Geoengineering refers to intentional and focused – and most often implemented on a large scale – interventions in the climate system, which are intended to mitigate climate warming due to human activities (anthropogenic climate warming).
Rather than combating the cause of climate change – anthropogenic greenhouse gas emissions – geoengineering seeks to reduce the impacts. Geoengineering approaches are usually divided into two groups:
Solar Radiation Management (SRM)
The goal of these approaches is to reduce the amount of incoming sunlight and, in the process, reduce the global mean temperature. They include proposals like installing giant mirrors in space or increasing the ability to reflect sunlight (albedo) by making communities “lighter” (e.g. painting roofs white). The most frequently discussed approach in the literature consists in releasing aerosols into the stratosphere in order to scatter sunlight and reduce the amount that reaches the surface.
Carbon Dioxide Removal (CDR)
The goal of these approaches is to reduce the concentration of the greenhouse gas CO2 in the atmosphere. This is to be achieved by “retrieving” the emitted CO2 and removing it from the carbon cycle for as long as possible (e.g. via subterranean storage).
Further information can be found in an FAQ provided by the IPCC.