Global warming refers to the increase in atmospheric temperatures and density attributed to higher levels of greenhouse gases emitted in the course of various human activities. Global warming is believed to have harmful effects on the environment, including a rise in sea level and more subtle changes to ecosystems. At the 1997 Kyoto Conference on Climate Change (COP3), quantitative targets were set requiring each industrialized country to reduce its emission of six greenhouse gases over a five year period beginning in 2008. The targets are defined as a rate of reduction compared to the 1990 emission level. Japan is mandated to achieve 6% reduction, while the overall target among industrialized nations is set at 5.2%. Of the six greenhouse gases, carbon dioxide accounts for the largest volume of emissions and contributes significantly to harming the environment. In the area of transportation, emission control measures are being explored primarily for automobile traffic, which emits vast volumes of greenhouse gas.
Issues related to carbon dioxide emission
Carbon dioxide is one of the greenhouse gases. It has a relatively small greenhouse effect per unit, but is believed to be a primary contributor to global warming because of its emission volume. Of Japans total carbon dioxide emission, the transportation sector accounts for approximately 20%. Of that, about 90% comes from automobiles. These figures show that the carbon dioxide issue in transportation is largely the issue of automobiles. Measures to control the problem include enhancing the energy efficiency of automobiles, developing and encouraging the use of low-pollution vehicles, promoting modal shifts to other transportation modes, and improving the efficiency of trucking services. One economic measure to control carbon dioxide is such a carbon tax as levied in four Scandinavian countries and the Netherlands.