Jan Crusius

Across the last 150 years, global CO 2 emissions have grown at an increasing, exponential pace. Based on the well‐documented tendency to underestimate such exponential growth, we hypothesize and test in three studies (total N = 1796, including one nationally representative US sample) that people would fail to understand the historical, exponential growth of global CO 2 emissions. However, we also show that providing a simple rule of thumb can serve as an effective educational boost that helps overcome this biased perception. Participants who were provided with the heuristic that historically, global CO 2 emissions have doubled every thirty years provided highly accurate estimates of past emission levels. Compared to participants who relied on intuition, those who applied this doubling heuristic avoided common errors in understanding the current state of the climate change threat and made more realistic expectations of the future consequences of uninterrupted growth. Together, these studies show that overcoming the exponential growth bias helps people form more accurate perceptions of historic CO 2 emissions growth and understand the difficulty of curbing future emissions.