Carissa Wong in New Scientist:
Launching a dust cloud from the moon to block sunlight reaching Earth could reduce global warming, but such a strategy may require more than a decade’s worth of research before it can be implemented. The risks involved with such an approach in terms of how it could affect agriculture, ecosystems and water quality in different parts of the world are also unclear.
Placing more than 100 million tonnes of dust between Earth and the sun to partially block light from reaching our planet has previously been explored as a way to combat climate change. Such dust particles would shade Earth by absorbing light energy or scattering light particles, known as photons, away from Earth.
To achieve this, the dust would need to be placed 1.5 million kilometres from Earth, where the gravitational pull of the sun and our planet cancel out. Here, objects stay at a fixed position known as the first Lagrange point, or L1.
More here.