The American Thoracic Society (ATS), in collaboration with George Mason University, surveyed a random sample of ATS members to assess their perceptions of, clinical experiences with, and preferred policy responses to climate change. A larger majority anticipated seeing these climate-related health impacts in the next 2 decades. Respondents indicated that physicians and physician organizations should play an active role in educating patients, the public, and policy makers on the human health effects of climate change. Overall, ATS members are observing that human health is already adversely affected by climate change and support responses to address this situation.