Impact of global climate change on urban climate and air quality

Against the backdrop of a continuing increase in global temperatures, (IPCC 2007), the paper considers the resulting changes in thermal and air quality conditions in urban areas. Investigations are carried out taking examples from the Ruhr metropolitan region in western Germany, Europe's largest industrial area. The first part of the paper analyses this question on the basis of air temperature, ozone and particulates (PM10) and compares current values with those to be expected in the future. The multi-faceted meteorological and chemical parameters and interactions between them which can lead to ozone and particle production are explained. It is shown that, in a climate subject to temperature changes, ozone concentrations will not only rise but will rise to a different extent depending on the region (urban or rural). The effects of biogenic and anthropogenic hydrocarbons on ozone production are discussed. The frequencies of ozone concentrations in excess of present and future limits are compared. While the statements on expected ozone concentrations are more or less clear, this does not apply to predicted future particulate concentrations as these are largely dependent on the relevant chemical precursors, which are subject to considerable spatial variation. The second part of the paper presents measures taken at the urban level to mitigate global climate change. These may lead not only to reduced carbon dioxide emission but also to lower air and radiation temperatures. The extent to which anthropogenic and biogenic hydrocarbon emissions can be reduced in addition to oxides of nitrogen as ozone precursor substances is also considered. The outlook section of the paper presents guidelines for action to counter climate change by the municipalities and local authorities of the Ruhr region.