Email outreach attracts the US policymakers' attention to climate change but common advocacy techniques do not improve engagement.

One of the most challenging aspects of climate change mitigation today is not identifying solutions but reaching political leaders with climate scientists' existing solutions. Although there is substantial research on climate change communication, research rarely focuses on one of the most impactful groups: policymakers. It is essential to test theoretically sound methods to increase lawmakers' attention to research evidence. In a series of four rapid-cycle randomized controlled email trials (N = 6642-7620 per trial), we test three common and theoretically derived advocacy tactics to increase U.S. policymaker engagement with a climate change fact sheet sent via email (i.e., a norms manipulation, a number focused manipulation, and emotional language manipulation). In all four trials, the control message increased engagement more than messages using advocacy tactics, measured by fact sheet clicks. This demonstrates the importance of testing communication methods within the appropriate populations, especially a population with considerable influence over climate policy.