OBJECTIVE: To discuss the nature of climate change and both its immediate and long-term effects on human respiratory health. METHODS: This review is based on information from a presentation of the American College of Chest Physicians course on Occupational and Environmental Lung Disease held in Toronto, Canada, June 2013. It is supplemented by a PubMed search for climate change, global warming, respiratory tract diseases, and respiratory health. It is also supplemented by a search of Web sites including the Environmental Protection Agency, National Oceanic and Atmospheric Administration, World Meteorological Association, National Snow and Ice Data Center, Carbon Dioxide Information Analysis Center, Inter-Governmental Panel on Climate Change, and the World Health Organization. RESULTS: Health effects of climate change include an increase in the prevalence of certain respiratory diseases, exacerbations of chronic lung disease, premature mortality, allergic responses, and declines in lung function. CONCLUSIONS: Climate change, mediated by greenhouse gases, causes adverse health effects to the most vulnerable patient populations-the elderly, children, and those in distressed socioeconomic strata.