Global warming is caused mainly by CO 2 emission from burning fossil fuels and is beginning to have large negative impacts on human well-being and ecosystems (IPCC 2014; IPCC 2018). Policies that mitigate CO 2 emissions will require public support. Here, we examine how support for several possible decarbonization policies varies as a function of the personal carbon footprint of a researcher who advocates the policy. We find that people are more likely to support policies if the advocate for these policies has a low carbon footprint. Replicating our prior work, we find that the communicators’ carbon footprint massively affect their credibility and intentions of their audience to conserve energy (Attari, Krantz and Weber 2016). Our new finding is that their carbon footprint also affects audience support for public policies advocated by the communicator. In a second study, we show that the negative effects of a large carbon footprint on credibility are greatly reduced if the communicator reforms their behavior by reducing their personal carbon footprints. The implications of these results are stark: effective communication of climate science and advocacy of both individual behavior change and public policy interventions are greatly helped when advocates lead the way by reducing their own carbon footprint.