Abstract Temperature records indicate that the global annual mean surface air temperature (referred to as the global temperature) has risen by 0.5°C since 1840. According to recent general circulation model calculations, by the year 2020 the global mean temperature will have risen to 1.3 to 2.5°C above the preindustrial (1840) mean. By the year 2070, the range of temperature increase will be 2.4 to 5.1°C, and sea level will have risen 33 to 75 cm. Measurements from Antarctic ice cores show temperature swings of 4 to 5°C between ice ages and interglacial periods. Fossil fuel-based energy use through power generation and transportation is viewed as the major cause of the very recent and projected future temperature rise. Recent arguments of scientists and policy makers have increasingly focused on the exact scope of global-scale changes and consequences of the globally rising energy appetite. The question of global warming has become the most important scientific issue.