In long-term energy strategies, one of the most crucial challenges will be fighting global warming. This requires considerable structural changes in energy production. There is clear evidence that the increase in atmospheric carbon dioxide causes the ‘greenhouse effect’, while opinions differ about its seriousness. However, it is the first real threat caused by mankind to his own life expectancy. Finland — as other European countries — has engaged to freeze and later also to reduce its CO2 emissions. Can energy production be based essentially on fossil fuels or are nuclear power and renewable energy sources the only energy alternatives in the future?