To assess the effectiveness of climate change communications, it is important to examine their long-term impacts on individuals’ attitudes and behavior. This article offers an example study and a discussion of the challenges of conducting long-term investigations of behavioral change related to climate change communications (a vital and underresearched area). The research reported is a longitudinal panel study of the impacts on UK viewers of the climate change movie The Age of Stupid. The heightened levels of concern, motivation to act, and sense of agency about action that were initially generated by the movie did not measurably persist over the long term. The results also show that behavioral intentions do not necessarily translate into action. Data analysis raised issues concerning the reliability of participants’ causal attributions of their behavior. This and other methodological challenges are discussed, and some ways of avoiding or lessening problems are suggested.