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Climate Change


Climate change reflects abnormal variations to the expected climate within the Earth's atmosphere and subsequent effects on other parts of the Earth


Context and Policies

Cities cover less than one per cent of the earth's surface but are disproportionately responsible for causing climate change. Greenhouse gas emissions from transport are a key contributor to global climate change. Over the past three decades, carbon dioxide emissions from transport have risen faster than those from all other sectors and are projected to rise more rapidly in the future.

At present industrialized countries are the main sources of transport emissions. However, the proportion of emissions being produced in developing countries is increasing rapidly, particularly in countries such as China, India, and Indonesia.

With the signing of the Kyoto Protocol in 1997, the first legally binding international agreement to reduce greenhouse gas emissions was established. As of May 2007, 175 parties have ratified the agreement, covering over 60% of global emissions. The industrialised countries who sign up to the treaty are legally bound to reduce worldwide emissions of six greenhouse gases by an average of 5,2% below their 1990 levels by the period 2008 to 2012. The Kyoto Protocol also includes mechanisms, which allow industrialised countries to meet their targets by reducing emissions elsewhere, either through purchasing carbon credits or by funding projects in developing countries using the Clean Development Mechanism (CDM) or Joint Implementation (JI).


Transport is proving to be one of the most difficult sectors in which to reduce greenhouse gas emissions as there are numerous small emission sources (i.e., vehicles) and, additionally, there is a seemingly close relationship with economic development.

Reducing greenhouse gas emissions may not be high on the local agenda of priorities for citizens. Controversial measures may result in (political) decision-makers coming under attack from the press and public—putting successful implementation at risk. It is therefore important to assess and present the range of co-benefits that can be achieved through the implementation of sustainable transport instruments, helping to meet local priorities. Co-benefits include health and safety, the economy, accessibility to key services and activities and reduced air pollution.


There are essentially three ways to reduce greenhouse gas emissions from urban transport:

  • Avoid travel or avoid travel by motorised modes;
  • Shift to more environmentally friendly modes; and
  • Improve the energy efficiency of transport modes and vehicle technology.

Although the level of greenhouse gas reduction that could be achieved by these approaches is difficult to predict, reductions are most likely to be achieved where a higher share of public transport and/or non-motorised modes is attained (for more information see "Transport and Climate Change" under Key Documents, below)


Sources of Funding

The Clean Development Mechanism (CDM) allows industrialised countries with a greenhouse gas reduction commitment under the Kyoto Protocol to invest in emission reduction projects in developing countries.

Joint Implementation (JI) allows industrialised countries with greenhouse gas reduction commitments to invest in emission reducing projects in other industrialised countries.

The Global Environment Facility (GEF) was set up to fund projects (including urban transport projects) and programmes aimed to protect the global environment in beneficiary nations.



Climate Action Plans: More and more cities around the world are developing dedicated Climate Action Plans to reduce Green House Gas (GHG) emissions and improve the local air quality for their inhabitants. The transport sector usually plays a crucial role in any such strategy. In many cases, transportation is the primary source of CO2 and other GHGs, contributing up to 40 percent of the cities’ total emissions. The measures initiated to reduce these negative impacts of urban transport take many forms. Increasing the share of Public Transport and non-motorised modes such as walking and cycling are core elements in many emission reduction strategies, but most often, they are supplemented by other short- and long-term measures. One key feature of most actions proposed is that they provide several co-benefits: Many options not only reduce GHG emissions and improve air quality, but also enhance energy efficiency and – especially in the developing world – contribute to better transport services for the poor (see "Urban Transport and Climate Change Action Plans", under Key Documents, below)


Key Presentations