Wikipedia page for geoengineering entry list a lot of proposals to decrease global temperature:
Solar radiation management methods may include:
- Surface-based: for example, surface-based mirror infrastructures, protecting or expanding polar sea ice and glaciers, including the use of insulating blankets or artificial snow, using pale-colors for roofing materials and other man-made surfaces (i.e. roadways and exterior paints), attempting to change the oceans' brightness, growing high-albedo crops, or by distributing hollow glass beads in selected areas to increase ice coverage and lower temperatures.
- Troposphere-based: for example, marine cloud brightening, which would spray fine sea water to whiten clouds and thus increase cloud reflectivity.
- Upper atmosphere-based: creating reflective aerosols, such as stratospheric sulfate aerosols, specifically designed
self-levitating aerosols, or other substances.
- Space-based: space sunshade – obstructing solar radiation with space-based mirrors, dust, etc.
Carbon dioxide removal
- Creating biochar (i.e. in biomass-fired thermal power plants), for mixing into the soil to create terra preta
- Bio-energy with carbon capture and storage to sequester carbon and simultaneously provide energy Carbon air capture to remove carbon
dioxide from ambient air
- Afforestation, reforestation and forest restoration to absorb carbon dioxide
- Ocean afforestation and ocean fertilization (which includes iron fertilization of the oceans)
Why have none of these methods been implemented?
What are the risks of developing geoengineering?