The world’s oceans are the largest carbon store on earth and one of the most important buffers of CO2. Annually, marine ecosystems can absorb about 3 gigatonnes of the greenhouse gas. This is a relevant magnitude. Even a transport of CO2 into deeper layers of the oceans beyond 3000 or 4000 metres is apparently possible, but has not been used so far. Hans Jürgen Wernicke shows that the oceans are also very important as a CO2-buffer for the GES reference model currently being developed to solve the climate problem.