Economic growth and urbanization move in tandem. Because most economic activity is concentrated in urban areas, cities have a key role in climate change. Affluence and lifestyle choices determine greenhouse gases emissions, and historically, developed countries have had greater greenhouse gas emissions than developing countries. The world is urbanizing fast; 70 percent of the world's population will live in cities by 2050. Under the business-as-usual scenario greenhouse gas emissions will also increase significantly.
Cities consume the vast majority of the world's energy
Cities meet approximately 72 percent of their energy demand from coal, oil, and natural gas, the main contributors to greenhouse gas emissions. Cities also use about 70 percent of the energy from renewable sources; however, these sources still make up just a small share of total energy consumed. National governments and cities have choices regarding their energy mix, and public policies can play an important role in improving energy efficiency and reducing carbon dioxide emissions.
Coastal cities are vulnerable to sea level rise
Cities are vulnerable to the impacts of climate change. Some 360 million urban inhabitants live in low-elevation coastal zones, exposing them to sea level rise and storm surges. The Intergovernmental Panel on Climate Change estimates that average sea level rose 0.17 meter in the 20th century and predicts a 1 meter rise over the next 100 years linked to climate change.
Infrastructure investments in urban areas
Urban areas, because of their density, offer mass-targeting options that provide access to water, sanitation, and solid waste management more cost-efficiently than rural areas can. Infrastructure investments can thus be cost effective in targeting beneficiaries. Latin America and the Caribbean and Eastern and Central Asia, with the highest urbanization rates, have greater access to sanitation services; South Asia and Sub-Saharan Africa, with the lowest urbanization rates, have the least access.
Policies to reduce greenhouse gas emissions can have a major impact. During the last 40 years Germany and Sweden adopted policies that have dramatically decreased per capita carbon dioxide emissions. As China and India urbanize and absorb an increasing share of global manufacturing, their carbon dioxide emissions will increase. Though their per capita carbon dioxide emission levels will be lower than those in developed countries, going forward, China and India will benefit from the experience of countries like Germany and Sweden.
Compact cities tend to use less energy
Compact cities tend to be more sustainable than sprawling cities. Urban form can be important in determining land and energy use and the cost of infrastructure and municipal services. Denser cities use less energy for transportation, which lowers transport-related emissions, can provide access to services at lower cost, and implement more energy efficiency measures.
Choice of transport modes affects energy use
Countries favoring private transport use more energy per passenger kilometer than countries with high levels of public and nonmotorized transport modes. As density increases, people tend to use more public transportation and nonmotorized forms of transport, lowering transportation energy use per capita. High energy use per capita in the United States and Western Europe can be explained by high incomes; in Middle Eastern countries, by fuel subsidies.
Improvements in air quality
Concentrations of PM10 (particulate matter 10 microns in diameter), a standard used to measure air quality, decreased significantly in all regions in 1990-2005, with the most pronounced drops in developing countries. This may be a result of multiple factors, such as policies to improve air quality standards in urban areas (through incentives to switch from diesel to compressed natural gas), fuel and vehicle quality improvements, and greater awareness of the impacts of air pollution on public health.
Modal split and urban density, 1995(%) * Nonmotorized private modes * Public transport * Private modes Energy used per passenger kilometer (megajoules) United States 14.9 Eastern Europe 52.9 Western Europe 54.9 Africa 59.9 Latin America 74.7 Middle East 118.8 High-Income Asia 150.3 Low-income Asia 204.1 Urban density (people per hectare) Source: Kenworthy and Laube 2001. Note: Table made from line graph.
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|Title Annotation:||THE LITTLE GREEN DATA BOOK 2009|
|Publication:||Little Green Data Book 2009|
|Date:||Jan 1, 2009|
|Next Article:||Data notes.|