<p>In order to mitigate climate change, actions apart from the reduction of CO<sub>2</sub> emissions are increasingly discussed. Approximately half of the global warming is due to climate-forcing substances such as soot, methane and ozone – without their reduction, the 2°C goal cannot be kept. In addition, there are now many proposals for interventions into the climate system, called “climate engineering” or “geo-engineering”.</p>