Are students influenced more by analyzing local or global examples of the biological impacts of climate change? Using a randomized trial in a large, introductory undergraduate biology course, we found that a single in-class activity led to a 45% increase in the frequency of correct answers on a test of conceptual understanding. Additionally, after completion of the activity, students more strongly believed that climate change would alter their lives, were more willing to modify their own behavior, and indicated more support for government action to address climate change. There was also a robust gender effect on the influence of local versus global examples: females learned better if they studied local examples. Women reported greater willingness to alter their behavior than men, and students with higher university grades were more likely to support government action to mitigate climate change. Our findings support the use of local examples in curricula and illustrate the power of large, randomized trials in determining effective methods in climate-change education.