Science

We already know the cooling effect of aerosols, including SO2. Noone is blocking academic research on impacts of adding/removing aerosol to change Earth's albedo. In fact we already know the impact, what is the lifetime of individual aerosol in the atmosphere, their negative (cooling) global warming potential, and their deleterious effect on human health as pollutant.

You can already show on a piece of paper why this experiment is not worth doing. The maximum lifetime of aerosol in the stratosphere is 2 years, you have to keep injecting and replacing the aerosol to maintain the cooling effect. Production of these reflective aerosol uses energy (i.e. produce GHG) so as the greenhouse gases accumulate in the atmosphere, you need more and more aerosol injection to offset the warming effect. On paper this is already a terrible idea, not even accounting for the additional particulate matter pollution from the fallout of this reflective aerosol injection, tldr, it's going to end up in someone's lung and other unintended consequences of injecting tons of dirt into Earth's stratosphere.

Why should we waste resources to conduct planetary scale geoengineering experiment for an idea that is already bad on paper? Remember there is no control experiment for planetary scale geoengineering, there is no Earth 2. Thousands of serious climate scientists waste their time writing IPCC reports every 5 years and arguing over countless hours and the solutions have been the same since 1990, reduce oil and gas consumption, plant trees, make solar panels and wind turbines.