Slowing the process of global warming will require sustained reductions in greenhouse gas (GHG) emissions over decades, which in turn depends on public support for decarbonization. We are beginning to see evidence of success in cutting emissions. Will wider recognition of this “good news” strengthen or soften support for further action? In contrast to previous research showing a demotivating effect of good news about climate mitigation, our pre-registered survey experiment finds no average impact of factual reports of climate progress on Americans’ worries about climate change, perception of efficacy in fighting climate change, willingness to pay additional taxes, support for green industrial policy, or willingness to donate to a climate NGO, and no evidence of heterogeneous effects across relevant subgroups. Given the importance of sustained public support for decarbonization, these null results can be seen as good news for mitigation policy, but more research is needed to assess the impact of the perceived tractability of climate mitigation on support for mitigation efforts.