Cities and towns are heavily vulnerable to climate change. Hundreds of millions of people in urban areas across the world will be affected by rising sea levels, increased precipitation (in some areas), inland floods, more frequent and stronger cyclones and storms, periods of more extreme heat and cold and the spread of diseases. Climate change may also negatively impact infrastructure and worsen access to basic urban services and quality of life in cities. Cities are also major contributors to climate change, producing more than 60% of all carbon dioxide and significant amounts of other greenhouse gas emissions, mainly through energy generation, vehicles, industry and biomass use.
Many major costal cities with populations of more than 10 million people are under threat: Buenos Aires, Rio de Janeiro, Los Angeles, New York, Lagos, Cairo, Karachi, Mumbai, Kolkata, Dhaka, Shanghai, Osaka-Kobe and Tokyo. By 2030, when three-quarters of the world's population is expected to be urban, the biggest cities will be found in the developing world. It is the medium-sized cities in these regions -- such as Esmeraldas, Ecuador; Maputo, Mozambique; and Sorsogon, Philippines – that face the largest population growth and increasing vulnerability to climate change-related impacts over the coming decades. UN-HABITAT's Cities and Climate Change Initiative (CCCI) targets these cities in particular.
In these cities the most affected populations are the urban poor – i.e. slum dwellers in developing countries – along beaches vulnerable to flooding, by railways, on slopes prone to landfalls, near polluted grounds, on desertified land and in shaky structures vulnerable to earthquakes. The risk of mass fatalities is greater given modern land use policies and rapid urbanisation.
However, cities are also places of innovation and efficiency when properly planned, capacitated and managed through the appropriate governance structures. Together with their local authorities they have the potential to diminish the causes of climate change (mitigation) and effectively protect themselves from its impacts (adaptation).