Now, having thought about this, I can think of one argument that would negate some of the above: If you are arguing specifically that renewables reduce the albedo of the earth, causing less radiation (and thus heat) to be reflected back into space I'll give you that side of the argument as a possibility.. I'll need to do some research to see if this is actually the case.
One of the only valid critiques of PoW mining, but I don't think we are even remotely close to it being an issue
I wish I would have thought to add this to my original reply.. yes, in the grand scheme of things, even if renewables reduce the albedo, I think the amount would be somewhat less than a rounding error and have an absolutely negligible effect when compared to other environmental concerns.