Geoengineering (or Geoengineering) is the art (because it is more an art than a science now) of trying to modify the climate, it is not necessarily a new science (see the Arte report above ) but it is currently becoming more and more important in order to limit global warming ... with or without the approval of the populations ...
Here are some techniques and techniques of Geo-Engineering that we analyzed and commented on in the subject How to cool the Earth?
Deflect solar radiation with a space "parasol" "
In my opinion, the most cranky of the proposed solutions is to send 20 millions of probes (if yes) filled with deflector at the Lagrange point at 1,5 Million km of Earth (or solar gravity = Earth's gravity).
Purpose: To reduce the solar flux of 1,8% by creating a permanent spot on the Earth of several thousand km.
Duration: 50 years ...
Deflect and absorb solar radiation by "sulfur" the atmosphere
Somewhat the same process as the 1) but staying on Earth (thus already more reasonable) by spraying H2S in the upper atmosphere which would quickly transform into SO2 deviating thus the solar rays.
Desired goal: to gain "a few degrees" over 10 years
ps: H2S is lethal at high concentrations. At low concentration it "stinks of egg". It can be felt near refinery fuel desulphurization units ...
Relaunch the Gulf Stream
By 8000 autonomous seawater pumping platforms intended to "boost" the Gulf Stream with cold salt water at the right time of the year (thaw).
Purpose: add 1 million m3 to thermo-marine circulation
When we know the strength and thermal power of the Gulf Stream (thermal power equivalent to 1 million nuclear reactors)… this solution seems very pitiful…
Boost plankton with iron sulfate
The most "realistic" and undoubtedly effective solution which consists in boosting the plankton (and therefore the marine food chain) of certain areas of the ocean which are in deficit. The CO2 absorbed by the plankton is permanently stored in the underwater sediments of the corpses of their predator.
goal: to compensate 15% of our emissions CO2