I am looking for an answer relating to the possibility of very tall volcanoes (maybe as tall as 6km high), scattered around Tropical Asia (Indian Subcontinent and Southeast Asia), that spew lots of ash into the sky in order to reduce solar radiation and to cool the climate down), except they are constantly erupting and not spewing too much lava. I am thinking about the possibility for this kind of volcano to make the most tropical parts of Asia temperate for longer than centuries if not even thousands of years. Can such a thing exist, even if that kind of thing were to be made by man? My goal is to create a new race of humans via genetic editing, and they are very white skinned in the middle and northern parts of the region (Southern Asia in the broader sense).
There is no need for climate change to make people whiter.
Evolution takes a long time to do such a thing. Interbreeding is faster. We have whole countries where colonisation by Europeans just 100+ years ago achieved the same thing.
So if you genetically engineered them to be white then they're white. They may get sunburn or a tan, but they're not suddenly going to turn black in a few thousand years because it's hot.