Greenhouse gases and aerosols - scenarios and uncertainties: Greenhouse gas emissions are the main cause of man-made climate change. The atmospheric concentration of the most important of these gases is still increasing and reaches a new record every year. Despite the annual world climate conferences, mankind will hardly be able to meet the binding limit of 1.5 or 2.0 degrees Celsius temperature increase set by the Paris Agreement. I is crucial reducing emissions of carbon dioxide, by far the most important greenhouse gas. If greenhouse gas emissions can actually be stoppt by the middle of the century, which is absolutely necessary to comply with the Paris Agreement, it is still scientifically unclear how the global climate will develop. The interactions of carbon dioxide with the ocean and land vegetation, and those of methane with wetlands are difficult to predict. The climate impact of anthropogenic, man-made aerosols is also only partially understood. This means that climate mitigation, but also adaptation to unavoidable climate changes, face major challenges.