Limestone, which is the principal component of concrete, can be made synthetically extracting CO2 from the atmosphere. Synthetic limestone, which has 44% CO2 by weight, can be used in buildings and roads and manufactured at a cost similar to natural limestone.

Blue Planet, a US based company, manufactures synthetic limestone and use it for a construction in San Francisco International Airport. Because of the high global demand for concrete, synthetic limestone is capable of restoring climate in 20 years, if the use of natural limestone is replaced by synthetic limestone.

Plants create their food using CO2 from the atmosphere and release oxygen into the atmosphere via photosynthesis. Because of the vast volume of ocean, marine plants produce 70% of atmospheric oxygen.Unfortunately, there has been a significant decline in marine

photosynthesis (40% since 1950) due to the depletion of iron in ocean chlorophyll, the key ingredient for photosynthesis. Marine plants used to obtain the iron particles from the dry land surfaces via wind. However, the CO2 emissions into the atmosphere in the last 200 years made those dry land surfaces slightly more moist and sticky, and consequently, the wind is carrying less amount of iron dust into the ocean. This problem can be easily solved by adding a small amount of iron into the ocean and revitalizing marine photosynthesis. This has the potential to remove the excess 1 trillion tons of CO2 from the atmosphere and thus restore climate in 20 years. It also has other benefits, for example: Photosynthesis will generate plankton, which will increase the fish population in the ocean providing food for people. In addition, the plankton will generate white clouds which will cool the earth by reflecting sunlight.

Planting trees can remove the atmospheric CO2 via photosynthesis, improve soil health and productivity, and thus, increase global food production.Afforestation refers to planting trees creating new forests and reforestation refers to restoring existing forests.

While planting trees can play an important role in removing CO2 from the atmosphere, they are not sufficient: trees take many years to grow, and require resources to protect them from human and natural impacts such as wildfires, drought and pest infestations. They could also compete for land used for agriculture just as food production needs to increase to feed the growing world population.