The Cli-Fi youth novel " °C Celsius " by #MarcElsberg https://www.lovelybooks.de/autor/Marc-Elsberg/-C-Celsius-7259470664-w/leserunde/8486314240/8921172467/#thread
weaves together a few SRM scenarios into a plot. One scenario goes like this: a few poor-ish tropical countries gang up and start SRM, while also sabotaging all means to counter their project.
The reasoning they give to the world is an analysis how only cold-ish countries managed to industrialise early on and still benefit from their fast development.
So logically, it should be expected that these tropical countries would make a similar evolution if only the mean temperature goes down to 21 °C or so, 8 degrees celsius cooler than today.
And off they go, blasting SO2 into the stratosphere according to their target.
^^
And no one can stop them.
Elsberg omits describing the potential mid- to long-term fallout in detail on ecosystems, economies. But he mentions a few short-term impacts like torrential rains from the now-colder atmosphere releasing the moisture it can no longer hold.
Reading the reasoning did sound justified at that moment, -8°C sounds shockingly justified. 
But now, while looking at Australia's and Brasil's weather stations for a new project of mine, it occurs to me that Australia is just outside Brasil's latitudes, and Australia is rich, Brasil is not. Brasil is of course member of Elsberg's tropical #SRM gang, Australia not.
Annual mean °C is
25.5 for Brazil
22.5 for Australia.
Following the scenario logic, it should have sufficed to aim for 3°C cooling in order to get to Australia's level. -4°C at the outside.
And to get colonised by Great Britain of course, in order to also migrate the societal order to the same system that worked so well for British colonies until the 1950s or so. ^^
