>>729
(setq frame-background-mode 'dark)
(load-theme 'solarized t)

https://github.com/sellout/emacs-color-theme-solarized
> To switch between the light and dark variations of Solarized, set the frame’s
> background-mode. This can be accomplished globally using M-x
> customize-variable frame-background-mode or on a per-frame basis with
> (set-frame-parameter nil 'background-mode 'light) (or 'dark).