Researchers use computers to solve large multidimensional equations and thus simulate processes in the Earth system. These climate models contain our knowledge of the physics of the planet. Whether they reliably reproduce temperature curves in past cold and warm periods can be checked using data from measurements or from natural climate archives such as ice drill cores. Models can then be used to calculate future developments - always based on certain assumptions, for example about the increase in CO2 emissions. The result are projections: not predictions, but complex if-then statements.
