I think its a good idea and we should do it. I regularly see areas which were snow covered and white now brown and much warmer. Unfortunately its also the plot of https://en.wikipedia.org/wiki/Snowpiercer where it overshoots.
>have so many second and third order effects you have no idea about
So has raising the Earth’s temperature, in addition to all the severe effects we know about.
I don’t know how to compare those risks.
For example, the wet bulb thermometer temperature forecasted for large swathes of land near the equator essentially means it's uninhabitable for mammals several weeks of the year.
Its the perceived choice between 1) Do nothing and watch everything die or 2) try something risky and if it goes wrong, watch everything die.
Farmland and logistics hubs in places that no longer get rain water and have run out of aquifers to tap need to be replaced somewhere more fertile. Desalination plants to replace dried up rivers need to be built. None of these can be operated on credit because giving someone a years supply of water after a year of drinking nothing just washes the corpse.
If the numbers shake out that there's a 10% shortfall, which 10% of population volunteers to starve their children? Or do fights break out? How does those fights stay constrained enough to not damage already strained infrastructure exacerbating the problem?
This is not a guaranteed outcome, but if you've seen how wide spread "just in time" logistics has gotten over the last 20 years and think it's impossible, I applaud your optimism.
And also don't want you anywhere near disaster planning.
If at any time during the next couple of thousands of years our society is unable or unwilling to send the required payloads to cool earth, then the temperature will increase by several degrees in a few years, and fewer organisms will be able to adapt.
Meanwhile, the whole ocean ecosystem has collapsed as acidification continued on up. The primary protein source of a billion+ people has vanished. They do not starve quietly.