This essential provides an overview of the changes in our climate, their causes and their consequences. Today, humanity's energy needs are largely met in ways that are harmful to the climate. The alternative to this, solar energy, would satisfy our needs thousands of times over. But this option is far too little used for mainly economic reasons. This essential then discusses the energy converters that can be used to make solar energy available. Some other modern energy sources, such as nuclear power, are either inadequate, still utopian, or otherwise environmentally harmful. An outlook shows that our energy problem could easily be solved with economic reason by global use of solar energy. The climate could thus still be stabilized in time.