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Climate change

Vulnerable megacities

Panel discusses impact of global warning on Rio de Janeiro and São Paulo

MIGUEL BOYAYANSão Paulo traffic: unsustainableMIGUEL BOYAYAN

An international panel of experts held last month produced an initial outline for the production of maps on the vulnerability to global climate change of the Rio da Janeiro and the São Paulo metropolitan areas. The debates emphasized both the susceptibilities of certain geographical areas and the population’s social vulnerability. The outline’s details are to be released in three months time and will provide elements for the preparation of the maps, which are to be based on regional data on climatology, pollution, topography, hydrography, use and occupation of the land, health, and social and demographic characteristics of the population, among other factors. The work will be used to provide guidance for research projects and as input for public policies regarding adaptation to global warming.

The panel, that comprised stages held at the Rio de Janeiro Botanical Garden and at the FAPESP auditorium in São Paulo, was attended by researchers from Brazil, Argentina, the United Kingdom and the United States, and was coordinated by Carlos Nobre, from the Center for Terrestrial System Science of Inpe (the National Space Research Institute); Daniel Hogan, demographics professor from the State University of Campinas (Unicamp); and Magda Lombardo, from the Geosciences and Exact Sciences Institute of Rio Claro, of Unesp (Paulista State University). The initiative is part of a study financed by the Global Opportunities Fund Climate Change and Energy Programme of the United Kingdom, by Rede Clima (the Brazilian Research Network on Global Climate Changes) and by the National Science and Technology Institute of Climate Change, and was supported by the FAPESP Program of Research into Global Climate Changes.

The data indicate differences and similarities in the vulnerability of Rio de Janeiro and São Paulo. The most obvious difference is that São Paulo is not subject to the risk of the sea level rising. Although the two cities have shantytowns, the situation of the Rio de Janeiro capital is more delicate, as over one million people live in precarious housing located on lowlands, areas that are subject to flooding. However, São Paulo is expected to undergo more flooding in the summer. “The rainfall is likely to be concentrated in storms and, because of the influence of islands of heat, the rain is likely to be stronger over the urban area,” says Magda Lombardo, who studies heat islands, which consist of a rise in temperature in highly urbanized areas.

The issues of health and pollution are of far more concern in São Paulo, however. According to Paulo Saldiva, a professor at USP’s Medical School, the high concentration of cars is one of the chief factors aggravating climate change in São Paulo. According to him, the number of cars is growing at a rate four times greater than the number of inhabitants of the São Paulo state capital. “The pressure to sell more cars is unsustainable from all points of view – including traffic, since the average speed in São Paulo is 10 km an hour, the same as in the seventeenth century. The map of such heat islands coincides with the map of mortality due to cardiovascular events in the city,” said Saldiva.

In Rio de Janeiro pollution is not a key danger. “The winds, the circulation and  sea breezes mean that this is not an acute problem, other than in certain areas of the Baixada Fluminense lowlands, which are not really influenced by the breeze because of the local topography,” said Carlos Nobre, the coordinator of the FAPESP Research Program into Global Climate Changes. Despite its hot climate, Rio de Janeiro will suffer less once heatwaves become more intense. “What causes vulnerability to temperature is the difference relative to what one is used to – i.e., when heat is above a person’s thermal comfort zone. Therefore, heatwaves may bring about more deaths in São Paulo,” says Nobre.