This study explores in-service teachers' attitudes and knowledge about a pressing environmental issue, "global climate change" (GCC), and how these may relate to their classroom teaching. In this work, nineteen teachers from Native American communities attended a professional development workshop that focused on enhancing their scientific understanding and classroom teaching of GCC. Teachers' responses to surveys and interviews revealed that the majority of them considered GCC as mainly human-induced and shared similar concerns about potential consequences of GCC, but their specific ecological beliefs varied to different degrees. Throughout the workshop, teachers became more aware of the urgency of GCC and the importance of incorporating climate issues into their science teaching. However, teachers' attitudes and beliefs about GCC were not strong indicators of their level of knowledge, as misconceptions were sometimes found among teachers who were very concerned about climate issues. This work opens up further discussions on the relationship between individuals' attitudes and knowledge about environmental issues. More importantly, it provides important implications for future professional development programs on climate change education and proposes effective tools to evaluate teachers' perspectives about GCC.