It's generally believed that we're already doing this by "accident". Along with carbon emissions, humans have released aerosols that block sunlight from reaching the Earth's surface + increase cloud cover, and are believed to be counteracting climate change to a significant extent (not enough to stop it, but enough to slow it down). We're pretty sure this works, because big volcanic eruptions that emit a bunch of sulfur aerosols are known to cool the Earth down (c.f. the "Year Without A Summer" [2]), and accounting for aerosol reduction has long been part of climate models.
A natural experiment of sorts has been going on for the past couple of years that further suggests this might matter. In 2020, new regulations on sulfur emissions (which are a significant pollutant in addition to their climate effects) went into effect for shipping around the world. Aerosols went way down almost overnight, and ocean temperatures promptly spiked to new record levels. Here's [3] an article from last year, when ocean temperatures were beginning to separate from the historical record; this process has continued dramatically through to the present [4], with global sea surface temperatures at record levels for the entirety of 2024 so far - despite the fact that last year's El Nino (which leaves a large patch of the Pacific warm) is largely gone and a La Nina (which leaves a large portion of the Pacific cold) is replacing it.
[1] https://www.ipcc.ch/site/assets/uploads/2018/02/WG1AR5_Chapt...
[2] https://en.wikipedia.org/wiki/Year_Without_a_Summer
[3] https://www.science.org/content/article/changing-clouds-unfo...
scientists were ordered to halt the experiment because it violated Alameda's lease with the USS Hornet, the aircraft carrier from which researchers were spraying saltwater into the air
'Marine Cloud Brightening Geoengineering Experiment Halted. Why do environmentalist ideologues oppose research on a possible emergency backup system to cool the climate?' https://reason.com/2024/05/15/marine-cloud-brightening-geoen...
