Using a dataset of more than 100,000 meal selections over three years, we examine the long-term effects of an informational intervention designed to increase awareness about the role of meat consumption in climate change. Students randomized to the treatment group reduced their meat consumption by 5.6 percentage points with no signs of reversal. Calculations indicate a high return on investment (conservative estimate: ~$14 per metric ton CO2eq). Our findings suggest that informational interventions can be cost-effective and generate long-lasting shifts towards more sustainable food options.