The increase in asthma incidence, prevalence, and morbility over recent decades presents a significant challenge to public health. Pollen is an important trigger of some types of asthma, and both pollen quantity and season depend on climatic and meteorologic variables. Over the same period as the global rise in asthma, there has been considerable increases in atmospheric carbon dioxide concentration and global average surface temperature. We hypothesize anthropogenic climate change as a plausible contributor to the rise in asthma. Greater concentrations of carbon dioxide and higher temperatores may increase pollen quantity and induce longer pollen seasons, such as eczema and allergic rhinitis. Although the etiology of asthma is complex, the recent glovbal rise in asthma could be an early health effect of anthropogenic climate change.