INterdisciplinary CLimate INvestigation cEnter

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Megacities / air pollution

Despite all the known problems associated with life in the cities it is necessary to recognize that there is an irreversible trend of migration from rural to urban areas. Overall more than 50% in world now lives in cities, and in South America this percentage is 75%. This configuration, on the one hand increases the participation of cities in global change on the other hand these are the areas most affected by adverse weather. It is noteworthy that the largest effects suffered by the urban areas are associated with inappropriate land use, with increased heat energy storage as a result of materials used in construction, with increased surface roughness and the emission of pollutants. The population has faced increasing temperatures, changing rainfall (with landslides and floods) and changes in atmospheric photochemical reactivity.

The report of the WMO (World Meteorological Organization), January 2009 (WMO Bulletin 58, 2009) highlights the importance of studies of the impact of cities on climate change: "between 1800 and 2007, the fraction of the global population living in cities has risen from about 3 per cent to 50 per cent. As a consequence, megacities and regional hot spots have developed with anthropogenic pollutant emissions and changes in land use that have large environmental implication both in the regional hot spots themselves and on a larger scale. "And later in that same editorial, the author mentions the question of the aerosols and gases emitted from urban sources, "Aerosols (directly and indirectly) and tropospheric ozone, exert regional radiative forcing on climate which is expected to modify the distribution of synoptic weather patterns and the distribution of weather elements such as precipitation and wind on a regional basis. The extend of the modification and its societal impact is not well known, but is likely to be important".

Climate change has consequences for the composition of the atmosphere through modification of factors that affect the life cycles (sources, transport, chemical and physical transformations as well as deposition processes, emissions and removals). Many studies are being conducted as part of improved emission inventory for urban areas (Gurjar et al., 2008), impacts of these emissions on the climate (Gurjar and Lelieveld, and 2005 Project Megalopolis: Megacities: Emissions, urban, regional and Global Atmospheric Pollution and climate effects, and Integrated tools for assessment and mitigation, available at and how climate change will impact on air quality, hydrological and radiative processes of more urbanized areas. And secondly, how these areas extensive contribute to greenhouse gas emissions. There will be a major impact on quality of life, here also considering the impact on human health (due to environmental concentrations of pollutants) and thermal comfort (extremes of precipitation, temperature and other adverse events).

Considering the importance of megacities to the emissions of aerosols (including here the particulate phase and gas) on a global scale and how the new climatic conditions can affect air quality in urban areas, this item of the core project aims to develop two lines of research: improving knowledge about the composition and emission of aerosols by urban processes and development coupled modeling of atmospheric chemical processes and their impact on populations.

It is possible to name a few topics to be discussed in this sub-project:

  • the characterization of pollutant emissions in the State of São Paulo, including mobile sources, industrial and agriculture to be integrated into the modeling of air quality;
  • the characterization of the spatial and temporal variations of physical and chemical properties of atmospheric aerosol;
  • the characterization of aerosol formation resulting from organic and inorganic secondary emissions of Volatile Organic Compounds from burning fuels and biomass;
  • the inclusion of a description of the aerosol in air quality models;
  • the development of integrated models of air quality and climate assessment feedback processes between atmospheric composition and climate change;
  • and finally the association of air quality models with models of environmental risk analysis for studies of health impacts of climate and weather.

These objectives aim to provide answers to the questions already listed:

  • what is the impact on air quality at regional scale due to global change scenarios, estimated from atmospheric models?
  • What is the effect of global climate and chemical composition on regional air quality?
  • What are the couplings and feedback mechanisms between climate change, air pollution and its effects on human health?