Global climatic change will affect all aspects of social life in the twenty-first century. The measures necessary to confront the challenges brought about by global warming and to mitigate its impact go far beyond the indispensable technological transition in the production process and changes in consumption habits of individuals. The future of cities and what we now call "urban" will also undergo transformations.

In the economic, social and political realms, these changes will be profound. The economy will have to progressively incorporate environmental costs into its budget. There is no technological miracle that could help avoid the need for a radical reconversion of the sources of energy-the end of fossil fuels will be one of the realities of the century. Of similar impact will be the emergence of a global perspective on the issue of social inequalities. In the last few decades, we witnessed global efforts to combat poverty, but inequality in the access to income remained an internal matter of national territories. We live in a world where the United States and other developed countries are responsible for two thirds of greenhouse gas (GHG) emissions, while approximately 900 million Africans are responsible for only 3 per cent. However, loss of agricultural productivity, droughts and flooding will adversely affect Africa more. This applies to all poor populations, who are much more vulnerable to the impacts of global warming.

Politics will also change in a significant manner. Following the globalization of markets, there are two historical processes that constitute an international civil society demanding the evolution of world governance: the incorporation into the global economy budget of the costs of short- and long-term goods and services provided by nature, which is until now neglected; and social inequality worldwide. The majority of the world's population lives in cities. In fact, it is a very heterogeneous reality, so much so that the geographic and statistical definitions of what is, or is not, consider "urban" vary considerably among regions, since there are no patterns that may be compared internationally.

The revolution in communications technology per se impels a great transformation in urban life, but global climate changes will highly accelerate this process. The reorientation of the means of energy production, the modes of production and consumption of goods and services, and an acceptable per capita production of energy for citizens of developed countries and the rich and middle-class of emerging countries will bring significant transformation in the way of life of large cities. Urban issues, such as the advancement of production factors, reduction of poverty, quality of life, mobility, characteristics of building construction and access to diversified natural landscapes will have consistent answers only within the context of the struggle against the worst scenarios of global warming.

Within this reality, Rio de Janeiro has a special locus among the large cities of the world. For the carioca (citizen of Rio) population, environmental issues are indispensable, whether on a daily basis or from a historical perspective. In the nineteenth century, one of the largest urban forests in the world, the Tijuca Forest, comprising of 105 square kilometres, was replanted in the heart of the city. Other mountain ranges and isolated hills make up approximately 29,000 hectares of forest coverage in a territory of 1.225 km2-in other words, 23 per cent of the municipality's area.

Besides the green vegetation, the blue waters (196 km of coastline) define the city's personality. An extensive coastline of beaches, along with the forests, is responsible for the emergence of a unique proximity between the urban population of over 6 million and an expansive built space, with the close presence of the natural environment. While the hillsides' forest areas have resisted pressures, due to urban occupation, forest fires and planting of banana cultures, an intensive programme of reforestation remains important. Moreover, sandbanks close to the coast lost a little over 30 per cent of coverage between 1984 and 2004, and are now facing a sea-level rise.

In the built space, there is also a unique proximity between man and nature. For the carioca, cycling is more than a leisure activity. The bicycle is an alternative means of transportation for short and medium distances, which directly impacts the quality of life of the city. Rio de Janeiro is the national capital of bicycling, with the largest network of bicycle paths and more than 140 km of cycle lanes. Its bicycling network is the largest in Latin America, second only to Bogotá, with approximately 300 km. In 1994, the Municipality developed a project called the Structuring Process of Transportation in the Metropolitan Area of Rio de Janeiro. As part of its work, a house survey of starting point and destination was carried out. The results were amazing-74 per cent of respondants agreed to possibly using bicycles if conditions were favourable, as a means of transportation.

Rio de Janeiro has the largest bicycling network in Latin America, second only to Bogotá, Colombia. Nearly 2 million pedestrians and bicyclists use the 153 kilometres of roadways that are closed to automobiles each Sunday in Bogotá. Photo courtesy of the Institute for Recreation and Sport, City of Bogotá

In 2001, the city adhered to the "Network 8-Urban Mobility" project. Among its activities was a contract signed with the Program of Transportation Engineering of the Coordination of Post-Graduate Engineering Programs of the Federal University of Rio de Janeiro, to evaluate the potential use of bicycles in trips and integrate them with other means of public transportation, such as trains, subways, boats and buses. In 2003, the Master Plan of Transportation was carried out. The new starting point and destination survey estimated 221,000 daily bicycle flux, which represents about 2 per cent of the total flow of all means of transportation, by approximately 320,000 people. It should be emphasized that the role of bicycles is significantly higher in some districts, such as in Realengo and Santa Cruz, where bicycle trips per day represent 6 and 8 per cent, respectively, of the flux of all means of transportation.

Since 2005, the Municipal Institute of Urbanism has taken part in Project "Mobilization", which aimed to maintain the accessibility of the cities through the promotion of the use of bicycles. In the first year of the project, the municipality promoted the "Pedaling is Cool" campaign, with the goal of fostering the use of bicycles in the city as a safe means of transportation. In the second year, the "Pedaling is Cool in School" campaign was carried out to promote the benefits of sustainable transportation and the use of bicycles. According to the Brazilian Association for Manufacturing of Motorcycles and Similar Vehicles, the world production of bicycles in 2002 was approximately 120 million, with Brazil contributing 5 per cent. It should be emphasized that Brazil is the third largest manufacturer of bicycles, after China and India. Between 1991 and 2005, Brazilian production of bicycles increased from 2.5 million to 5.2 million units.

The city of Rio is the gateway of Brazil to the world, not only because of its historical infrastructure, but also because its population is so cosmopolitan, with a cultural production capable of influencing artistic and cultural events worldwide. In the twenty-first century, local and global realities intertwined. The city is ready to take up its place in the immense challenge of confronting the consequences of global warming and in changing the world in order to counterbalance the state of "business as usual", thus avoiding the worst possible scenarios outlined by the Intergovernmental Panel on Climate Change (IPCC).

Rio de Janeiro, a pioneer among the cities of Latin America in inventory accountability of GHG emissions since 1998, decided in 2007 to give a permanent and structural status to this effort through an initiative called "Protocol of Intentions of Rio de Janeiro", whose goals are to:

• Support and take part in the mobilization of carioca society in the struggle against global warming;
• Promote awareness and dissemination of information among children, with emphasis on the school network and community debates;
• Broaden knowledge about the impacts and consequences of global warming with regard to the city;
• Initiate the action plan necessary to confront these consequences, in order to preserve the city and protect the population at higher risk;
• Integrate climatic change variables in all municipal planning;
• Promote actions in reducing GHG emissions and contributing to the capture of carbon from the atmosphere;
• Support public and private initiatives/projects, which may foster fundraising through the Clean Development Mechanism; and
• Convey to the Federal Government the city's willingness to host the Conference of the Parties of the United Nations Framework Convention on Climate Change in 2009, expected to take place in Latin America.

The consequences of global warming, especially sea-level rise, threaten the existence of Rio de Janeiro in its present form. This will not happen. We cannot lose our green and our blue, as they are part of who we are in this extraordinary city. With more than 6 million inhabitants, and despite great metropolitan problems and violence, the city managed to preserve and enrich its soul. But in order to overcome all these challenges, cariocas will have to be more than citizens of Rio, they must also be citizens of the world.