The problem with geo engineering is that in the proposed shape it doesn't solve two major problems: ocean acidification and impact of CO2 levels on animals (including humans).
Even if we get back to lofting sulphur, it won't stop aquatic life from dying. And our cognitive function won't be better if it's 1000ppm CO2 at 1.5°C degree increase rather than 1000ppm CO2 at 3°C degree increase.
Cognitive impairment isn’t an issue. High temp already impairs cognition—air conditioning can fix excess co2 and excess heat — indoors.
The ocean ph is currently 8.08. At 1000ppm (worst case scenario) the ph drops to 8.03. Disruptive to ecosystems, but not as bad as people think. Changes in heat will be worse.
The other piece— we can do geoengineering with calcium carbonate! That is alkaline.
Even if we get back to lofting sulphur, it won't stop aquatic life from dying. And our cognitive function won't be better if it's 1000ppm CO2 at 1.5°C degree increase rather than 1000ppm CO2 at 3°C degree increase.
Geoengineering is insufficient.