Science teachers play an important role promoting civic scientific literacy, but recent research suggests they are less effective than they could be in educating the next generation of citizens about climate change and its causes. One particular area of concern is that many science teachers in the USA encourage students to debate settled empirical findings, such as the role of human-generated emissions of greenhouse gases in raising global temperatures. A common reaction is to call for science teachers to receive more formal training in climate science to increase their knowledge, which will then improve teaching. Using a nationally representative survey of 1500 middle school and high school science teachers, we investigate each element in this argument, and show that increased science coursework in college has modest effects on teachers’ content knowledge and on their teaching choices, including decisions about debating “both sides.” We also find that teachers’ personal political orientations play a large role in their teaching strategies: right-leaning teachers devote somewhat less time to global warming and are much more likely to encourage student debate on the causes of global warming. We discuss the implications of these findings and argue teacher education might be more effective if informed by insights from the emerging discipline of science communication. However, although knowledge and ideology are predictive of pedagogy, a large number of teachers of all ideological positions and all levels of subject expertise encourage students to debate established findings. We discuss this and highlight potential explanations.