I want to create a world where there is very little sunlight during the day -- at noon the light would be about the same as an Earth sunset. The planet would be Earth-like until something causes the sunlight to be reduced (so that life can evolve normally first).
So, what are my options? What could possibly prevent most of sunlight (not ALL) to reach the planet's ground, considering these requirements:
- It must be stable, meaning, continuously block some sunlight during millions of years, if not forever
- It can be something completely natural or "kickstarted" by humans (because of their environmental damage for example)
- The planet setup and the star must stay the same: an Earth-like planet with 1.4 earth masses, in a double planet system with another, smaller Earth-like planet. The star is sun-like. Anything can be added to this as long as it doesn't hijack the setup.
- It should keep the climate as close to Earth-like as possible. I read that dense clouds can have this less-sunlight effect, but I don't want dense clouds everywhere all the time. I want to keep the Earth's diversity in climate and environments.
My goal is an alternate Earth with just the sunlight being missing, I'm trying to get everything else as normal as possible, so I need to know what effect each option will have on the planet (ex. temperature drop) so I can work on solving those problems one by one later.
So it's alright if life is supposed to go extinct, the humans will have plenty of time to find ways to avoid that. I also expect life to evolve very differently with less sunlight, even if the rest is the same, so no issues about that.
Magic or a bit of handwavium is acceptable, as long as there is a somewhat clear understanding of how it works and its consequences.