The Perception of Daily Temperatures as Evidence of Global Warming

Unlike the scientific definition of global warming (GW), public discussion often links the existence of GW to daily temperatures rather than long-term averages. Previous research found that daily weather is perceived as personal experiences with GW. Additionally, prior beliefs about GW can affect interpretations of such experiences as evidence for the existence of GW. However, previous studies demonstrating that beliefs affect interpretations of experiences were based on correlational designs—limiting causal inferences—and relied only on self-reports of remembered personal experiences instead of direct interpretations of weather. The authors present the first randomized experiment investigating how people interpret daily temperatures in terms of the evidence that it provides about GW, clarifying the psychological causes for different interpretations of the same experiences across individuals. They test the influence of knowledge about (and beliefs in) GW on the interpretation of daily temperatures across two framing conditions labeled weather (interpreting a temperature as abnormal weather) and climate (interpreting a temperature as evidence of GW). The authors use signal detection theory to measure the decision-maker’s (a) ability to discriminate between temperatures, called sensitivity, and (b) threshold for describing a temperature as abnormal, called the decision threshold. The results replicate previous research finding a motivational distortion in interpreting temperatures as evidence of GW and further find belief-consistent distortions in decision thresholds while observing no measurable change in sensitivity. In other words, people know when temperatures are abnormally hot, but classify ambiguous events (i.e., less extreme abnormalities) differently based on their beliefs in GW.