Controlling the emissions of carbon dioxide (CO2) as a measure against global warming is one of the crucial environmental issues that the steel industry must undertake. As shown on the left side of the figure, the average temperature of the earth began to rise in the latter half of the 1970s, and this trend became more pronounced in the 1980s. Global warming is considered to be due to an increase in the concentration of greenhouse-effect gases, including CO2, in the atmosphere. The present CO2 concentration in the atmosphere is about 340 ppm and is increasing annually by about 1.5 ppm. The main cause of this increase in CO2 concentration is believed to be the increasing combustion of carbon in fossil fuels from the 1950s onward. According to a joint research prediction by the United Nations and the World Meteorological Organization, if the emission of greenhouse-effect gases by human activities continues without any preventive measures, the average global temperature will be 3 degrees higher in the early 22nd century than at present. The energy we use at present depends on fossil fuel to a great extent. To control the emission of CO2, therefore, it is necessary to seek alternative energy sources and to use energy more efficiently. The shift to new energy sources and the technology to fix CO2 are mostly in the development stage, and considerable time will be needed to put these measures into practical use. Accordingly,the focus today must be on the effective use of energy, i.e., energy saving, and the steel industry is no exception to this principle. As shown in the figure, the Japanese steel industry cut its unit energy consumption by about 20% from 1973 to 1986. During this period, the Japanese steel industry made equipment investments of 1.4 trillion for environmental measures and 1.3 trillion for energy saving measures.