discussed carbon footprint [1,2,3] recent political developments in the U.S.[4] create significant uncertainty regarding policies to combat climate change. Thus, as 58% of Americans worry about climate change [5] and since consumers and households significantly contribute to greenhouse gas emissions, it is becoming even more important that part of the burden be carried at the individual level [6,7]. However, individuals are not clear about the relative contribution to greenhouse gas emissions of their behavior [8]. Metrics such as carbon footprint remain unclear, intangible byproducts of day-to-day consumer activities, as well as activities that connect to the consumer through complex material and energy supply chains. Such metrics are largely irrelevant for personal decisions by many individuals.

Ben-Gurion University’s Guilford Glazer School of Business’ Human Subjects Research Committee has approved the project “Carbon Illiteracy: Demonstrating a Prevalent Lack of Quantitative Environmental Intuition” (AG_05022015). Written informed consent was obtained from participants in all our studies.

Results from three studies provide evidence supporting the hypothesis that people have a higher degree of carbon innumeracy tied to consumption than they have for other more commonly practiced and understood metrics like calories and distances (and even more than less practiced metrics like the weight of an average family car). We define estimation error and bias measures and analyze those through mixed effect ANOVA models. Results show that on average respondents consistently estimate the amount of CO2 from one gallon of standard gasoline significantly less accurately than they are able to estimate the number of calories in a gallon of whole milk, the travel distance from Los Angeles to New York City, or the weight of an average family car. The higher estimation error may not come as a surprise since, unlike food calories or distance that are practiced by individuals in everyday life [17], measurements of CO2 are not part of everyday decisions. This innumeracy is also evident in our final survey where CO2 estimates fall short even when compared to respondents’ ability to estimate the weight of an average family car, even though car weight is not a measure that is practiced commonly.