By geoengineering, you mean blocking out the light of the sun? Won't that significantly reduce the photosynthetic potential of Earth, and significantly reduce

By geoengineering, you mean blocking out the light of the sun? Won't that significantly reduce the photosynthetic potential of Earth, and significantly reduce the carrying capacity of the Earth for life? There are plenty of planets and moons that are cooler because they receive less sunlight. None of them host any life that we can detect. Isn't there a real risk that geoengineering would just end up turning the Earth into something resembling Mars, irreversibly? The Earth has supported abundant life with an atmosphere with a higher concentration of C02 than it has now. Has it ever supported abundant life with the solar energy being reduced to the extent required to reduce climate change?