Climate engineering (also called geoengineering) is a term used for both carbon dioxide removal (CDR) and solar radiation management (SRM), also called solar geoengineering, when applied at a planetary scale. However, they have very different geophysical characteristics which is why the IPCC (Intergovernmental Panel on Climate Change) no longer uses this overarching term. Carbon dioxide removal approaches are part of climate change mitigation. Solar geoengineering involves reflecting some sunlight (solar radiation) back to space. All forms of geoengineering are not a standalone solution to climate change, but need to be coupled with other forms of climate change mitigation. Another approach to geoengineering is to increase the Earth's thermal emittance through passive radiative cooling. Carbon dioxide removal (CDR) is defined as "Anthropogenic activities removing carbon dioxide (CO2) from the atmosphere and durably storing it in geological, terrestrial, or ocean reservoirs, or in products. It includes existing and potential anthropogenic enhancement of biological or geochemical CO2 sinks and direct air carbon dioxide capture and storage (DACCS), but excludes natural CO2 uptake not directly caused by human activities." Some types of climate engineering are highly controversial due to the large uncertainties around effectiveness, side effects and unforeseen consequences. However, the risks of such interventions must be seen in the context of the trajectory of climate change without them. Definitions Climate engineering (or geoengineering) has been used as an umbrella term for both CDR (carbon dioxide removal) and SRM (Solar radiation management or solar geoengineering), when applied at a planetary scale. However, these two methods have very different geophysical characteristics, which is why the Intergovernmental Panel on Climate Change (IPCC) no longer uses this term. This decision was communicated in around 2018, see for example the "Special Report on Global Warming of 1.5 °C". Some authors, for example in the mainstream media, also include passive daytime radiative cooling (PDRC), "ocean geoengineering" and others in the term of climate engineering. Specific technologies that fall into the "climate engineering" umbrella term include: Carbon dioxide removal (CDR) Biochar - Biochar is a high-carbon, fine-grained residue that is produced via pyrolysis Bioenergy with carbon capture and storage (BECCS) - the process of extracting bioenergy from biomass and capturing and storing the carbon, thereby removing it from the atmosphere. Direct air capture and carbon storage (DACCS) - a process of capturing carbon dioxide () directly from the ambient air (as opposed to capturing from point sources, such as a