Question

Which of the following has been proposed as a potential strategy for mitigating the increase of co2 in the atmosphere ?

Answer 1

Injecting into geological formation, adding iron to the ocean to increase phytoplankton, and shooting into space

All of the above proposed methods are being proposed to help decrease global warming but adding aerosols into the atmosphere does not involve the mitigation of the increase in CO2 in the atmosphere. 

1. Adding aerosol to the atmosphere - aerosols added to the atmosphere have the potential to block the sun's rays and reduce global warming. They reflect the sun's rays back to the atmosphere while at the same time providing "seeds" around which water droplets can come together to form clouds. Cloud formation can also help increase the earth's reflectivity against the sun's rays.

2. Injecting into geological formation - carbon dioxide from stationary sources (e.g. powerplants and factories) can be captured and eliminated from the atmosphere, compressed into a fluid state, and injected deep underground into permeable and porous geological formations and overlain with a layer of impermeable rock to seal the CO2 underground. 

3. Adding iron to oceans to increase phytoplankton - phytoplanktons take up carbon dioxide from the atmosphere for photosynthesis. Thus, adding iron to the oceans, which acts as a fertilizer to the phytoplanktons, can encourage the growth of the phytoplankton population. The more phytoplanktons, the more CO2 that can be removed from the atmosphere. 

4. Shoot it into space - some scientists propose that a conveyor can be built in the Arctic to take advantage of the Earth's magnetic field and allow for the venting or expelling of CO2 into outer space.