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Climate Change
The greenhouse effect occurs when certain gases and particles allow sunlight to penetrate to the earth but partially trap the planet's radiated infrared heat in the atmosphere.

Catalog of Global Emissions Inventories and Emission Inventory Tools for Carbon BlackCatalog of Global Emissions Inventories and Emission Inventory Tools for Carbon Black
[.pdf, 336.6Kb]

Literature review of greenhouse gas and carbon black global and regional emission inventories.

(US EPA (Jan 2002))

Air pollution emissions contribute to global warming or the "greenhouse effect." The greenhouse effect occurs when certain gases and particles allow sunlight to penetrate to the earth but partially trap the planet's radiated infrared heat in the atmosphere.

Sometimes, such warming is natural and necessary. If there were no water vapor, carbon dioxide, methane, and other infrared absorbing (greenhouse) gases in the atmosphere trapping the earth's radiant heat, our planet would be about 60 F (33 C) colder, and life as we know it would be impossible. Naturally occurring greenhouse gases include water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). Particles such as black (elemental) carbon absorb and reflect solar radiation.

Several classes of halogenated substances that contain fluorine, chlorine, or bromine are also greenhouse gases, but these are, for the most part, solely a product of industrial activities. Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are halocarbons that contain chlorine, while halocarbons that contain bromine are referred to as halons. Other fluorine containing halogenated substances include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6).

There are also several gases that, although they do not have a direct global warming effect, do influence the formation and destruction of ozone, which does have such a terrestrial radiation absorbing effect. These gases include carbon monoxide (CO), oxides of nitrogen (NOx), and nonmethane volatile organic compounds (NMVOCs).

Aerosols, extremely small particles or liquid droplets often produced by emissions of sulfur dioxide (SO2), can also affect the absorptive characteristics of the atmosphere.

Although CO2, CH4, and N2O occur naturally in the atmosphere, the atmospheric concentration of each of them has risen, largely as a result of human activities. Since 1800, atmospheric concentrations of these greenhouse gases have increased by 30%, 145%, and 15%, respectively (IPCC, 1996). This build-up has altered the composition of the earth's atmosphere, and may affect the global climate system.

Beginning in the 1950s, the use of CFCs and other ozone depleting substances (ODSs) increased by nearly 10 percent a year, until the mid-1980s when international concern about ozone depletion led to the signing of the Montreal Protocol. Since then, the consumption of ODSs has rapidly declined, as they are phased-out. In contrast, use of ODS substitutes such as HFCs, PFCs, and SF6 has grown significantly and all have strong greenhouse forcing effects.

In late November 1995, the IPCC Working Group 1 concluded, "the balance of evidence suggests that there is a discernible human influence on global climate." In December 1997, acting on this consensus, countries around the world approved the Kyoto Protocol to the 1992 Climate Change Treaty. When and if ratified by 55 nations, representing 55% of 1990 carbon dioxide emissions, thirty-eight industrialized nations will be required to reduce their "greenhouse" gas emissions from 1990 levels between 2008 and 2012. The European Union would reduce them by 8 percent, the United States by 7 percent and Japan by 6%. Some would face smaller reductions, and a few would not face any now. As a group, the industrialized nations would cut back on the emissions of such gases by just more than 5%.

Emissions of six gases would be affected: carbon dioxide, methane, nitrous oxide, and three halocarbons used as substitutes for ozone-damaging chlorofluorocarbons.

The greenhouse gases most closely identified with the transportation sector include carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). These gases have the following global warming potentials relative to carbon dioxide.


Methane (CH4)

Nitrous Oxide (N2O)

20 Year Horizon



100 Year Horizon



500 Year Horizon



However, it is important to note that other vehicle-related pollutants contribute to global warming although their quantification has been more difficult. These include CO, NMHC, and NO2. According to the original (1990) IPCC report, the following global warming potentials were attributed to these gases. Because of difficulty reaching agreement on the appropriate quantification, specific GWPs for these gases were not contained in the most recent IPCC report.





20 Year Horizon




100 Year Horizon




500 Year Horizon




In most countries, over 90% of the global warming potential of the direct-acting greenhouse gases from the transportation sector comes from carbon dioxide. The transportation sector is responsible for approximately 17% of global carbon dioxide emissions and these emissions are increasing in virtually every part of the world.

Even the potential global warming benefits of diesel vehicles, due to their substantial fuel economy benefits relative to gasoline-fueled vehicles, have been undercut by recent studies, which indicate that diesel particles may, by reducing cloud cover and rainfall, more than offset any CO2 advantage. As noted by NASA's Dr. James Hansen, "Black carbon reduces aerosol albedo, causes a semi-direct reduction of cloud cover, and reduces cloud particle albedo."

While the US has abandoned the Kyoto agreement, most other countries around the world are proceeding toward ratification and it is considered likely that the treaty will come into force before the end of 2002.

Implementing this agreement will require significant improvements in fuel economy and reduction in carbon dioxide emissions from vehicles.

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Regional and global effects > Climate change

Secretariat: The World Bank & Asian Development Bank