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First planned small nuclear reactor plant in the US has been canceled
(arstechnica.com)
This is a most excellent place for technology news and articles.
There's a lag between human activity and climate change. Rolling out nuclear might have helped a bit, but whether we'd have seen the results today I'm not sure.. the benefits would be in the future.
I doubt cars could have evolved any faster though (well they could, but capitalism, so realistically things went as fast as they could).. so it might not have had much impact at all.