Climate change mitigation requires changes in greenhouse gas emitting behaviours. This dissertation aims to provide insights into the influences of behaviour change for two high-impact pro-environmental behaviours: climate policy support and consumption of animal products. It does so by using quasi-and randomized experiments and by monitoring changes in behaviour over time. Study 1 examined changes in climate policy support and climate change risk perception over the course of a naturally occurring event: seasonal forest fires. It employed growth curve modeling techniques in a structural equation modeling framework to analyze longitudinal relations between these two constructs over time, and to examine growth in climate change risk perception while controlling for the effect of exposure to forest fires and other extreme weather. Indirect exposure to forest fires (e.g., media) had a modest effect on climate change risk perception. Climate change risk perception for individuals with above-mean perceptions of scientific agreement tended to increase faster than for those with below-mean perceptions. Individuals whose climate change risk perception grew at a faster-than-average rate tended to also grow at a faster-than-average rate for climate policy support. Study 2 provided insight into the psychological influences on consumption of animal products and on willingness to reduce. Following a comprehensive literature review, known influences were examined using Latent Profile Analysis to identify groups of individuals with similar perceptions of facilitators of meat consumption and obstacles to reducing it. Three groups were identified: stronghindrance meat eaters, moderate-hindrance meat eaters, and reducers. Validation variables confirmed the practicality of the three profiles: groups differed in their current consumption of animal products and in their willingness to reduce. Using these findings, three group-matched interventions were designed in Study 3. Intervention design was informed by four behaviour-iv change frameworks. Participants were randomly assigned to one of four conditions: control condition, implementation-intention condition, information-and-healthy-recipe condition, and information-and-substitution condition. Then, they completed up to 28 days of food diaries.Multilevel model analyses were employed to examine changes in the consumption of animal products over time. Participants reduced their consumption by 20 grams of CO2 per day on average. Individuals that were randomly assigned to an intervention condition that matched their meat-eater profile reduced their consumption of animal products by 40 grams CO2 per day on average. Taken together, these studies highlight the importance of considering individual differences (i.e., tailoring) when designing pro-environmental behaviour interventions. v