Geoengineering is the deliberate large scale intervention in the Earth's natural systems to counteract climate change. It can be divided into two categories.
1- Solar Radiation Management (SRM) or Solar Geoengineering
For example, through introducing small aerosols into the atmosphere whic will reflect some of the solar radiations.
2- Carbon Dioxide Removal or Carbon Geoengineering
For example, through carbon sequestration and afforestation.
You can get more information through this link http://www.geoengineering.ox.ac.uk/what-is-geoengineering/what-is-geoengineering/
Thanks a lot for asking this question. I didn't knew about it beforehand.