Also consider climate cycles such as ice ages. Imagine a coalition finds a wildy successful heat reduction strategy and it impacts well beyond what was anticipated? How would things go if we accelerrated glaciation down to the gulf of Mexico? The Earth’s wobble and axial tilt are part of this process over incredible periods of time… CFC’s and the ozone are a good example of rapid and unanticipated results of human inputs. No easy answer even with stakes as high as they appear.

It might backfire and cause more problems.

Because we don’t know wtf we’re doing when it comes to geoengineering?

Agreed. Hell, when we decided that the global shipping industry should not use the dirtiest fuel possible, the lack of sulfur oxide being emitted raised the ocean temperature quite a bit almost immediately. There are things we can do that will have the same effect without the massive negative consequences that sulfur oxide carries.