Oh... I was holding out building the Dome, because I thought that would be a negative ending despite calling it "winning" the game. I figured the true "win" would be lowering the temperature again. I won't bother then, that's a shame.
I was thinking the same and hoping for a rainbow. Or at least a, yay, humanity is doing great, our planet has advanced and as long as we follow how we got here, it'll be fine, kind of thing to win. idk