Submitted to: American Meteorological Society
Publication Type: Proceedings
Publication Acceptance Date: 10/15/1998
Publication Date: N/A
Interpretive Summary: Many people are worried about the rising carbon dioxide (CO2) content of earth's atmosphere and how it might affect world climate and vegetation. Scientists have historically broached these questions via computer model studies of climate and growth chamber studies of plants, both of which approaches introduce artifacts that are not characteristic of natural settings. To partially overcome this problem, we documented the existence of an urban CO2 dome over the metropolitan area of Phoenix, Arizona, where centrally-located CO2 concentrations produced by industry and vehicular traffic were found to rise as much as 50% above CO2 concentrations observed in surrounding rural areas. Because cities also exhibit elevated temperatures due to the well-known urban heat island effect, they may thus be especially good analogues of our global future, where both atmospheric temperature and carbon dioxide levels are expected to be substantially higher than they are today. Present-day cities may thus serve as experimental microcosms of what our entire planet may be like a century or so hence, providing us a unique opportunity to explore the nature of ongoing global change in a whole new, but readily available, setting.
Technical Abstract: Atmospheric carbon dioxide concentrations were measured at one-mile intervals prior to sunrise and in the middle of the afternoon on a number of different transects through the metropolitan area of Phoenix, Arizona, in January and July. Maps of the data reveal the existence of an urban CO2 dome over the city, which is nearly identical in winter and summer. Carbon dioxide concentrations at the center of the dome are as much as 50% greater than those observed over surrounding rural areas in the morning and as much as 25% greater in the afternoon. These high CO2 concentrations, which are produced primarily by the burning of fossil fuels such as gas and oil, have the ability to enhance the growth of urban vegetation and provide some protection against the debilitating effects of local air pollution. Hence, some of the positive effects of one of the major end-products of the combustion process (CO2) tend to counteract one of the negative effects of some of the minor by-products of that same process (air pollution).